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authorAl Viro <viro@zeniv.linux.org.uk>2017-07-07 14:51:19 -0400
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2017-08-06 19:19:42 -0700
commit407669f2c9fe9f32aeb39f715d748fe456718aac (patch)
treed05f6b074f7085b59dfeb243ec53ee0fc01cb1e7 /fs/dcache.c
parent9909e61c100621792be24cc255253cf8352ed925 (diff)
dentry name snapshots
commit 49d31c2f389acfe83417083e1208422b4091cd9e upstream. take_dentry_name_snapshot() takes a safe snapshot of dentry name; if the name is a short one, it gets copied into caller-supplied structure, otherwise an extra reference to external name is grabbed (those are never modified). In either case the pointer to stable string is stored into the same structure. dentry must be held by the caller of take_dentry_name_snapshot(), but may be freely dropped afterwards - the snapshot will stay until destroyed by release_dentry_name_snapshot(). Intended use: struct name_snapshot s; take_dentry_name_snapshot(&s, dentry); ... access s.name ... release_dentry_name_snapshot(&s); Replaces fsnotify_oldname_...(), gets used in fsnotify to obtain the name to pass down with event. Signed-off-by: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'fs/dcache.c')
-rw-r--r--fs/dcache.c27
1 files changed, 27 insertions, 0 deletions
diff --git a/fs/dcache.c b/fs/dcache.c
index 3000cbb54949..3ed642e0a0c2 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -269,6 +269,33 @@ static inline int dname_external(const struct dentry *dentry)
return dentry->d_name.name != dentry->d_iname;
}
+void take_dentry_name_snapshot(struct name_snapshot *name, struct dentry *dentry)
+{
+ spin_lock(&dentry->d_lock);
+ if (unlikely(dname_external(dentry))) {
+ struct external_name *p = external_name(dentry);
+ atomic_inc(&p->u.count);
+ spin_unlock(&dentry->d_lock);
+ name->name = p->name;
+ } else {
+ memcpy(name->inline_name, dentry->d_iname, DNAME_INLINE_LEN);
+ spin_unlock(&dentry->d_lock);
+ name->name = name->inline_name;
+ }
+}
+EXPORT_SYMBOL(take_dentry_name_snapshot);
+
+void release_dentry_name_snapshot(struct name_snapshot *name)
+{
+ if (unlikely(name->name != name->inline_name)) {
+ struct external_name *p;
+ p = container_of(name->name, struct external_name, name[0]);
+ if (unlikely(atomic_dec_and_test(&p->u.count)))
+ kfree_rcu(p, u.head);
+ }
+}
+EXPORT_SYMBOL(release_dentry_name_snapshot);
+
static inline void __d_set_inode_and_type(struct dentry *dentry,
struct inode *inode,
unsigned type_flags)