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autofs4 - dont clear DCACHE_NEED_AUTOMOUNT on rootless mount

PATCH New Ian Kent 1 participant 2 messages Dec 14, 2012

Subsystems (2)
VFS Kernel automounter
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Share & tools
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Ian Kent

author maintainer
#0 lore raw

PATCH 1/2 autofs4 - dont clear DCACHE_NEED_AUTOMOUNT on rootless mount

The DCACHE_NEED_AUTOMOUNT flag is cleared on mount and set on expire for autofs rootless multi-mount dentrys to prevent unnecessary calls to ->d_automount().

Since DCACHE_MANAGE_TRANSIT is always set on autofs dentrys ->d_managed() is always called so the check can be done in ->d_manage() without the need to change the flag. This still avoids unnecessary calls to ->d_automount(), adds negligible overhead and eliminates a seriously ugly check in the expire code.

Signed-off-by Ian Kent <[email protected]>

---

 fs/autofs4/expire.c |    9 --------
 fs/autofs4/root.c   |   61 ++++++++++++++++++++++++++++++---------------------
 2 files changed, 36 insertions(+), 34 deletions(-)
fs/autofs4/expire.c +0 -9
index 842d000..01443ce 100644
@@ -548,15 +548,6 @@ int autofs4_do_expire_multi(struct super_block *sb, struct vfsmount *mnt,
 
 		spin_lock(&sbi->fs_lock);
 		ino->flags &= ~AUTOFS_INF_EXPIRING;
-		spin_lock(&dentry->d_lock);
-		if (!ret) {
-			if ((IS_ROOT(dentry) ||
-			    (autofs_type_indirect(sbi->type) &&
-			     IS_ROOT(dentry->d_parent))) &&
-			    !(dentry->d_flags & DCACHE_NEED_AUTOMOUNT))
-				__managed_dentry_set_automount(dentry);
-		}
-		spin_unlock(&dentry->d_lock);
 		complete_all(&ino->expire_complete);
 		spin_unlock(&sbi->fs_lock);
 		dput(dentry);
fs/autofs4/root.c +36 -25

100 lines not on this page · raw message

author maintainer
#1 lore raw

PATCH 2/2 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 <[email protected]>

---

 fs/autofs4/root.c |   22 +++++-----------------
 1 files changed, 5 insertions(+), 17 deletions(-)
fs/autofs4/root.c +5 -17
index 30a6ab66..c934476 100644
@@ -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:

@@ -386,12 +383,8 @@ static struct vfsmount *autofs4_d_automount(struct path *path)
 				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 @@ static int autofs4_dir_unlink(struct inode *dir, struct dentry *dentry)
 
 	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 @@ static int autofs4_dir_rmdir(struct inode *dir, struct dentry *dentry)
 		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)