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	Version: linux-6.0.1 spark-3.0.0 hadoop-3.2.0-src hadoop-3.3.0-src spark-2.4.7 linux-4.15.13 hadoop-2.7.4-src Revert   Change

 // SPDX-License-Identifier: GPL-2.0-only
 /*
  * (C) 1997 Linus Torvalds
  * (C) 1999 Andrea Arcangeli <andrea@suse.de> (dynamic inode allocation)
  */
 #include <linux/export.h>
 #include <linux/fs.h>
 #include <linux/mm.h>
 #include <linux/backing-dev.h>
 #include <linux/hash.h>
 #include <linux/swap.h>
 #include <linux/security.h>
 #include <linux/cdev.h>
 #include <linux/memblock.h>
 #include <linux/fsnotify.h>
 #include <linux/mount.h>
 #include <linux/posix_acl.h>
 #include <linux/prefetch.h>
 #include <linux/buffer_head.h> /* for inode_has_buffers */
 #include <linux/ratelimit.h>
 #include <linux/list_lru.h>
 #include <linux/iversion.h>
 #include <trace/events/writeback.h>
 #include "internal.h"
 
 /*
  * Inode locking rules:
  *
  * inode->i_lock protects:
  *   inode->i_state, inode->i_hash, __iget(), inode->i_io_list
  * Inode LRU list locks protect:
  *   inode->i_sb->s_inode_lru, inode->i_lru
  * inode->i_sb->s_inode_list_lock protects:
  *   inode->i_sb->s_inodes, inode->i_sb_list
  * bdi->wb.list_lock protects:
  *   bdi->wb.b_{dirty,io,more_io,dirty_time}, inode->i_io_list
  * inode_hash_lock protects:
  *   inode_hashtable, inode->i_hash
  *
  * Lock ordering:
  *
  * inode->i_sb->s_inode_list_lock
  *   inode->i_lock
  *     Inode LRU list locks
  *
  * bdi->wb.list_lock
  *   inode->i_lock
  *
  * inode_hash_lock
  *   inode->i_sb->s_inode_list_lock
  *   inode->i_lock
  *
  * iunique_lock
  *   inode_hash_lock
  */
 
 static unsigned int i_hash_mask __read_mostly;
 static unsigned int i_hash_shift __read_mostly;
 static struct hlist_head *inode_hashtable __read_mostly;
 static __cacheline_aligned_in_smp DEFINE_SPINLOCK(inode_hash_lock);
 
 /*
  * Empty aops. Can be used for the cases where the user does not
  * define any of the address_space operations.
  */
 const struct address_space_operations empty_aops = {
 };
 EXPORT_SYMBOL(empty_aops);
 
 static DEFINE_PER_CPU(unsigned long, nr_inodes);
 static DEFINE_PER_CPU(unsigned long, nr_unused);
 
 static struct kmem_cache *inode_cachep __read_mostly;
 
 static long get_nr_inodes(void)
 {
     int i;
     long sum = 0;
     for_each_possible_cpu(i)
         sum += per_cpu(nr_inodes, i);
     return sum < 0 ? 0 : sum;
 }
 
 static inline long get_nr_inodes_unused(void)
 {
     int i;
     long sum = 0;
     for_each_possible_cpu(i)
         sum += per_cpu(nr_unused, i);
     return sum < 0 ? 0 : sum;
 }
 
 long get_nr_dirty_inodes(void)
 {
     /* not actually dirty inodes, but a wild approximation */
     long nr_dirty = get_nr_inodes() - get_nr_inodes_unused();
     return nr_dirty > 0 ? nr_dirty : 0;
 }
 
 /*
  * Handle nr_inode sysctl
  */
 #ifdef CONFIG_SYSCTL
 /*
  * Statistics gathering..
  */
 static struct inodes_stat_t inodes_stat;
 
 static int proc_nr_inodes(struct ctl_table *table, int write, void *buffer,
               size_t *lenp, loff_t *ppos)
 {
     inodes_stat.nr_inodes = get_nr_inodes();
     inodes_stat.nr_unused = get_nr_inodes_unused();
     return proc_doulongvec_minmax(table, write, buffer, lenp, ppos);
 }
 
 static struct ctl_table inodes_sysctls[] = {
     {
         .procname   = "inode-nr",
         .data       = &inodes_stat,
         .maxlen     = 2*sizeof(long),
         .mode       = 0444,
         .proc_handler   = proc_nr_inodes,
     },
     {
         .procname   = "inode-state",
         .data       = &inodes_stat,
         .maxlen     = 7*sizeof(long),
         .mode       = 0444,
         .proc_handler   = proc_nr_inodes,
     },
     { }
 };
 
 static int __init init_fs_inode_sysctls(void)
 {
     register_sysctl_init("fs", inodes_sysctls);
     return 0;
 }
 early_initcall(init_fs_inode_sysctls);
 #endif
 
 static int no_open(struct inode *inode, struct file *file)
 {
     return -ENXIO;
 }
 
 /**
  * inode_init_always - perform inode structure initialisation
  * @sb: superblock inode belongs to
  * @inode: inode to initialise
  *
  * These are initializations that need to be done on every inode
  * allocation as the fields are not initialised by slab allocation.
  */
 int inode_init_always(struct super_block *sb, struct inode *inode)
 {
     static const struct inode_operations empty_iops;
     static const struct file_operations no_open_fops = {.open = no_open};
     struct address_space *const mapping = &inode->i_data;
 
     inode->i_sb = sb;
     inode->i_blkbits = sb->s_blocksize_bits;
     inode->i_flags = 0;
     atomic64_set(&inode->i_sequence, 0);
     atomic_set(&inode->i_count, 1);
     inode->i_op = &empty_iops;
     inode->i_fop = &no_open_fops;
     inode->i_ino = 0;
     inode->__i_nlink = 1;
     inode->i_opflags = 0;
     if (sb->s_xattr)
         inode->i_opflags |= IOP_XATTR;
     i_uid_write(inode, 0);
     i_gid_write(inode, 0);
     atomic_set(&inode->i_writecount, 0);
     inode->i_size = 0;
     inode->i_write_hint = WRITE_LIFE_NOT_SET;
     inode->i_blocks = 0;
     inode->i_bytes = 0;
     inode->i_generation = 0;
     inode->i_pipe = NULL;
     inode->i_cdev = NULL;
     inode->i_link = NULL;
     inode->i_dir_seq = 0;
     inode->i_rdev = 0;
     inode->dirtied_when = 0;
 
 #ifdef CONFIG_CGROUP_WRITEBACK
     inode->i_wb_frn_winner = 0;
     inode->i_wb_frn_avg_time = 0;
     inode->i_wb_frn_history = 0;
 #endif
 
     spin_lock_init(&inode->i_lock);
     lockdep_set_class(&inode->i_lock, &sb->s_type->i_lock_key);
 
     init_rwsem(&inode->i_rwsem);
     lockdep_set_class(&inode->i_rwsem, &sb->s_type->i_mutex_key);
 
     atomic_set(&inode->i_dio_count, 0);
 
     mapping->a_ops = &empty_aops;
     mapping->host = inode;
     mapping->flags = 0;
     mapping->wb_err = 0;
     atomic_set(&mapping->i_mmap_writable, 0);
 #ifdef CONFIG_READ_ONLY_THP_FOR_FS
     atomic_set(&mapping->nr_thps, 0);
 #endif
     mapping_set_gfp_mask(mapping, GFP_HIGHUSER_MOVABLE);
     mapping->private_data = NULL;
     mapping->writeback_index = 0;
     init_rwsem(&mapping->invalidate_lock);
     lockdep_set_class_and_name(&mapping->invalidate_lock,
                    &sb->s_type->invalidate_lock_key,
                    "mapping.invalidate_lock");
     inode->i_private = NULL;
     inode->i_mapping = mapping;
     INIT_HLIST_HEAD(&inode->i_dentry);  /* buggered by rcu freeing */
 #ifdef CONFIG_FS_POSIX_ACL
     inode->i_acl = inode->i_default_acl = ACL_NOT_CACHED;
 #endif
 
 #ifdef CONFIG_FSNOTIFY
     inode->i_fsnotify_mask = 0;
 #endif
     inode->i_flctx = NULL;
 
     if (unlikely(security_inode_alloc(inode)))
         return -ENOMEM;
     this_cpu_inc(nr_inodes);
 
     return 0;
 }
 EXPORT_SYMBOL(inode_init_always);
 
 void free_inode_nonrcu(struct inode *inode)
 {
     kmem_cache_free(inode_cachep, inode);
 }
 EXPORT_SYMBOL(free_inode_nonrcu);
 
 static void i_callback(struct rcu_head *head)
 {
     struct inode *inode = container_of(head, struct inode, i_rcu);
     if (inode->free_inode)
         inode->free_inode(inode);
     else
         free_inode_nonrcu(inode);
 }
 
 static struct inode *alloc_inode(struct super_block *sb)
 {
     const struct super_operations *ops = sb->s_op;
     struct inode *inode;
 
     if (ops->alloc_inode)
         inode = ops->alloc_inode(sb);
     else
         inode = alloc_inode_sb(sb, inode_cachep, GFP_KERNEL);
 
     if (!inode)
         return NULL;
 
     if (unlikely(inode_init_always(sb, inode))) {
         if (ops->destroy_inode) {
             ops->destroy_inode(inode);
             if (!ops->free_inode)
                 return NULL;
         }
         inode->free_inode = ops->free_inode;
         i_callback(&inode->i_rcu);
         return NULL;
     }
 
     return inode;
 }
 
 void __destroy_inode(struct inode *inode)
 {
     BUG_ON(inode_has_buffers(inode));
     inode_detach_wb(inode);
     security_inode_free(inode);
     fsnotify_inode_delete(inode);
     locks_free_lock_context(inode);
     if (!inode->i_nlink) {
         WARN_ON(atomic_long_read(&inode->i_sb->s_remove_count) == 0);
         atomic_long_dec(&inode->i_sb->s_remove_count);
     }
 
 #ifdef CONFIG_FS_POSIX_ACL
     if (inode->i_acl && !is_uncached_acl(inode->i_acl))
         posix_acl_release(inode->i_acl);
     if (inode->i_default_acl && !is_uncached_acl(inode->i_default_acl))
         posix_acl_release(inode->i_default_acl);
 #endif
     this_cpu_dec(nr_inodes);
 }
 EXPORT_SYMBOL(__destroy_inode);
 
 static void destroy_inode(struct inode *inode)
 {
     const struct super_operations *ops = inode->i_sb->s_op;
 
     BUG_ON(!list_empty(&inode->i_lru));
     __destroy_inode(inode);
     if (ops->destroy_inode) {
         ops->destroy_inode(inode);
         if (!ops->free_inode)
             return;
     }
     inode->free_inode = ops->free_inode;
     call_rcu(&inode->i_rcu, i_callback);
 }
 
 /**
  * drop_nlink - directly drop an inode's link count
  * @inode: inode
  *
  * This is a low-level filesystem helper to replace any
  * direct filesystem manipulation of i_nlink.  In cases
  * where we are attempting to track writes to the
  * filesystem, a decrement to zero means an imminent
  * write when the file is truncated and actually unlinked
  * on the filesystem.
  */
 void drop_nlink(struct inode *inode)
 {
     WARN_ON(inode->i_nlink == 0);
     inode->__i_nlink--;
     if (!inode->i_nlink)
         atomic_long_inc(&inode->i_sb->s_remove_count);
 }
 EXPORT_SYMBOL(drop_nlink);
 
 /**
  * clear_nlink - directly zero an inode's link count
  * @inode: inode
  *
  * This is a low-level filesystem helper to replace any
  * direct filesystem manipulation of i_nlink.  See
  * drop_nlink() for why we care about i_nlink hitting zero.
  */
 void clear_nlink(struct inode *inode)
 {
     if (inode->i_nlink) {
         inode->__i_nlink = 0;
         atomic_long_inc(&inode->i_sb->s_remove_count);
     }
 }
 EXPORT_SYMBOL(clear_nlink);
 
 /**
  * set_nlink - directly set an inode's link count
  * @inode: inode
  * @nlink: new nlink (should be non-zero)
  *
  * This is a low-level filesystem helper to replace any
  * direct filesystem manipulation of i_nlink.
  */
 void set_nlink(struct inode *inode, unsigned int nlink)
 {
     if (!nlink) {
         clear_nlink(inode);
     } else {
         /* Yes, some filesystems do change nlink from zero to one */
         if (inode->i_nlink == 0)
             atomic_long_dec(&inode->i_sb->s_remove_count);
 
         inode->__i_nlink = nlink;
     }
 }
 EXPORT_SYMBOL(set_nlink);
 
 /**
  * inc_nlink - directly increment an inode's link count
  * @inode: inode
  *
  * This is a low-level filesystem helper to replace any
  * direct filesystem manipulation of i_nlink.  Currently,
  * it is only here for parity with dec_nlink().
  */
 void inc_nlink(struct inode *inode)
 {
     if (unlikely(inode->i_nlink == 0)) {
         WARN_ON(!(inode->i_state & I_LINKABLE));
         atomic_long_dec(&inode->i_sb->s_remove_count);
     }
 
     inode->__i_nlink++;
 }
 EXPORT_SYMBOL(inc_nlink);
 
 static void __address_space_init_once(struct address_space *mapping)
 {
     xa_init_flags(&mapping->i_pages, XA_FLAGS_LOCK_IRQ | XA_FLAGS_ACCOUNT);
     init_rwsem(&mapping->i_mmap_rwsem);
     INIT_LIST_HEAD(&mapping->private_list);
     spin_lock_init(&mapping->private_lock);
     mapping->i_mmap = RB_ROOT_CACHED;
 }
 
 void address_space_init_once(struct address_space *mapping)
 {
     memset(mapping, 0, sizeof(*mapping));
     __address_space_init_once(mapping);
 }
 EXPORT_SYMBOL(address_space_init_once);
 
 /*
  * These are initializations that only need to be done
  * once, because the fields are idempotent across use
  * of the inode, so let the slab aware of that.
  */
 void inode_init_once(struct inode *inode)
 {
     memset(inode, 0, sizeof(*inode));
     INIT_HLIST_NODE(&inode->i_hash);
     INIT_LIST_HEAD(&inode->i_devices);
     INIT_LIST_HEAD(&inode->i_io_list);
     INIT_LIST_HEAD(&inode->i_wb_list);
     INIT_LIST_HEAD(&inode->i_lru);
     INIT_LIST_HEAD(&inode->i_sb_list);
     __address_space_init_once(&inode->i_data);
     i_size_ordered_init(inode);
 }
 EXPORT_SYMBOL(inode_init_once);
 
 static void init_once(void *foo)
 {
     struct inode *inode = (struct inode *) foo;
 
     inode_init_once(inode);
 }
 
 /*
  * inode->i_lock must be held
  */
 void __iget(struct inode *inode)
 {
     atomic_inc(&inode->i_count);
 }
 
 /*
  * get additional reference to inode; caller must already hold one.
  */
 void ihold(struct inode *inode)
 {
     WARN_ON(atomic_inc_return(&inode->i_count) < 2);
 }
 EXPORT_SYMBOL(ihold);
 
 static void __inode_add_lru(struct inode *inode, bool rotate)
 {
     if (inode->i_state & (I_DIRTY_ALL | I_SYNC | I_FREEING | I_WILL_FREE))
         return;
     if (atomic_read(&inode->i_count))
         return;
     if (!(inode->i_sb->s_flags & SB_ACTIVE))
         return;
     if (!mapping_shrinkable(&inode->i_data))
         return;
 
     if (list_lru_add(&inode->i_sb->s_inode_lru, &inode->i_lru))
         this_cpu_inc(nr_unused);
     else if (rotate)
         inode->i_state |= I_REFERENCED;
 }
 
 /*
  * Add inode to LRU if needed (inode is unused and clean).
  *
  * Needs inode->i_lock held.
  */
 void inode_add_lru(struct inode *inode)
 {
     __inode_add_lru(inode, false);
 }
 
 static void inode_lru_list_del(struct inode *inode)
 {
     if (list_lru_del(&inode->i_sb->s_inode_lru, &inode->i_lru))
         this_cpu_dec(nr_unused);
 }
 
 /**
  * inode_sb_list_add - add inode to the superblock list of inodes
  * @inode: inode to add
  */
 void inode_sb_list_add(struct inode *inode)
 {
     spin_lock(&inode->i_sb->s_inode_list_lock);
     list_add(&inode->i_sb_list, &inode->i_sb->s_inodes);
     spin_unlock(&inode->i_sb->s_inode_list_lock);
 }
 EXPORT_SYMBOL_GPL(inode_sb_list_add);
 
 static inline void inode_sb_list_del(struct inode *inode)
 {
     if (!list_empty(&inode->i_sb_list)) {
         spin_lock(&inode->i_sb->s_inode_list_lock);
         list_del_init(&inode->i_sb_list);
         spin_unlock(&inode->i_sb->s_inode_list_lock);
     }
 }
 
 static unsigned long hash(struct super_block *sb, unsigned long hashval)
 {
     unsigned long tmp;
 
     tmp = (hashval * (unsigned long)sb) ^ (GOLDEN_RATIO_PRIME + hashval) /
             L1_CACHE_BYTES;
     tmp = tmp ^ ((tmp ^ GOLDEN_RATIO_PRIME) >> i_hash_shift);
     return tmp & i_hash_mask;
 }
 
 /**
  *  __insert_inode_hash - hash an inode
  *  @inode: unhashed inode
  *  @hashval: unsigned long value used to locate this object in the
  *      inode_hashtable.
  *
  *  Add an inode to the inode hash for this superblock.
  */
 void __insert_inode_hash(struct inode *inode, unsigned long hashval)
 {
     struct hlist_head *b = inode_hashtable + hash(inode->i_sb, hashval);
 
     spin_lock(&inode_hash_lock);
     spin_lock(&inode->i_lock);
     hlist_add_head_rcu(&inode->i_hash, b);
     spin_unlock(&inode->i_lock);
     spin_unlock(&inode_hash_lock);
 }
 EXPORT_SYMBOL(__insert_inode_hash);
 
 /**
  *  __remove_inode_hash - remove an inode from the hash
  *  @inode: inode to unhash
  *
  *  Remove an inode from the superblock.
  */
 void __remove_inode_hash(struct inode *inode)
 {
     spin_lock(&inode_hash_lock);
     spin_lock(&inode->i_lock);
     hlist_del_init_rcu(&inode->i_hash);
     spin_unlock(&inode->i_lock);
     spin_unlock(&inode_hash_lock);
 }
 EXPORT_SYMBOL(__remove_inode_hash);
 
 void dump_mapping(const struct address_space *mapping)
 {
     struct inode *host;
     const struct address_space_operations *a_ops;
     struct hlist_node *dentry_first;
     struct dentry *dentry_ptr;
     struct dentry dentry;
     unsigned long ino;
 
     /*
      * If mapping is an invalid pointer, we don't want to crash
      * accessing it, so probe everything depending on it carefully.
      */
     if (get_kernel_nofault(host, &mapping->host) ||
         get_kernel_nofault(a_ops, &mapping->a_ops)) {
         pr_warn("invalid mapping:%px\n", mapping);
         return;
     }
 
     if (!host) {
         pr_warn("aops:%ps\n", a_ops);
         return;
     }
 
     if (get_kernel_nofault(dentry_first, &host->i_dentry.first) ||
         get_kernel_nofault(ino, &host->i_ino)) {
         pr_warn("aops:%ps invalid inode:%px\n", a_ops, host);
         return;
     }
 
     if (!dentry_first) {
         pr_warn("aops:%ps ino:%lx\n", a_ops, ino);
         return;
     }
 
     dentry_ptr = container_of(dentry_first, struct dentry, d_u.d_alias);
     if (get_kernel_nofault(dentry, dentry_ptr)) {
         pr_warn("aops:%ps ino:%lx invalid dentry:%px\n",
                 a_ops, ino, dentry_ptr);
         return;
     }
 
     /*
      * if dentry is corrupted, the %pd handler may still crash,
      * but it's unlikely that we reach here with a corrupt mapping
      */
     pr_warn("aops:%ps ino:%lx dentry name:\"%pd\"\n", a_ops, ino, &dentry);
 }
 
 void clear_inode(struct inode *inode)
 {
     /*
      * We have to cycle the i_pages lock here because reclaim can be in the
      * process of removing the last page (in __filemap_remove_folio())
      * and we must not free the mapping under it.
      */
     xa_lock_irq(&inode->i_data.i_pages);
     BUG_ON(inode->i_data.nrpages);
     /*
      * Almost always, mapping_empty(&inode->i_data) here; but there are
      * two known and long-standing ways in which nodes may get left behind
      * (when deep radix-tree node allocation failed partway; or when THP
      * collapse_file() failed). Until those two known cases are cleaned up,
      * or a cleanup function is called here, do not BUG_ON(!mapping_empty),
      * nor even WARN_ON(!mapping_empty).
      */
     xa_unlock_irq(&inode->i_data.i_pages);
     BUG_ON(!list_empty(&inode->i_data.private_list));
     BUG_ON(!(inode->i_state & I_FREEING));
     BUG_ON(inode->i_state & I_CLEAR);
     BUG_ON(!list_empty(&inode->i_wb_list));
     /* don't need i_lock here, no concurrent mods to i_state */
     inode->i_state = I_FREEING | I_CLEAR;
 }
 EXPORT_SYMBOL(clear_inode);
 
 /*
  * Free the inode passed in, removing it from the lists it is still connected
  * to. We remove any pages still attached to the inode and wait for any IO that
  * is still in progress before finally destroying the inode.
  *
  * An inode must already be marked I_FREEING so that we avoid the inode being
  * moved back onto lists if we race with other code that manipulates the lists
  * (e.g. writeback_single_inode). The caller is responsible for setting this.
  *
  * An inode must already be removed from the LRU list before being evicted from
  * the cache. This should occur atomically with setting the I_FREEING state
  * flag, so no inodes here should ever be on the LRU when being evicted.
  */
 static void evict(struct inode *inode)
 {
     const struct super_operations *op = inode->i_sb->s_op;
 
     BUG_ON(!(inode->i_state & I_FREEING));
     BUG_ON(!list_empty(&inode->i_lru));
 
     if (!list_empty(&inode->i_io_list))
         inode_io_list_del(inode);
 
     inode_sb_list_del(inode);
 
     /*
      * Wait for flusher thread to be done with the inode so that filesystem
      * does not start destroying it while writeback is still running. Since
      * the inode has I_FREEING set, flusher thread won't start new work on
      * the inode.  We just have to wait for running writeback to finish.
      */
     inode_wait_for_writeback(inode);
 
     if (op->evict_inode) {
         op->evict_inode(inode);
     } else {
         truncate_inode_pages_final(&inode->i_data);
         clear_inode(inode);
     }
     if (S_ISCHR(inode->i_mode) && inode->i_cdev)
         cd_forget(inode);
 
     remove_inode_hash(inode);
 
     spin_lock(&inode->i_lock);
     wake_up_bit(&inode->i_state, __I_NEW);
     BUG_ON(inode->i_state != (I_FREEING | I_CLEAR));
     spin_unlock(&inode->i_lock);
 
     destroy_inode(inode);
 }
 
 /*
  * dispose_list - dispose of the contents of a local list
  * @head: the head of the list to free
  *
  * Dispose-list gets a local list with local inodes in it, so it doesn't
  * need to worry about list corruption and SMP locks.
  */
 static void dispose_list(struct list_head *head)
 {
     while (!list_empty(head)) {
         struct inode *inode;
 
         inode = list_first_entry(head, struct inode, i_lru);
         list_del_init(&inode->i_lru);
 
         evict(inode);
         cond_resched();
     }
 }
 
 /**
  * evict_inodes - evict all evictable inodes for a superblock
  * @sb:     superblock to operate on
  *
  * Make sure that no inodes with zero refcount are retained.  This is
  * called by superblock shutdown after having SB_ACTIVE flag removed,
  * so any inode reaching zero refcount during or after that call will
  * be immediately evicted.
  */
 void evict_inodes(struct super_block *sb)
 {
     struct inode *inode, *next;
     LIST_HEAD(dispose);
 
 again:
     spin_lock(&sb->s_inode_list_lock);
     list_for_each_entry_safe(inode, next, &sb->s_inodes, i_sb_list) {
         if (atomic_read(&inode->i_count))
             continue;
 
         spin_lock(&inode->i_lock);
         if (inode->i_state & (I_NEW | I_FREEING | I_WILL_FREE)) {
             spin_unlock(&inode->i_lock);
             continue;
         }
 
         inode->i_state |= I_FREEING;
         inode_lru_list_del(inode);
         spin_unlock(&inode->i_lock);
         list_add(&inode->i_lru, &dispose);
 
         /*
          * We can have a ton of inodes to evict at unmount time given
          * enough memory, check to see if we need to go to sleep for a
          * bit so we don't livelock.
          */
         if (need_resched()) {
             spin_unlock(&sb->s_inode_list_lock);
             cond_resched();
             dispose_list(&dispose);
             goto again;
         }
     }
     spin_unlock(&sb->s_inode_list_lock);
 
     dispose_list(&dispose);
 }
 EXPORT_SYMBOL_GPL(evict_inodes);
 
 /**
  * invalidate_inodes    - attempt to free all inodes on a superblock
  * @sb:     superblock to operate on
  * @kill_dirty: flag to guide handling of dirty inodes
  *
  * Attempts to free all inodes for a given superblock.  If there were any
  * busy inodes return a non-zero value, else zero.
  * If @kill_dirty is set, discard dirty inodes too, otherwise treat
  * them as busy.
  */
 int invalidate_inodes(struct super_block *sb, bool kill_dirty)
 {
     int busy = 0;
     struct inode *inode, *next;
     LIST_HEAD(dispose);
 
 again:
     spin_lock(&sb->s_inode_list_lock);
     list_for_each_entry_safe(inode, next, &sb->s_inodes, i_sb_list) {
         spin_lock(&inode->i_lock);
         if (inode->i_state & (I_NEW | I_FREEING | I_WILL_FREE)) {
             spin_unlock(&inode->i_lock);
             continue;
         }
         if (inode->i_state & I_DIRTY_ALL && !kill_dirty) {
             spin_unlock(&inode->i_lock);
             busy = 1;
             continue;
         }
         if (atomic_read(&inode->i_count)) {
             spin_unlock(&inode->i_lock);
             busy = 1;
             continue;
         }
 
         inode->i_state |= I_FREEING;
         inode_lru_list_del(inode);
         spin_unlock(&inode->i_lock);
         list_add(&inode->i_lru, &dispose);
         if (need_resched()) {
             spin_unlock(&sb->s_inode_list_lock);
             cond_resched();
             dispose_list(&dispose);
             goto again;
         }
     }
     spin_unlock(&sb->s_inode_list_lock);
 
     dispose_list(&dispose);
 
     return busy;
 }
 
 /*
  * Isolate the inode from the LRU in preparation for freeing it.
  *
  * If the inode has the I_REFERENCED flag set, then it means that it has been
  * used recently - the flag is set in iput_final(). When we encounter such an
  * inode, clear the flag and move it to the back of the LRU so it gets another
  * pass through the LRU before it gets reclaimed. This is necessary because of
  * the fact we are doing lazy LRU updates to minimise lock contention so the
  * LRU does not have strict ordering. Hence we don't want to reclaim inodes
  * with this flag set because they are the inodes that are out of order.
  */
 static enum lru_status inode_lru_isolate(struct list_head *item,
         struct list_lru_one *lru, spinlock_t *lru_lock, void *arg)
 {
     struct list_head *freeable = arg;
     struct inode    *inode = container_of(item, struct inode, i_lru);
 
     /*
      * We are inverting the lru lock/inode->i_lock here, so use a
      * trylock. If we fail to get the lock, just skip it.
      */
     if (!spin_trylock(&inode->i_lock))
         return LRU_SKIP;
 
     /*
      * Inodes can get referenced, redirtied, or repopulated while
      * they're already on the LRU, and this can make them
      * unreclaimable for a while. Remove them lazily here; iput,
      * sync, or the last page cache deletion will requeue them.
      */
     if (atomic_read(&inode->i_count) ||
         (inode->i_state & ~I_REFERENCED) ||
         !mapping_shrinkable(&inode->i_data)) {
         list_lru_isolate(lru, &inode->i_lru);
         spin_unlock(&inode->i_lock);
         this_cpu_dec(nr_unused);
         return LRU_REMOVED;
     }
 
     /* Recently referenced inodes get one more pass */
     if (inode->i_state & I_REFERENCED) {
         inode->i_state &= ~I_REFERENCED;
         spin_unlock(&inode->i_lock);
         return LRU_ROTATE;
     }
 
     /*
      * On highmem systems, mapping_shrinkable() permits dropping
      * page cache in order to free up struct inodes: lowmem might
      * be under pressure before the cache inside the highmem zone.
      */
     if (inode_has_buffers(inode) || !mapping_empty(&inode->i_data)) {
         __iget(inode);
         spin_unlock(&inode->i_lock);
         spin_unlock(lru_lock);
         if (remove_inode_buffers(inode)) {
             unsigned long reap;
             reap = invalidate_mapping_pages(&inode->i_data, 0, -1);
             if (current_is_kswapd())
                 __count_vm_events(KSWAPD_INODESTEAL, reap);
             else
                 __count_vm_events(PGINODESTEAL, reap);
             if (current->reclaim_state)
                 current->reclaim_state->reclaimed_slab += reap;
         }
         iput(inode);
         spin_lock(lru_lock);
         return LRU_RETRY;
     }
 
     WARN_ON(inode->i_state & I_NEW);
     inode->i_state |= I_FREEING;
     list_lru_isolate_move(lru, &inode->i_lru, freeable);
     spin_unlock(&inode->i_lock);
 
     this_cpu_dec(nr_unused);
     return LRU_REMOVED;
 }
 
 /*
  * Walk the superblock inode LRU for freeable inodes and attempt to free them.
  * This is called from the superblock shrinker function with a number of inodes
  * to trim from the LRU. Inodes to be freed are moved to a temporary list and
  * then are freed outside inode_lock by dispose_list().
  */
 long prune_icache_sb(struct super_block *sb, struct shrink_control *sc)
 {
     LIST_HEAD(freeable);
     long freed;
 
     freed = list_lru_shrink_walk(&sb->s_inode_lru, sc,
                      inode_lru_isolate, &freeable);
     dispose_list(&freeable);
     return freed;
 }
 
 static void __wait_on_freeing_inode(struct inode *inode);
 /*
  * Called with the inode lock held.
  */
 static struct inode *find_inode(struct super_block *sb,
                 struct hlist_head *head,
                 int (*test)(struct inode *, void *),
                 void *data)
 {
     struct inode *inode = NULL;
 
 repeat:
     hlist_for_each_entry(inode, head, i_hash) {
         if (inode->i_sb != sb)
             continue;
         if (!test(inode, data))
             continue;
         spin_lock(&inode->i_lock);
         if (inode->i_state & (I_FREEING|I_WILL_FREE)) {
             __wait_on_freeing_inode(inode);
             goto repeat;
         }
         if (unlikely(inode->i_state & I_CREATING)) {
             spin_unlock(&inode->i_lock);
             return ERR_PTR(-ESTALE);
         }
         __iget(inode);
         spin_unlock(&inode->i_lock);
         return inode;
     }
     return NULL;
 }
 
 /*
  * find_inode_fast is the fast path version of find_inode, see the comment at
  * iget_locked for details.
  */
 static struct inode *find_inode_fast(struct super_block *sb,
                 struct hlist_head *head, unsigned long ino)
 {
     struct inode *inode = NULL;
 
 repeat:
     hlist_for_each_entry(inode, head, i_hash) {
         if (inode->i_ino != ino)
             continue;
         if (inode->i_sb != sb)
             continue;
         spin_lock(&inode->i_lock);
         if (inode->i_state & (I_FREEING|I_WILL_FREE)) {
             __wait_on_freeing_inode(inode);
             goto repeat;
         }
         if (unlikely(inode->i_state & I_CREATING)) {
             spin_unlock(&inode->i_lock);
             return ERR_PTR(-ESTALE);
         }
         __iget(inode);
         spin_unlock(&inode->i_lock);
         return inode;
     }
     return NULL;
 }
 
 /*
  * Each cpu owns a range of LAST_INO_BATCH numbers.
  * 'shared_last_ino' is dirtied only once out of LAST_INO_BATCH allocations,
  * to renew the exhausted range.
  *
  * This does not significantly increase overflow rate because every CPU can
  * consume at most LAST_INO_BATCH-1 unused inode numbers. So there is
  * NR_CPUS*(LAST_INO_BATCH-1) wastage. At 4096 and 1024, this is ~0.1% of the
  * 2^32 range, and is a worst-case. Even a 50% wastage would only increase
  * overflow rate by 2x, which does not seem too significant.
  *
  * On a 32bit, non LFS stat() call, glibc will generate an EOVERFLOW
  * error if st_ino won't fit in target struct field. Use 32bit counter
  * here to attempt to avoid that.
  */
 #define LAST_INO_BATCH 1024
 static DEFINE_PER_CPU(unsigned int, last_ino);
 
 unsigned int get_next_ino(void)
 {
     unsigned int *p = &get_cpu_var(last_ino);
     unsigned int res = *p;
 
 #ifdef CONFIG_SMP
     if (unlikely((res & (LAST_INO_BATCH-1)) == 0)) {
         static atomic_t shared_last_ino;
         int next = atomic_add_return(LAST_INO_BATCH, &shared_last_ino);
 
         res = next - LAST_INO_BATCH;
     }
 #endif
 
     res++;
     /* get_next_ino should not provide a 0 inode number */
     if (unlikely(!res))
         res++;
     *p = res;
     put_cpu_var(last_ino);
     return res;
 }
 EXPORT_SYMBOL(get_next_ino);
 
 /**
  *  new_inode_pseudo    - obtain an inode
  *  @sb: superblock
  *
  *  Allocates a new inode for given superblock.
  *  Inode wont be chained in superblock s_inodes list
  *  This means :
  *  - fs can't be unmount
  *  - quotas, fsnotify, writeback can't work
  */
 struct inode *new_inode_pseudo(struct super_block *sb)
 {
     struct inode *inode = alloc_inode(sb);
 
     if (inode) {
         spin_lock(&inode->i_lock);
         inode->i_state = 0;
         spin_unlock(&inode->i_lock);
     }
     return inode;
 }
 
 /**
  *  new_inode   - obtain an inode
  *  @sb: superblock
  *
  *  Allocates a new inode for given superblock. The default gfp_mask
  *  for allocations related to inode->i_mapping is GFP_HIGHUSER_MOVABLE.
  *  If HIGHMEM pages are unsuitable or it is known that pages allocated
  *  for the page cache are not reclaimable or migratable,
  *  mapping_set_gfp_mask() must be called with suitable flags on the
  *  newly created inode's mapping
  *
  */
 struct inode *new_inode(struct super_block *sb)
 {
     struct inode *inode;
 
     spin_lock_prefetch(&sb->s_inode_list_lock);
 
     inode = new_inode_pseudo(sb);
     if (inode)
         inode_sb_list_add(inode);
     return inode;
 }
 EXPORT_SYMBOL(new_inode);
 
 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 void lockdep_annotate_inode_mutex_key(struct inode *inode)
 {
     if (S_ISDIR(inode->i_mode)) {
         struct file_system_type *type = inode->i_sb->s_type;
 
         /* Set new key only if filesystem hasn't already changed it */
         if (lockdep_match_class(&inode->i_rwsem, &type->i_mutex_key)) {
             /*
              * ensure nobody is actually holding i_mutex
              */
             // mutex_destroy(&inode->i_mutex);
             init_rwsem(&inode->i_rwsem);
             lockdep_set_class(&inode->i_rwsem,
                       &type->i_mutex_dir_key);
         }
     }
 }
 EXPORT_SYMBOL(lockdep_annotate_inode_mutex_key);
 #endif
 
 /**
  * unlock_new_inode - clear the I_NEW state and wake up any waiters
  * @inode:  new inode to unlock
  *
  * Called when the inode is fully initialised to clear the new state of the
  * inode and wake up anyone waiting for the inode to finish initialisation.
  */
 void unlock_new_inode(struct inode *inode)
 {
     lockdep_annotate_inode_mutex_key(inode);
     spin_lock(&inode->i_lock);
     WARN_ON(!(inode->i_state & I_NEW));
     inode->i_state &= ~I_NEW & ~I_CREATING;
     smp_mb();
     wake_up_bit(&inode->i_state, __I_NEW);
     spin_unlock(&inode->i_lock);
 }
 EXPORT_SYMBOL(unlock_new_inode);
 
 void discard_new_inode(struct inode *inode)
 {
     lockdep_annotate_inode_mutex_key(inode);
     spin_lock(&inode->i_lock);
     WARN_ON(!(inode->i_state & I_NEW));
     inode->i_state &= ~I_NEW;
     smp_mb();
     wake_up_bit(&inode->i_state, __I_NEW);
     spin_unlock(&inode->i_lock);
     iput(inode);
 }
 EXPORT_SYMBOL(discard_new_inode);
 
 /**
  * lock_two_nondirectories - take two i_mutexes on non-directory objects
  *
  * Lock any non-NULL argument that is not a directory.
  * Zero, one or two objects may be locked by this function.
  *
  * @inode1: first inode to lock
  * @inode2: second inode to lock
  */
 void lock_two_nondirectories(struct inode *inode1, struct inode *inode2)
 {
     if (inode1 > inode2)
         swap(inode1, inode2);
 
     if (inode1 && !S_ISDIR(inode1->i_mode))
         inode_lock(inode1);
     if (inode2 && !S_ISDIR(inode2->i_mode) && inode2 != inode1)
         inode_lock_nested(inode2, I_MUTEX_NONDIR2);
 }
 EXPORT_SYMBOL(lock_two_nondirectories);
 
 /**
  * unlock_two_nondirectories - release locks from lock_two_nondirectories()
  * @inode1: first inode to unlock
  * @inode2: second inode to unlock
  */
 void unlock_two_nondirectories(struct inode *inode1, struct inode *inode2)
 {
     if (inode1 && !S_ISDIR(inode1->i_mode))
         inode_unlock(inode1);
     if (inode2 && !S_ISDIR(inode2->i_mode) && inode2 != inode1)
         inode_unlock(inode2);
 }
 EXPORT_SYMBOL(unlock_two_nondirectories);
 
 /**
  * inode_insert5 - obtain an inode from a mounted file system
  * @inode:  pre-allocated inode to use for insert to cache
  * @hashval:    hash value (usually inode number) to get
  * @test:   callback used for comparisons between inodes
  * @set:    callback used to initialize a new struct inode
  * @data:   opaque data pointer to pass to @test and @set
  *
  * Search for the inode specified by @hashval and @data in the inode cache,
  * and if present it is return it with an increased reference count. This is
  * a variant of iget5_locked() for callers that don't want to fail on memory
  * allocation of inode.
  *
  * If the inode is not in cache, insert the pre-allocated inode to cache and
  * return it locked, hashed, and with the I_NEW flag set. The file system gets
  * to fill it in before unlocking it via unlock_new_inode().
  *
  * Note both @test and @set are called with the inode_hash_lock held, so can't
  * sleep.
  */
 struct inode *inode_insert5(struct inode *inode, unsigned long hashval,
                 int (*test)(struct inode *, void *),
                 int (*set)(struct inode *, void *), void *data)
 {
     struct hlist_head *head = inode_hashtable + hash(inode->i_sb, hashval);
     struct inode *old;
 
 again:
     spin_lock(&inode_hash_lock);
     old = find_inode(inode->i_sb, head, test, data);
     if (unlikely(old)) {
         /*
          * Uhhuh, somebody else created the same inode under us.
          * Use the old inode instead of the preallocated one.
          */
         spin_unlock(&inode_hash_lock);
         if (IS_ERR(old))
             return NULL;
         wait_on_inode(old);
         if (unlikely(inode_unhashed(old))) {
             iput(old);
             goto again;
         }
         return old;
     }
 
     if (set && unlikely(set(inode, data))) {
         inode = NULL;
         goto unlock;
     }
 
     /*
      * Return the locked inode with I_NEW set, the
      * caller is responsible for filling in the contents
      */
     spin_lock(&inode->i_lock);
     inode->i_state |= I_NEW;
     hlist_add_head_rcu(&inode->i_hash, head);
     spin_unlock(&inode->i_lock);
 
     /*
      * Add inode to the sb list if it's not already. It has I_NEW at this
      * point, so it should be safe to test i_sb_list locklessly.
      */
     if (list_empty(&inode->i_sb_list))
         inode_sb_list_add(inode);
 unlock:
     spin_unlock(&inode_hash_lock);
 
     return inode;
 }
 EXPORT_SYMBOL(inode_insert5);
 
 /**
  * iget5_locked - obtain an inode from a mounted file system
  * @sb:     super block of file system
  * @hashval:    hash value (usually inode number) to get
  * @test:   callback used for comparisons between inodes
  * @set:    callback used to initialize a new struct inode
  * @data:   opaque data pointer to pass to @test and @set
  *
  * Search for the inode specified by @hashval and @data in the inode cache,
  * and if present it is return it with an increased reference count. This is
  * a generalized version of iget_locked() for file systems where the inode
  * number is not sufficient for unique identification of an inode.
  *
  * If the inode is not in cache, allocate a new inode and return it locked,
  * hashed, and with the I_NEW flag set. The file system gets to fill it in
  * before unlocking it via unlock_new_inode().
  *
  * Note both @test and @set are called with the inode_hash_lock held, so can't
  * sleep.
  */
 struct inode *iget5_locked(struct super_block *sb, unsigned long hashval,
         int (*test)(struct inode *, void *),
         int (*set)(struct inode *, void *), void *data)
 {
     struct inode *inode = ilookup5(sb, hashval, test, data);
 
     if (!inode) {
         struct inode *new = alloc_inode(sb);
 
         if (new) {
             new->i_state = 0;
             inode = inode_insert5(new, hashval, test, set, data);
             if (unlikely(inode != new))
                 destroy_inode(new);
         }
     }
     return inode;
 }
 EXPORT_SYMBOL(iget5_locked);
 
 /**
  * iget_locked - obtain an inode from a mounted file system
  * @sb:     super block of file system
  * @ino:    inode number to get
  *
  * Search for the inode specified by @ino in the inode cache and if present
  * return it with an increased reference count. This is for file systems
  * where the inode number is sufficient for unique identification of an inode.
  *
  * If the inode is not in cache, allocate a new inode and return it locked,
  * hashed, and with the I_NEW flag set.  The file system gets to fill it in
  * before unlocking it via unlock_new_inode().
  */
 struct inode *iget_locked(struct super_block *sb, unsigned long ino)
 {
     struct hlist_head *head = inode_hashtable + hash(sb, ino);
     struct inode *inode;
 again:
     spin_lock(&inode_hash_lock);
     inode = find_inode_fast(sb, head, ino);
     spin_unlock(&inode_hash_lock);
     if (inode) {
         if (IS_ERR(inode))
             return NULL;
         wait_on_inode(inode);
         if (unlikely(inode_unhashed(inode))) {
             iput(inode);
             goto again;
         }
         return inode;
     }
 
     inode = alloc_inode(sb);
     if (inode) {
         struct inode *old;
 
         spin_lock(&inode_hash_lock);
         /* We released the lock, so.. */
         old = find_inode_fast(sb, head, ino);
         if (!old) {
             inode->i_ino = ino;
             spin_lock(&inode->i_lock);
             inode->i_state = I_NEW;
             hlist_add_head_rcu(&inode->i_hash, head);
             spin_unlock(&inode->i_lock);
             inode_sb_list_add(inode);
             spin_unlock(&inode_hash_lock);
 
             /* Return the locked inode with I_NEW set, the
              * caller is responsible for filling in the contents
              */
             return inode;
         }
 
         /*
          * Uhhuh, somebody else created the same inode under
          * us. Use the old inode instead of the one we just
          * allocated.
          */
         spin_unlock(&inode_hash_lock);
         destroy_inode(inode);
         if (IS_ERR(old))
             return NULL;
         inode = old;
         wait_on_inode(inode);
         if (unlikely(inode_unhashed(inode))) {
             iput(inode);
             goto again;
         }
     }
     return inode;
 }
 EXPORT_SYMBOL(iget_locked);
 
 /*
  * search the inode cache for a matching inode number.
  * If we find one, then the inode number we are trying to
  * allocate is not unique and so we should not use it.
  *
  * Returns 1 if the inode number is unique, 0 if it is not.
  */
 static int test_inode_iunique(struct super_block *sb, unsigned long ino)
 {
     struct hlist_head *b = inode_hashtable + hash(sb, ino);
     struct inode *inode;
 
     hlist_for_each_entry_rcu(inode, b, i_hash) {
         if (inode->i_ino == ino && inode->i_sb == sb)
             return 0;
     }
     return 1;
 }
 
 /**
  *  iunique - get a unique inode number
  *  @sb: superblock
  *  @max_reserved: highest reserved inode number
  *
  *  Obtain an inode number that is unique on the system for a given
  *  superblock. This is used by file systems that have no natural
  *  permanent inode numbering system. An inode number is returned that
  *  is higher than the reserved limit but unique.
  *
  *  BUGS:
  *  With a large number of inodes live on the file system this function
  *  currently becomes quite slow.
  */
 ino_t iunique(struct super_block *sb, ino_t max_reserved)
 {
     /*
      * On a 32bit, non LFS stat() call, glibc will generate an EOVERFLOW
      * error if st_ino won't fit in target struct field. Use 32bit counter
      * here to attempt to avoid that.
      */
     static DEFINE_SPINLOCK(iunique_lock);
     static unsigned int counter;
     ino_t res;
 
     rcu_read_lock();
     spin_lock(&iunique_lock);
     do {
         if (counter <= max_reserved)
             counter = max_reserved + 1;
         res = counter++;
     } while (!test_inode_iunique(sb, res));
     spin_unlock(&iunique_lock);
     rcu_read_unlock();
 
     return res;
 }
 EXPORT_SYMBOL(iunique);
 
 struct inode *igrab(struct inode *inode)
 {
     spin_lock(&inode->i_lock);
     if (!(inode->i_state & (I_FREEING|I_WILL_FREE))) {
         __iget(inode);
         spin_unlock(&inode->i_lock);
     } else {
         spin_unlock(&inode->i_lock);
         /*
          * Handle the case where s_op->clear_inode is not been
          * called yet, and somebody is calling igrab
          * while the inode is getting freed.
          */
         inode = NULL;
     }
     return inode;
 }
 EXPORT_SYMBOL(igrab);
 
 /**
  * ilookup5_nowait - search for an inode in the inode cache
  * @sb:     super block of file system to search
  * @hashval:    hash value (usually inode number) to search for
  * @test:   callback used for comparisons between inodes
  * @data:   opaque data pointer to pass to @test
  *
  * Search for the inode specified by @hashval and @data in the inode cache.
  * If the inode is in the cache, the inode is returned with an incremented
  * reference count.
  *
  * Note: I_NEW is not waited upon so you have to be very careful what you do
  * with the returned inode.  You probably should be using ilookup5() instead.
  *
  * Note2: @test is called with the inode_hash_lock held, so can't sleep.
  */
 struct inode *ilookup5_nowait(struct super_block *sb, unsigned long hashval,
         int (*test)(struct inode *, void *), void *data)
 {
     struct hlist_head *head = inode_hashtable + hash(sb, hashval);
     struct inode *inode;
 
     spin_lock(&inode_hash_lock);
     inode = find_inode(sb, head, test, data);
     spin_unlock(&inode_hash_lock);
 
     return IS_ERR(inode) ? NULL : inode;
 }
 EXPORT_SYMBOL(ilookup5_nowait);
 
 /**
  * ilookup5 - search for an inode in the inode cache
  * @sb:     super block of file system to search
  * @hashval:    hash value (usually inode number) to search for
  * @test:   callback used for comparisons between inodes
  * @data:   opaque data pointer to pass to @test
  *
  * Search for the inode specified by @hashval and @data in the inode cache,
  * and if the inode is in the cache, return the inode with an incremented
  * reference count.  Waits on I_NEW before returning the inode.
  * returned with an incremented reference count.
  *
  * This is a generalized version of ilookup() for file systems where the
  * inode number is not sufficient for unique identification of an inode.
  *
  * Note: @test is called with the inode_hash_lock held, so can't sleep.
  */
 struct inode *ilookup5(struct super_block *sb, unsigned long hashval,
         int (*test)(struct inode *, void *), void *data)
 {
     struct inode *inode;
 again:
     inode = ilookup5_nowait(sb, hashval, test, data);
     if (inode) {
         wait_on_inode(inode);
         if (unlikely(inode_unhashed(inode))) {
             iput(inode);
             goto again;
         }
     }
     return inode;
 }
 EXPORT_SYMBOL(ilookup5);
 
 /**
  * ilookup - search for an inode in the inode cache
  * @sb:     super block of file system to search
  * @ino:    inode number to search for
  *
  * Search for the inode @ino in the inode cache, and if the inode is in the
  * cache, the inode is returned with an incremented reference count.
  */
 struct inode *ilookup(struct super_block *sb, unsigned long ino)
 {
     struct hlist_head *head = inode_hashtable + hash(sb, ino);
     struct inode *inode;
 again:
     spin_lock(&inode_hash_lock);
     inode = find_inode_fast(sb, head, ino);
     spin_unlock(&inode_hash_lock);
 
     if (inode) {
         if (IS_ERR(inode))
             return NULL;
         wait_on_inode(inode);
         if (unlikely(inode_unhashed(inode))) {
             iput(inode);
             goto again;
         }
     }
     return inode;
 }
 EXPORT_SYMBOL(ilookup);
 
 /**
  * find_inode_nowait - find an inode in the inode cache
  * @sb:     super block of file system to search
  * @hashval:    hash value (usually inode number) to search for
  * @match:  callback used for comparisons between inodes
  * @data:   opaque data pointer to pass to @match
  *
  * Search for the inode specified by @hashval and @data in the inode
  * cache, where the helper function @match will return 0 if the inode
  * does not match, 1 if the inode does match, and -1 if the search
  * should be stopped.  The @match function must be responsible for
  * taking the i_lock spin_lock and checking i_state for an inode being
  * freed or being initialized, and incrementing the reference count
  * before returning 1.  It also must not sleep, since it is called with
  * the inode_hash_lock spinlock held.
  *
  * This is a even more generalized version of ilookup5() when the
  * function must never block --- find_inode() can block in
  * __wait_on_freeing_inode() --- or when the caller can not increment
  * the reference count because the resulting iput() might cause an
  * inode eviction.  The tradeoff is that the @match funtion must be
  * very carefully implemented.
  */
 struct inode *find_inode_nowait(struct super_block *sb,
                 unsigned long hashval,
                 int (*match)(struct inode *, unsigned long,
                          void *),
                 void *data)
 {
     struct hlist_head *head = inode_hashtable + hash(sb, hashval);
     struct inode *inode, *ret_inode = NULL;
     int mval;
 
     spin_lock(&inode_hash_lock);
     hlist_for_each_entry(inode, head, i_hash) {
         if (inode->i_sb != sb)
             continue;
         mval = match(inode, hashval, data);
         if (mval == 0)
             continue;
         if (mval == 1)
             ret_inode = inode;
         goto out;
     }
 out:
     spin_unlock(&inode_hash_lock);
     return ret_inode;
 }
 EXPORT_SYMBOL(find_inode_nowait);
 
 /**
  * find_inode_rcu - find an inode in the inode cache
  * @sb:     Super block of file system to search
  * @hashval:    Key to hash
  * @test:   Function to test match on an inode
  * @data:   Data for test function
  *
  * Search for the inode specified by @hashval and @data in the inode cache,
  * where the helper function @test will return 0 if the inode does not match
  * and 1 if it does.  The @test function must be responsible for taking the
  * i_lock spin_lock and checking i_state for an inode being freed or being
  * initialized.
  *
  * If successful, this will return the inode for which the @test function
  * returned 1 and NULL otherwise.
  *
  * The @test function is not permitted to take a ref on any inode presented.
  * It is also not permitted to sleep.
  *
  * The caller must hold the RCU read lock.
  */
 struct inode *find_inode_rcu(struct super_block *sb, unsigned long hashval,
                  int (*test)(struct inode *, void *), void *data)
 {
     struct hlist_head *head = inode_hashtable + hash(sb, hashval);
     struct inode *inode;
 
     RCU_LOCKDEP_WARN(!rcu_read_lock_held(),
              "suspicious find_inode_rcu() usage");
 
     hlist_for_each_entry_rcu(inode, head, i_hash) {
         if (inode->i_sb == sb &&
             !(READ_ONCE(inode->i_state) & (I_FREEING | I_WILL_FREE)) &&
             test(inode, data))
             return inode;
     }
     return NULL;
 }
 EXPORT_SYMBOL(find_inode_rcu);
 
 /**
  * find_inode_by_ino_rcu - Find an inode in the inode cache
  * @sb:     Super block of file system to search
  * @ino:    The inode number to match
  *
  * Search for the inode specified by @hashval and @data in the inode cache,
  * where the helper function @test will return 0 if the inode does not match
  * and 1 if it does.  The @test function must be responsible for taking the
  * i_lock spin_lock and checking i_state for an inode being freed or being
  * initialized.
  *
  * If successful, this will return the inode for which the @test function
  * returned 1 and NULL otherwise.
  *
  * The @test function is not permitted to take a ref on any inode presented.
  * It is also not permitted to sleep.
  *
  * The caller must hold the RCU read lock.
  */
 struct inode *find_inode_by_ino_rcu(struct super_block *sb,
                     unsigned long ino)
 {
     struct hlist_head *head = inode_hashtable + hash(sb, ino);
     struct inode *inode;
 
     RCU_LOCKDEP_WARN(!rcu_read_lock_held(),
              "suspicious find_inode_by_ino_rcu() usage");
 
     hlist_for_each_entry_rcu(inode, head, i_hash) {
         if (inode->i_ino == ino &&
             inode->i_sb == sb &&
             !(READ_ONCE(inode->i_state) & (I_FREEING | I_WILL_FREE)))
             return inode;
     }
     return NULL;
 }
 EXPORT_SYMBOL(find_inode_by_ino_rcu);
 
 int insert_inode_locked(struct inode *inode)
 {
     struct super_block *sb = inode->i_sb;
     ino_t ino = inode->i_ino;
     struct hlist_head *head = inode_hashtable + hash(sb, ino);
 
     while (1) {
         struct inode *old = NULL;
         spin_lock(&inode_hash_lock);
         hlist_for_each_entry(old, head, i_hash) {
             if (old->i_ino != ino)
                 continue;
             if (old->i_sb != sb)
                 continue;
             spin_lock(&old->i_lock);
             if (old->i_state & (I_FREEING|I_WILL_FREE)) {
                 spin_unlock(&old->i_lock);
                 continue;
             }
             break;
         }
         if (likely(!old)) {
             spin_lock(&inode->i_lock);
             inode->i_state |= I_NEW | I_CREATING;
             hlist_add_head_rcu(&inode->i_hash, head);
             spin_unlock(&inode->i_lock);
             spin_unlock(&inode_hash_lock);
             return 0;
         }
         if (unlikely(old->i_state & I_CREATING)) {
             spin_unlock(&old->i_lock);
             spin_unlock(&inode_hash_lock);
             return -EBUSY;
         }
         __iget(old);
         spin_unlock(&old->i_lock);
         spin_unlock(&inode_hash_lock);
         wait_on_inode(old);
         if (unlikely(!inode_unhashed(old))) {
             iput(old);
             return -EBUSY;
         }
         iput(old);
     }
 }
 EXPORT_SYMBOL(insert_inode_locked);
 
 int insert_inode_locked4(struct inode *inode, unsigned long hashval,
         int (*test)(struct inode *, void *), void *data)
 {
     struct inode *old;
 
     inode->i_state |= I_CREATING;
     old = inode_insert5(inode, hashval, test, NULL, data);
 
     if (old != inode) {
         iput(old);
         return -EBUSY;
     }
     return 0;
 }
 EXPORT_SYMBOL(insert_inode_locked4);
 
 
 int generic_delete_inode(struct inode *inode)
 {
     return 1;
 }
 EXPORT_SYMBOL(generic_delete_inode);
 
 /*
  * Called when we're dropping the last reference
  * to an inode.
  *
  * Call the FS "drop_inode()" function, defaulting to
  * the legacy UNIX filesystem behaviour.  If it tells
  * us to evict inode, do so.  Otherwise, retain inode
  * in cache if fs is alive, sync and evict if fs is
  * shutting down.
  */
 static void iput_final(struct inode *inode)
 {
     struct super_block *sb = inode->i_sb;
     const struct super_operations *op = inode->i_sb->s_op;
     unsigned long state;
     int drop;
 
     WARN_ON(inode->i_state & I_NEW);
 
     if (op->drop_inode)
         drop = op->drop_inode(inode);
     else
         drop = generic_drop_inode(inode);
 
     if (!drop &&
         !(inode->i_state & I_DONTCACHE) &&
         (sb->s_flags & SB_ACTIVE)) {
         __inode_add_lru(inode, true);
         spin_unlock(&inode->i_lock);
         return;
     }
 
     state = inode->i_state;
     if (!drop) {
         WRITE_ONCE(inode->i_state, state | I_WILL_FREE);
         spin_unlock(&inode->i_lock);
 
         write_inode_now(inode, 1);
 
         spin_lock(&inode->i_lock);
         state = inode->i_state;
         WARN_ON(state & I_NEW);
         state &= ~I_WILL_FREE;
     }
 
     WRITE_ONCE(inode->i_state, state | I_FREEING);
     if (!list_empty(&inode->i_lru))
         inode_lru_list_del(inode);
     spin_unlock(&inode->i_lock);
 
     evict(inode);
 }
 
 /**
  *  iput    - put an inode
  *  @inode: inode to put
  *
  *  Puts an inode, dropping its usage count. If the inode use count hits
  *  zero, the inode is then freed and may also be destroyed.
  *
  *  Consequently, iput() can sleep.
  */
 void iput(struct inode *inode)
 {
     if (!inode)
         return;
     BUG_ON(inode->i_state & I_CLEAR);
 retry:
     if (atomic_dec_and_lock(&inode->i_count, &inode->i_lock)) {
         if (inode->i_nlink && (inode->i_state & I_DIRTY_TIME)) {
             atomic_inc(&inode->i_count);
             spin_unlock(&inode->i_lock);
             trace_writeback_lazytime_iput(inode);
             mark_inode_dirty_sync(inode);
             goto retry;
         }
         iput_final(inode);
     }
 }
 EXPORT_SYMBOL(iput);
 
 #ifdef CONFIG_BLOCK
 /**
  *  bmap    - find a block number in a file
  *  @inode:  inode owning the block number being requested
  *  @block: pointer containing the block to find
  *
  *  Replaces the value in ``*block`` with the block number on the device holding
  *  corresponding to the requested block number in the file.
  *  That is, asked for block 4 of inode 1 the function will replace the
  *  4 in ``*block``, with disk block relative to the disk start that holds that
  *  block of the file.
  *
  *  Returns -EINVAL in case of error, 0 otherwise. If mapping falls into a
  *  hole, returns 0 and ``*block`` is also set to 0.
  */
 int bmap(struct inode *inode, sector_t *block)
 {
     if (!inode->i_mapping->a_ops->bmap)
         return -EINVAL;
 
     *block = inode->i_mapping->a_ops->bmap(inode->i_mapping, *block);
     return 0;
 }
 EXPORT_SYMBOL(bmap);
 #endif
 
 /*
  * With relative atime, only update atime if the previous atime is
  * earlier than either the ctime or mtime or if at least a day has
  * passed since the last atime update.
  */
 static int relatime_need_update(struct vfsmount *mnt, struct inode *inode,
                  struct timespec64 now)
 {
 
     if (!(mnt->mnt_flags & MNT_RELATIME))
         return 1;
     /*
      * Is mtime younger than atime? If yes, update atime:
      */
     if (timespec64_compare(&inode->i_mtime, &inode->i_atime) >= 0)
         return 1;
     /*
      * Is ctime younger than atime? If yes, update atime:
      */
     if (timespec64_compare(&inode->i_ctime, &inode->i_atime) >= 0)
         return 1;
 
     /*
      * Is the previous atime value older than a day? If yes,
      * update atime:
      */
     if ((long)(now.tv_sec - inode->i_atime.tv_sec) >= 24*60*60)
         return 1;
     /*
      * Good, we can skip the atime update:
      */
     return 0;
 }
 
 int generic_update_time(struct inode *inode, struct timespec64 *time, int flags)
 {
     int dirty_flags = 0;
 
     if (flags & (S_ATIME | S_CTIME | S_MTIME)) {
         if (flags & S_ATIME)
             inode->i_atime = *time;
         if (flags & S_CTIME)
             inode->i_ctime = *time;
         if (flags & S_MTIME)
             inode->i_mtime = *time;
 
         if (inode->i_sb->s_flags & SB_LAZYTIME)
             dirty_flags |= I_DIRTY_TIME;
         else
             dirty_flags |= I_DIRTY_SYNC;
     }
 
     if ((flags & S_VERSION) && inode_maybe_inc_iversion(inode, false))
         dirty_flags |= I_DIRTY_SYNC;
 
     __mark_inode_dirty(inode, dirty_flags);
     return 0;
 }
 EXPORT_SYMBOL(generic_update_time);
 
 /*
  * This does the actual work of updating an inodes time or version.  Must have
  * had called mnt_want_write() before calling this.
  */
 int inode_update_time(struct inode *inode, struct timespec64 *time, int flags)
 {
     if (inode->i_op->update_time)
         return inode->i_op->update_time(inode, time, flags);
     return generic_update_time(inode, time, flags);
 }
 EXPORT_SYMBOL(inode_update_time);
 
 /**
  *  atime_needs_update  -   update the access time
  *  @path: the &struct path to update
  *  @inode: inode to update
  *
  *  Update the accessed time on an inode and mark it for writeback.
  *  This function automatically handles read only file systems and media,
  *  as well as the "noatime" flag and inode specific "noatime" markers.
  */
 bool atime_needs_update(const struct path *path, struct inode *inode)
 {
     struct vfsmount *mnt = path->mnt;
     struct timespec64 now;
 
     if (inode->i_flags & S_NOATIME)
         return false;
 
     /* Atime updates will likely cause i_uid and i_gid to be written
      * back improprely if their true value is unknown to the vfs.
      */
     if (HAS_UNMAPPED_ID(mnt_user_ns(mnt), inode))
         return false;
 
     if (IS_NOATIME(inode))
         return false;
     if ((inode->i_sb->s_flags & SB_NODIRATIME) && S_ISDIR(inode->i_mode))
         return false;
 
     if (mnt->mnt_flags & MNT_NOATIME)
         return false;
     if ((mnt->mnt_flags & MNT_NODIRATIME) && S_ISDIR(inode->i_mode))
         return false;
 
     now = current_time(inode);
 
     if (!relatime_need_update(mnt, inode, now))
         return false;
 
     if (timespec64_equal(&inode->i_atime, &now))
         return false;
 
     return true;
 }
 
 void touch_atime(const struct path *path)
 {
     struct vfsmount *mnt = path->mnt;
     struct inode *inode = d_inode(path->dentry);
     struct timespec64 now;
 
     if (!atime_needs_update(path, inode))
         return;
 
     if (!sb_start_write_trylock(inode->i_sb))
         return;
 
     if (__mnt_want_write(mnt) != 0)
         goto skip_update;
     /*
      * File systems can error out when updating inodes if they need to
      * allocate new space to modify an inode (such is the case for
      * Btrfs), but since we touch atime while walking down the path we
      * really don't care if we failed to update the atime of the file,
      * so just ignore the return value.
      * We may also fail on filesystems that have the ability to make parts
      * of the fs read only, e.g. subvolumes in Btrfs.
      */
     now = current_time(inode);
     inode_update_time(inode, &now, S_ATIME);
     __mnt_drop_write(mnt);
 skip_update:
     sb_end_write(inode->i_sb);
 }
 EXPORT_SYMBOL(touch_atime);
 
 /*
  * The logic we want is
  *
  *  if suid or (sgid and xgrp)
  *      remove privs
  */
 int should_remove_suid(struct dentry *dentry)
 {
     umode_t mode = d_inode(dentry)->i_mode;
     int kill = 0;
 
     /* suid always must be killed */
     if (unlikely(mode & S_ISUID))
         kill = ATTR_KILL_SUID;
 
     /*
      * sgid without any exec bits is just a mandatory locking mark; leave
      * it alone.  If some exec bits are set, it's a real sgid; kill it.
      */
     if (unlikely((mode & S_ISGID) && (mode & S_IXGRP)))
         kill |= ATTR_KILL_SGID;
 
     if (unlikely(kill && !capable(CAP_FSETID) && S_ISREG(mode)))
         return kill;
 
     return 0;
 }
 EXPORT_SYMBOL(should_remove_suid);
 
 /*
  * Return mask of changes for notify_change() that need to be done as a
  * response to write or truncate. Return 0 if nothing has to be changed.
  * Negative value on error (change should be denied).
  */
 int dentry_needs_remove_privs(struct dentry *dentry)
 {
     struct inode *inode = d_inode(dentry);
     int mask = 0;
     int ret;
 
     if (IS_NOSEC(inode))
         return 0;
 
     mask = should_remove_suid(dentry);
     ret = security_inode_need_killpriv(dentry);
     if (ret < 0)
         return ret;
     if (ret)
         mask |= ATTR_KILL_PRIV;
     return mask;
 }
 
 static int __remove_privs(struct user_namespace *mnt_userns,
               struct dentry *dentry, int kill)
 {
     struct iattr newattrs;
 
     newattrs.ia_valid = ATTR_FORCE | kill;
     /*
      * Note we call this on write, so notify_change will not
      * encounter any conflicting delegations:
      */
     return notify_change(mnt_userns, dentry, &newattrs, NULL);
 }
 
 static int __file_remove_privs(struct file *file, unsigned int flags)
 {
     struct dentry *dentry = file_dentry(file);
     struct inode *inode = file_inode(file);
     int error = 0;
     int kill;
 
     if (IS_NOSEC(inode) || !S_ISREG(inode->i_mode))
         return 0;
 
     kill = dentry_needs_remove_privs(dentry);
     if (kill < 0)
         return kill;
 
     if (kill) {
         if (flags & IOCB_NOWAIT)
             return -EAGAIN;
 
         error = __remove_privs(file_mnt_user_ns(file), dentry, kill);
     }
 
     if (!error)
         inode_has_no_xattr(inode);
     return error;
 }
 
 /**
  * file_remove_privs - remove special file privileges (suid, capabilities)
  * @file: file to remove privileges from
  *
  * When file is modified by a write or truncation ensure that special
  * file privileges are removed.
  *
  * Return: 0 on success, negative errno on failure.
  */
 int file_remove_privs(struct file *file)
 {
     return __file_remove_privs(file, 0);
 }
 EXPORT_SYMBOL(file_remove_privs);
 
 static int inode_needs_update_time(struct inode *inode, struct timespec64 *now)
 {
     int sync_it = 0;
 
     /* First try to exhaust all avenues to not sync */
     if (IS_NOCMTIME(inode))
         return 0;
 
     if (!timespec64_equal(&inode->i_mtime, now))
         sync_it = S_MTIME;
 
     if (!timespec64_equal(&inode->i_ctime, now))
         sync_it |= S_CTIME;
 
     if (IS_I_VERSION(inode) && inode_iversion_need_inc(inode))
         sync_it |= S_VERSION;
 
     if (!sync_it)
         return 0;
 
     return sync_it;
 }
 
 static int __file_update_time(struct file *file, struct timespec64 *now,
             int sync_mode)
 {
     int ret = 0;
     struct inode *inode = file_inode(file);
 
     /* try to update time settings */
     if (!__mnt_want_write_file(file)) {
         ret = inode_update_time(inode, now, sync_mode);
         __mnt_drop_write_file(file);
     }
 
     return ret;
 }
 
 /**
  * file_update_time - update mtime and ctime time
  * @file: file accessed
  *
  * Update the mtime and ctime members of an inode and mark the inode for
  * writeback. Note that this function is meant exclusively for usage in
  * the file write path of filesystems, and filesystems may choose to
  * explicitly ignore updates via this function with the _NOCMTIME inode
  * flag, e.g. for network filesystem where these imestamps are handled
  * by the server. This can return an error for file systems who need to
  * allocate space in order to update an inode.
  *
  * Return: 0 on success, negative errno on failure.
  */
 int file_update_time(struct file *file)
 {
     int ret;
     struct inode *inode = file_inode(file);
     struct timespec64 now = current_time(inode);
 
     ret = inode_needs_update_time(inode, &now);
     if (ret <= 0)
         return ret;
 
     return __file_update_time(file, &now, ret);
 }
 EXPORT_SYMBOL(file_update_time);
 
 /**
  * file_modified_flags - handle mandated vfs changes when modifying a file
  * @file: file that was modified
  * @flags: kiocb flags
  *
  * When file has been modified ensure that special
  * file privileges are removed and time settings are updated.
  *
  * If IOCB_NOWAIT is set, special file privileges will not be removed and
  * time settings will not be updated. It will return -EAGAIN.
  *
  * Context: Caller must hold the file's inode lock.
  *
  * Return: 0 on success, negative errno on failure.
  */
 static int file_modified_flags(struct file *file, int flags)
 {
     int ret;
     struct inode *inode = file_inode(file);
     struct timespec64 now = current_time(inode);
 
     /*
      * Clear the security bits if the process is not being run by root.
      * This keeps people from modifying setuid and setgid binaries.
      */
     ret = __file_remove_privs(file, flags);
     if (ret)
         return ret;
 
     if (unlikely(file->f_mode & FMODE_NOCMTIME))
         return 0;
 
     ret = inode_needs_update_time(inode, &now);
     if (ret <= 0)
         return ret;
     if (flags & IOCB_NOWAIT)
         return -EAGAIN;
 
     return __file_update_time(file, &now, ret);
 }
 
 /**
  * file_modified - handle mandated vfs changes when modifying a file
  * @file: file that was modified
  *
  * When file has been modified ensure that special
  * file privileges are removed and time settings are updated.
  *
  * Context: Caller must hold the file's inode lock.
  *
  * Return: 0 on success, negative errno on failure.
  */
 int file_modified(struct file *file)
 {
     return file_modified_flags(file, 0);
 }
 EXPORT_SYMBOL(file_modified);
 
 /**
  * kiocb_modified - handle mandated vfs changes when modifying a file
  * @iocb: iocb that was modified
  *
  * When file has been modified ensure that special
  * file privileges are removed and time settings are updated.
  *
  * Context: Caller must hold the file's inode lock.
  *
  * Return: 0 on success, negative errno on failure.
  */
 int kiocb_modified(struct kiocb *iocb)
 {
     return file_modified_flags(iocb->ki_filp, iocb->ki_flags);
 }
 EXPORT_SYMBOL_GPL(kiocb_modified);
 
 int inode_needs_sync(struct inode *inode)
 {
     if (IS_SYNC(inode))
         return 1;
     if (S_ISDIR(inode->i_mode) && IS_DIRSYNC(inode))
         return 1;
     return 0;
 }
 EXPORT_SYMBOL(inode_needs_sync);
 
 /*
  * If we try to find an inode in the inode hash while it is being
  * deleted, we have to wait until the filesystem completes its
  * deletion before reporting that it isn't found.  This function waits
  * until the deletion _might_ have completed.  Callers are responsible
  * to recheck inode state.
  *
  * It doesn't matter if I_NEW is not set initially, a call to
  * wake_up_bit(&inode->i_state, __I_NEW) after removing from the hash list
  * will DTRT.
  */
 static void __wait_on_freeing_inode(struct inode *inode)
 {
     wait_queue_head_t *wq;
     DEFINE_WAIT_BIT(wait, &inode->i_state, __I_NEW);
     wq = bit_waitqueue(&inode->i_state, __I_NEW);
     prepare_to_wait(wq, &wait.wq_entry, TASK_UNINTERRUPTIBLE);
     spin_unlock(&inode->i_lock);
     spin_unlock(&inode_hash_lock);
     schedule();
     finish_wait(wq, &wait.wq_entry);
     spin_lock(&inode_hash_lock);
 }
 
 static __initdata unsigned long ihash_entries;
 static int __init set_ihash_entries(char *str)
 {
     if (!str)
         return 0;
     ihash_entries = simple_strtoul(str, &str, 0);
     return 1;
 }
 __setup("ihash_entries=", set_ihash_entries);
 
 /*
  * Initialize the waitqueues and inode hash table.
  */
 void __init inode_init_early(void)
 {
     /* If hashes are distributed across NUMA nodes, defer
      * hash allocation until vmalloc space is available.
      */
     if (hashdist)
         return;
 
     inode_hashtable =
         alloc_large_system_hash("Inode-cache",
                     sizeof(struct hlist_head),
                     ihash_entries,
                     14,
                     HASH_EARLY | HASH_ZERO,
                     &i_hash_shift,
                     &i_hash_mask,
                     0,
                     0);
 }
 
 void __init inode_init(void)
 {
     /* inode slab cache */
     inode_cachep = kmem_cache_create("inode_cache",
                      sizeof(struct inode),
                      0,
                      (SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|
                      SLAB_MEM_SPREAD|SLAB_ACCOUNT),
                      init_once);
 
     /* Hash may have been set up in inode_init_early */
     if (!hashdist)
         return;
 
     inode_hashtable =
         alloc_large_system_hash("Inode-cache",
                     sizeof(struct hlist_head),
                     ihash_entries,
                     14,
                     HASH_ZERO,
                     &i_hash_shift,
                     &i_hash_mask,
                     0,
                     0);
 }
 
 void init_special_inode(struct inode *inode, umode_t mode, dev_t rdev)
 {
     inode->i_mode = mode;
     if (S_ISCHR(mode)) {
         inode->i_fop = &def_chr_fops;
         inode->i_rdev = rdev;
     } else if (S_ISBLK(mode)) {
         inode->i_fop = &def_blk_fops;
         inode->i_rdev = rdev;
     } else if (S_ISFIFO(mode))
         inode->i_fop = &pipefifo_fops;
     else if (S_ISSOCK(mode))
         ;   /* leave it no_open_fops */
     else
         printk(KERN_DEBUG "init_special_inode: bogus i_mode (%o) for"
                   " inode %s:%lu\n", mode, inode->i_sb->s_id,
                   inode->i_ino);
 }
 EXPORT_SYMBOL(init_special_inode);
 
 /**
  * inode_init_owner - Init uid,gid,mode for new inode according to posix standards
  * @mnt_userns: User namespace of the mount the inode was created from
  * @inode: New inode
  * @dir: Directory inode
  * @mode: mode of the new inode
  *
  * If the inode has been created through an idmapped mount the user namespace of
  * the vfsmount must be passed through @mnt_userns. This function will then take
  * care to map the inode according to @mnt_userns before checking permissions
  * and initializing i_uid and i_gid. On non-idmapped mounts or if permission
  * checking is to be performed on the raw inode simply passs init_user_ns.
  */
 void inode_init_owner(struct user_namespace *mnt_userns, struct inode *inode,
               const struct inode *dir, umode_t mode)
 {
     inode_fsuid_set(inode, mnt_userns);
     if (dir && dir->i_mode & S_ISGID) {
         inode->i_gid = dir->i_gid;
 
         /* Directories are special, and always inherit S_ISGID */
         if (S_ISDIR(mode))
             mode |= S_ISGID;
     } else
         inode_fsgid_set(inode, mnt_userns);
     inode->i_mode = mode;
 }
 EXPORT_SYMBOL(inode_init_owner);
 
 /**
  * inode_owner_or_capable - check current task permissions to inode
  * @mnt_userns: user namespace of the mount the inode was found from
  * @inode: inode being checked
  *
  * Return true if current either has CAP_FOWNER in a namespace with the
  * inode owner uid mapped, or owns the file.
  *
  * If the inode has been found through an idmapped mount the user namespace of
  * the vfsmount must be passed through @mnt_userns. This function will then take
  * care to map the inode according to @mnt_userns before checking permissions.
  * On non-idmapped mounts or if permission checking is to be performed on the
  * raw inode simply passs init_user_ns.
  */
 bool inode_owner_or_capable(struct user_namespace *mnt_userns,
                 const struct inode *inode)
 {
     kuid_t i_uid;
     struct user_namespace *ns;
 
     i_uid = i_uid_into_mnt(mnt_userns, inode);
     if (uid_eq(current_fsuid(), i_uid))
         return true;
 
     ns = current_user_ns();
     if (kuid_has_mapping(ns, i_uid) && ns_capable(ns, CAP_FOWNER))
         return true;
     return false;
 }
 EXPORT_SYMBOL(inode_owner_or_capable);
 
 /*
  * Direct i/o helper functions
  */
 static void __inode_dio_wait(struct inode *inode)
 {
     wait_queue_head_t *wq = bit_waitqueue(&inode->i_state, __I_DIO_WAKEUP);
     DEFINE_WAIT_BIT(q, &inode->i_state, __I_DIO_WAKEUP);
 
     do {
         prepare_to_wait(wq, &q.wq_entry, TASK_UNINTERRUPTIBLE);
         if (atomic_read(&inode->i_dio_count))
             schedule();
     } while (atomic_read(&inode->i_dio_count));
     finish_wait(wq, &q.wq_entry);
 }
 
 /**
  * inode_dio_wait - wait for outstanding DIO requests to finish
  * @inode: inode to wait for
  *
  * Waits for all pending direct I/O requests to finish so that we can
  * proceed with a truncate or equivalent operation.
  *
  * Must be called under a lock that serializes taking new references
  * to i_dio_count, usually by inode->i_mutex.
  */
 void inode_dio_wait(struct inode *inode)
 {
     if (atomic_read(&inode->i_dio_count))
         __inode_dio_wait(inode);
 }
 EXPORT_SYMBOL(inode_dio_wait);
 
 /*
  * inode_set_flags - atomically set some inode flags
  *
  * Note: the caller should be holding i_mutex, or else be sure that
  * they have exclusive access to the inode structure (i.e., while the
  * inode is being instantiated).  The reason for the cmpxchg() loop
  * --- which wouldn't be necessary if all code paths which modify
  * i_flags actually followed this rule, is that there is at least one
  * code path which doesn't today so we use cmpxchg() out of an abundance
  * of caution.
  *
  * In the long run, i_mutex is overkill, and we should probably look
  * at using the i_lock spinlock to protect i_flags, and then make sure
  * it is so documented in include/linux/fs.h and that all code follows
  * the locking convention!!
  */
 void inode_set_flags(struct inode *inode, unsigned int flags,
              unsigned int mask)
 {
     WARN_ON_ONCE(flags & ~mask);
     set_mask_bits(&inode->i_flags, mask, flags);
 }
 EXPORT_SYMBOL(inode_set_flags);
 
 void inode_nohighmem(struct inode *inode)
 {
     mapping_set_gfp_mask(inode->i_mapping, GFP_USER);
 }
 EXPORT_SYMBOL(inode_nohighmem);
 
 /**
  * timestamp_truncate - Truncate timespec to a granularity
  * @t: Timespec
  * @inode: inode being updated
  *
  * Truncate a timespec to the granularity supported by the fs
  * containing the inode. Always rounds down. gran must
  * not be 0 nor greater than a second (NSEC_PER_SEC, or 10^9 ns).
  */
 struct timespec64 timestamp_truncate(struct timespec64 t, struct inode *inode)
 {
     struct super_block *sb = inode->i_sb;
     unsigned int gran = sb->s_time_gran;
 
     t.tv_sec = clamp(t.tv_sec, sb->s_time_min, sb->s_time_max);
     if (unlikely(t.tv_sec == sb->s_time_max || t.tv_sec == sb->s_time_min))
         t.tv_nsec = 0;
 
     /* Avoid division in the common cases 1 ns and 1 s. */
     if (gran == 1)
         ; /* nothing */
     else if (gran == NSEC_PER_SEC)
         t.tv_nsec = 0;
     else if (gran > 1 && gran < NSEC_PER_SEC)
         t.tv_nsec -= t.tv_nsec % gran;
     else
         WARN(1, "invalid file time granularity: %u", gran);
     return t;
 }
 EXPORT_SYMBOL(timestamp_truncate);
 
 /**
  * current_time - Return FS time
  * @inode: inode.
  *
  * Return the current time truncated to the time granularity supported by
  * the fs.
  *
  * Note that inode and inode->sb cannot be NULL.
  * Otherwise, the function warns and returns time without truncation.
  */
 struct timespec64 current_time(struct inode *inode)
 {
     struct timespec64 now;
 
     ktime_get_coarse_real_ts64(&now);
 
     if (unlikely(!inode->i_sb)) {
         WARN(1, "current_time() called with uninitialized super_block in the inode");
         return now;
     }
 
     return timestamp_truncate(now, inode);
 }
 EXPORT_SYMBOL(current_time);
 
 /**
  * mode_strip_sgid - handle the sgid bit for non-directories
  * @mnt_userns: User namespace of the mount the inode was created from
  * @dir: parent directory inode
  * @mode: mode of the file to be created in @dir
  *
  * If the @mode of the new file has both the S_ISGID and S_IXGRP bit
  * raised and @dir has the S_ISGID bit raised ensure that the caller is
  * either in the group of the parent directory or they have CAP_FSETID
  * in their user namespace and are privileged over the parent directory.
  * In all other cases, strip the S_ISGID bit from @mode.
  *
  * Return: the new mode to use for the file
  */
 umode_t mode_strip_sgid(struct user_namespace *mnt_userns,
             const struct inode *dir, umode_t mode)
 {
     if ((mode & (S_ISGID | S_IXGRP)) != (S_ISGID | S_IXGRP))
         return mode;
     if (S_ISDIR(mode) || !dir || !(dir->i_mode & S_ISGID))
         return mode;
     if (in_group_p(i_gid_into_mnt(mnt_userns, dir)))
         return mode;
     if (capable_wrt_inode_uidgid(mnt_userns, dir, CAP_FSETID))
         return mode;
 
     return mode & ~S_ISGID;
 }
 EXPORT_SYMBOL(mode_strip_sgid);

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