From: Jan Blunck <j.blunck@tu-harburg.de>
d_drop() must use the dentry->d_lock spinlock. In some cases __d_drop()
was used without holding the dentry->d_lock spinlock, too. This could end
in a race with __d_lookup().
Signed-off-by: Jan Blunck <j.blunck@tu-harburg.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
---
25-akpm/fs/autofs4/root.c | 2 ++
25-akpm/fs/dcache.c | 3 +++
25-akpm/fs/namei.c | 14 +++++---------
25-akpm/fs/proc/base.c | 6 +++++-
25-akpm/fs/sysfs/inode.c | 6 +++++-
25-akpm/include/linux/dcache.h | 19 ++++++++++---------
6 files changed, 30 insertions(+), 20 deletions(-)
diff -puN fs/autofs4/root.c~d_drop-should-use-per-dentry-lock fs/autofs4/root.c
--- 25/fs/autofs4/root.c~d_drop-should-use-per-dentry-lock 2005-02-22 18:16:46.000000000 -0800
+++ 25-akpm/fs/autofs4/root.c 2005-02-22 18:16:46.000000000 -0800
@@ -605,7 +605,9 @@ static int autofs4_dir_rmdir(struct inod
spin_unlock(&dcache_lock);
return -ENOTEMPTY;
}
+ spin_lock(&dentry->d_lock);
__d_drop(dentry);
+ spin_unlock(&dentry->d_lock);
spin_unlock(&dcache_lock);
dput(ino->dentry);
diff -puN fs/dcache.c~d_drop-should-use-per-dentry-lock fs/dcache.c
--- 25/fs/dcache.c~d_drop-should-use-per-dentry-lock 2005-02-22 18:16:46.000000000 -0800
+++ 25-akpm/fs/dcache.c 2005-02-22 18:16:46.000000000 -0800
@@ -340,13 +340,16 @@ restart:
tmp = head;
while ((tmp = tmp->next) != head) {
struct dentry *dentry = list_entry(tmp, struct dentry, d_alias);
+ spin_lock(&dentry->d_lock);
if (!atomic_read(&dentry->d_count)) {
__dget_locked(dentry);
__d_drop(dentry);
+ spin_unlock(&dentry->d_lock);
spin_unlock(&dcache_lock);
dput(dentry);
goto restart;
}
+ spin_unlock(&dentry->d_lock);
}
spin_unlock(&dcache_lock);
}
diff -puN fs/namei.c~d_drop-should-use-per-dentry-lock fs/namei.c
--- 25/fs/namei.c~d_drop-should-use-per-dentry-lock 2005-02-22 18:16:46.000000000 -0800
+++ 25-akpm/fs/namei.c 2005-02-22 18:16:46.000000000 -0800
@@ -1685,17 +1685,13 @@ out:
void dentry_unhash(struct dentry *dentry)
{
dget(dentry);
- spin_lock(&dcache_lock);
- switch (atomic_read(&dentry->d_count)) {
- default:
- spin_unlock(&dcache_lock);
+ if (atomic_read(&dentry->d_count))
shrink_dcache_parent(dentry);
- spin_lock(&dcache_lock);
- if (atomic_read(&dentry->d_count) != 2)
- break;
- case 2:
+ spin_lock(&dcache_lock);
+ spin_lock(&dentry->d_lock);
+ if (atomic_read(&dentry->d_count) == 2)
__d_drop(dentry);
- }
+ spin_unlock(&dentry->d_lock);
spin_unlock(&dcache_lock);
}
diff -puN fs/proc/base.c~d_drop-should-use-per-dentry-lock fs/proc/base.c
--- 25/fs/proc/base.c~d_drop-should-use-per-dentry-lock 2005-02-22 18:16:46.000000000 -0800
+++ 25-akpm/fs/proc/base.c 2005-02-22 18:16:46.000000000 -0800
@@ -1630,11 +1630,15 @@ struct dentry *proc_pid_unhash(struct ta
if (proc_dentry != NULL) {
spin_lock(&dcache_lock);
+ spin_lock(&proc_dentry->d_lock);
if (!d_unhashed(proc_dentry)) {
dget_locked(proc_dentry);
__d_drop(proc_dentry);
- } else
+ spin_unlock(&proc_dentry->d_lock);
+ } else {
+ spin_unlock(&proc_dentry->d_lock);
proc_dentry = NULL;
+ }
spin_unlock(&dcache_lock);
}
return proc_dentry;
diff -puN fs/sysfs/inode.c~d_drop-should-use-per-dentry-lock fs/sysfs/inode.c
--- 25/fs/sysfs/inode.c~d_drop-should-use-per-dentry-lock 2005-02-22 18:16:46.000000000 -0800
+++ 25-akpm/fs/sysfs/inode.c 2005-02-22 18:16:46.000000000 -0800
@@ -129,13 +129,17 @@ void sysfs_drop_dentry(struct sysfs_dire
if (dentry) {
spin_lock(&dcache_lock);
+ spin_lock(&dentry->d_lock);
if (!(d_unhashed(dentry) && dentry->d_inode)) {
dget_locked(dentry);
__d_drop(dentry);
+ spin_unlock(&dentry->d_lock);
spin_unlock(&dcache_lock);
simple_unlink(parent->d_inode, dentry);
- } else
+ } else {
+ spin_unlock(&dentry->d_lock);
spin_unlock(&dcache_lock);
+ }
}
}
diff -puN include/linux/dcache.h~d_drop-should-use-per-dentry-lock include/linux/dcache.h
--- 25/include/linux/dcache.h~d_drop-should-use-per-dentry-lock 2005-02-22 18:16:46.000000000 -0800
+++ 25-akpm/include/linux/dcache.h 2005-02-22 18:16:46.000000000 -0800
@@ -162,17 +162,16 @@ extern spinlock_t dcache_lock;
* d_drop - drop a dentry
* @dentry: dentry to drop
*
- * d_drop() unhashes the entry from the parent
- * dentry hashes, so that it won't be found through
- * a VFS lookup any more. Note that this is different
- * from deleting the dentry - d_delete will try to
- * mark the dentry negative if possible, giving a
- * successful _negative_ lookup, while d_drop will
+ * d_drop() unhashes the entry from the parent dentry hashes, so that it won't
+ * be found through a VFS lookup any more. Note that this is different from
+ * deleting the dentry - d_delete will try to mark the dentry negative if
+ * possible, giving a successful _negative_ lookup, while d_drop will
* just make the cache lookup fail.
*
- * d_drop() is used mainly for stuff that wants
- * to invalidate a dentry for some reason (NFS
- * timeouts or autofs deletes).
+ * d_drop() is used mainly for stuff that wants to invalidate a dentry for some
+ * reason (NFS timeouts or autofs deletes).
+ *
+ * __d_drop requires dentry->d_lock.
*/
static inline void __d_drop(struct dentry *dentry)
@@ -186,7 +185,9 @@ static inline void __d_drop(struct dentr
static inline void d_drop(struct dentry *dentry)
{
spin_lock(&dcache_lock);
+ spin_lock(&dentry->d_lock);
__d_drop(dentry);
+ spin_unlock(&dentry->d_lock);
spin_unlock(&dcache_lock);
}
_