summaryrefslogtreecommitdiff
path: root/fs/dcache.c
diff options
context:
space:
mode:
authorAl Viro <viro@zeniv.linux.org.uk>2017-07-07 14:51:19 -0400
committerAl Viro <viro@zeniv.linux.org.uk>2017-07-07 20:09:10 -0400
commit49d31c2f389acfe83417083e1208422b4091cd9e (patch)
treeb4ab96fd8300dd73a398a7d587f8839fa052c03b /fs/dcache.c
parenta8e2b6367794e6cee9eecba6d5ff425f338e0754 (diff)
dentry name snapshots
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>
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 b85da8897ffa..831f3a9a8f05 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -277,6 +277,33 @@ 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)