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0001 /*
0002  *  linux/fs/locks.c
0003  *
0004  *  Provide support for fcntl()'s F_GETLK, F_SETLK, and F_SETLKW calls.
0005  *  Doug Evans (dje@spiff.uucp), August 07, 1992
0006  *
0007  *  Deadlock detection added.
0008  *  FIXME: one thing isn't handled yet:
0009  *  - mandatory locks (requires lots of changes elsewhere)
0010  *  Kelly Carmichael (kelly@[142.24.8.65]), September 17, 1994.
0011  *
0012  *  Miscellaneous edits, and a total rewrite of posix_lock_file() code.
0013  *  Kai Petzke (wpp@marie.physik.tu-berlin.de), 1994
0014  *  
0015  *  Converted file_lock_table to a linked list from an array, which eliminates
0016  *  the limits on how many active file locks are open.
0017  *  Chad Page (pageone@netcom.com), November 27, 1994
0018  * 
0019  *  Removed dependency on file descriptors. dup()'ed file descriptors now
0020  *  get the same locks as the original file descriptors, and a close() on
0021  *  any file descriptor removes ALL the locks on the file for the current
0022  *  process. Since locks still depend on the process id, locks are inherited
0023  *  after an exec() but not after a fork(). This agrees with POSIX, and both
0024  *  BSD and SVR4 practice.
0025  *  Andy Walker (andy@lysaker.kvaerner.no), February 14, 1995
0026  *
0027  *  Scrapped free list which is redundant now that we allocate locks
0028  *  dynamically with kmalloc()/kfree().
0029  *  Andy Walker (andy@lysaker.kvaerner.no), February 21, 1995
0030  *
0031  *  Implemented two lock personalities - FL_FLOCK and FL_POSIX.
0032  *
0033  *  FL_POSIX locks are created with calls to fcntl() and lockf() through the
0034  *  fcntl() system call. They have the semantics described above.
0035  *
0036  *  FL_FLOCK locks are created with calls to flock(), through the flock()
0037  *  system call, which is new. Old C libraries implement flock() via fcntl()
0038  *  and will continue to use the old, broken implementation.
0039  *
0040  *  FL_FLOCK locks follow the 4.4 BSD flock() semantics. They are associated
0041  *  with a file pointer (filp). As a result they can be shared by a parent
0042  *  process and its children after a fork(). They are removed when the last
0043  *  file descriptor referring to the file pointer is closed (unless explicitly
0044  *  unlocked). 
0045  *
0046  *  FL_FLOCK locks never deadlock, an existing lock is always removed before
0047  *  upgrading from shared to exclusive (or vice versa). When this happens
0048  *  any processes blocked by the current lock are woken up and allowed to
0049  *  run before the new lock is applied.
0050  *  Andy Walker (andy@lysaker.kvaerner.no), June 09, 1995
0051  *
0052  *  Removed some race conditions in flock_lock_file(), marked other possible
0053  *  races. Just grep for FIXME to see them. 
0054  *  Dmitry Gorodchanin (pgmdsg@ibi.com), February 09, 1996.
0055  *
0056  *  Addressed Dmitry's concerns. Deadlock checking no longer recursive.
0057  *  Lock allocation changed to GFP_ATOMIC as we can't afford to sleep
0058  *  once we've checked for blocking and deadlocking.
0059  *  Andy Walker (andy@lysaker.kvaerner.no), April 03, 1996.
0060  *
0061  *  Initial implementation of mandatory locks. SunOS turned out to be
0062  *  a rotten model, so I implemented the "obvious" semantics.
0063  *  See 'Documentation/filesystems/mandatory-locking.txt' for details.
0064  *  Andy Walker (andy@lysaker.kvaerner.no), April 06, 1996.
0065  *
0066  *  Don't allow mandatory locks on mmap()'ed files. Added simple functions to
0067  *  check if a file has mandatory locks, used by mmap(), open() and creat() to
0068  *  see if system call should be rejected. Ref. HP-UX/SunOS/Solaris Reference
0069  *  Manual, Section 2.
0070  *  Andy Walker (andy@lysaker.kvaerner.no), April 09, 1996.
0071  *
0072  *  Tidied up block list handling. Added '/proc/locks' interface.
0073  *  Andy Walker (andy@lysaker.kvaerner.no), April 24, 1996.
0074  *
0075  *  Fixed deadlock condition for pathological code that mixes calls to
0076  *  flock() and fcntl().
0077  *  Andy Walker (andy@lysaker.kvaerner.no), April 29, 1996.
0078  *
0079  *  Allow only one type of locking scheme (FL_POSIX or FL_FLOCK) to be in use
0080  *  for a given file at a time. Changed the CONFIG_LOCK_MANDATORY scheme to
0081  *  guarantee sensible behaviour in the case where file system modules might
0082  *  be compiled with different options than the kernel itself.
0083  *  Andy Walker (andy@lysaker.kvaerner.no), May 15, 1996.
0084  *
0085  *  Added a couple of missing wake_up() calls. Thanks to Thomas Meckel
0086  *  (Thomas.Meckel@mni.fh-giessen.de) for spotting this.
0087  *  Andy Walker (andy@lysaker.kvaerner.no), May 15, 1996.
0088  *
0089  *  Changed FL_POSIX locks to use the block list in the same way as FL_FLOCK
0090  *  locks. Changed process synchronisation to avoid dereferencing locks that
0091  *  have already been freed.
0092  *  Andy Walker (andy@lysaker.kvaerner.no), Sep 21, 1996.
0093  *
0094  *  Made the block list a circular list to minimise searching in the list.
0095  *  Andy Walker (andy@lysaker.kvaerner.no), Sep 25, 1996.
0096  *
0097  *  Made mandatory locking a mount option. Default is not to allow mandatory
0098  *  locking.
0099  *  Andy Walker (andy@lysaker.kvaerner.no), Oct 04, 1996.
0100  *
0101  *  Some adaptations for NFS support.
0102  *  Olaf Kirch (okir@monad.swb.de), Dec 1996,
0103  *
0104  *  Fixed /proc/locks interface so that we can't overrun the buffer we are handed.
0105  *  Andy Walker (andy@lysaker.kvaerner.no), May 12, 1997.
0106  *
0107  *  Use slab allocator instead of kmalloc/kfree.
0108  *  Use generic list implementation from <linux/list.h>.
0109  *  Sped up posix_locks_deadlock by only considering blocked locks.
0110  *  Matthew Wilcox <willy@debian.org>, March, 2000.
0111  *
0112  *  Leases and LOCK_MAND
0113  *  Matthew Wilcox <willy@debian.org>, June, 2000.
0114  *  Stephen Rothwell <sfr@canb.auug.org.au>, June, 2000.
0115  */
0116 
0117 #include <linux/capability.h>
0118 #include <linux/file.h>
0119 #include <linux/fdtable.h>
0120 #include <linux/fs.h>
0121 #include <linux/init.h>
0122 #include <linux/security.h>
0123 #include <linux/slab.h>
0124 #include <linux/syscalls.h>
0125 #include <linux/time.h>
0126 #include <linux/rcupdate.h>
0127 #include <linux/pid_namespace.h>
0128 #include <linux/hashtable.h>
0129 #include <linux/percpu.h>
0130 
0131 #define CREATE_TRACE_POINTS
0132 #include <trace/events/filelock.h>
0133 
0134 #include <linux/uaccess.h>
0135 
0136 #define IS_POSIX(fl)    (fl->fl_flags & FL_POSIX)
0137 #define IS_FLOCK(fl)    (fl->fl_flags & FL_FLOCK)
0138 #define IS_LEASE(fl)    (fl->fl_flags & (FL_LEASE|FL_DELEG|FL_LAYOUT))
0139 #define IS_OFDLCK(fl)   (fl->fl_flags & FL_OFDLCK)
0140 
0141 static inline bool is_remote_lock(struct file *filp)
0142 {
0143     return likely(!(filp->f_path.dentry->d_sb->s_flags & MS_NOREMOTELOCK));
0144 }
0145 
0146 static bool lease_breaking(struct file_lock *fl)
0147 {
0148     return fl->fl_flags & (FL_UNLOCK_PENDING | FL_DOWNGRADE_PENDING);
0149 }
0150 
0151 static int target_leasetype(struct file_lock *fl)
0152 {
0153     if (fl->fl_flags & FL_UNLOCK_PENDING)
0154         return F_UNLCK;
0155     if (fl->fl_flags & FL_DOWNGRADE_PENDING)
0156         return F_RDLCK;
0157     return fl->fl_type;
0158 }
0159 
0160 int leases_enable = 1;
0161 int lease_break_time = 45;
0162 
0163 /*
0164  * The global file_lock_list is only used for displaying /proc/locks, so we
0165  * keep a list on each CPU, with each list protected by its own spinlock.
0166  * Global serialization is done using file_rwsem.
0167  *
0168  * Note that alterations to the list also require that the relevant flc_lock is
0169  * held.
0170  */
0171 struct file_lock_list_struct {
0172     spinlock_t      lock;
0173     struct hlist_head   hlist;
0174 };
0175 static DEFINE_PER_CPU(struct file_lock_list_struct, file_lock_list);
0176 DEFINE_STATIC_PERCPU_RWSEM(file_rwsem);
0177 
0178 /*
0179  * The blocked_hash is used to find POSIX lock loops for deadlock detection.
0180  * It is protected by blocked_lock_lock.
0181  *
0182  * We hash locks by lockowner in order to optimize searching for the lock a
0183  * particular lockowner is waiting on.
0184  *
0185  * FIXME: make this value scale via some heuristic? We generally will want more
0186  * buckets when we have more lockowners holding locks, but that's a little
0187  * difficult to determine without knowing what the workload will look like.
0188  */
0189 #define BLOCKED_HASH_BITS   7
0190 static DEFINE_HASHTABLE(blocked_hash, BLOCKED_HASH_BITS);
0191 
0192 /*
0193  * This lock protects the blocked_hash. Generally, if you're accessing it, you
0194  * want to be holding this lock.
0195  *
0196  * In addition, it also protects the fl->fl_block list, and the fl->fl_next
0197  * pointer for file_lock structures that are acting as lock requests (in
0198  * contrast to those that are acting as records of acquired locks).
0199  *
0200  * Note that when we acquire this lock in order to change the above fields,
0201  * we often hold the flc_lock as well. In certain cases, when reading the fields
0202  * protected by this lock, we can skip acquiring it iff we already hold the
0203  * flc_lock.
0204  *
0205  * In particular, adding an entry to the fl_block list requires that you hold
0206  * both the flc_lock and the blocked_lock_lock (acquired in that order).
0207  * Deleting an entry from the list however only requires the file_lock_lock.
0208  */
0209 static DEFINE_SPINLOCK(blocked_lock_lock);
0210 
0211 static struct kmem_cache *flctx_cache __read_mostly;
0212 static struct kmem_cache *filelock_cache __read_mostly;
0213 
0214 static struct file_lock_context *
0215 locks_get_lock_context(struct inode *inode, int type)
0216 {
0217     struct file_lock_context *ctx;
0218 
0219     /* paired with cmpxchg() below */
0220     ctx = smp_load_acquire(&inode->i_flctx);
0221     if (likely(ctx) || type == F_UNLCK)
0222         goto out;
0223 
0224     ctx = kmem_cache_alloc(flctx_cache, GFP_KERNEL);
0225     if (!ctx)
0226         goto out;
0227 
0228     spin_lock_init(&ctx->flc_lock);
0229     INIT_LIST_HEAD(&ctx->flc_flock);
0230     INIT_LIST_HEAD(&ctx->flc_posix);
0231     INIT_LIST_HEAD(&ctx->flc_lease);
0232 
0233     /*
0234      * Assign the pointer if it's not already assigned. If it is, then
0235      * free the context we just allocated.
0236      */
0237     if (cmpxchg(&inode->i_flctx, NULL, ctx)) {
0238         kmem_cache_free(flctx_cache, ctx);
0239         ctx = smp_load_acquire(&inode->i_flctx);
0240     }
0241 out:
0242     trace_locks_get_lock_context(inode, type, ctx);
0243     return ctx;
0244 }
0245 
0246 static void
0247 locks_dump_ctx_list(struct list_head *list, char *list_type)
0248 {
0249     struct file_lock *fl;
0250 
0251     list_for_each_entry(fl, list, fl_list) {
0252         pr_warn("%s: fl_owner=%p fl_flags=0x%x fl_type=0x%x fl_pid=%u\n", list_type, fl->fl_owner, fl->fl_flags, fl->fl_type, fl->fl_pid);
0253     }
0254 }
0255 
0256 static void
0257 locks_check_ctx_lists(struct inode *inode)
0258 {
0259     struct file_lock_context *ctx = inode->i_flctx;
0260 
0261     if (unlikely(!list_empty(&ctx->flc_flock) ||
0262              !list_empty(&ctx->flc_posix) ||
0263              !list_empty(&ctx->flc_lease))) {
0264         pr_warn("Leaked locks on dev=0x%x:0x%x ino=0x%lx:\n",
0265             MAJOR(inode->i_sb->s_dev), MINOR(inode->i_sb->s_dev),
0266             inode->i_ino);
0267         locks_dump_ctx_list(&ctx->flc_flock, "FLOCK");
0268         locks_dump_ctx_list(&ctx->flc_posix, "POSIX");
0269         locks_dump_ctx_list(&ctx->flc_lease, "LEASE");
0270     }
0271 }
0272 
0273 void
0274 locks_free_lock_context(struct inode *inode)
0275 {
0276     struct file_lock_context *ctx = inode->i_flctx;
0277 
0278     if (unlikely(ctx)) {
0279         locks_check_ctx_lists(inode);
0280         kmem_cache_free(flctx_cache, ctx);
0281     }
0282 }
0283 
0284 static void locks_init_lock_heads(struct file_lock *fl)
0285 {
0286     INIT_HLIST_NODE(&fl->fl_link);
0287     INIT_LIST_HEAD(&fl->fl_list);
0288     INIT_LIST_HEAD(&fl->fl_block);
0289     init_waitqueue_head(&fl->fl_wait);
0290 }
0291 
0292 /* Allocate an empty lock structure. */
0293 struct file_lock *locks_alloc_lock(void)
0294 {
0295     struct file_lock *fl = kmem_cache_zalloc(filelock_cache, GFP_KERNEL);
0296 
0297     if (fl)
0298         locks_init_lock_heads(fl);
0299 
0300     return fl;
0301 }
0302 EXPORT_SYMBOL_GPL(locks_alloc_lock);
0303 
0304 void locks_release_private(struct file_lock *fl)
0305 {
0306     if (fl->fl_ops) {
0307         if (fl->fl_ops->fl_release_private)
0308             fl->fl_ops->fl_release_private(fl);
0309         fl->fl_ops = NULL;
0310     }
0311 
0312     if (fl->fl_lmops) {
0313         if (fl->fl_lmops->lm_put_owner) {
0314             fl->fl_lmops->lm_put_owner(fl->fl_owner);
0315             fl->fl_owner = NULL;
0316         }
0317         fl->fl_lmops = NULL;
0318     }
0319 }
0320 EXPORT_SYMBOL_GPL(locks_release_private);
0321 
0322 /* Free a lock which is not in use. */
0323 void locks_free_lock(struct file_lock *fl)
0324 {
0325     BUG_ON(waitqueue_active(&fl->fl_wait));
0326     BUG_ON(!list_empty(&fl->fl_list));
0327     BUG_ON(!list_empty(&fl->fl_block));
0328     BUG_ON(!hlist_unhashed(&fl->fl_link));
0329 
0330     locks_release_private(fl);
0331     kmem_cache_free(filelock_cache, fl);
0332 }
0333 EXPORT_SYMBOL(locks_free_lock);
0334 
0335 static void
0336 locks_dispose_list(struct list_head *dispose)
0337 {
0338     struct file_lock *fl;
0339 
0340     while (!list_empty(dispose)) {
0341         fl = list_first_entry(dispose, struct file_lock, fl_list);
0342         list_del_init(&fl->fl_list);
0343         locks_free_lock(fl);
0344     }
0345 }
0346 
0347 void locks_init_lock(struct file_lock *fl)
0348 {
0349     memset(fl, 0, sizeof(struct file_lock));
0350     locks_init_lock_heads(fl);
0351 }
0352 
0353 EXPORT_SYMBOL(locks_init_lock);
0354 
0355 /*
0356  * Initialize a new lock from an existing file_lock structure.
0357  */
0358 void locks_copy_conflock(struct file_lock *new, struct file_lock *fl)
0359 {
0360     new->fl_owner = fl->fl_owner;
0361     new->fl_pid = fl->fl_pid;
0362     new->fl_file = NULL;
0363     new->fl_flags = fl->fl_flags;
0364     new->fl_type = fl->fl_type;
0365     new->fl_start = fl->fl_start;
0366     new->fl_end = fl->fl_end;
0367     new->fl_lmops = fl->fl_lmops;
0368     new->fl_ops = NULL;
0369 
0370     if (fl->fl_lmops) {
0371         if (fl->fl_lmops->lm_get_owner)
0372             fl->fl_lmops->lm_get_owner(fl->fl_owner);
0373     }
0374 }
0375 EXPORT_SYMBOL(locks_copy_conflock);
0376 
0377 void locks_copy_lock(struct file_lock *new, struct file_lock *fl)
0378 {
0379     /* "new" must be a freshly-initialized lock */
0380     WARN_ON_ONCE(new->fl_ops);
0381 
0382     locks_copy_conflock(new, fl);
0383 
0384     new->fl_file = fl->fl_file;
0385     new->fl_ops = fl->fl_ops;
0386 
0387     if (fl->fl_ops) {
0388         if (fl->fl_ops->fl_copy_lock)
0389             fl->fl_ops->fl_copy_lock(new, fl);
0390     }
0391 }
0392 
0393 EXPORT_SYMBOL(locks_copy_lock);
0394 
0395 static inline int flock_translate_cmd(int cmd) {
0396     if (cmd & LOCK_MAND)
0397         return cmd & (LOCK_MAND | LOCK_RW);
0398     switch (cmd) {
0399     case LOCK_SH:
0400         return F_RDLCK;
0401     case LOCK_EX:
0402         return F_WRLCK;
0403     case LOCK_UN:
0404         return F_UNLCK;
0405     }
0406     return -EINVAL;
0407 }
0408 
0409 /* Fill in a file_lock structure with an appropriate FLOCK lock. */
0410 static struct file_lock *
0411 flock_make_lock(struct file *filp, unsigned int cmd)
0412 {
0413     struct file_lock *fl;
0414     int type = flock_translate_cmd(cmd);
0415 
0416     if (type < 0)
0417         return ERR_PTR(type);
0418     
0419     fl = locks_alloc_lock();
0420     if (fl == NULL)
0421         return ERR_PTR(-ENOMEM);
0422 
0423     fl->fl_file = filp;
0424     fl->fl_owner = filp;
0425     fl->fl_pid = current->tgid;
0426     fl->fl_flags = FL_FLOCK;
0427     fl->fl_type = type;
0428     fl->fl_end = OFFSET_MAX;
0429     
0430     return fl;
0431 }
0432 
0433 static int assign_type(struct file_lock *fl, long type)
0434 {
0435     switch (type) {
0436     case F_RDLCK:
0437     case F_WRLCK:
0438     case F_UNLCK:
0439         fl->fl_type = type;
0440         break;
0441     default:
0442         return -EINVAL;
0443     }
0444     return 0;
0445 }
0446 
0447 static int flock64_to_posix_lock(struct file *filp, struct file_lock *fl,
0448                  struct flock64 *l)
0449 {
0450     switch (l->l_whence) {
0451     case SEEK_SET:
0452         fl->fl_start = 0;
0453         break;
0454     case SEEK_CUR:
0455         fl->fl_start = filp->f_pos;
0456         break;
0457     case SEEK_END:
0458         fl->fl_start = i_size_read(file_inode(filp));
0459         break;
0460     default:
0461         return -EINVAL;
0462     }
0463     if (l->l_start > OFFSET_MAX - fl->fl_start)
0464         return -EOVERFLOW;
0465     fl->fl_start += l->l_start;
0466     if (fl->fl_start < 0)
0467         return -EINVAL;
0468 
0469     /* POSIX-1996 leaves the case l->l_len < 0 undefined;
0470        POSIX-2001 defines it. */
0471     if (l->l_len > 0) {
0472         if (l->l_len - 1 > OFFSET_MAX - fl->fl_start)
0473             return -EOVERFLOW;
0474         fl->fl_end = fl->fl_start + l->l_len - 1;
0475 
0476     } else if (l->l_len < 0) {
0477         if (fl->fl_start + l->l_len < 0)
0478             return -EINVAL;
0479         fl->fl_end = fl->fl_start - 1;
0480         fl->fl_start += l->l_len;
0481     } else
0482         fl->fl_end = OFFSET_MAX;
0483 
0484     fl->fl_owner = current->files;
0485     fl->fl_pid = current->tgid;
0486     fl->fl_file = filp;
0487     fl->fl_flags = FL_POSIX;
0488     fl->fl_ops = NULL;
0489     fl->fl_lmops = NULL;
0490 
0491     return assign_type(fl, l->l_type);
0492 }
0493 
0494 /* Verify a "struct flock" and copy it to a "struct file_lock" as a POSIX
0495  * style lock.
0496  */
0497 static int flock_to_posix_lock(struct file *filp, struct file_lock *fl,
0498                    struct flock *l)
0499 {
0500     struct flock64 ll = {
0501         .l_type = l->l_type,
0502         .l_whence = l->l_whence,
0503         .l_start = l->l_start,
0504         .l_len = l->l_len,
0505     };
0506 
0507     return flock64_to_posix_lock(filp, fl, &ll);
0508 }
0509 
0510 /* default lease lock manager operations */
0511 static bool
0512 lease_break_callback(struct file_lock *fl)
0513 {
0514     kill_fasync(&fl->fl_fasync, SIGIO, POLL_MSG);
0515     return false;
0516 }
0517 
0518 static void
0519 lease_setup(struct file_lock *fl, void **priv)
0520 {
0521     struct file *filp = fl->fl_file;
0522     struct fasync_struct *fa = *priv;
0523 
0524     /*
0525      * fasync_insert_entry() returns the old entry if any. If there was no
0526      * old entry, then it used "priv" and inserted it into the fasync list.
0527      * Clear the pointer to indicate that it shouldn't be freed.
0528      */
0529     if (!fasync_insert_entry(fa->fa_fd, filp, &fl->fl_fasync, fa))
0530         *priv = NULL;
0531 
0532     __f_setown(filp, task_pid(current), PIDTYPE_PID, 0);
0533 }
0534 
0535 static const struct lock_manager_operations lease_manager_ops = {
0536     .lm_break = lease_break_callback,
0537     .lm_change = lease_modify,
0538     .lm_setup = lease_setup,
0539 };
0540 
0541 /*
0542  * Initialize a lease, use the default lock manager operations
0543  */
0544 static int lease_init(struct file *filp, long type, struct file_lock *fl)
0545  {
0546     if (assign_type(fl, type) != 0)
0547         return -EINVAL;
0548 
0549     fl->fl_owner = filp;
0550     fl->fl_pid = current->tgid;
0551 
0552     fl->fl_file = filp;
0553     fl->fl_flags = FL_LEASE;
0554     fl->fl_start = 0;
0555     fl->fl_end = OFFSET_MAX;
0556     fl->fl_ops = NULL;
0557     fl->fl_lmops = &lease_manager_ops;
0558     return 0;
0559 }
0560 
0561 /* Allocate a file_lock initialised to this type of lease */
0562 static struct file_lock *lease_alloc(struct file *filp, long type)
0563 {
0564     struct file_lock *fl = locks_alloc_lock();
0565     int error = -ENOMEM;
0566 
0567     if (fl == NULL)
0568         return ERR_PTR(error);
0569 
0570     error = lease_init(filp, type, fl);
0571     if (error) {
0572         locks_free_lock(fl);
0573         return ERR_PTR(error);
0574     }
0575     return fl;
0576 }
0577 
0578 /* Check if two locks overlap each other.
0579  */
0580 static inline int locks_overlap(struct file_lock *fl1, struct file_lock *fl2)
0581 {
0582     return ((fl1->fl_end >= fl2->fl_start) &&
0583         (fl2->fl_end >= fl1->fl_start));
0584 }
0585 
0586 /*
0587  * Check whether two locks have the same owner.
0588  */
0589 static int posix_same_owner(struct file_lock *fl1, struct file_lock *fl2)
0590 {
0591     if (fl1->fl_lmops && fl1->fl_lmops->lm_compare_owner)
0592         return fl2->fl_lmops == fl1->fl_lmops &&
0593             fl1->fl_lmops->lm_compare_owner(fl1, fl2);
0594     return fl1->fl_owner == fl2->fl_owner;
0595 }
0596 
0597 /* Must be called with the flc_lock held! */
0598 static void locks_insert_global_locks(struct file_lock *fl)
0599 {
0600     struct file_lock_list_struct *fll = this_cpu_ptr(&file_lock_list);
0601 
0602     percpu_rwsem_assert_held(&file_rwsem);
0603 
0604     spin_lock(&fll->lock);
0605     fl->fl_link_cpu = smp_processor_id();
0606     hlist_add_head(&fl->fl_link, &fll->hlist);
0607     spin_unlock(&fll->lock);
0608 }
0609 
0610 /* Must be called with the flc_lock held! */
0611 static void locks_delete_global_locks(struct file_lock *fl)
0612 {
0613     struct file_lock_list_struct *fll;
0614 
0615     percpu_rwsem_assert_held(&file_rwsem);
0616 
0617     /*
0618      * Avoid taking lock if already unhashed. This is safe since this check
0619      * is done while holding the flc_lock, and new insertions into the list
0620      * also require that it be held.
0621      */
0622     if (hlist_unhashed(&fl->fl_link))
0623         return;
0624 
0625     fll = per_cpu_ptr(&file_lock_list, fl->fl_link_cpu);
0626     spin_lock(&fll->lock);
0627     hlist_del_init(&fl->fl_link);
0628     spin_unlock(&fll->lock);
0629 }
0630 
0631 static unsigned long
0632 posix_owner_key(struct file_lock *fl)
0633 {
0634     if (fl->fl_lmops && fl->fl_lmops->lm_owner_key)
0635         return fl->fl_lmops->lm_owner_key(fl);
0636     return (unsigned long)fl->fl_owner;
0637 }
0638 
0639 static void locks_insert_global_blocked(struct file_lock *waiter)
0640 {
0641     lockdep_assert_held(&blocked_lock_lock);
0642 
0643     hash_add(blocked_hash, &waiter->fl_link, posix_owner_key(waiter));
0644 }
0645 
0646 static void locks_delete_global_blocked(struct file_lock *waiter)
0647 {
0648     lockdep_assert_held(&blocked_lock_lock);
0649 
0650     hash_del(&waiter->fl_link);
0651 }
0652 
0653 /* Remove waiter from blocker's block list.
0654  * When blocker ends up pointing to itself then the list is empty.
0655  *
0656  * Must be called with blocked_lock_lock held.
0657  */
0658 static void __locks_delete_block(struct file_lock *waiter)
0659 {
0660     locks_delete_global_blocked(waiter);
0661     list_del_init(&waiter->fl_block);
0662     waiter->fl_next = NULL;
0663 }
0664 
0665 static void locks_delete_block(struct file_lock *waiter)
0666 {
0667     spin_lock(&blocked_lock_lock);
0668     __locks_delete_block(waiter);
0669     spin_unlock(&blocked_lock_lock);
0670 }
0671 
0672 /* Insert waiter into blocker's block list.
0673  * We use a circular list so that processes can be easily woken up in
0674  * the order they blocked. The documentation doesn't require this but
0675  * it seems like the reasonable thing to do.
0676  *
0677  * Must be called with both the flc_lock and blocked_lock_lock held. The
0678  * fl_block list itself is protected by the blocked_lock_lock, but by ensuring
0679  * that the flc_lock is also held on insertions we can avoid taking the
0680  * blocked_lock_lock in some cases when we see that the fl_block list is empty.
0681  */
0682 static void __locks_insert_block(struct file_lock *blocker,
0683                     struct file_lock *waiter)
0684 {
0685     BUG_ON(!list_empty(&waiter->fl_block));
0686     waiter->fl_next = blocker;
0687     list_add_tail(&waiter->fl_block, &blocker->fl_block);
0688     if (IS_POSIX(blocker) && !IS_OFDLCK(blocker))
0689         locks_insert_global_blocked(waiter);
0690 }
0691 
0692 /* Must be called with flc_lock held. */
0693 static void locks_insert_block(struct file_lock *blocker,
0694                     struct file_lock *waiter)
0695 {
0696     spin_lock(&blocked_lock_lock);
0697     __locks_insert_block(blocker, waiter);
0698     spin_unlock(&blocked_lock_lock);
0699 }
0700 
0701 /*
0702  * Wake up processes blocked waiting for blocker.
0703  *
0704  * Must be called with the inode->flc_lock held!
0705  */
0706 static void locks_wake_up_blocks(struct file_lock *blocker)
0707 {
0708     /*
0709      * Avoid taking global lock if list is empty. This is safe since new
0710      * blocked requests are only added to the list under the flc_lock, and
0711      * the flc_lock is always held here. Note that removal from the fl_block
0712      * list does not require the flc_lock, so we must recheck list_empty()
0713      * after acquiring the blocked_lock_lock.
0714      */
0715     if (list_empty(&blocker->fl_block))
0716         return;
0717 
0718     spin_lock(&blocked_lock_lock);
0719     while (!list_empty(&blocker->fl_block)) {
0720         struct file_lock *waiter;
0721 
0722         waiter = list_first_entry(&blocker->fl_block,
0723                 struct file_lock, fl_block);
0724         __locks_delete_block(waiter);
0725         if (waiter->fl_lmops && waiter->fl_lmops->lm_notify)
0726             waiter->fl_lmops->lm_notify(waiter);
0727         else
0728             wake_up(&waiter->fl_wait);
0729     }
0730     spin_unlock(&blocked_lock_lock);
0731 }
0732 
0733 static void
0734 locks_insert_lock_ctx(struct file_lock *fl, struct list_head *before)
0735 {
0736     fl->fl_nspid = get_pid(task_tgid(current));
0737     list_add_tail(&fl->fl_list, before);
0738     locks_insert_global_locks(fl);
0739 }
0740 
0741 static void
0742 locks_unlink_lock_ctx(struct file_lock *fl)
0743 {
0744     locks_delete_global_locks(fl);
0745     list_del_init(&fl->fl_list);
0746     if (fl->fl_nspid) {
0747         put_pid(fl->fl_nspid);
0748         fl->fl_nspid = NULL;
0749     }
0750     locks_wake_up_blocks(fl);
0751 }
0752 
0753 static void
0754 locks_delete_lock_ctx(struct file_lock *fl, struct list_head *dispose)
0755 {
0756     locks_unlink_lock_ctx(fl);
0757     if (dispose)
0758         list_add(&fl->fl_list, dispose);
0759     else
0760         locks_free_lock(fl);
0761 }
0762 
0763 /* Determine if lock sys_fl blocks lock caller_fl. Common functionality
0764  * checks for shared/exclusive status of overlapping locks.
0765  */
0766 static int locks_conflict(struct file_lock *caller_fl, struct file_lock *sys_fl)
0767 {
0768     if (sys_fl->fl_type == F_WRLCK)
0769         return 1;
0770     if (caller_fl->fl_type == F_WRLCK)
0771         return 1;
0772     return 0;
0773 }
0774 
0775 /* Determine if lock sys_fl blocks lock caller_fl. POSIX specific
0776  * checking before calling the locks_conflict().
0777  */
0778 static int posix_locks_conflict(struct file_lock *caller_fl, struct file_lock *sys_fl)
0779 {
0780     /* POSIX locks owned by the same process do not conflict with
0781      * each other.
0782      */
0783     if (posix_same_owner(caller_fl, sys_fl))
0784         return (0);
0785 
0786     /* Check whether they overlap */
0787     if (!locks_overlap(caller_fl, sys_fl))
0788         return 0;
0789 
0790     return (locks_conflict(caller_fl, sys_fl));
0791 }
0792 
0793 /* Determine if lock sys_fl blocks lock caller_fl. FLOCK specific
0794  * checking before calling the locks_conflict().
0795  */
0796 static int flock_locks_conflict(struct file_lock *caller_fl, struct file_lock *sys_fl)
0797 {
0798     /* FLOCK locks referring to the same filp do not conflict with
0799      * each other.
0800      */
0801     if (caller_fl->fl_file == sys_fl->fl_file)
0802         return (0);
0803     if ((caller_fl->fl_type & LOCK_MAND) || (sys_fl->fl_type & LOCK_MAND))
0804         return 0;
0805 
0806     return (locks_conflict(caller_fl, sys_fl));
0807 }
0808 
0809 void
0810 posix_test_lock(struct file *filp, struct file_lock *fl)
0811 {
0812     struct file_lock *cfl;
0813     struct file_lock_context *ctx;
0814     struct inode *inode = locks_inode(filp);
0815 
0816     ctx = smp_load_acquire(&inode->i_flctx);
0817     if (!ctx || list_empty_careful(&ctx->flc_posix)) {
0818         fl->fl_type = F_UNLCK;
0819         return;
0820     }
0821 
0822     spin_lock(&ctx->flc_lock);
0823     list_for_each_entry(cfl, &ctx->flc_posix, fl_list) {
0824         if (posix_locks_conflict(fl, cfl)) {
0825             locks_copy_conflock(fl, cfl);
0826             if (cfl->fl_nspid)
0827                 fl->fl_pid = pid_vnr(cfl->fl_nspid);
0828             goto out;
0829         }
0830     }
0831     fl->fl_type = F_UNLCK;
0832 out:
0833     spin_unlock(&ctx->flc_lock);
0834     return;
0835 }
0836 EXPORT_SYMBOL(posix_test_lock);
0837 
0838 /*
0839  * Deadlock detection:
0840  *
0841  * We attempt to detect deadlocks that are due purely to posix file
0842  * locks.
0843  *
0844  * We assume that a task can be waiting for at most one lock at a time.
0845  * So for any acquired lock, the process holding that lock may be
0846  * waiting on at most one other lock.  That lock in turns may be held by
0847  * someone waiting for at most one other lock.  Given a requested lock
0848  * caller_fl which is about to wait for a conflicting lock block_fl, we
0849  * follow this chain of waiters to ensure we are not about to create a
0850  * cycle.
0851  *
0852  * Since we do this before we ever put a process to sleep on a lock, we
0853  * are ensured that there is never a cycle; that is what guarantees that
0854  * the while() loop in posix_locks_deadlock() eventually completes.
0855  *
0856  * Note: the above assumption may not be true when handling lock
0857  * requests from a broken NFS client. It may also fail in the presence
0858  * of tasks (such as posix threads) sharing the same open file table.
0859  * To handle those cases, we just bail out after a few iterations.
0860  *
0861  * For FL_OFDLCK locks, the owner is the filp, not the files_struct.
0862  * Because the owner is not even nominally tied to a thread of
0863  * execution, the deadlock detection below can't reasonably work well. Just
0864  * skip it for those.
0865  *
0866  * In principle, we could do a more limited deadlock detection on FL_OFDLCK
0867  * locks that just checks for the case where two tasks are attempting to
0868  * upgrade from read to write locks on the same inode.
0869  */
0870 
0871 #define MAX_DEADLK_ITERATIONS 10
0872 
0873 /* Find a lock that the owner of the given block_fl is blocking on. */
0874 static struct file_lock *what_owner_is_waiting_for(struct file_lock *block_fl)
0875 {
0876     struct file_lock *fl;
0877 
0878     hash_for_each_possible(blocked_hash, fl, fl_link, posix_owner_key(block_fl)) {
0879         if (posix_same_owner(fl, block_fl))
0880             return fl->fl_next;
0881     }
0882     return NULL;
0883 }
0884 
0885 /* Must be called with the blocked_lock_lock held! */
0886 static int posix_locks_deadlock(struct file_lock *caller_fl,
0887                 struct file_lock *block_fl)
0888 {
0889     int i = 0;
0890 
0891     lockdep_assert_held(&blocked_lock_lock);
0892 
0893     /*
0894      * This deadlock detector can't reasonably detect deadlocks with
0895      * FL_OFDLCK locks, since they aren't owned by a process, per-se.
0896      */
0897     if (IS_OFDLCK(caller_fl))
0898         return 0;
0899 
0900     while ((block_fl = what_owner_is_waiting_for(block_fl))) {
0901         if (i++ > MAX_DEADLK_ITERATIONS)
0902             return 0;
0903         if (posix_same_owner(caller_fl, block_fl))
0904             return 1;
0905     }
0906     return 0;
0907 }
0908 
0909 /* Try to create a FLOCK lock on filp. We always insert new FLOCK locks
0910  * after any leases, but before any posix locks.
0911  *
0912  * Note that if called with an FL_EXISTS argument, the caller may determine
0913  * whether or not a lock was successfully freed by testing the return
0914  * value for -ENOENT.
0915  */
0916 static int flock_lock_inode(struct inode *inode, struct file_lock *request)
0917 {
0918     struct file_lock *new_fl = NULL;
0919     struct file_lock *fl;
0920     struct file_lock_context *ctx;
0921     int error = 0;
0922     bool found = false;
0923     LIST_HEAD(dispose);
0924 
0925     ctx = locks_get_lock_context(inode, request->fl_type);
0926     if (!ctx) {
0927         if (request->fl_type != F_UNLCK)
0928             return -ENOMEM;
0929         return (request->fl_flags & FL_EXISTS) ? -ENOENT : 0;
0930     }
0931 
0932     if (!(request->fl_flags & FL_ACCESS) && (request->fl_type != F_UNLCK)) {
0933         new_fl = locks_alloc_lock();
0934         if (!new_fl)
0935             return -ENOMEM;
0936     }
0937 
0938     percpu_down_read_preempt_disable(&file_rwsem);
0939     spin_lock(&ctx->flc_lock);
0940     if (request->fl_flags & FL_ACCESS)
0941         goto find_conflict;
0942 
0943     list_for_each_entry(fl, &ctx->flc_flock, fl_list) {
0944         if (request->fl_file != fl->fl_file)
0945             continue;
0946         if (request->fl_type == fl->fl_type)
0947             goto out;
0948         found = true;
0949         locks_delete_lock_ctx(fl, &dispose);
0950         break;
0951     }
0952 
0953     if (request->fl_type == F_UNLCK) {
0954         if ((request->fl_flags & FL_EXISTS) && !found)
0955             error = -ENOENT;
0956         goto out;
0957     }
0958 
0959 find_conflict:
0960     list_for_each_entry(fl, &ctx->flc_flock, fl_list) {
0961         if (!flock_locks_conflict(request, fl))
0962             continue;
0963         error = -EAGAIN;
0964         if (!(request->fl_flags & FL_SLEEP))
0965             goto out;
0966         error = FILE_LOCK_DEFERRED;
0967         locks_insert_block(fl, request);
0968         goto out;
0969     }
0970     if (request->fl_flags & FL_ACCESS)
0971         goto out;
0972     locks_copy_lock(new_fl, request);
0973     locks_insert_lock_ctx(new_fl, &ctx->flc_flock);
0974     new_fl = NULL;
0975     error = 0;
0976 
0977 out:
0978     spin_unlock(&ctx->flc_lock);
0979     percpu_up_read_preempt_enable(&file_rwsem);
0980     if (new_fl)
0981         locks_free_lock(new_fl);
0982     locks_dispose_list(&dispose);
0983     return error;
0984 }
0985 
0986 static int posix_lock_inode(struct inode *inode, struct file_lock *request,
0987                 struct file_lock *conflock)
0988 {
0989     struct file_lock *fl, *tmp;
0990     struct file_lock *new_fl = NULL;
0991     struct file_lock *new_fl2 = NULL;
0992     struct file_lock *left = NULL;
0993     struct file_lock *right = NULL;
0994     struct file_lock_context *ctx;
0995     int error;
0996     bool added = false;
0997     LIST_HEAD(dispose);
0998 
0999     ctx = locks_get_lock_context(inode, request->fl_type);
1000     if (!ctx)
1001         return (request->fl_type == F_UNLCK) ? 0 : -ENOMEM;
1002 
1003     /*
1004      * We may need two file_lock structures for this operation,
1005      * so we get them in advance to avoid races.
1006      *
1007      * In some cases we can be sure, that no new locks will be needed
1008      */
1009     if (!(request->fl_flags & FL_ACCESS) &&
1010         (request->fl_type != F_UNLCK ||
1011          request->fl_start != 0 || request->fl_end != OFFSET_MAX)) {
1012         new_fl = locks_alloc_lock();
1013         new_fl2 = locks_alloc_lock();
1014     }
1015 
1016     percpu_down_read_preempt_disable(&file_rwsem);
1017     spin_lock(&ctx->flc_lock);
1018     /*
1019      * New lock request. Walk all POSIX locks and look for conflicts. If
1020      * there are any, either return error or put the request on the
1021      * blocker's list of waiters and the global blocked_hash.
1022      */
1023     if (request->fl_type != F_UNLCK) {
1024         list_for_each_entry(fl, &ctx->flc_posix, fl_list) {
1025             if (!posix_locks_conflict(request, fl))
1026                 continue;
1027             if (conflock)
1028                 locks_copy_conflock(conflock, fl);
1029             error = -EAGAIN;
1030             if (!(request->fl_flags & FL_SLEEP))
1031                 goto out;
1032             /*
1033              * Deadlock detection and insertion into the blocked
1034              * locks list must be done while holding the same lock!
1035              */
1036             error = -EDEADLK;
1037             spin_lock(&blocked_lock_lock);
1038             if (likely(!posix_locks_deadlock(request, fl))) {
1039                 error = FILE_LOCK_DEFERRED;
1040                 __locks_insert_block(fl, request);
1041             }
1042             spin_unlock(&blocked_lock_lock);
1043             goto out;
1044         }
1045     }
1046 
1047     /* If we're just looking for a conflict, we're done. */
1048     error = 0;
1049     if (request->fl_flags & FL_ACCESS)
1050         goto out;
1051 
1052     /* Find the first old lock with the same owner as the new lock */
1053     list_for_each_entry(fl, &ctx->flc_posix, fl_list) {
1054         if (posix_same_owner(request, fl))
1055             break;
1056     }
1057 
1058     /* Process locks with this owner. */
1059     list_for_each_entry_safe_from(fl, tmp, &ctx->flc_posix, fl_list) {
1060         if (!posix_same_owner(request, fl))
1061             break;
1062 
1063         /* Detect adjacent or overlapping regions (if same lock type) */
1064         if (request->fl_type == fl->fl_type) {
1065             /* In all comparisons of start vs end, use
1066              * "start - 1" rather than "end + 1". If end
1067              * is OFFSET_MAX, end + 1 will become negative.
1068              */
1069             if (fl->fl_end < request->fl_start - 1)
1070                 continue;
1071             /* If the next lock in the list has entirely bigger
1072              * addresses than the new one, insert the lock here.
1073              */
1074             if (fl->fl_start - 1 > request->fl_end)
1075                 break;
1076 
1077             /* If we come here, the new and old lock are of the
1078              * same type and adjacent or overlapping. Make one
1079              * lock yielding from the lower start address of both
1080              * locks to the higher end address.
1081              */
1082             if (fl->fl_start > request->fl_start)
1083                 fl->fl_start = request->fl_start;
1084             else
1085                 request->fl_start = fl->fl_start;
1086             if (fl->fl_end < request->fl_end)
1087                 fl->fl_end = request->fl_end;
1088             else
1089                 request->fl_end = fl->fl_end;
1090             if (added) {
1091                 locks_delete_lock_ctx(fl, &dispose);
1092                 continue;
1093             }
1094             request = fl;
1095             added = true;
1096         } else {
1097             /* Processing for different lock types is a bit
1098              * more complex.
1099              */
1100             if (fl->fl_end < request->fl_start)
1101                 continue;
1102             if (fl->fl_start > request->fl_end)
1103                 break;
1104             if (request->fl_type == F_UNLCK)
1105                 added = true;
1106             if (fl->fl_start < request->fl_start)
1107                 left = fl;
1108             /* If the next lock in the list has a higher end
1109              * address than the new one, insert the new one here.
1110              */
1111             if (fl->fl_end > request->fl_end) {
1112                 right = fl;
1113                 break;
1114             }
1115             if (fl->fl_start >= request->fl_start) {
1116                 /* The new lock completely replaces an old
1117                  * one (This may happen several times).
1118                  */
1119                 if (added) {
1120                     locks_delete_lock_ctx(fl, &dispose);
1121                     continue;
1122                 }
1123                 /*
1124                  * Replace the old lock with new_fl, and
1125                  * remove the old one. It's safe to do the
1126                  * insert here since we know that we won't be
1127                  * using new_fl later, and that the lock is
1128                  * just replacing an existing lock.
1129                  */
1130                 error = -ENOLCK;
1131                 if (!new_fl)
1132                     goto out;
1133                 locks_copy_lock(new_fl, request);
1134                 request = new_fl;
1135                 new_fl = NULL;
1136                 locks_insert_lock_ctx(request, &fl->fl_list);
1137                 locks_delete_lock_ctx(fl, &dispose);
1138                 added = true;
1139             }
1140         }
1141     }
1142 
1143     /*
1144      * The above code only modifies existing locks in case of merging or
1145      * replacing. If new lock(s) need to be inserted all modifications are
1146      * done below this, so it's safe yet to bail out.
1147      */
1148     error = -ENOLCK; /* "no luck" */
1149     if (right && left == right && !new_fl2)
1150         goto out;
1151 
1152     error = 0;
1153     if (!added) {
1154         if (request->fl_type == F_UNLCK) {
1155             if (request->fl_flags & FL_EXISTS)
1156                 error = -ENOENT;
1157             goto out;
1158         }
1159 
1160         if (!new_fl) {
1161             error = -ENOLCK;
1162             goto out;
1163         }
1164         locks_copy_lock(new_fl, request);
1165         locks_insert_lock_ctx(new_fl, &fl->fl_list);
1166         fl = new_fl;
1167         new_fl = NULL;
1168     }
1169     if (right) {
1170         if (left == right) {
1171             /* The new lock breaks the old one in two pieces,
1172              * so we have to use the second new lock.
1173              */
1174             left = new_fl2;
1175             new_fl2 = NULL;
1176             locks_copy_lock(left, right);
1177             locks_insert_lock_ctx(left, &fl->fl_list);
1178         }
1179         right->fl_start = request->fl_end + 1;
1180         locks_wake_up_blocks(right);
1181     }
1182     if (left) {
1183         left->fl_end = request->fl_start - 1;
1184         locks_wake_up_blocks(left);
1185     }
1186  out:
1187     spin_unlock(&ctx->flc_lock);
1188     percpu_up_read_preempt_enable(&file_rwsem);
1189     /*
1190      * Free any unused locks.
1191      */
1192     if (new_fl)
1193         locks_free_lock(new_fl);
1194     if (new_fl2)
1195         locks_free_lock(new_fl2);
1196     locks_dispose_list(&dispose);
1197     trace_posix_lock_inode(inode, request, error);
1198 
1199     return error;
1200 }
1201 
1202 /**
1203  * posix_lock_file - Apply a POSIX-style lock to a file
1204  * @filp: The file to apply the lock to
1205  * @fl: The lock to be applied
1206  * @conflock: Place to return a copy of the conflicting lock, if found.
1207  *
1208  * Add a POSIX style lock to a file.
1209  * We merge adjacent & overlapping locks whenever possible.
1210  * POSIX locks are sorted by owner task, then by starting address
1211  *
1212  * Note that if called with an FL_EXISTS argument, the caller may determine
1213  * whether or not a lock was successfully freed by testing the return
1214  * value for -ENOENT.
1215  */
1216 int posix_lock_file(struct file *filp, struct file_lock *fl,
1217             struct file_lock *conflock)
1218 {
1219     return posix_lock_inode(locks_inode(filp), fl, conflock);
1220 }
1221 EXPORT_SYMBOL(posix_lock_file);
1222 
1223 /**
1224  * posix_lock_inode_wait - Apply a POSIX-style lock to a file
1225  * @inode: inode of file to which lock request should be applied
1226  * @fl: The lock to be applied
1227  *
1228  * Apply a POSIX style lock request to an inode.
1229  */
1230 static int posix_lock_inode_wait(struct inode *inode, struct file_lock *fl)
1231 {
1232     int error;
1233     might_sleep ();
1234     for (;;) {
1235         error = posix_lock_inode(inode, fl, NULL);
1236         if (error != FILE_LOCK_DEFERRED)
1237             break;
1238         error = wait_event_interruptible(fl->fl_wait, !fl->fl_next);
1239         if (!error)
1240             continue;
1241 
1242         locks_delete_block(fl);
1243         break;
1244     }
1245     return error;
1246 }
1247 
1248 #ifdef CONFIG_MANDATORY_FILE_LOCKING
1249 /**
1250  * locks_mandatory_locked - Check for an active lock
1251  * @file: the file to check
1252  *
1253  * Searches the inode's list of locks to find any POSIX locks which conflict.
1254  * This function is called from locks_verify_locked() only.
1255  */
1256 int locks_mandatory_locked(struct file *file)
1257 {
1258     int ret;
1259     struct inode *inode = locks_inode(file);
1260     struct file_lock_context *ctx;
1261     struct file_lock *fl;
1262 
1263     ctx = smp_load_acquire(&inode->i_flctx);
1264     if (!ctx || list_empty_careful(&ctx->flc_posix))
1265         return 0;
1266 
1267     /*
1268      * Search the lock list for this inode for any POSIX locks.
1269      */
1270     spin_lock(&ctx->flc_lock);
1271     ret = 0;
1272     list_for_each_entry(fl, &ctx->flc_posix, fl_list) {
1273         if (fl->fl_owner != current->files &&
1274             fl->fl_owner != file) {
1275             ret = -EAGAIN;
1276             break;
1277         }
1278     }
1279     spin_unlock(&ctx->flc_lock);
1280     return ret;
1281 }
1282 
1283 /**
1284  * locks_mandatory_area - Check for a conflicting lock
1285  * @inode:  the file to check
1286  * @filp:       how the file was opened (if it was)
1287  * @start:  first byte in the file to check
1288  * @end:    lastbyte in the file to check
1289  * @type:   %F_WRLCK for a write lock, else %F_RDLCK
1290  *
1291  * Searches the inode's list of locks to find any POSIX locks which conflict.
1292  */
1293 int locks_mandatory_area(struct inode *inode, struct file *filp, loff_t start,
1294              loff_t end, unsigned char type)
1295 {
1296     struct file_lock fl;
1297     int error;
1298     bool sleep = false;
1299 
1300     locks_init_lock(&fl);
1301     fl.fl_pid = current->tgid;
1302     fl.fl_file = filp;
1303     fl.fl_flags = FL_POSIX | FL_ACCESS;
1304     if (filp && !(filp->f_flags & O_NONBLOCK))
1305         sleep = true;
1306     fl.fl_type = type;
1307     fl.fl_start = start;
1308     fl.fl_end = end;
1309 
1310     for (;;) {
1311         if (filp) {
1312             fl.fl_owner = filp;
1313             fl.fl_flags &= ~FL_SLEEP;
1314             error = posix_lock_inode(inode, &fl, NULL);
1315             if (!error)
1316                 break;
1317         }
1318 
1319         if (sleep)
1320             fl.fl_flags |= FL_SLEEP;
1321         fl.fl_owner = current->files;
1322         error = posix_lock_inode(inode, &fl, NULL);
1323         if (error != FILE_LOCK_DEFERRED)
1324             break;
1325         error = wait_event_interruptible(fl.fl_wait, !fl.fl_next);
1326         if (!error) {
1327             /*
1328              * If we've been sleeping someone might have
1329              * changed the permissions behind our back.
1330              */
1331             if (__mandatory_lock(inode))
1332                 continue;
1333         }
1334 
1335         locks_delete_block(&fl);
1336         break;
1337     }
1338 
1339     return error;
1340 }
1341 
1342 EXPORT_SYMBOL(locks_mandatory_area);
1343 #endif /* CONFIG_MANDATORY_FILE_LOCKING */
1344 
1345 static void lease_clear_pending(struct file_lock *fl, int arg)
1346 {
1347     switch (arg) {
1348     case F_UNLCK:
1349         fl->fl_flags &= ~FL_UNLOCK_PENDING;
1350         /* fall through: */
1351     case F_RDLCK:
1352         fl->fl_flags &= ~FL_DOWNGRADE_PENDING;
1353     }
1354 }
1355 
1356 /* We already had a lease on this file; just change its type */
1357 int lease_modify(struct file_lock *fl, int arg, struct list_head *dispose)
1358 {
1359     int error = assign_type(fl, arg);
1360 
1361     if (error)
1362         return error;
1363     lease_clear_pending(fl, arg);
1364     locks_wake_up_blocks(fl);
1365     if (arg == F_UNLCK) {
1366         struct file *filp = fl->fl_file;
1367 
1368         f_delown(filp);
1369         filp->f_owner.signum = 0;
1370         fasync_helper(0, fl->fl_file, 0, &fl->fl_fasync);
1371         if (fl->fl_fasync != NULL) {
1372             printk(KERN_ERR "locks_delete_lock: fasync == %p\n", fl->fl_fasync);
1373             fl->fl_fasync = NULL;
1374         }
1375         locks_delete_lock_ctx(fl, dispose);
1376     }
1377     return 0;
1378 }
1379 EXPORT_SYMBOL(lease_modify);
1380 
1381 static bool past_time(unsigned long then)
1382 {
1383     if (!then)
1384         /* 0 is a special value meaning "this never expires": */
1385         return false;
1386     return time_after(jiffies, then);
1387 }
1388 
1389 static void time_out_leases(struct inode *inode, struct list_head *dispose)
1390 {
1391     struct file_lock_context *ctx = inode->i_flctx;
1392     struct file_lock *fl, *tmp;
1393 
1394     lockdep_assert_held(&ctx->flc_lock);
1395 
1396     list_for_each_entry_safe(fl, tmp, &ctx->flc_lease, fl_list) {
1397         trace_time_out_leases(inode, fl);
1398         if (past_time(fl->fl_downgrade_time))
1399             lease_modify(fl, F_RDLCK, dispose);
1400         if (past_time(fl->fl_break_time))
1401             lease_modify(fl, F_UNLCK, dispose);
1402     }
1403 }
1404 
1405 static bool leases_conflict(struct file_lock *lease, struct file_lock *breaker)
1406 {
1407     if ((breaker->fl_flags & FL_LAYOUT) != (lease->fl_flags & FL_LAYOUT))
1408         return false;
1409     if ((breaker->fl_flags & FL_DELEG) && (lease->fl_flags & FL_LEASE))
1410         return false;
1411     return locks_conflict(breaker, lease);
1412 }
1413 
1414 static bool
1415 any_leases_conflict(struct inode *inode, struct file_lock *breaker)
1416 {
1417     struct file_lock_context *ctx = inode->i_flctx;
1418     struct file_lock *fl;
1419 
1420     lockdep_assert_held(&ctx->flc_lock);
1421 
1422     list_for_each_entry(fl, &ctx->flc_lease, fl_list) {
1423         if (leases_conflict(fl, breaker))
1424             return true;
1425     }
1426     return false;
1427 }
1428 
1429 /**
1430  *  __break_lease   -   revoke all outstanding leases on file
1431  *  @inode: the inode of the file to return
1432  *  @mode: O_RDONLY: break only write leases; O_WRONLY or O_RDWR:
1433  *      break all leases
1434  *  @type: FL_LEASE: break leases and delegations; FL_DELEG: break
1435  *      only delegations
1436  *
1437  *  break_lease (inlined for speed) has checked there already is at least
1438  *  some kind of lock (maybe a lease) on this file.  Leases are broken on
1439  *  a call to open() or truncate().  This function can sleep unless you
1440  *  specified %O_NONBLOCK to your open().
1441  */
1442 int __break_lease(struct inode *inode, unsigned int mode, unsigned int type)
1443 {
1444     int error = 0;
1445     struct file_lock_context *ctx;
1446     struct file_lock *new_fl, *fl, *tmp;
1447     unsigned long break_time;
1448     int want_write = (mode & O_ACCMODE) != O_RDONLY;
1449     LIST_HEAD(dispose);
1450 
1451     new_fl = lease_alloc(NULL, want_write ? F_WRLCK : F_RDLCK);
1452     if (IS_ERR(new_fl))
1453         return PTR_ERR(new_fl);
1454     new_fl->fl_flags = type;
1455 
1456     /* typically we will check that ctx is non-NULL before calling */
1457     ctx = smp_load_acquire(&inode->i_flctx);
1458     if (!ctx) {
1459         WARN_ON_ONCE(1);
1460         return error;
1461     }
1462 
1463     percpu_down_read_preempt_disable(&file_rwsem);
1464     spin_lock(&ctx->flc_lock);
1465 
1466     time_out_leases(inode, &dispose);
1467 
1468     if (!any_leases_conflict(inode, new_fl))
1469         goto out;
1470 
1471     break_time = 0;
1472     if (lease_break_time > 0) {
1473         break_time = jiffies + lease_break_time * HZ;
1474         if (break_time == 0)
1475             break_time++;   /* so that 0 means no break time */
1476     }
1477 
1478     list_for_each_entry_safe(fl, tmp, &ctx->flc_lease, fl_list) {
1479         if (!leases_conflict(fl, new_fl))
1480             continue;
1481         if (want_write) {
1482             if (fl->fl_flags & FL_UNLOCK_PENDING)
1483                 continue;
1484             fl->fl_flags |= FL_UNLOCK_PENDING;
1485             fl->fl_break_time = break_time;
1486         } else {
1487             if (lease_breaking(fl))
1488                 continue;
1489             fl->fl_flags |= FL_DOWNGRADE_PENDING;
1490             fl->fl_downgrade_time = break_time;
1491         }
1492         if (fl->fl_lmops->lm_break(fl))
1493             locks_delete_lock_ctx(fl, &dispose);
1494     }
1495 
1496     if (list_empty(&ctx->flc_lease))
1497         goto out;
1498 
1499     if (mode & O_NONBLOCK) {
1500         trace_break_lease_noblock(inode, new_fl);
1501         error = -EWOULDBLOCK;
1502         goto out;
1503     }
1504 
1505 restart:
1506     fl = list_first_entry(&ctx->flc_lease, struct file_lock, fl_list);
1507     break_time = fl->fl_break_time;
1508     if (break_time != 0)
1509         break_time -= jiffies;
1510     if (break_time == 0)
1511         break_time++;
1512     locks_insert_block(fl, new_fl);
1513     trace_break_lease_block(inode, new_fl);
1514     spin_unlock(&ctx->flc_lock);
1515     percpu_up_read_preempt_enable(&file_rwsem);
1516 
1517     locks_dispose_list(&dispose);
1518     error = wait_event_interruptible_timeout(new_fl->fl_wait,
1519                         !new_fl->fl_next, break_time);
1520 
1521     percpu_down_read_preempt_disable(&file_rwsem);
1522     spin_lock(&ctx->flc_lock);
1523     trace_break_lease_unblock(inode, new_fl);
1524     locks_delete_block(new_fl);
1525     if (error >= 0) {
1526         /*
1527          * Wait for the next conflicting lease that has not been
1528          * broken yet
1529          */
1530         if (error == 0)
1531             time_out_leases(inode, &dispose);
1532         if (any_leases_conflict(inode, new_fl))
1533             goto restart;
1534         error = 0;
1535     }
1536 out:
1537     spin_unlock(&ctx->flc_lock);
1538     percpu_up_read_preempt_enable(&file_rwsem);
1539     locks_dispose_list(&dispose);
1540     locks_free_lock(new_fl);
1541     return error;
1542 }
1543 
1544 EXPORT_SYMBOL(__break_lease);
1545 
1546 /**
1547  *  lease_get_mtime - get the last modified time of an inode
1548  *  @inode: the inode
1549  *      @time:  pointer to a timespec which will contain the last modified time
1550  *
1551  * This is to force NFS clients to flush their caches for files with
1552  * exclusive leases.  The justification is that if someone has an
1553  * exclusive lease, then they could be modifying it.
1554  */
1555 void lease_get_mtime(struct inode *inode, struct timespec *time)
1556 {
1557     bool has_lease = false;
1558     struct file_lock_context *ctx;
1559     struct file_lock *fl;
1560 
1561     ctx = smp_load_acquire(&inode->i_flctx);
1562     if (ctx && !list_empty_careful(&ctx->flc_lease)) {
1563         spin_lock(&ctx->flc_lock);
1564         fl = list_first_entry_or_null(&ctx->flc_lease,
1565                           struct file_lock, fl_list);
1566         if (fl && (fl->fl_type == F_WRLCK))
1567             has_lease = true;
1568         spin_unlock(&ctx->flc_lock);
1569     }
1570 
1571     if (has_lease)
1572         *time = current_time(inode);
1573     else
1574         *time = inode->i_mtime;
1575 }
1576 
1577 EXPORT_SYMBOL(lease_get_mtime);
1578 
1579 /**
1580  *  fcntl_getlease - Enquire what lease is currently active
1581  *  @filp: the file
1582  *
1583  *  The value returned by this function will be one of
1584  *  (if no lease break is pending):
1585  *
1586  *  %F_RDLCK to indicate a shared lease is held.
1587  *
1588  *  %F_WRLCK to indicate an exclusive lease is held.
1589  *
1590  *  %F_UNLCK to indicate no lease is held.
1591  *
1592  *  (if a lease break is pending):
1593  *
1594  *  %F_RDLCK to indicate an exclusive lease needs to be
1595  *      changed to a shared lease (or removed).
1596  *
1597  *  %F_UNLCK to indicate the lease needs to be removed.
1598  *
1599  *  XXX: sfr & willy disagree over whether F_INPROGRESS
1600  *  should be returned to userspace.
1601  */
1602 int fcntl_getlease(struct file *filp)
1603 {
1604     struct file_lock *fl;
1605     struct inode *inode = locks_inode(filp);
1606     struct file_lock_context *ctx;
1607     int type = F_UNLCK;
1608     LIST_HEAD(dispose);
1609 
1610     ctx = smp_load_acquire(&inode->i_flctx);
1611     if (ctx && !list_empty_careful(&ctx->flc_lease)) {
1612         percpu_down_read_preempt_disable(&file_rwsem);
1613         spin_lock(&ctx->flc_lock);
1614         time_out_leases(inode, &dispose);
1615         list_for_each_entry(fl, &ctx->flc_lease, fl_list) {
1616             if (fl->fl_file != filp)
1617                 continue;
1618             type = target_leasetype(fl);
1619             break;
1620         }
1621         spin_unlock(&ctx->flc_lock);
1622         percpu_up_read_preempt_enable(&file_rwsem);
1623 
1624         locks_dispose_list(&dispose);
1625     }
1626     return type;
1627 }
1628 
1629 /**
1630  * check_conflicting_open - see if the given dentry points to a file that has
1631  *              an existing open that would conflict with the
1632  *              desired lease.
1633  * @dentry: dentry to check
1634  * @arg:    type of lease that we're trying to acquire
1635  * @flags:  current lock flags
1636  *
1637  * Check to see if there's an existing open fd on this file that would
1638  * conflict with the lease we're trying to set.
1639  */
1640 static int
1641 check_conflicting_open(const struct dentry *dentry, const long arg, int flags)
1642 {
1643     int ret = 0;
1644     struct inode *inode = dentry->d_inode;
1645 
1646     if (flags & FL_LAYOUT)
1647         return 0;
1648 
1649     if ((arg == F_RDLCK) &&
1650         (atomic_read(&d_real_inode(dentry)->i_writecount) > 0))
1651         return -EAGAIN;
1652 
1653     if ((arg == F_WRLCK) && ((d_count(dentry) > 1) ||
1654         (atomic_read(&inode->i_count) > 1)))
1655         ret = -EAGAIN;
1656 
1657     return ret;
1658 }
1659 
1660 static int
1661 generic_add_lease(struct file *filp, long arg, struct file_lock **flp, void **priv)
1662 {
1663     struct file_lock *fl, *my_fl = NULL, *lease;
1664     struct dentry *dentry = filp->f_path.dentry;
1665     struct inode *inode = dentry->d_inode;
1666     struct file_lock_context *ctx;
1667     bool is_deleg = (*flp)->fl_flags & FL_DELEG;
1668     int error;
1669     LIST_HEAD(dispose);
1670 
1671     lease = *flp;
1672     trace_generic_add_lease(inode, lease);
1673 
1674     /* Note that arg is never F_UNLCK here */
1675     ctx = locks_get_lock_context(inode, arg);
1676     if (!ctx)
1677         return -ENOMEM;
1678 
1679     /*
1680      * In the delegation case we need mutual exclusion with
1681      * a number of operations that take the i_mutex.  We trylock
1682      * because delegations are an optional optimization, and if
1683      * there's some chance of a conflict--we'd rather not
1684      * bother, maybe that's a sign this just isn't a good file to
1685      * hand out a delegation on.
1686      */
1687     if (is_deleg && !inode_trylock(inode))
1688         return -EAGAIN;
1689 
1690     if (is_deleg && arg == F_WRLCK) {
1691         /* Write delegations are not currently supported: */
1692         inode_unlock(inode);
1693         WARN_ON_ONCE(1);
1694         return -EINVAL;
1695     }
1696 
1697     percpu_down_read_preempt_disable(&file_rwsem);
1698     spin_lock(&ctx->flc_lock);
1699     time_out_leases(inode, &dispose);
1700     error = check_conflicting_open(dentry, arg, lease->fl_flags);
1701     if (error)
1702         goto out;
1703 
1704     /*
1705      * At this point, we know that if there is an exclusive
1706      * lease on this file, then we hold it on this filp
1707      * (otherwise our open of this file would have blocked).
1708      * And if we are trying to acquire an exclusive lease,
1709      * then the file is not open by anyone (including us)
1710      * except for this filp.
1711      */
1712     error = -EAGAIN;
1713     list_for_each_entry(fl, &ctx->flc_lease, fl_list) {
1714         if (fl->fl_file == filp &&
1715             fl->fl_owner == lease->fl_owner) {
1716             my_fl = fl;
1717             continue;
1718         }
1719 
1720         /*
1721          * No exclusive leases if someone else has a lease on
1722          * this file:
1723          */
1724         if (arg == F_WRLCK)
1725             goto out;
1726         /*
1727          * Modifying our existing lease is OK, but no getting a
1728          * new lease if someone else is opening for write:
1729          */
1730         if (fl->fl_flags & FL_UNLOCK_PENDING)
1731             goto out;
1732     }
1733 
1734     if (my_fl != NULL) {
1735         lease = my_fl;
1736         error = lease->fl_lmops->lm_change(lease, arg, &dispose);
1737         if (error)
1738             goto out;
1739         goto out_setup;
1740     }
1741 
1742     error = -EINVAL;
1743     if (!leases_enable)
1744         goto out;
1745 
1746     locks_insert_lock_ctx(lease, &ctx->flc_lease);
1747     /*
1748      * The check in break_lease() is lockless. It's possible for another
1749      * open to race in after we did the earlier check for a conflicting
1750      * open but before the lease was inserted. Check again for a
1751      * conflicting open and cancel the lease if there is one.
1752      *
1753      * We also add a barrier here to ensure that the insertion of the lock
1754      * precedes these checks.
1755      */
1756     smp_mb();
1757     error = check_conflicting_open(dentry, arg, lease->fl_flags);
1758     if (error) {
1759         locks_unlink_lock_ctx(lease);
1760         goto out;
1761     }
1762 
1763 out_setup:
1764     if (lease->fl_lmops->lm_setup)
1765         lease->fl_lmops->lm_setup(lease, priv);
1766 out:
1767     spin_unlock(&ctx->flc_lock);
1768     percpu_up_read_preempt_enable(&file_rwsem);
1769     locks_dispose_list(&dispose);
1770     if (is_deleg)
1771         inode_unlock(inode);
1772     if (!error && !my_fl)
1773         *flp = NULL;
1774     return error;
1775 }
1776 
1777 static int generic_delete_lease(struct file *filp, void *owner)
1778 {
1779     int error = -EAGAIN;
1780     struct file_lock *fl, *victim = NULL;
1781     struct inode *inode = locks_inode(filp);
1782     struct file_lock_context *ctx;
1783     LIST_HEAD(dispose);
1784 
1785     ctx = smp_load_acquire(&inode->i_flctx);
1786     if (!ctx) {
1787         trace_generic_delete_lease(inode, NULL);
1788         return error;
1789     }
1790 
1791     percpu_down_read_preempt_disable(&file_rwsem);
1792     spin_lock(&ctx->flc_lock);
1793     list_for_each_entry(fl, &ctx->flc_lease, fl_list) {
1794         if (fl->fl_file == filp &&
1795             fl->fl_owner == owner) {
1796             victim = fl;
1797             break;
1798         }
1799     }
1800     trace_generic_delete_lease(inode, victim);
1801     if (victim)
1802         error = fl->fl_lmops->lm_change(victim, F_UNLCK, &dispose);
1803     spin_unlock(&ctx->flc_lock);
1804     percpu_up_read_preempt_enable(&file_rwsem);
1805     locks_dispose_list(&dispose);
1806     return error;
1807 }
1808 
1809 /**
1810  *  generic_setlease    -   sets a lease on an open file
1811  *  @filp:  file pointer
1812  *  @arg:   type of lease to obtain
1813  *  @flp:   input - file_lock to use, output - file_lock inserted
1814  *  @priv:  private data for lm_setup (may be NULL if lm_setup
1815  *      doesn't require it)
1816  *
1817  *  The (input) flp->fl_lmops->lm_break function is required
1818  *  by break_lease().
1819  */
1820 int generic_setlease(struct file *filp, long arg, struct file_lock **flp,
1821             void **priv)
1822 {
1823     struct inode *inode = locks_inode(filp);
1824     int error;
1825 
1826     if ((!uid_eq(current_fsuid(), inode->i_uid)) && !capable(CAP_LEASE))
1827         return -EACCES;
1828     if (!S_ISREG(inode->i_mode))
1829         return -EINVAL;
1830     error = security_file_lock(filp, arg);
1831     if (error)
1832         return error;
1833 
1834     switch (arg) {
1835     case F_UNLCK:
1836         return generic_delete_lease(filp, *priv);
1837     case F_RDLCK:
1838     case F_WRLCK:
1839         if (!(*flp)->fl_lmops->lm_break) {
1840             WARN_ON_ONCE(1);
1841             return -ENOLCK;
1842         }
1843 
1844         return generic_add_lease(filp, arg, flp, priv);
1845     default:
1846         return -EINVAL;
1847     }
1848 }
1849 EXPORT_SYMBOL(generic_setlease);
1850 
1851 /**
1852  * vfs_setlease        -       sets a lease on an open file
1853  * @filp:   file pointer
1854  * @arg:    type of lease to obtain
1855  * @lease:  file_lock to use when adding a lease
1856  * @priv:   private info for lm_setup when adding a lease (may be
1857  *      NULL if lm_setup doesn't require it)
1858  *
1859  * Call this to establish a lease on the file. The "lease" argument is not
1860  * used for F_UNLCK requests and may be NULL. For commands that set or alter
1861  * an existing lease, the (*lease)->fl_lmops->lm_break operation must be set;
1862  * if not, this function will return -ENOLCK (and generate a scary-looking
1863  * stack trace).
1864  *
1865  * The "priv" pointer is passed directly to the lm_setup function as-is. It
1866  * may be NULL if the lm_setup operation doesn't require it.
1867  */
1868 int
1869 vfs_setlease(struct file *filp, long arg, struct file_lock **lease, void **priv)
1870 {
1871     if (filp->f_op->setlease && is_remote_lock(filp))
1872         return filp->f_op->setlease(filp, arg, lease, priv);
1873     else
1874         return generic_setlease(filp, arg, lease, priv);
1875 }
1876 EXPORT_SYMBOL_GPL(vfs_setlease);
1877 
1878 static int do_fcntl_add_lease(unsigned int fd, struct file *filp, long arg)
1879 {
1880     struct file_lock *fl;
1881     struct fasync_struct *new;
1882     int error;
1883 
1884     fl = lease_alloc(filp, arg);
1885     if (IS_ERR(fl))
1886         return PTR_ERR(fl);
1887 
1888     new = fasync_alloc();
1889     if (!new) {
1890         locks_free_lock(fl);
1891         return -ENOMEM;
1892     }
1893     new->fa_fd = fd;
1894 
1895     error = vfs_setlease(filp, arg, &fl, (void **)&new);
1896     if (fl)
1897         locks_free_lock(fl);
1898     if (new)
1899         fasync_free(new);
1900     return error;
1901 }
1902 
1903 /**
1904  *  fcntl_setlease  -   sets a lease on an open file
1905  *  @fd: open file descriptor
1906  *  @filp: file pointer
1907  *  @arg: type of lease to obtain
1908  *
1909  *  Call this fcntl to establish a lease on the file.
1910  *  Note that you also need to call %F_SETSIG to
1911  *  receive a signal when the lease is broken.
1912  */
1913 int fcntl_setlease(unsigned int fd, struct file *filp, long arg)
1914 {
1915     if (arg == F_UNLCK)
1916         return vfs_setlease(filp, F_UNLCK, NULL, (void **)&filp);
1917     return do_fcntl_add_lease(fd, filp, arg);
1918 }
1919 
1920 /**
1921  * flock_lock_inode_wait - Apply a FLOCK-style lock to a file
1922  * @inode: inode of the file to apply to
1923  * @fl: The lock to be applied
1924  *
1925  * Apply a FLOCK style lock request to an inode.
1926  */
1927 static int flock_lock_inode_wait(struct inode *inode, struct file_lock *fl)
1928 {
1929     int error;
1930     might_sleep();
1931     for (;;) {
1932         error = flock_lock_inode(inode, fl);
1933         if (error != FILE_LOCK_DEFERRED)
1934             break;
1935         error = wait_event_interruptible(fl->fl_wait, !fl->fl_next);
1936         if (!error)
1937             continue;
1938 
1939         locks_delete_block(fl);
1940         break;
1941     }
1942     return error;
1943 }
1944 
1945 /**
1946  * locks_lock_inode_wait - Apply a lock to an inode
1947  * @inode: inode of the file to apply to
1948  * @fl: The lock to be applied
1949  *
1950  * Apply a POSIX or FLOCK style lock request to an inode.
1951  */
1952 int locks_lock_inode_wait(struct inode *inode, struct file_lock *fl)
1953 {
1954     int res = 0;
1955     switch (fl->fl_flags & (FL_POSIX|FL_FLOCK)) {
1956         case FL_POSIX:
1957             res = posix_lock_inode_wait(inode, fl);
1958             break;
1959         case FL_FLOCK:
1960             res = flock_lock_inode_wait(inode, fl);
1961             break;
1962         default:
1963             BUG();
1964     }
1965     return res;
1966 }
1967 EXPORT_SYMBOL(locks_lock_inode_wait);
1968 
1969 /**
1970  *  sys_flock: - flock() system call.
1971  *  @fd: the file descriptor to lock.
1972  *  @cmd: the type of lock to apply.
1973  *
1974  *  Apply a %FL_FLOCK style lock to an open file descriptor.
1975  *  The @cmd can be one of
1976  *
1977  *  %LOCK_SH -- a shared lock.
1978  *
1979  *  %LOCK_EX -- an exclusive lock.
1980  *
1981  *  %LOCK_UN -- remove an existing lock.
1982  *
1983  *  %LOCK_MAND -- a `mandatory' flock.  This exists to emulate Windows Share Modes.
1984  *
1985  *  %LOCK_MAND can be combined with %LOCK_READ or %LOCK_WRITE to allow other
1986  *  processes read and write access respectively.
1987  */
1988 SYSCALL_DEFINE2(flock, unsigned int, fd, unsigned int, cmd)
1989 {
1990     struct fd f = fdget(fd);
1991     struct file_lock *lock;
1992     int can_sleep, unlock;
1993     int error;
1994 
1995     error = -EBADF;
1996     if (!f.file)
1997         goto out;
1998 
1999     can_sleep = !(cmd & LOCK_NB);
2000     cmd &= ~LOCK_NB;
2001     unlock = (cmd == LOCK_UN);
2002 
2003     if (!unlock && !(cmd & LOCK_MAND) &&
2004         !(f.file->f_mode & (FMODE_READ|FMODE_WRITE)))
2005         goto out_putf;
2006 
2007     lock = flock_make_lock(f.file, cmd);
2008     if (IS_ERR(lock)) {
2009         error = PTR_ERR(lock);
2010         goto out_putf;
2011     }
2012 
2013     if (can_sleep)
2014         lock->fl_flags |= FL_SLEEP;
2015 
2016     error = security_file_lock(f.file, lock->fl_type);
2017     if (error)
2018         goto out_free;
2019 
2020     if (f.file->f_op->flock && is_remote_lock(f.file))
2021         error = f.file->f_op->flock(f.file,
2022                       (can_sleep) ? F_SETLKW : F_SETLK,
2023                       lock);
2024     else
2025         error = locks_lock_file_wait(f.file, lock);
2026 
2027  out_free:
2028     locks_free_lock(lock);
2029 
2030  out_putf:
2031     fdput(f);
2032  out:
2033     return error;
2034 }
2035 
2036 /**
2037  * vfs_test_lock - test file byte range lock
2038  * @filp: The file to test lock for
2039  * @fl: The lock to test; also used to hold result
2040  *
2041  * Returns -ERRNO on failure.  Indicates presence of conflicting lock by
2042  * setting conf->fl_type to something other than F_UNLCK.
2043  */
2044 int vfs_test_lock(struct file *filp, struct file_lock *fl)
2045 {
2046     if (filp->f_op->lock && is_remote_lock(filp))
2047         return filp->f_op->lock(filp, F_GETLK, fl);
2048     posix_test_lock(filp, fl);
2049     return 0;
2050 }
2051 EXPORT_SYMBOL_GPL(vfs_test_lock);
2052 
2053 static int posix_lock_to_flock(struct flock *flock, struct file_lock *fl)
2054 {
2055     flock->l_pid = IS_OFDLCK(fl) ? -1 : fl->fl_pid;
2056 #if BITS_PER_LONG == 32
2057     /*
2058      * Make sure we can represent the posix lock via
2059      * legacy 32bit flock.
2060      */
2061     if (fl->fl_start > OFFT_OFFSET_MAX)
2062         return -EOVERFLOW;
2063     if (fl->fl_end != OFFSET_MAX && fl->fl_end > OFFT_OFFSET_MAX)
2064         return -EOVERFLOW;
2065 #endif
2066     flock->l_start = fl->fl_start;
2067     flock->l_len = fl->fl_end == OFFSET_MAX ? 0 :
2068         fl->fl_end - fl->fl_start + 1;
2069     flock->l_whence = 0;
2070     flock->l_type = fl->fl_type;
2071     return 0;
2072 }
2073 
2074 #if BITS_PER_LONG == 32
2075 static void posix_lock_to_flock64(struct flock64 *flock, struct file_lock *fl)
2076 {
2077     flock->l_pid = IS_OFDLCK(fl) ? -1 : fl->fl_pid;
2078     flock->l_start = fl->fl_start;
2079     flock->l_len = fl->fl_end == OFFSET_MAX ? 0 :
2080         fl->fl_end - fl->fl_start + 1;
2081     flock->l_whence = 0;
2082     flock->l_type = fl->fl_type;
2083 }
2084 #endif
2085 
2086 /* Report the first existing lock that would conflict with l.
2087  * This implements the F_GETLK command of fcntl().
2088  */
2089 int fcntl_getlk(struct file *filp, unsigned int cmd, struct flock __user *l)
2090 {
2091     struct file_lock file_lock;
2092     struct flock flock;
2093     int error;
2094 
2095     error = -EFAULT;
2096     if (copy_from_user(&flock, l, sizeof(flock)))
2097         goto out;
2098     error = -EINVAL;
2099     if ((flock.l_type != F_RDLCK) && (flock.l_type != F_WRLCK))
2100         goto out;
2101 
2102     error = flock_to_posix_lock(filp, &file_lock, &flock);
2103     if (error)
2104         goto out;
2105 
2106     if (cmd == F_OFD_GETLK) {
2107         error = -EINVAL;
2108         if (flock.l_pid != 0)
2109             goto out;
2110 
2111         cmd = F_GETLK;
2112         file_lock.fl_flags |= FL_OFDLCK;
2113         file_lock.fl_owner = filp;
2114     }
2115 
2116     error = vfs_test_lock(filp, &file_lock);
2117     if (error)
2118         goto out;
2119  
2120     flock.l_type = file_lock.fl_type;
2121     if (file_lock.fl_type != F_UNLCK) {
2122         error = posix_lock_to_flock(&flock, &file_lock);
2123         if (error)
2124             goto rel_priv;
2125     }
2126     error = -EFAULT;
2127     if (!copy_to_user(l, &flock, sizeof(flock)))
2128         error = 0;
2129 rel_priv:
2130     locks_release_private(&file_lock);
2131 out:
2132     return error;
2133 }
2134 
2135 /**
2136  * vfs_lock_file - file byte range lock
2137  * @filp: The file to apply the lock to
2138  * @cmd: type of locking operation (F_SETLK, F_GETLK, etc.)
2139  * @fl: The lock to be applied
2140  * @conf: Place to return a copy of the conflicting lock, if found.
2141  *
2142  * A caller that doesn't care about the conflicting lock may pass NULL
2143  * as the final argument.
2144  *
2145  * If the filesystem defines a private ->lock() method, then @conf will
2146  * be left unchanged; so a caller that cares should initialize it to
2147  * some acceptable default.
2148  *
2149  * To avoid blocking kernel daemons, such as lockd, that need to acquire POSIX
2150  * locks, the ->lock() interface may return asynchronously, before the lock has
2151  * been granted or denied by the underlying filesystem, if (and only if)
2152  * lm_grant is set. Callers expecting ->lock() to return asynchronously
2153  * will only use F_SETLK, not F_SETLKW; they will set FL_SLEEP if (and only if)
2154  * the request is for a blocking lock. When ->lock() does return asynchronously,
2155  * it must return FILE_LOCK_DEFERRED, and call ->lm_grant() when the lock
2156  * request completes.
2157  * If the request is for non-blocking lock the file system should return
2158  * FILE_LOCK_DEFERRED then try to get the lock and call the callback routine
2159  * with the result. If the request timed out the callback routine will return a
2160  * nonzero return code and the file system should release the lock. The file
2161  * system is also responsible to keep a corresponding posix lock when it
2162  * grants a lock so the VFS can find out which locks are locally held and do
2163  * the correct lock cleanup when required.
2164  * The underlying filesystem must not drop the kernel lock or call
2165  * ->lm_grant() before returning to the caller with a FILE_LOCK_DEFERRED
2166  * return code.
2167  */
2168 int vfs_lock_file(struct file *filp, unsigned int cmd, struct file_lock *fl, struct file_lock *conf)
2169 {
2170     if (filp->f_op->lock && is_remote_lock(filp))
2171         return filp->f_op->lock(filp, cmd, fl);
2172     else
2173         return posix_lock_file(filp, fl, conf);
2174 }
2175 EXPORT_SYMBOL_GPL(vfs_lock_file);
2176 
2177 static int do_lock_file_wait(struct file *filp, unsigned int cmd,
2178                  struct file_lock *fl)
2179 {
2180     int error;
2181 
2182     error = security_file_lock(filp, fl->fl_type);
2183     if (error)
2184         return error;
2185 
2186     for (;;) {
2187         error = vfs_lock_file(filp, cmd, fl, NULL);
2188         if (error != FILE_LOCK_DEFERRED)
2189             break;
2190         error = wait_event_interruptible(fl->fl_wait, !fl->fl_next);
2191         if (!error)
2192             continue;
2193 
2194         locks_delete_block(fl);
2195         break;
2196     }
2197 
2198     return error;
2199 }
2200 
2201 /* Ensure that fl->fl_file has compatible f_mode for F_SETLK calls */
2202 static int
2203 check_fmode_for_setlk(struct file_lock *fl)
2204 {
2205     switch (fl->fl_type) {
2206     case F_RDLCK:
2207         if (!(fl->fl_file->f_mode & FMODE_READ))
2208             return -EBADF;
2209         break;
2210     case F_WRLCK:
2211         if (!(fl->fl_file->f_mode & FMODE_WRITE))
2212             return -EBADF;
2213     }
2214     return 0;
2215 }
2216 
2217 /* Apply the lock described by l to an open file descriptor.
2218  * This implements both the F_SETLK and F_SETLKW commands of fcntl().
2219  */
2220 int fcntl_setlk(unsigned int fd, struct file *filp, unsigned int cmd,
2221         struct flock __user *l)
2222 {
2223     struct file_lock *file_lock = locks_alloc_lock();
2224     struct flock flock;
2225     struct inode *inode;
2226     struct file *f;
2227     int error;
2228 
2229     if (file_lock == NULL)
2230         return -ENOLCK;
2231 
2232     inode = locks_inode(filp);
2233 
2234     /*
2235      * This might block, so we do it before checking the inode.
2236      */
2237     error = -EFAULT;
2238     if (copy_from_user(&flock, l, sizeof(flock)))
2239         goto out;
2240 
2241     /* Don't allow mandatory locks on files that may be memory mapped
2242      * and shared.
2243      */
2244     if (mandatory_lock(inode) && mapping_writably_mapped(filp->f_mapping)) {
2245         error = -EAGAIN;
2246         goto out;
2247     }
2248 
2249     error = flock_to_posix_lock(filp, file_lock, &flock);
2250     if (error)
2251         goto out;
2252 
2253     error = check_fmode_for_setlk(file_lock);
2254     if (error)
2255         goto out;
2256 
2257     /*
2258      * If the cmd is requesting file-private locks, then set the
2259      * FL_OFDLCK flag and override the owner.
2260      */
2261     switch (cmd) {
2262     case F_OFD_SETLK:
2263         error = -EINVAL;
2264         if (flock.l_pid != 0)
2265             goto out;
2266 
2267         cmd = F_SETLK;
2268         file_lock->fl_flags |= FL_OFDLCK;
2269         file_lock->fl_owner = filp;
2270         break;
2271     case F_OFD_SETLKW:
2272         error = -EINVAL;
2273         if (flock.l_pid != 0)
2274             goto out;
2275 
2276         cmd = F_SETLKW;
2277         file_lock->fl_flags |= FL_OFDLCK;
2278         file_lock->fl_owner = filp;
2279         /* Fallthrough */
2280     case F_SETLKW:
2281         file_lock->fl_flags |= FL_SLEEP;
2282     }
2283 
2284     error = do_lock_file_wait(filp, cmd, file_lock);
2285 
2286     /*
2287      * Attempt to detect a close/fcntl race and recover by releasing the
2288      * lock that was just acquired. There is no need to do that when we're
2289      * unlocking though, or for OFD locks.
2290      */
2291     if (!error && file_lock->fl_type != F_UNLCK &&
2292         !(file_lock->fl_flags & FL_OFDLCK)) {
2293         /*
2294          * We need that spin_lock here - it prevents reordering between
2295          * update of i_flctx->flc_posix and check for it done in
2296          * close(). rcu_read_lock() wouldn't do.
2297          */
2298         spin_lock(&current->files->file_lock);
2299         f = fcheck(fd);
2300         spin_unlock(&current->files->file_lock);
2301         if (f != filp) {
2302             file_lock->fl_type = F_UNLCK;
2303             error = do_lock_file_wait(filp, cmd, file_lock);
2304             WARN_ON_ONCE(error);
2305             error = -EBADF;
2306         }
2307     }
2308 out:
2309     trace_fcntl_setlk(inode, file_lock, error);
2310     locks_free_lock(file_lock);
2311     return error;
2312 }
2313 
2314 #if BITS_PER_LONG == 32
2315 /* Report the first existing lock that would conflict with l.
2316  * This implements the F_GETLK command of fcntl().
2317  */
2318 int fcntl_getlk64(struct file *filp, unsigned int cmd, struct flock64 __user *l)
2319 {
2320     struct file_lock file_lock;
2321     struct flock64 flock;
2322     int error;
2323 
2324     error = -EFAULT;
2325     if (copy_from_user(&flock, l, sizeof(flock)))
2326         goto out;
2327     error = -EINVAL;
2328     if ((flock.l_type != F_RDLCK) && (flock.l_type != F_WRLCK))
2329         goto out;
2330 
2331     error = flock64_to_posix_lock(filp, &file_lock, &flock);
2332     if (error)
2333         goto out;
2334 
2335     if (cmd == F_OFD_GETLK) {
2336         error = -EINVAL;
2337         if (flock.l_pid != 0)
2338             goto out;
2339 
2340         cmd = F_GETLK64;
2341         file_lock.fl_flags |= FL_OFDLCK;
2342         file_lock.fl_owner = filp;
2343     }
2344 
2345     error = vfs_test_lock(filp, &file_lock);
2346     if (error)
2347         goto out;
2348 
2349     flock.l_type = file_lock.fl_type;
2350     if (file_lock.fl_type != F_UNLCK)
2351         posix_lock_to_flock64(&flock, &file_lock);
2352 
2353     error = -EFAULT;
2354     if (!copy_to_user(l, &flock, sizeof(flock)))
2355         error = 0;
2356 
2357     locks_release_private(&file_lock);
2358 out:
2359     return error;
2360 }
2361 
2362 /* Apply the lock described by l to an open file descriptor.
2363  * This implements both the F_SETLK and F_SETLKW commands of fcntl().
2364  */
2365 int fcntl_setlk64(unsigned int fd, struct file *filp, unsigned int cmd,
2366         struct flock64 __user *l)
2367 {
2368     struct file_lock *file_lock = locks_alloc_lock();
2369     struct flock64 flock;
2370     struct inode *inode;
2371     struct file *f;
2372     int error;
2373 
2374     if (file_lock == NULL)
2375         return -ENOLCK;
2376 
2377     /*
2378      * This might block, so we do it before checking the inode.
2379      */
2380     error = -EFAULT;
2381     if (copy_from_user(&flock, l, sizeof(flock)))
2382         goto out;
2383 
2384     inode = locks_inode(filp);
2385 
2386     /* Don't allow mandatory locks on files that may be memory mapped
2387      * and shared.
2388      */
2389     if (mandatory_lock(inode) && mapping_writably_mapped(filp->f_mapping)) {
2390         error = -EAGAIN;
2391         goto out;
2392     }
2393 
2394     error = flock64_to_posix_lock(filp, file_lock, &flock);
2395     if (error)
2396         goto out;
2397 
2398     error = check_fmode_for_setlk(file_lock);
2399     if (error)
2400         goto out;
2401 
2402     /*
2403      * If the cmd is requesting file-private locks, then set the
2404      * FL_OFDLCK flag and override the owner.
2405      */
2406     switch (cmd) {
2407     case F_OFD_SETLK:
2408         error = -EINVAL;
2409         if (flock.l_pid != 0)
2410             goto out;
2411 
2412         cmd = F_SETLK64;
2413         file_lock->fl_flags |= FL_OFDLCK;
2414         file_lock->fl_owner = filp;
2415         break;
2416     case F_OFD_SETLKW:
2417         error = -EINVAL;
2418         if (flock.l_pid != 0)
2419             goto out;
2420 
2421         cmd = F_SETLKW64;
2422         file_lock->fl_flags |= FL_OFDLCK;
2423         file_lock->fl_owner = filp;
2424         /* Fallthrough */
2425     case F_SETLKW64:
2426         file_lock->fl_flags |= FL_SLEEP;
2427     }
2428 
2429     error = do_lock_file_wait(filp, cmd, file_lock);
2430 
2431     /*
2432      * Attempt to detect a close/fcntl race and recover by releasing the
2433      * lock that was just acquired. There is no need to do that when we're
2434      * unlocking though, or for OFD locks.
2435      */
2436     if (!error && file_lock->fl_type != F_UNLCK &&
2437         !(file_lock->fl_flags & FL_OFDLCK)) {
2438         /*
2439          * We need that spin_lock here - it prevents reordering between
2440          * update of i_flctx->flc_posix and check for it done in
2441          * close(). rcu_read_lock() wouldn't do.
2442          */
2443         spin_lock(&current->files->file_lock);
2444         f = fcheck(fd);
2445         spin_unlock(&current->files->file_lock);
2446         if (f != filp) {
2447             file_lock->fl_type = F_UNLCK;
2448             error = do_lock_file_wait(filp, cmd, file_lock);
2449             WARN_ON_ONCE(error);
2450             error = -EBADF;
2451         }
2452     }
2453 out:
2454     locks_free_lock(file_lock);
2455     return error;
2456 }
2457 #endif /* BITS_PER_LONG == 32 */
2458 
2459 /*
2460  * This function is called when the file is being removed
2461  * from the task's fd array.  POSIX locks belonging to this task
2462  * are deleted at this time.
2463  */
2464 void locks_remove_posix(struct file *filp, fl_owner_t owner)
2465 {
2466     int error;
2467     struct inode *inode = locks_inode(filp);
2468     struct file_lock lock;
2469     struct file_lock_context *ctx;
2470 
2471     /*
2472      * If there are no locks held on this file, we don't need to call
2473      * posix_lock_file().  Another process could be setting a lock on this
2474      * file at the same time, but we wouldn't remove that lock anyway.
2475      */
2476     ctx =  smp_load_acquire(&inode->i_flctx);
2477     if (!ctx || list_empty(&ctx->flc_posix))
2478         return;
2479 
2480     lock.fl_type = F_UNLCK;
2481     lock.fl_flags = FL_POSIX | FL_CLOSE;
2482     lock.fl_start = 0;
2483     lock.fl_end = OFFSET_MAX;
2484     lock.fl_owner = owner;
2485     lock.fl_pid = current->tgid;
2486     lock.fl_file = filp;
2487     lock.fl_ops = NULL;
2488     lock.fl_lmops = NULL;
2489 
2490     error = vfs_lock_file(filp, F_SETLK, &lock, NULL);
2491 
2492     if (lock.fl_ops && lock.fl_ops->fl_release_private)
2493         lock.fl_ops->fl_release_private(&lock);
2494     trace_locks_remove_posix(inode, &lock, error);
2495 }
2496 
2497 EXPORT_SYMBOL(locks_remove_posix);
2498 
2499 /* The i_flctx must be valid when calling into here */
2500 static void
2501 locks_remove_flock(struct file *filp, struct file_lock_context *flctx)
2502 {
2503     struct file_lock fl = {
2504         .fl_owner = filp,
2505         .fl_pid = current->tgid,
2506         .fl_file = filp,
2507         .fl_flags = FL_FLOCK,
2508         .fl_type = F_UNLCK,
2509         .fl_end = OFFSET_MAX,
2510     };
2511     struct inode *inode = locks_inode(filp);
2512 
2513     if (list_empty(&flctx->flc_flock))
2514         return;
2515 
2516     if (filp->f_op->flock && is_remote_lock(filp))
2517         filp->f_op->flock(filp, F_SETLKW, &fl);
2518     else
2519         flock_lock_inode(inode, &fl);
2520 
2521     if (fl.fl_ops && fl.fl_ops->fl_release_private)
2522         fl.fl_ops->fl_release_private(&fl);
2523 }
2524 
2525 /* The i_flctx must be valid when calling into here */
2526 static void
2527 locks_remove_lease(struct file *filp, struct file_lock_context *ctx)
2528 {
2529     struct file_lock *fl, *tmp;
2530     LIST_HEAD(dispose);
2531 
2532     if (list_empty(&ctx->flc_lease))
2533         return;
2534 
2535     percpu_down_read_preempt_disable(&file_rwsem);
2536     spin_lock(&ctx->flc_lock);
2537     list_for_each_entry_safe(fl, tmp, &ctx->flc_lease, fl_list)
2538         if (filp == fl->fl_file)
2539             lease_modify(fl, F_UNLCK, &dispose);
2540     spin_unlock(&ctx->flc_lock);
2541     percpu_up_read_preempt_enable(&file_rwsem);
2542 
2543     locks_dispose_list(&dispose);
2544 }
2545 
2546 /*
2547  * This function is called on the last close of an open file.
2548  */
2549 void locks_remove_file(struct file *filp)
2550 {
2551     struct file_lock_context *ctx;
2552 
2553     ctx = smp_load_acquire(&locks_inode(filp)->i_flctx);
2554     if (!ctx)
2555         return;
2556 
2557     /* remove any OFD locks */
2558     locks_remove_posix(filp, filp);
2559 
2560     /* remove flock locks */
2561     locks_remove_flock(filp, ctx);
2562 
2563     /* remove any leases */
2564     locks_remove_lease(filp, ctx);
2565 }
2566 
2567 /**
2568  *  posix_unblock_lock - stop waiting for a file lock
2569  *  @waiter: the lock which was waiting
2570  *
2571  *  lockd needs to block waiting for locks.
2572  */
2573 int
2574 posix_unblock_lock(struct file_lock *waiter)
2575 {
2576     int status = 0;
2577 
2578     spin_lock(&blocked_lock_lock);
2579     if (waiter->fl_next)
2580         __locks_delete_block(waiter);
2581     else
2582         status = -ENOENT;
2583     spin_unlock(&blocked_lock_lock);
2584     return status;
2585 }
2586 EXPORT_SYMBOL(posix_unblock_lock);
2587 
2588 /**
2589  * vfs_cancel_lock - file byte range unblock lock
2590  * @filp: The file to apply the unblock to
2591  * @fl: The lock to be unblocked
2592  *
2593  * Used by lock managers to cancel blocked requests
2594  */
2595 int vfs_cancel_lock(struct file *filp, struct file_lock *fl)
2596 {
2597     if (filp->f_op->lock && is_remote_lock(filp))
2598         return filp->f_op->lock(filp, F_CANCELLK, fl);
2599     return 0;
2600 }
2601 
2602 EXPORT_SYMBOL_GPL(vfs_cancel_lock);
2603 
2604 #ifdef CONFIG_PROC_FS
2605 #include <linux/proc_fs.h>
2606 #include <linux/seq_file.h>
2607 
2608 struct locks_iterator {
2609     int li_cpu;
2610     loff_t  li_pos;
2611 };
2612 
2613 static void lock_get_status(struct seq_file *f, struct file_lock *fl,
2614                 loff_t id, char *pfx)
2615 {
2616     struct inode *inode = NULL;
2617     unsigned int fl_pid;
2618 
2619     if (fl->fl_nspid) {
2620         struct pid_namespace *proc_pidns = file_inode(f->file)->i_sb->s_fs_info;
2621 
2622         /* Don't let fl_pid change based on who is reading the file */
2623         fl_pid = pid_nr_ns(fl->fl_nspid, proc_pidns);
2624 
2625         /*
2626          * If there isn't a fl_pid don't display who is waiting on
2627          * the lock if we are called from locks_show, or if we are
2628          * called from __show_fd_info - skip lock entirely
2629          */
2630         if (fl_pid == 0)
2631             return;
2632     } else
2633         fl_pid = fl->fl_pid;
2634 
2635     if (fl->fl_file != NULL)
2636         inode = locks_inode(fl->fl_file);
2637 
2638     seq_printf(f, "%lld:%s ", id, pfx);
2639     if (IS_POSIX(fl)) {
2640         if (fl->fl_flags & FL_ACCESS)
2641             seq_puts(f, "ACCESS");
2642         else if (IS_OFDLCK(fl))
2643             seq_puts(f, "OFDLCK");
2644         else
2645             seq_puts(f, "POSIX ");
2646 
2647         seq_printf(f, " %s ",
2648                  (inode == NULL) ? "*NOINODE*" :
2649                  mandatory_lock(inode) ? "MANDATORY" : "ADVISORY ");
2650     } else if (IS_FLOCK(fl)) {
2651         if (fl->fl_type & LOCK_MAND) {
2652             seq_puts(f, "FLOCK  MSNFS     ");
2653         } else {
2654             seq_puts(f, "FLOCK  ADVISORY  ");
2655         }
2656     } else if (IS_LEASE(fl)) {
2657         if (fl->fl_flags & FL_DELEG)
2658             seq_puts(f, "DELEG  ");
2659         else
2660             seq_puts(f, "LEASE  ");
2661 
2662         if (lease_breaking(fl))
2663             seq_puts(f, "BREAKING  ");
2664         else if (fl->fl_file)
2665             seq_puts(f, "ACTIVE    ");
2666         else
2667             seq_puts(f, "BREAKER   ");
2668     } else {
2669         seq_puts(f, "UNKNOWN UNKNOWN  ");
2670     }
2671     if (fl->fl_type & LOCK_MAND) {
2672         seq_printf(f, "%s ",
2673                    (fl->fl_type & LOCK_READ)
2674                    ? (fl->fl_type & LOCK_WRITE) ? "RW   " : "READ "
2675                    : (fl->fl_type & LOCK_WRITE) ? "WRITE" : "NONE ");
2676     } else {
2677         seq_printf(f, "%s ",
2678                    (lease_breaking(fl))
2679                    ? (fl->fl_type == F_UNLCK) ? "UNLCK" : "READ "
2680                    : (fl->fl_type == F_WRLCK) ? "WRITE" : "READ ");
2681     }
2682     if (inode) {
2683         /* userspace relies on this representation of dev_t */
2684         seq_printf(f, "%d %02x:%02x:%ld ", fl_pid,
2685                 MAJOR(inode->i_sb->s_dev),
2686                 MINOR(inode->i_sb->s_dev), inode->i_ino);
2687     } else {
2688         seq_printf(f, "%d <none>:0 ", fl_pid);
2689     }
2690     if (IS_POSIX(fl)) {
2691         if (fl->fl_end == OFFSET_MAX)
2692             seq_printf(f, "%Ld EOF\n", fl->fl_start);
2693         else
2694             seq_printf(f, "%Ld %Ld\n", fl->fl_start, fl->fl_end);
2695     } else {
2696         seq_puts(f, "0 EOF\n");
2697     }
2698 }
2699 
2700 static int locks_show(struct seq_file *f, void *v)
2701 {
2702     struct locks_iterator *iter = f->private;
2703     struct file_lock *fl, *bfl;
2704     struct pid_namespace *proc_pidns = file_inode(f->file)->i_sb->s_fs_info;
2705 
2706     fl = hlist_entry(v, struct file_lock, fl_link);
2707 
2708     if (fl->fl_nspid && !pid_nr_ns(fl->fl_nspid, proc_pidns))
2709         return 0;
2710 
2711     lock_get_status(f, fl, iter->li_pos, "");
2712 
2713     list_for_each_entry(bfl, &fl->fl_block, fl_block)
2714         lock_get_status(f, bfl, iter->li_pos, " ->");
2715 
2716     return 0;
2717 }
2718 
2719 static void __show_fd_locks(struct seq_file *f,
2720             struct list_head *head, int *id,
2721             struct file *filp, struct files_struct *files)
2722 {
2723     struct file_lock *fl;
2724 
2725     list_for_each_entry(fl, head, fl_list) {
2726 
2727         if (filp != fl->fl_file)
2728             continue;
2729         if (fl->fl_owner != files &&
2730             fl->fl_owner != filp)
2731             continue;
2732 
2733         (*id)++;
2734         seq_puts(f, "lock:\t");
2735         lock_get_status(f, fl, *id, "");
2736     }
2737 }
2738 
2739 void show_fd_locks(struct seq_file *f,
2740           struct file *filp, struct files_struct *files)
2741 {
2742     struct inode *inode = locks_inode(filp);
2743     struct file_lock_context *ctx;
2744     int id = 0;
2745 
2746     ctx = smp_load_acquire(&inode->i_flctx);
2747     if (!ctx)
2748         return;
2749 
2750     spin_lock(&ctx->flc_lock);
2751     __show_fd_locks(f, &ctx->flc_flock, &id, filp, files);
2752     __show_fd_locks(f, &ctx->flc_posix, &id, filp, files);
2753     __show_fd_locks(f, &ctx->flc_lease, &id, filp, files);
2754     spin_unlock(&ctx->flc_lock);
2755 }
2756 
2757 static void *locks_start(struct seq_file *f, loff_t *pos)
2758     __acquires(&blocked_lock_lock)
2759 {
2760     struct locks_iterator *iter = f->private;
2761 
2762     iter->li_pos = *pos + 1;
2763     percpu_down_write(&file_rwsem);
2764     spin_lock(&blocked_lock_lock);
2765     return seq_hlist_start_percpu(&file_lock_list.hlist, &iter->li_cpu, *pos);
2766 }
2767 
2768 static void *locks_next(struct seq_file *f, void *v, loff_t *pos)
2769 {
2770     struct locks_iterator *iter = f->private;
2771 
2772     ++iter->li_pos;
2773     return seq_hlist_next_percpu(v, &file_lock_list.hlist, &iter->li_cpu, pos);
2774 }
2775 
2776 static void locks_stop(struct seq_file *f, void *v)
2777     __releases(&blocked_lock_lock)
2778 {
2779     spin_unlock(&blocked_lock_lock);
2780     percpu_up_write(&file_rwsem);
2781 }
2782 
2783 static const struct seq_operations locks_seq_operations = {
2784     .start  = locks_start,
2785     .next   = locks_next,
2786     .stop   = locks_stop,
2787     .show   = locks_show,
2788 };
2789 
2790 static int locks_open(struct inode *inode, struct file *filp)
2791 {
2792     return seq_open_private(filp, &locks_seq_operations,
2793                     sizeof(struct locks_iterator));
2794 }
2795 
2796 static const struct file_operations proc_locks_operations = {
2797     .open       = locks_open,
2798     .read       = seq_read,
2799     .llseek     = seq_lseek,
2800     .release    = seq_release_private,
2801 };
2802 
2803 static int __init proc_locks_init(void)
2804 {
2805     proc_create("locks", 0, NULL, &proc_locks_operations);
2806     return 0;
2807 }
2808 fs_initcall(proc_locks_init);
2809 #endif
2810 
2811 static int __init filelock_init(void)
2812 {
2813     int i;
2814 
2815     flctx_cache = kmem_cache_create("file_lock_ctx",
2816             sizeof(struct file_lock_context), 0, SLAB_PANIC, NULL);
2817 
2818     filelock_cache = kmem_cache_create("file_lock_cache",
2819             sizeof(struct file_lock), 0, SLAB_PANIC, NULL);
2820 
2821 
2822     for_each_possible_cpu(i) {
2823         struct file_lock_list_struct *fll = per_cpu_ptr(&file_lock_list, i);
2824 
2825         spin_lock_init(&fll->lock);
2826         INIT_HLIST_HEAD(&fll->hlist);
2827     }
2828 
2829     return 0;
2830 }
2831 
2832 core_initcall(filelock_init);