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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

 /*
  * Open file cache.
  *
  * (c) 2015 - Jeff Layton <jeff.layton@primarydata.com>
  */
 
 #include <linux/hash.h>
 #include <linux/slab.h>
 #include <linux/file.h>
 #include <linux/pagemap.h>
 #include <linux/sched.h>
 #include <linux/list_lru.h>
 #include <linux/fsnotify_backend.h>
 #include <linux/fsnotify.h>
 #include <linux/seq_file.h>
 #include <linux/rhashtable.h>
 
 #include "vfs.h"
 #include "nfsd.h"
 #include "nfsfh.h"
 #include "netns.h"
 #include "filecache.h"
 #include "trace.h"
 
 #define NFSD_LAUNDRETTE_DELAY            (2 * HZ)
 
 #define NFSD_FILE_CACHE_UP           (0)
 
 /* We only care about NFSD_MAY_READ/WRITE for this cache */
 #define NFSD_FILE_MAY_MASK  (NFSD_MAY_READ|NFSD_MAY_WRITE)
 
 static DEFINE_PER_CPU(unsigned long, nfsd_file_cache_hits);
 static DEFINE_PER_CPU(unsigned long, nfsd_file_acquisitions);
 static DEFINE_PER_CPU(unsigned long, nfsd_file_releases);
 static DEFINE_PER_CPU(unsigned long, nfsd_file_total_age);
 static DEFINE_PER_CPU(unsigned long, nfsd_file_pages_flushed);
 static DEFINE_PER_CPU(unsigned long, nfsd_file_evictions);
 
 struct nfsd_fcache_disposal {
     struct work_struct work;
     spinlock_t lock;
     struct list_head freeme;
 };
 
 static struct workqueue_struct *nfsd_filecache_wq __read_mostly;
 
 static struct kmem_cache        *nfsd_file_slab;
 static struct kmem_cache        *nfsd_file_mark_slab;
 static struct list_lru          nfsd_file_lru;
 static unsigned long            nfsd_file_flags;
 static struct fsnotify_group        *nfsd_file_fsnotify_group;
 static struct delayed_work      nfsd_filecache_laundrette;
 static struct rhashtable        nfsd_file_rhash_tbl
                         ____cacheline_aligned_in_smp;
 
 enum nfsd_file_lookup_type {
     NFSD_FILE_KEY_INODE,
     NFSD_FILE_KEY_FULL,
 };
 
 struct nfsd_file_lookup_key {
     struct inode            *inode;
     struct net          *net;
     const struct cred       *cred;
     unsigned char           need;
     enum nfsd_file_lookup_type  type;
 };
 
 /*
  * The returned hash value is based solely on the address of an in-code
  * inode, a pointer to a slab-allocated object. The entropy in such a
  * pointer is concentrated in its middle bits.
  */
 static u32 nfsd_file_inode_hash(const struct inode *inode, u32 seed)
 {
     unsigned long ptr = (unsigned long)inode;
     u32 k;
 
     k = ptr >> L1_CACHE_SHIFT;
     k &= 0x00ffffff;
     return jhash2(&k, 1, seed);
 }
 
 /**
  * nfsd_file_key_hashfn - Compute the hash value of a lookup key
  * @data: key on which to compute the hash value
  * @len: rhash table's key_len parameter (unused)
  * @seed: rhash table's random seed of the day
  *
  * Return value:
  *   Computed 32-bit hash value
  */
 static u32 nfsd_file_key_hashfn(const void *data, u32 len, u32 seed)
 {
     const struct nfsd_file_lookup_key *key = data;
 
     return nfsd_file_inode_hash(key->inode, seed);
 }
 
 /**
  * nfsd_file_obj_hashfn - Compute the hash value of an nfsd_file
  * @data: object on which to compute the hash value
  * @len: rhash table's key_len parameter (unused)
  * @seed: rhash table's random seed of the day
  *
  * Return value:
  *   Computed 32-bit hash value
  */
 static u32 nfsd_file_obj_hashfn(const void *data, u32 len, u32 seed)
 {
     const struct nfsd_file *nf = data;
 
     return nfsd_file_inode_hash(nf->nf_inode, seed);
 }
 
 static bool
 nfsd_match_cred(const struct cred *c1, const struct cred *c2)
 {
     int i;
 
     if (!uid_eq(c1->fsuid, c2->fsuid))
         return false;
     if (!gid_eq(c1->fsgid, c2->fsgid))
         return false;
     if (c1->group_info == NULL || c2->group_info == NULL)
         return c1->group_info == c2->group_info;
     if (c1->group_info->ngroups != c2->group_info->ngroups)
         return false;
     for (i = 0; i < c1->group_info->ngroups; i++) {
         if (!gid_eq(c1->group_info->gid[i], c2->group_info->gid[i]))
             return false;
     }
     return true;
 }
 
 /**
  * nfsd_file_obj_cmpfn - Match a cache item against search criteria
  * @arg: search criteria
  * @ptr: cache item to check
  *
  * Return values:
  *   %0 - Item matches search criteria
  *   %1 - Item does not match search criteria
  */
 static int nfsd_file_obj_cmpfn(struct rhashtable_compare_arg *arg,
                    const void *ptr)
 {
     const struct nfsd_file_lookup_key *key = arg->key;
     const struct nfsd_file *nf = ptr;
 
     switch (key->type) {
     case NFSD_FILE_KEY_INODE:
         if (nf->nf_inode != key->inode)
             return 1;
         break;
     case NFSD_FILE_KEY_FULL:
         if (nf->nf_inode != key->inode)
             return 1;
         if (nf->nf_may != key->need)
             return 1;
         if (nf->nf_net != key->net)
             return 1;
         if (!nfsd_match_cred(nf->nf_cred, key->cred))
             return 1;
         if (test_bit(NFSD_FILE_HASHED, &nf->nf_flags) == 0)
             return 1;
         break;
     }
     return 0;
 }
 
 static const struct rhashtable_params nfsd_file_rhash_params = {
     .key_len        = sizeof_field(struct nfsd_file, nf_inode),
     .key_offset     = offsetof(struct nfsd_file, nf_inode),
     .head_offset        = offsetof(struct nfsd_file, nf_rhash),
     .hashfn         = nfsd_file_key_hashfn,
     .obj_hashfn     = nfsd_file_obj_hashfn,
     .obj_cmpfn      = nfsd_file_obj_cmpfn,
     /* Reduce resizing churn on light workloads */
     .min_size       = 512,      /* buckets */
     .automatic_shrinking    = true,
 };
 
 static void
 nfsd_file_schedule_laundrette(void)
 {
     if ((atomic_read(&nfsd_file_rhash_tbl.nelems) == 0) ||
         test_bit(NFSD_FILE_CACHE_UP, &nfsd_file_flags) == 0)
         return;
 
     queue_delayed_work(system_wq, &nfsd_filecache_laundrette,
             NFSD_LAUNDRETTE_DELAY);
 }
 
 static void
 nfsd_file_slab_free(struct rcu_head *rcu)
 {
     struct nfsd_file *nf = container_of(rcu, struct nfsd_file, nf_rcu);
 
     put_cred(nf->nf_cred);
     kmem_cache_free(nfsd_file_slab, nf);
 }
 
 static void
 nfsd_file_mark_free(struct fsnotify_mark *mark)
 {
     struct nfsd_file_mark *nfm = container_of(mark, struct nfsd_file_mark,
                           nfm_mark);
 
     kmem_cache_free(nfsd_file_mark_slab, nfm);
 }
 
 static struct nfsd_file_mark *
 nfsd_file_mark_get(struct nfsd_file_mark *nfm)
 {
     if (!refcount_inc_not_zero(&nfm->nfm_ref))
         return NULL;
     return nfm;
 }
 
 static void
 nfsd_file_mark_put(struct nfsd_file_mark *nfm)
 {
     if (refcount_dec_and_test(&nfm->nfm_ref)) {
         fsnotify_destroy_mark(&nfm->nfm_mark, nfsd_file_fsnotify_group);
         fsnotify_put_mark(&nfm->nfm_mark);
     }
 }
 
 static struct nfsd_file_mark *
 nfsd_file_mark_find_or_create(struct nfsd_file *nf, struct inode *inode)
 {
     int         err;
     struct fsnotify_mark    *mark;
     struct nfsd_file_mark   *nfm = NULL, *new;
 
     do {
         fsnotify_group_lock(nfsd_file_fsnotify_group);
         mark = fsnotify_find_mark(&inode->i_fsnotify_marks,
                       nfsd_file_fsnotify_group);
         if (mark) {
             nfm = nfsd_file_mark_get(container_of(mark,
                          struct nfsd_file_mark,
                          nfm_mark));
             fsnotify_group_unlock(nfsd_file_fsnotify_group);
             if (nfm) {
                 fsnotify_put_mark(mark);
                 break;
             }
             /* Avoid soft lockup race with nfsd_file_mark_put() */
             fsnotify_destroy_mark(mark, nfsd_file_fsnotify_group);
             fsnotify_put_mark(mark);
         } else {
             fsnotify_group_unlock(nfsd_file_fsnotify_group);
         }
 
         /* allocate a new nfm */
         new = kmem_cache_alloc(nfsd_file_mark_slab, GFP_KERNEL);
         if (!new)
             return NULL;
         fsnotify_init_mark(&new->nfm_mark, nfsd_file_fsnotify_group);
         new->nfm_mark.mask = FS_ATTRIB|FS_DELETE_SELF;
         refcount_set(&new->nfm_ref, 1);
 
         err = fsnotify_add_inode_mark(&new->nfm_mark, inode, 0);
 
         /*
          * If the add was successful, then return the object.
          * Otherwise, we need to put the reference we hold on the
          * nfm_mark. The fsnotify code will take a reference and put
          * it on failure, so we can't just free it directly. It's also
          * not safe to call fsnotify_destroy_mark on it as the
          * mark->group will be NULL. Thus, we can't let the nfm_ref
          * counter drive the destruction at this point.
          */
         if (likely(!err))
             nfm = new;
         else
             fsnotify_put_mark(&new->nfm_mark);
     } while (unlikely(err == -EEXIST));
 
     return nfm;
 }
 
 static struct nfsd_file *
 nfsd_file_alloc(struct nfsd_file_lookup_key *key, unsigned int may)
 {
     struct nfsd_file *nf;
 
     nf = kmem_cache_alloc(nfsd_file_slab, GFP_KERNEL);
     if (nf) {
         INIT_LIST_HEAD(&nf->nf_lru);
         nf->nf_birthtime = ktime_get();
         nf->nf_file = NULL;
         nf->nf_cred = get_current_cred();
         nf->nf_net = key->net;
         nf->nf_flags = 0;
         __set_bit(NFSD_FILE_HASHED, &nf->nf_flags);
         __set_bit(NFSD_FILE_PENDING, &nf->nf_flags);
         nf->nf_inode = key->inode;
         /* nf_ref is pre-incremented for hash table */
         refcount_set(&nf->nf_ref, 2);
         nf->nf_may = key->need;
         nf->nf_mark = NULL;
     }
     return nf;
 }
 
 static bool
 nfsd_file_free(struct nfsd_file *nf)
 {
     s64 age = ktime_to_ms(ktime_sub(ktime_get(), nf->nf_birthtime));
     bool flush = false;
 
     this_cpu_inc(nfsd_file_releases);
     this_cpu_add(nfsd_file_total_age, age);
 
     trace_nfsd_file_put_final(nf);
     if (nf->nf_mark)
         nfsd_file_mark_put(nf->nf_mark);
     if (nf->nf_file) {
         get_file(nf->nf_file);
         filp_close(nf->nf_file, NULL);
         fput(nf->nf_file);
         flush = true;
     }
 
     /*
      * If this item is still linked via nf_lru, that's a bug.
      * WARN and leak it to preserve system stability.
      */
     if (WARN_ON_ONCE(!list_empty(&nf->nf_lru)))
         return flush;
 
     call_rcu(&nf->nf_rcu, nfsd_file_slab_free);
     return flush;
 }
 
 static bool
 nfsd_file_check_writeback(struct nfsd_file *nf)
 {
     struct file *file = nf->nf_file;
     struct address_space *mapping;
 
     if (!file || !(file->f_mode & FMODE_WRITE))
         return false;
     mapping = file->f_mapping;
     return mapping_tagged(mapping, PAGECACHE_TAG_DIRTY) ||
         mapping_tagged(mapping, PAGECACHE_TAG_WRITEBACK);
 }
 
 static int
 nfsd_file_check_write_error(struct nfsd_file *nf)
 {
     struct file *file = nf->nf_file;
 
     if (!file || !(file->f_mode & FMODE_WRITE))
         return 0;
     return filemap_check_wb_err(file->f_mapping, READ_ONCE(file->f_wb_err));
 }
 
 static void
 nfsd_file_flush(struct nfsd_file *nf)
 {
     struct file *file = nf->nf_file;
 
     if (!file || !(file->f_mode & FMODE_WRITE))
         return;
     this_cpu_add(nfsd_file_pages_flushed, file->f_mapping->nrpages);
     if (vfs_fsync(file, 1) != 0)
         nfsd_reset_write_verifier(net_generic(nf->nf_net, nfsd_net_id));
 }
 
 static void nfsd_file_lru_add(struct nfsd_file *nf)
 {
     set_bit(NFSD_FILE_REFERENCED, &nf->nf_flags);
     if (list_lru_add(&nfsd_file_lru, &nf->nf_lru))
         trace_nfsd_file_lru_add(nf);
 }
 
 static void nfsd_file_lru_remove(struct nfsd_file *nf)
 {
     if (list_lru_del(&nfsd_file_lru, &nf->nf_lru))
         trace_nfsd_file_lru_del(nf);
 }
 
 static void
 nfsd_file_hash_remove(struct nfsd_file *nf)
 {
     trace_nfsd_file_unhash(nf);
 
     if (nfsd_file_check_write_error(nf))
         nfsd_reset_write_verifier(net_generic(nf->nf_net, nfsd_net_id));
     rhashtable_remove_fast(&nfsd_file_rhash_tbl, &nf->nf_rhash,
                    nfsd_file_rhash_params);
 }
 
 static bool
 nfsd_file_unhash(struct nfsd_file *nf)
 {
     if (test_and_clear_bit(NFSD_FILE_HASHED, &nf->nf_flags)) {
         nfsd_file_hash_remove(nf);
         return true;
     }
     return false;
 }
 
 /*
  * Return true if the file was unhashed.
  */
 static bool
 nfsd_file_unhash_and_dispose(struct nfsd_file *nf, struct list_head *dispose)
 {
     trace_nfsd_file_unhash_and_dispose(nf);
     if (!nfsd_file_unhash(nf))
         return false;
     /* keep final reference for nfsd_file_lru_dispose */
     if (refcount_dec_not_one(&nf->nf_ref))
         return true;
 
     nfsd_file_lru_remove(nf);
     list_add(&nf->nf_lru, dispose);
     return true;
 }
 
 static void
 nfsd_file_put_noref(struct nfsd_file *nf)
 {
     trace_nfsd_file_put(nf);
 
     if (refcount_dec_and_test(&nf->nf_ref)) {
         WARN_ON(test_bit(NFSD_FILE_HASHED, &nf->nf_flags));
         nfsd_file_lru_remove(nf);
         nfsd_file_free(nf);
     }
 }
 
 void
 nfsd_file_put(struct nfsd_file *nf)
 {
     might_sleep();
 
     nfsd_file_lru_add(nf);
     if (test_bit(NFSD_FILE_HASHED, &nf->nf_flags) == 0) {
         nfsd_file_flush(nf);
         nfsd_file_put_noref(nf);
     } else if (nf->nf_file) {
         nfsd_file_put_noref(nf);
         nfsd_file_schedule_laundrette();
     } else
         nfsd_file_put_noref(nf);
 }
 
 /**
  * nfsd_file_close - Close an nfsd_file
  * @nf: nfsd_file to close
  *
  * If this is the final reference for @nf, free it immediately.
  * This reflects an on-the-wire CLOSE or DELEGRETURN into the
  * VFS and exported filesystem.
  */
 void nfsd_file_close(struct nfsd_file *nf)
 {
     nfsd_file_put(nf);
     if (refcount_dec_if_one(&nf->nf_ref)) {
         nfsd_file_unhash(nf);
         nfsd_file_lru_remove(nf);
         nfsd_file_free(nf);
     }
 }
 
 struct nfsd_file *
 nfsd_file_get(struct nfsd_file *nf)
 {
     if (likely(refcount_inc_not_zero(&nf->nf_ref)))
         return nf;
     return NULL;
 }
 
 static void
 nfsd_file_dispose_list(struct list_head *dispose)
 {
     struct nfsd_file *nf;
 
     while(!list_empty(dispose)) {
         nf = list_first_entry(dispose, struct nfsd_file, nf_lru);
         list_del_init(&nf->nf_lru);
         nfsd_file_flush(nf);
         nfsd_file_put_noref(nf);
     }
 }
 
 static void
 nfsd_file_dispose_list_sync(struct list_head *dispose)
 {
     bool flush = false;
     struct nfsd_file *nf;
 
     while(!list_empty(dispose)) {
         nf = list_first_entry(dispose, struct nfsd_file, nf_lru);
         list_del_init(&nf->nf_lru);
         nfsd_file_flush(nf);
         if (!refcount_dec_and_test(&nf->nf_ref))
             continue;
         if (nfsd_file_free(nf))
             flush = true;
     }
     if (flush)
         flush_delayed_fput();
 }
 
 static void
 nfsd_file_list_remove_disposal(struct list_head *dst,
         struct nfsd_fcache_disposal *l)
 {
     spin_lock(&l->lock);
     list_splice_init(&l->freeme, dst);
     spin_unlock(&l->lock);
 }
 
 static void
 nfsd_file_list_add_disposal(struct list_head *files, struct net *net)
 {
     struct nfsd_net *nn = net_generic(net, nfsd_net_id);
     struct nfsd_fcache_disposal *l = nn->fcache_disposal;
 
     spin_lock(&l->lock);
     list_splice_tail_init(files, &l->freeme);
     spin_unlock(&l->lock);
     queue_work(nfsd_filecache_wq, &l->work);
 }
 
 static void
 nfsd_file_list_add_pernet(struct list_head *dst, struct list_head *src,
         struct net *net)
 {
     struct nfsd_file *nf, *tmp;
 
     list_for_each_entry_safe(nf, tmp, src, nf_lru) {
         if (nf->nf_net == net)
             list_move_tail(&nf->nf_lru, dst);
     }
 }
 
 static void
 nfsd_file_dispose_list_delayed(struct list_head *dispose)
 {
     LIST_HEAD(list);
     struct nfsd_file *nf;
 
     while(!list_empty(dispose)) {
         nf = list_first_entry(dispose, struct nfsd_file, nf_lru);
         nfsd_file_list_add_pernet(&list, dispose, nf->nf_net);
         nfsd_file_list_add_disposal(&list, nf->nf_net);
     }
 }
 
 /**
  * nfsd_file_lru_cb - Examine an entry on the LRU list
  * @item: LRU entry to examine
  * @lru: controlling LRU
  * @lock: LRU list lock (unused)
  * @arg: dispose list
  *
  * Note this can deadlock with nfsd_file_cache_purge.
  *
  * Return values:
  *   %LRU_REMOVED: @item was removed from the LRU
  *   %LRU_ROTATE: @item is to be moved to the LRU tail
  *   %LRU_SKIP: @item cannot be evicted
  */
 static enum lru_status
 nfsd_file_lru_cb(struct list_head *item, struct list_lru_one *lru,
          spinlock_t *lock, void *arg)
     __releases(lock)
     __acquires(lock)
 {
     struct list_head *head = arg;
     struct nfsd_file *nf = list_entry(item, struct nfsd_file, nf_lru);
 
     /*
      * Do a lockless refcount check. The hashtable holds one reference, so
      * we look to see if anything else has a reference, or if any have
      * been put since the shrinker last ran. Those don't get unhashed and
      * released.
      *
      * Note that in the put path, we set the flag and then decrement the
      * counter. Here we check the counter and then test and clear the flag.
      * That order is deliberate to ensure that we can do this locklessly.
      */
     if (refcount_read(&nf->nf_ref) > 1) {
         list_lru_isolate(lru, &nf->nf_lru);
         trace_nfsd_file_gc_in_use(nf);
         return LRU_REMOVED;
     }
 
     /*
      * Don't throw out files that are still undergoing I/O or
      * that have uncleared errors pending.
      */
     if (nfsd_file_check_writeback(nf)) {
         trace_nfsd_file_gc_writeback(nf);
         return LRU_SKIP;
     }
 
     if (test_and_clear_bit(NFSD_FILE_REFERENCED, &nf->nf_flags)) {
         trace_nfsd_file_gc_referenced(nf);
         return LRU_ROTATE;
     }
 
     if (!test_and_clear_bit(NFSD_FILE_HASHED, &nf->nf_flags)) {
         trace_nfsd_file_gc_hashed(nf);
         return LRU_SKIP;
     }
 
     list_lru_isolate_move(lru, &nf->nf_lru, head);
     this_cpu_inc(nfsd_file_evictions);
     trace_nfsd_file_gc_disposed(nf);
     return LRU_REMOVED;
 }
 
 /*
  * Unhash items on @dispose immediately, then queue them on the
  * disposal workqueue to finish releasing them in the background.
  *
  * cel: Note that between the time list_lru_shrink_walk runs and
  * now, these items are in the hash table but marked unhashed.
  * Why release these outside of lru_cb ? There's no lock ordering
  * problem since lru_cb currently takes no lock.
  */
 static void nfsd_file_gc_dispose_list(struct list_head *dispose)
 {
     struct nfsd_file *nf;
 
     list_for_each_entry(nf, dispose, nf_lru)
         nfsd_file_hash_remove(nf);
     nfsd_file_dispose_list_delayed(dispose);
 }
 
 static void
 nfsd_file_gc(void)
 {
     LIST_HEAD(dispose);
     unsigned long ret;
 
     ret = list_lru_walk(&nfsd_file_lru, nfsd_file_lru_cb,
                 &dispose, list_lru_count(&nfsd_file_lru));
     trace_nfsd_file_gc_removed(ret, list_lru_count(&nfsd_file_lru));
     nfsd_file_gc_dispose_list(&dispose);
 }
 
 static void
 nfsd_file_gc_worker(struct work_struct *work)
 {
     nfsd_file_gc();
     nfsd_file_schedule_laundrette();
 }
 
 static unsigned long
 nfsd_file_lru_count(struct shrinker *s, struct shrink_control *sc)
 {
     return list_lru_count(&nfsd_file_lru);
 }
 
 static unsigned long
 nfsd_file_lru_scan(struct shrinker *s, struct shrink_control *sc)
 {
     LIST_HEAD(dispose);
     unsigned long ret;
 
     ret = list_lru_shrink_walk(&nfsd_file_lru, sc,
                    nfsd_file_lru_cb, &dispose);
     trace_nfsd_file_shrinker_removed(ret, list_lru_count(&nfsd_file_lru));
     nfsd_file_gc_dispose_list(&dispose);
     return ret;
 }
 
 static struct shrinker  nfsd_file_shrinker = {
     .scan_objects = nfsd_file_lru_scan,
     .count_objects = nfsd_file_lru_count,
     .seeks = 1,
 };
 
 /*
  * Find all cache items across all net namespaces that match @inode and
  * move them to @dispose. The lookup is atomic wrt nfsd_file_acquire().
  */
 static unsigned int
 __nfsd_file_close_inode(struct inode *inode, struct list_head *dispose)
 {
     struct nfsd_file_lookup_key key = {
         .type   = NFSD_FILE_KEY_INODE,
         .inode  = inode,
     };
     unsigned int count = 0;
     struct nfsd_file *nf;
 
     rcu_read_lock();
     do {
         nf = rhashtable_lookup(&nfsd_file_rhash_tbl, &key,
                        nfsd_file_rhash_params);
         if (!nf)
             break;
         nfsd_file_unhash_and_dispose(nf, dispose);
         count++;
     } while (1);
     rcu_read_unlock();
     return count;
 }
 
 /**
  * nfsd_file_close_inode_sync - attempt to forcibly close a nfsd_file
  * @inode: inode of the file to attempt to remove
  *
  * Unhash and put, then flush and fput all cache items associated with @inode.
  */
 void
 nfsd_file_close_inode_sync(struct inode *inode)
 {
     LIST_HEAD(dispose);
     unsigned int count;
 
     count = __nfsd_file_close_inode(inode, &dispose);
     trace_nfsd_file_close_inode_sync(inode, count);
     nfsd_file_dispose_list_sync(&dispose);
 }
 
 /**
  * nfsd_file_close_inode - attempt a delayed close of a nfsd_file
  * @inode: inode of the file to attempt to remove
  *
  * Unhash and put all cache item associated with @inode.
  */
 static void
 nfsd_file_close_inode(struct inode *inode)
 {
     LIST_HEAD(dispose);
     unsigned int count;
 
     count = __nfsd_file_close_inode(inode, &dispose);
     trace_nfsd_file_close_inode(inode, count);
     nfsd_file_dispose_list_delayed(&dispose);
 }
 
 /**
  * nfsd_file_delayed_close - close unused nfsd_files
  * @work: dummy
  *
  * Walk the LRU list and close any entries that have not been used since
  * the last scan.
  *
  * Note this can deadlock with nfsd_file_cache_purge.
  */
 static void
 nfsd_file_delayed_close(struct work_struct *work)
 {
     LIST_HEAD(head);
     struct nfsd_fcache_disposal *l = container_of(work,
             struct nfsd_fcache_disposal, work);
 
     nfsd_file_list_remove_disposal(&head, l);
     nfsd_file_dispose_list(&head);
 }
 
 static int
 nfsd_file_lease_notifier_call(struct notifier_block *nb, unsigned long arg,
                 void *data)
 {
     struct file_lock *fl = data;
 
     /* Only close files for F_SETLEASE leases */
     if (fl->fl_flags & FL_LEASE)
         nfsd_file_close_inode_sync(file_inode(fl->fl_file));
     return 0;
 }
 
 static struct notifier_block nfsd_file_lease_notifier = {
     .notifier_call = nfsd_file_lease_notifier_call,
 };
 
 static int
 nfsd_file_fsnotify_handle_event(struct fsnotify_mark *mark, u32 mask,
                 struct inode *inode, struct inode *dir,
                 const struct qstr *name, u32 cookie)
 {
     if (WARN_ON_ONCE(!inode))
         return 0;
 
     trace_nfsd_file_fsnotify_handle_event(inode, mask);
 
     /* Should be no marks on non-regular files */
     if (!S_ISREG(inode->i_mode)) {
         WARN_ON_ONCE(1);
         return 0;
     }
 
     /* don't close files if this was not the last link */
     if (mask & FS_ATTRIB) {
         if (inode->i_nlink)
             return 0;
     }
 
     nfsd_file_close_inode(inode);
     return 0;
 }
 
 
 static const struct fsnotify_ops nfsd_file_fsnotify_ops = {
     .handle_inode_event = nfsd_file_fsnotify_handle_event,
     .free_mark = nfsd_file_mark_free,
 };
 
 int
 nfsd_file_cache_init(void)
 {
     int ret;
 
     lockdep_assert_held(&nfsd_mutex);
     if (test_and_set_bit(NFSD_FILE_CACHE_UP, &nfsd_file_flags) == 1)
         return 0;
 
     ret = rhashtable_init(&nfsd_file_rhash_tbl, &nfsd_file_rhash_params);
     if (ret)
         return ret;
 
     ret = -ENOMEM;
     nfsd_filecache_wq = alloc_workqueue("nfsd_filecache", 0, 0);
     if (!nfsd_filecache_wq)
         goto out;
 
     nfsd_file_slab = kmem_cache_create("nfsd_file",
                 sizeof(struct nfsd_file), 0, 0, NULL);
     if (!nfsd_file_slab) {
         pr_err("nfsd: unable to create nfsd_file_slab\n");
         goto out_err;
     }
 
     nfsd_file_mark_slab = kmem_cache_create("nfsd_file_mark",
                     sizeof(struct nfsd_file_mark), 0, 0, NULL);
     if (!nfsd_file_mark_slab) {
         pr_err("nfsd: unable to create nfsd_file_mark_slab\n");
         goto out_err;
     }
 
 
     ret = list_lru_init(&nfsd_file_lru);
     if (ret) {
         pr_err("nfsd: failed to init nfsd_file_lru: %d\n", ret);
         goto out_err;
     }
 
     ret = register_shrinker(&nfsd_file_shrinker, "nfsd-filecache");
     if (ret) {
         pr_err("nfsd: failed to register nfsd_file_shrinker: %d\n", ret);
         goto out_lru;
     }
 
     ret = lease_register_notifier(&nfsd_file_lease_notifier);
     if (ret) {
         pr_err("nfsd: unable to register lease notifier: %d\n", ret);
         goto out_shrinker;
     }
 
     nfsd_file_fsnotify_group = fsnotify_alloc_group(&nfsd_file_fsnotify_ops,
                             FSNOTIFY_GROUP_NOFS);
     if (IS_ERR(nfsd_file_fsnotify_group)) {
         pr_err("nfsd: unable to create fsnotify group: %ld\n",
             PTR_ERR(nfsd_file_fsnotify_group));
         ret = PTR_ERR(nfsd_file_fsnotify_group);
         nfsd_file_fsnotify_group = NULL;
         goto out_notifier;
     }
 
     INIT_DELAYED_WORK(&nfsd_filecache_laundrette, nfsd_file_gc_worker);
 out:
     return ret;
 out_notifier:
     lease_unregister_notifier(&nfsd_file_lease_notifier);
 out_shrinker:
     unregister_shrinker(&nfsd_file_shrinker);
 out_lru:
     list_lru_destroy(&nfsd_file_lru);
 out_err:
     kmem_cache_destroy(nfsd_file_slab);
     nfsd_file_slab = NULL;
     kmem_cache_destroy(nfsd_file_mark_slab);
     nfsd_file_mark_slab = NULL;
     destroy_workqueue(nfsd_filecache_wq);
     nfsd_filecache_wq = NULL;
     rhashtable_destroy(&nfsd_file_rhash_tbl);
     goto out;
 }
 
 /*
  * Note this can deadlock with nfsd_file_lru_cb.
  */
 static void
 __nfsd_file_cache_purge(struct net *net)
 {
     struct rhashtable_iter iter;
     struct nfsd_file *nf;
     LIST_HEAD(dispose);
     bool del;
 
     rhashtable_walk_enter(&nfsd_file_rhash_tbl, &iter);
     do {
         rhashtable_walk_start(&iter);
 
         nf = rhashtable_walk_next(&iter);
         while (!IS_ERR_OR_NULL(nf)) {
             if (net && nf->nf_net != net)
                 continue;
             del = nfsd_file_unhash_and_dispose(nf, &dispose);
 
             /*
              * Deadlock detected! Something marked this entry as
              * unhased, but hasn't removed it from the hash list.
              */
             WARN_ON_ONCE(!del);
 
             nf = rhashtable_walk_next(&iter);
         }
 
         rhashtable_walk_stop(&iter);
     } while (nf == ERR_PTR(-EAGAIN));
     rhashtable_walk_exit(&iter);
 
     nfsd_file_dispose_list(&dispose);
 }
 
 static struct nfsd_fcache_disposal *
 nfsd_alloc_fcache_disposal(void)
 {
     struct nfsd_fcache_disposal *l;
 
     l = kmalloc(sizeof(*l), GFP_KERNEL);
     if (!l)
         return NULL;
     INIT_WORK(&l->work, nfsd_file_delayed_close);
     spin_lock_init(&l->lock);
     INIT_LIST_HEAD(&l->freeme);
     return l;
 }
 
 static void
 nfsd_free_fcache_disposal(struct nfsd_fcache_disposal *l)
 {
     cancel_work_sync(&l->work);
     nfsd_file_dispose_list(&l->freeme);
     kfree(l);
 }
 
 static void
 nfsd_free_fcache_disposal_net(struct net *net)
 {
     struct nfsd_net *nn = net_generic(net, nfsd_net_id);
     struct nfsd_fcache_disposal *l = nn->fcache_disposal;
 
     nfsd_free_fcache_disposal(l);
 }
 
 int
 nfsd_file_cache_start_net(struct net *net)
 {
     struct nfsd_net *nn = net_generic(net, nfsd_net_id);
 
     nn->fcache_disposal = nfsd_alloc_fcache_disposal();
     return nn->fcache_disposal ? 0 : -ENOMEM;
 }
 
 /**
  * nfsd_file_cache_purge - Remove all cache items associated with @net
  * @net: target net namespace
  *
  */
 void
 nfsd_file_cache_purge(struct net *net)
 {
     lockdep_assert_held(&nfsd_mutex);
     if (test_bit(NFSD_FILE_CACHE_UP, &nfsd_file_flags) == 1)
         __nfsd_file_cache_purge(net);
 }
 
 void
 nfsd_file_cache_shutdown_net(struct net *net)
 {
     nfsd_file_cache_purge(net);
     nfsd_free_fcache_disposal_net(net);
 }
 
 void
 nfsd_file_cache_shutdown(void)
 {
     int i;
 
     lockdep_assert_held(&nfsd_mutex);
     if (test_and_clear_bit(NFSD_FILE_CACHE_UP, &nfsd_file_flags) == 0)
         return;
 
     lease_unregister_notifier(&nfsd_file_lease_notifier);
     unregister_shrinker(&nfsd_file_shrinker);
     /*
      * make sure all callers of nfsd_file_lru_cb are done before
      * calling nfsd_file_cache_purge
      */
     cancel_delayed_work_sync(&nfsd_filecache_laundrette);
     __nfsd_file_cache_purge(NULL);
     list_lru_destroy(&nfsd_file_lru);
     rcu_barrier();
     fsnotify_put_group(nfsd_file_fsnotify_group);
     nfsd_file_fsnotify_group = NULL;
     kmem_cache_destroy(nfsd_file_slab);
     nfsd_file_slab = NULL;
     fsnotify_wait_marks_destroyed();
     kmem_cache_destroy(nfsd_file_mark_slab);
     nfsd_file_mark_slab = NULL;
     destroy_workqueue(nfsd_filecache_wq);
     nfsd_filecache_wq = NULL;
     rhashtable_destroy(&nfsd_file_rhash_tbl);
 
     for_each_possible_cpu(i) {
         per_cpu(nfsd_file_cache_hits, i) = 0;
         per_cpu(nfsd_file_acquisitions, i) = 0;
         per_cpu(nfsd_file_releases, i) = 0;
         per_cpu(nfsd_file_total_age, i) = 0;
         per_cpu(nfsd_file_pages_flushed, i) = 0;
         per_cpu(nfsd_file_evictions, i) = 0;
     }
 }
 
 /**
  * nfsd_file_is_cached - are there any cached open files for this inode?
  * @inode: inode to check
  *
  * The lookup matches inodes in all net namespaces and is atomic wrt
  * nfsd_file_acquire().
  *
  * Return values:
  *   %true: filecache contains at least one file matching this inode
  *   %false: filecache contains no files matching this inode
  */
 bool
 nfsd_file_is_cached(struct inode *inode)
 {
     struct nfsd_file_lookup_key key = {
         .type   = NFSD_FILE_KEY_INODE,
         .inode  = inode,
     };
     bool ret = false;
 
     if (rhashtable_lookup_fast(&nfsd_file_rhash_tbl, &key,
                    nfsd_file_rhash_params) != NULL)
         ret = true;
     trace_nfsd_file_is_cached(inode, (int)ret);
     return ret;
 }
 
 static __be32
 nfsd_file_do_acquire(struct svc_rqst *rqstp, struct svc_fh *fhp,
              unsigned int may_flags, struct nfsd_file **pnf, bool open)
 {
     struct nfsd_file_lookup_key key = {
         .type   = NFSD_FILE_KEY_FULL,
         .need   = may_flags & NFSD_FILE_MAY_MASK,
         .net    = SVC_NET(rqstp),
     };
     struct nfsd_file *nf, *new;
     bool retry = true;
     __be32 status;
 
     status = fh_verify(rqstp, fhp, S_IFREG,
                 may_flags|NFSD_MAY_OWNER_OVERRIDE);
     if (status != nfs_ok)
         return status;
     key.inode = d_inode(fhp->fh_dentry);
     key.cred = get_current_cred();
 
 retry:
     /* Avoid allocation if the item is already in cache */
     nf = rhashtable_lookup_fast(&nfsd_file_rhash_tbl, &key,
                     nfsd_file_rhash_params);
     if (nf)
         nf = nfsd_file_get(nf);
     if (nf)
         goto wait_for_construction;
 
     new = nfsd_file_alloc(&key, may_flags);
     if (!new) {
         status = nfserr_jukebox;
         goto out_status;
     }
 
     nf = rhashtable_lookup_get_insert_key(&nfsd_file_rhash_tbl,
                           &key, &new->nf_rhash,
                           nfsd_file_rhash_params);
     if (!nf) {
         nf = new;
         goto open_file;
     }
     if (IS_ERR(nf))
         goto insert_err;
     nf = nfsd_file_get(nf);
     if (nf == NULL) {
         nf = new;
         goto open_file;
     }
     nfsd_file_slab_free(&new->nf_rcu);
 
 wait_for_construction:
     wait_on_bit(&nf->nf_flags, NFSD_FILE_PENDING, TASK_UNINTERRUPTIBLE);
 
     /* Did construction of this file fail? */
     if (!test_bit(NFSD_FILE_HASHED, &nf->nf_flags)) {
         trace_nfsd_file_cons_err(rqstp, key.inode, may_flags, nf);
         if (!retry) {
             status = nfserr_jukebox;
             goto out;
         }
         retry = false;
         nfsd_file_put_noref(nf);
         goto retry;
     }
 
     nfsd_file_lru_remove(nf);
     this_cpu_inc(nfsd_file_cache_hits);
 
     status = nfserrno(nfsd_open_break_lease(file_inode(nf->nf_file), may_flags));
 out:
     if (status == nfs_ok) {
         if (open)
             this_cpu_inc(nfsd_file_acquisitions);
         *pnf = nf;
     } else {
         nfsd_file_put(nf);
         nf = NULL;
     }
 
 out_status:
     put_cred(key.cred);
     if (open)
         trace_nfsd_file_acquire(rqstp, key.inode, may_flags, nf, status);
     return status;
 
 open_file:
     trace_nfsd_file_alloc(nf);
     nf->nf_mark = nfsd_file_mark_find_or_create(nf, key.inode);
     if (nf->nf_mark) {
         if (open) {
             status = nfsd_open_verified(rqstp, fhp, may_flags,
                             &nf->nf_file);
             trace_nfsd_file_open(nf, status);
         } else
             status = nfs_ok;
     } else
         status = nfserr_jukebox;
     /*
      * If construction failed, or we raced with a call to unlink()
      * then unhash.
      */
     if (status != nfs_ok || key.inode->i_nlink == 0)
         if (nfsd_file_unhash(nf))
             nfsd_file_put_noref(nf);
     clear_bit_unlock(NFSD_FILE_PENDING, &nf->nf_flags);
     smp_mb__after_atomic();
     wake_up_bit(&nf->nf_flags, NFSD_FILE_PENDING);
     goto out;
 
 insert_err:
     nfsd_file_slab_free(&new->nf_rcu);
     trace_nfsd_file_insert_err(rqstp, key.inode, may_flags, PTR_ERR(nf));
     nf = NULL;
     status = nfserr_jukebox;
     goto out_status;
 }
 
 /**
  * nfsd_file_acquire - Get a struct nfsd_file with an open file
  * @rqstp: the RPC transaction being executed
  * @fhp: the NFS filehandle of the file to be opened
  * @may_flags: NFSD_MAY_ settings for the file
  * @pnf: OUT: new or found "struct nfsd_file" object
  *
  * Returns nfs_ok and sets @pnf on success; otherwise an nfsstat in
  * network byte order is returned.
  */
 __be32
 nfsd_file_acquire(struct svc_rqst *rqstp, struct svc_fh *fhp,
           unsigned int may_flags, struct nfsd_file **pnf)
 {
     return nfsd_file_do_acquire(rqstp, fhp, may_flags, pnf, true);
 }
 
 /**
  * nfsd_file_create - Get a struct nfsd_file, do not open
  * @rqstp: the RPC transaction being executed
  * @fhp: the NFS filehandle of the file just created
  * @may_flags: NFSD_MAY_ settings for the file
  * @pnf: OUT: new or found "struct nfsd_file" object
  *
  * Returns nfs_ok and sets @pnf on success; otherwise an nfsstat in
  * network byte order is returned.
  */
 __be32
 nfsd_file_create(struct svc_rqst *rqstp, struct svc_fh *fhp,
          unsigned int may_flags, struct nfsd_file **pnf)
 {
     return nfsd_file_do_acquire(rqstp, fhp, may_flags, pnf, false);
 }
 
 /*
  * Note that fields may be added, removed or reordered in the future. Programs
  * scraping this file for info should test the labels to ensure they're
  * getting the correct field.
  */
 static int nfsd_file_cache_stats_show(struct seq_file *m, void *v)
 {
     unsigned long releases = 0, pages_flushed = 0, evictions = 0;
     unsigned long hits = 0, acquisitions = 0;
     unsigned int i, count = 0, buckets = 0;
     unsigned long lru = 0, total_age = 0;
 
     /* Serialize with server shutdown */
     mutex_lock(&nfsd_mutex);
     if (test_bit(NFSD_FILE_CACHE_UP, &nfsd_file_flags) == 1) {
         struct bucket_table *tbl;
         struct rhashtable *ht;
 
         lru = list_lru_count(&nfsd_file_lru);
 
         rcu_read_lock();
         ht = &nfsd_file_rhash_tbl;
         count = atomic_read(&ht->nelems);
         tbl = rht_dereference_rcu(ht->tbl, ht);
         buckets = tbl->size;
         rcu_read_unlock();
     }
     mutex_unlock(&nfsd_mutex);
 
     for_each_possible_cpu(i) {
         hits += per_cpu(nfsd_file_cache_hits, i);
         acquisitions += per_cpu(nfsd_file_acquisitions, i);
         releases += per_cpu(nfsd_file_releases, i);
         total_age += per_cpu(nfsd_file_total_age, i);
         evictions += per_cpu(nfsd_file_evictions, i);
         pages_flushed += per_cpu(nfsd_file_pages_flushed, i);
     }
 
     seq_printf(m, "total entries: %u\n", count);
     seq_printf(m, "hash buckets:  %u\n", buckets);
     seq_printf(m, "lru entries:   %lu\n", lru);
     seq_printf(m, "cache hits:    %lu\n", hits);
     seq_printf(m, "acquisitions:  %lu\n", acquisitions);
     seq_printf(m, "releases:      %lu\n", releases);
     seq_printf(m, "evictions:     %lu\n", evictions);
     if (releases)
         seq_printf(m, "mean age (ms): %ld\n", total_age / releases);
     else
         seq_printf(m, "mean age (ms): -\n");
     seq_printf(m, "pages flushed: %lu\n", pages_flushed);
     return 0;
 }
 
 int nfsd_file_cache_stats_open(struct inode *inode, struct file *file)
 {
     return single_open(file, nfsd_file_cache_stats_show, NULL);
 }

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