From: Ian Kent <raven@xxxxxxxxxx>
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.
It happens because, when the 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@xxxxxxxxxx>
---
fs/autofs4/autofs_i.h | 18 ++++++++++++++++++
fs/autofs4/root.c | 16 ++++------------
2 files changed, 22 insertions(+), 12 deletions(-)
diff --git a/fs/autofs4/autofs_i.h b/fs/autofs4/autofs_i.h
index 908e184..4c3f589 100644
--- a/fs/autofs4/autofs_i.h
+++ b/fs/autofs4/autofs_i.h
@@ -301,6 +301,24 @@ static inline int simple_positive(struct dentry *dentry)
return dentry->d_inode && !d_unhashed(dentry);
}
+static inline int __simple_empty(struct dentry *dentry)
+{
+ struct dentry *child;
+ int ret = 0;
+
+ list_for_each_entry(child, &dentry->d_subdirs, d_u.d_child) {
+ spin_lock_nested(&child->d_lock, DENTRY_D_LOCK_NESTED);
+ if (simple_positive(child)) {
+ spin_unlock(&child->d_lock);
+ goto out;
+ }
+ spin_unlock(&child->d_lock);
+ }
+ ret = 1;
+out:
+ return ret;
+}
+
static inline void __autofs4_add_expiring(struct dentry *dentry)
{
struct autofs_sb_info *sbi = autofs4_sbi(dentry->d_sb);
diff --git a/fs/autofs4/root.c b/fs/autofs4/root.c
index 91b1165..f39bf4b 100644
--- a/fs/autofs4/root.c
+++ b/fs/autofs4/root.c
@@ -124,13 +124,10 @@ static int autofs4_dir_open(struct inode *inode, struct file *file)
* 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:
@@ -382,12 +379,8 @@ static struct vfsmount *autofs4_d_automount(struct path *path)
if (have_submounts(dentry))
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);
@@ -413,8 +406,7 @@ done:
* the follow.
*/
spin_lock(&dentry->d_lock);
- if ((!d_mountpoint(dentry) &&
- !list_empty(&dentry->d_subdirs)) ||
+ if ((!d_mountpoint(dentry) && !__simple_empty(dentry)) ||
(dentry->d_inode && S_ISLNK(dentry->d_inode->i_mode)))
__managed_dentry_clear_automount(dentry);
spin_unlock(&dentry->d_lock);
@@ -673,7 +665,7 @@ static int autofs4_dir_rmdir(struct inode *dir, struct dentry *dentry)
spin_lock(&sbi->lookup_lock);
spin_lock(&dentry->d_lock);
- if (!list_empty(&dentry->d_subdirs)) {
+ if (!__simple_empty(dentry)) {
spin_unlock(&dentry->d_lock);
spin_unlock(&sbi->lookup_lock);
return -ENOTEMPTY;
--
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