autofs4 - use simple_empty() for empty directory check
For direct (and offset) mounts, if an automounted mount is manually
umounted the trigger mount dentry can appear non-empty causing it to
not trigger mounts. This can also happen if there is a file handle
leak in a user space automounting application.
This happens because, when a ioctl control file handle is opened
on the mount, a cursor dentry is created which causes list_empty()
to see the dentry as non-empty. Since there is a case where listing
the directory of these dentrys is needed, the use of dcache_dir_*()
functions for .open() and .release() is needed.
Consequently simple_empty() must be used instead of list_empty()
when checking for an empty directory.
Signed-off-by: Ian Kent <raven@themaw.net>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/fs/autofs4/root.c b/fs/autofs4/root.c
index 30a6ab66..c9344760 100644
--- a/fs/autofs4/root.c
+++ b/fs/autofs4/root.c
@@ -124,13 +124,10 @@
* it.
*/
spin_lock(&sbi->lookup_lock);
- spin_lock(&dentry->d_lock);
- if (!d_mountpoint(dentry) && list_empty(&dentry->d_subdirs)) {
- spin_unlock(&dentry->d_lock);
+ if (!d_mountpoint(dentry) && simple_empty(dentry)) {
spin_unlock(&sbi->lookup_lock);
return -ENOENT;
}
- spin_unlock(&dentry->d_lock);
spin_unlock(&sbi->lookup_lock);
out:
@@ -386,12 +383,8 @@
goto done;
}
} else {
- spin_lock(&dentry->d_lock);
- if (!list_empty(&dentry->d_subdirs)) {
- spin_unlock(&dentry->d_lock);
+ if (!simple_empty(dentry))
goto done;
- }
- spin_unlock(&dentry->d_lock);
}
ino->flags |= AUTOFS_INF_PENDING;
spin_unlock(&sbi->fs_lock);
@@ -610,9 +603,7 @@
spin_lock(&sbi->lookup_lock);
__autofs4_add_expiring(dentry);
- spin_lock(&dentry->d_lock);
- __d_drop(dentry);
- spin_unlock(&dentry->d_lock);
+ d_drop(dentry);
spin_unlock(&sbi->lookup_lock);
return 0;
@@ -683,15 +674,12 @@
return -EACCES;
spin_lock(&sbi->lookup_lock);
- spin_lock(&dentry->d_lock);
- if (!list_empty(&dentry->d_subdirs)) {
- spin_unlock(&dentry->d_lock);
+ if (!simple_empty(dentry)) {
spin_unlock(&sbi->lookup_lock);
return -ENOTEMPTY;
}
__autofs4_add_expiring(dentry);
- __d_drop(dentry);
- spin_unlock(&dentry->d_lock);
+ d_drop(dentry);
spin_unlock(&sbi->lookup_lock);
if (sbi->version < 5)