diff --git a/Documentation/filesystems/nfs/Exporting b/Documentation/filesystems/nfs/Exporting
index 520a4becb75c..63889149f532 100644
--- a/Documentation/filesystems/nfs/Exporting
+++ b/Documentation/filesystems/nfs/Exporting
@@ -56,13 +56,25 @@ a/ A dentry flag DCACHE_DISCONNECTED which is set on
any dentry that might not be part of the proper prefix.
This is set when anonymous dentries are created, and cleared when a
dentry is noticed to be a child of a dentry which is in the proper
- prefix.
+ prefix. If the refcount on a dentry with this flag set
+ becomes zero, the dentry is immediately discarded, rather than being
+ kept in the dcache. If a dentry that is not already in the dcache
+ is repeatedly accessed by filehandle (as NFSD might do), an new dentry
+ will be a allocated for each access, and discarded at the end of
+ the access.
-b/ A per-superblock list "s_anon" of dentries which are the roots of
- subtrees that are not in the proper prefix. These dentries, as
- well as the proper prefix, need to be released at unmount time. As
- these dentries will not be hashed, they are linked together on the
- d_hash list_head.
+ Note that such a dentry can acquire children, name, ancestors, etc.
+ without losing DCACHE_DISCONNECTED - that flag is only cleared when
+ subtree is successfully reconnected to root. Until then dentries
+ in such subtree are retained only as long as there are references;
+ refcount reaching zero means immediate eviction, same as for unhashed
+ dentries. That guarantees that we won't need to hunt them down upon
+ umount.
+
+b/ A primitive for creation of secondary roots - d_obtain_root(inode).
+ Those do _not_ bear DCACHE_DISCONNECTED. They are placed on the
+ per-superblock list (->s_roots), so they can be located at umount
+ time for eviction purposes.
c/ Helper routines to allocate anonymous dentries, and to help attach
loose directory dentries at lookup time. They are:
@@ -77,7 +89,6 @@ c/ Helper routines to allocate anonymous dentries, and to help attach
(such as an anonymous one created by d_obtain_alias), if appropriate.
It returns NULL when the passed-in dentry is used, following the calling
convention of ->lookup.
-
Filesystem Issues
-----------------
diff --git a/drivers/staging/lustre/lustre/llite/llite_internal.h b/drivers/staging/lustre/lustre/llite/llite_internal.h
index b133fd00c08c..0d62fcf016dc 100644
--- a/drivers/staging/lustre/lustre/llite/llite_internal.h
+++ b/drivers/staging/lustre/lustre/llite/llite_internal.h
@@ -1296,15 +1296,7 @@ static inline void d_lustre_invalidate(struct dentry *dentry, int nested)
spin_lock_nested(&dentry->d_lock,
nested ? DENTRY_D_LOCK_NESTED : DENTRY_D_LOCK_NORMAL);
ll_d2d(dentry)->lld_invalid = 1;
- /*
- * We should be careful about dentries created by d_obtain_alias().
- * These dentries are not put in the dentry tree, instead they are
- * linked to sb->s_anon through dentry->d_hash.
- * shrink_dcache_for_umount() shrinks the tree and sb->s_anon list.
- * If we unhashed such a dentry, unmount would not be able to find
- * it and busy inodes would be reported.
- */
- if (d_count(dentry) == 0 && !(dentry->d_flags & DCACHE_DISCONNECTED))
+ if (d_count(dentry) == 0)
__d_drop(dentry);
spin_unlock(&dentry->d_lock);
}
diff --git a/fs/dcache.c b/fs/dcache.c
index b99a39206930..17e6b84b9656 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -48,8 +48,8 @@
* - i_dentry, d_u.d_alias, d_inode of aliases
* dcache_hash_bucket lock protects:
* - the dcache hash table
- * s_anon bl list spinlock protects:
- * - the s_anon list (see __d_drop)
+ * s_roots bl list spinlock protects:
+ * - the s_roots list (see __d_drop)
* dentry->d_sb->s_dentry_lru_lock protects:
* - the dcache lru lists and counters
* d_lock protects:
@@ -67,7 +67,7 @@
* dentry->d_lock
* dentry->d_sb->s_dentry_lru_lock
* dcache_hash_bucket lock
- * s_anon lock
+ * s_roots lock
*
* If there is an ancestor relationship:
* dentry->d_parent->...->d_parent->d_lock
@@ -476,10 +476,10 @@ void __d_drop(struct dentry *dentry)
/*
* Hashed dentries are normally on the dentry hashtable,
* with the exception of those newly allocated by
- * d_obtain_alias, which are always IS_ROOT:
+ * d_obtain_root, which are always IS_ROOT:
*/
if (unlikely(IS_ROOT(dentry)))
- b = &dentry->d_sb->s_anon;
+ b = &dentry->d_sb->s_roots;
else
b = d_hash(dentry->d_name.hash);
@@ -1499,8 +1499,8 @@ void shrink_dcache_for_umount(struct super_block *sb)
sb->s_root = NULL;
do_one_tree(dentry);
- while (!hlist_bl_empty(&sb->s_anon)) {
- dentry = dget(hlist_bl_entry(hlist_bl_first(&sb->s_anon), struct dentry, d_hash));
+ while (!hlist_bl_empty(&sb->s_roots)) {
+ dentry = dget(hlist_bl_entry(hlist_bl_first(&sb->s_roots), struct dentry, d_hash));
do_one_tree(dentry);
}
}
@@ -1964,9 +1964,11 @@ static struct dentry *__d_obtain_alias(struct inode *inode, int disconnected)
spin_lock(&tmp->d_lock);
__d_set_inode_and_type(tmp, inode, add_flags);
hlist_add_head(&tmp->d_u.d_alias, &inode->i_dentry);
- hlist_bl_lock(&tmp->d_sb->s_anon);
- hlist_bl_add_head(&tmp->d_hash, &tmp->d_sb->s_anon);
- hlist_bl_unlock(&tmp->d_sb->s_anon);
+ if (!disconnected) {
+ hlist_bl_lock(&tmp->d_sb->s_roots);
+ hlist_bl_add_head(&tmp->d_hash, &tmp->d_sb->s_roots);
+ hlist_bl_unlock(&tmp->d_sb->s_roots);
+ }
spin_unlock(&tmp->d_lock);
spin_unlock(&inode->i_lock);
diff --git a/fs/super.c b/fs/super.c
index d4e33e8f1e6f..9ea66601d664 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -207,7 +207,7 @@ static struct super_block *alloc_super(struct file_system_type *type, int flags,
if (s->s_user_ns != &init_user_ns)
s->s_iflags |= SB_I_NODEV;
INIT_HLIST_NODE(&s->s_instances);
- INIT_HLIST_BL_HEAD(&s->s_anon);
+ INIT_HLIST_BL_HEAD(&s->s_roots);
mutex_init(&s->s_sync_lock);
INIT_LIST_HEAD(&s->s_inodes);
spin_lock_init(&s->s_inode_list_lock);
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 2995a271ec46..6276f8315e5b 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1359,7 +1359,7 @@ struct super_block {
const struct fscrypt_operations *s_cop;
- struct hlist_bl_head s_anon; /* anonymous dentries for (nfs) exporting */
+ struct hlist_bl_head s_roots; /* alternate root dentries for NFS */
struct list_head s_mounts; /* list of mounts; _not_ for fs use */
struct block_device *s_bdev;
struct backing_dev_info *s_bdi;