UPSTREAM: 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.
BUG=chromium:754205
TEST=Build and run
Change-Id: Ic11a9c94b484d10ae8d7b04ec00ec0dd3e45ef59
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Guenter Roeck <groeck@chromium.org>
(cherry picked from commit 49d31c2f389)
Reviewed-on: https://chromium-review.googlesource.com/610515
Reviewed-by: Sonny Rao <sonnyrao@chromium.org>
(cherry picked from commit 9cb7a61dceeb06c15a47ccdb57b9c5f66a588a1f)
Reviewed-on: https://chromium-review.googlesource.com/617418
diff --git a/fs/dcache.c b/fs/dcache.c
index 7b8feb6..bdf37d8 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -269,6 +269,33 @@
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)
diff --git a/fs/debugfs/inode.c b/fs/debugfs/inode.c
index 0dccc0c..d4b8462 100644
--- a/fs/debugfs/inode.c
+++ b/fs/debugfs/inode.c
@@ -732,7 +732,7 @@
{
int error;
struct dentry *dentry = NULL, *trap;
- const char *old_name;
+ struct name_snapshot old_name;
trap = lock_rename(new_dir, old_dir);
/* Source or destination directories don't exist? */
@@ -747,19 +747,19 @@
if (IS_ERR(dentry) || dentry == trap || d_really_is_positive(dentry))
goto exit;
- old_name = fsnotify_oldname_init(old_dentry->d_name.name);
+ take_dentry_name_snapshot(&old_name, old_dentry);
error = simple_rename(d_inode(old_dir), old_dentry, d_inode(new_dir),
dentry);
if (error) {
- fsnotify_oldname_free(old_name);
+ release_dentry_name_snapshot(&old_name);
goto exit;
}
d_move(old_dentry, dentry);
- fsnotify_move(d_inode(old_dir), d_inode(new_dir), old_name,
+ fsnotify_move(d_inode(old_dir), d_inode(new_dir), old_name.name,
d_is_dir(old_dentry),
NULL, old_dentry);
- fsnotify_oldname_free(old_name);
+ release_dentry_name_snapshot(&old_name);
unlock_rename(new_dir, old_dir);
dput(dentry);
return old_dentry;
diff --git a/fs/namei.c b/fs/namei.c
index 144e45c..8b7d7b1 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -4232,11 +4232,11 @@
{
int error;
bool is_dir = d_is_dir(old_dentry);
- const unsigned char *old_name;
struct inode *source = old_dentry->d_inode;
struct inode *target = new_dentry->d_inode;
bool new_is_dir = false;
unsigned max_links = new_dir->i_sb->s_max_links;
+ struct name_snapshot old_name;
/*
* Check source == target.
@@ -4290,7 +4290,7 @@
if (error)
return error;
- old_name = fsnotify_oldname_init(old_dentry->d_name.name);
+ take_dentry_name_snapshot(&old_name, old_dentry);
dget(new_dentry);
if (!is_dir || (flags & RENAME_EXCHANGE))
lock_two_nondirectories(source, target);
@@ -4351,14 +4351,14 @@
mutex_unlock(&target->i_mutex);
dput(new_dentry);
if (!error) {
- fsnotify_move(old_dir, new_dir, old_name, is_dir,
+ fsnotify_move(old_dir, new_dir, old_name.name, is_dir,
!(flags & RENAME_EXCHANGE) ? target : NULL, old_dentry);
if (flags & RENAME_EXCHANGE) {
fsnotify_move(new_dir, old_dir, old_dentry->d_name.name,
new_is_dir, NULL, new_dentry);
}
}
- fsnotify_oldname_free(old_name);
+ release_dentry_name_snapshot(&old_name);
return error;
}
diff --git a/fs/notify/fsnotify.c b/fs/notify/fsnotify.c
index db39de2..a64adc2 100644
--- a/fs/notify/fsnotify.c
+++ b/fs/notify/fsnotify.c
@@ -104,16 +104,20 @@
if (unlikely(!fsnotify_inode_watches_children(p_inode)))
__fsnotify_update_child_dentry_flags(p_inode);
else if (p_inode->i_fsnotify_mask & mask) {
+ struct name_snapshot name;
+
/* we are notifying a parent so come up with the new mask which
* specifies these are events which came from a child. */
mask |= FS_EVENT_ON_CHILD;
+ take_dentry_name_snapshot(&name, dentry);
if (path)
ret = fsnotify(p_inode, mask, path, FSNOTIFY_EVENT_PATH,
- dentry->d_name.name, 0);
+ name.name, 0);
else
ret = fsnotify(p_inode, mask, dentry->d_inode, FSNOTIFY_EVENT_INODE,
- dentry->d_name.name, 0);
+ name.name, 0);
+ release_dentry_name_snapshot(&name);
}
dput(parent);
diff --git a/include/linux/dcache.h b/include/linux/dcache.h
index 702b6c5..0acbb85 100644
--- a/include/linux/dcache.h
+++ b/include/linux/dcache.h
@@ -616,5 +616,11 @@
return d_backing_inode(d_real(dentry));
}
+struct name_snapshot {
+ const char *name;
+ char inline_name[DNAME_INLINE_LEN];
+};
+void take_dentry_name_snapshot(struct name_snapshot *, struct dentry *);
+void release_dentry_name_snapshot(struct name_snapshot *);
#endif /* __LINUX_DCACHE_H */
diff --git a/include/linux/fsnotify.h b/include/linux/fsnotify.h
index 7ee1774..a7789559 100644
--- a/include/linux/fsnotify.h
+++ b/include/linux/fsnotify.h
@@ -310,35 +310,4 @@
}
}
-#if defined(CONFIG_FSNOTIFY) /* notify helpers */
-
-/*
- * fsnotify_oldname_init - save off the old filename before we change it
- */
-static inline const unsigned char *fsnotify_oldname_init(const unsigned char *name)
-{
- return kstrdup(name, GFP_KERNEL);
-}
-
-/*
- * fsnotify_oldname_free - free the name we got from fsnotify_oldname_init
- */
-static inline void fsnotify_oldname_free(const unsigned char *old_name)
-{
- kfree(old_name);
-}
-
-#else /* CONFIG_FSNOTIFY */
-
-static inline const char *fsnotify_oldname_init(const unsigned char *name)
-{
- return NULL;
-}
-
-static inline void fsnotify_oldname_free(const unsigned char *old_name)
-{
-}
-
-#endif /* CONFIG_FSNOTIFY */
-
#endif /* _LINUX_FS_NOTIFY_H */
