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Commit f55fb0c2 authored by Ian Kent's avatar Ian Kent Committed by Linus Torvalds
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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: default avatarIan Kent <raven@themaw.net>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 29594404

fs/autofs4/expire.c

+0 −9
Original line number Diff line number Diff line
@@ -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
Original line number Diff line number Diff line
@@ -355,7 +355,6 @@ static struct vfsmount *autofs4_d_automount(struct path *path) 
		status = autofs4_mount_wait(dentry);

		if (status)

			return ERR_PTR(status);

		spin_lock(&sbi->fs_lock);

		goto done;

	}
@@ -364,8 +363,11 @@ static struct vfsmount *autofs4_d_automount(struct path *path) 
	 * having d_mountpoint() true, so there's no need to call back

	 * to the daemon.

	 */

	if (dentry->d_inode && S_ISLNK(dentry->d_inode->i_mode))

	if (dentry->d_inode && S_ISLNK(dentry->d_inode->i_mode)) {

		spin_unlock(&sbi->fs_lock);

		goto done;

	}



	if (!d_mountpoint(dentry)) {

		/*

		 * It's possible that user space hasn't removed directories
@@ -379,8 +381,10 @@ static struct vfsmount *autofs4_d_automount(struct path *path) 
		 * require user space behave.

		 */

		if (sbi->version > 4) {

			if (have_submounts(dentry))

			if (have_submounts(dentry)) {

				spin_unlock(&sbi->fs_lock);

				goto done;

			}

		} else {

			spin_lock(&dentry->d_lock);

			if (!list_empty(&dentry->d_subdirs)) {
@@ -399,28 +403,8 @@ static struct vfsmount *autofs4_d_automount(struct path *path) 
			return ERR_PTR(status);

		}

	}

done:

	if (!(ino->flags & AUTOFS_INF_EXPIRING)) {

		/*

		 * Any needed mounting has been completed and the path

		 * updated so clear DCACHE_NEED_AUTOMOUNT so we don't

		 * call ->d_automount() on rootless multi-mounts since

		 * it can lead to an incorrect ELOOP error return.

		 *

		 * Only clear DMANAGED_AUTOMOUNT for rootless multi-mounts and

		 * symlinks as in all other cases the dentry will be covered by

		 * an actual mount so ->d_automount() won't be called during

		 * the follow.

		 */

		spin_lock(&dentry->d_lock);

		if ((!d_mountpoint(dentry) &&

		    !list_empty(&dentry->d_subdirs)) ||

		    (dentry->d_inode && S_ISLNK(dentry->d_inode->i_mode)))

			__managed_dentry_clear_automount(dentry);

		spin_unlock(&dentry->d_lock);

	}

	spin_unlock(&sbi->fs_lock);



done:

	/* Mount succeeded, check if we ended up with a new dentry */

	dentry = autofs4_mountpoint_changed(path);

	if (!dentry)
@@ -432,6 +416,8 @@ static struct vfsmount *autofs4_d_automount(struct path *path) 
int autofs4_d_manage(struct dentry *dentry, bool rcu_walk)

{

	struct autofs_sb_info *sbi = autofs4_sbi(dentry->d_sb);

	struct autofs_info *ino = autofs4_dentry_ino(dentry);

	int status;



	DPRINTK("dentry=%p %.*s",

		dentry, dentry->d_name.len, dentry->d_name.name);
@@ -456,7 +442,32 @@ int autofs4_d_manage(struct dentry *dentry, bool rcu_walk) 
	 * This dentry may be under construction so wait on mount

	 * completion.

	 */

	return autofs4_mount_wait(dentry);

	status = autofs4_mount_wait(dentry);

	if (status)

		return status;



	spin_lock(&sbi->fs_lock);

	/*

	 * If the dentry has been selected for expire while we slept

	 * on the lock then it might go away. We'll deal with that in

	 * ->d_automount() and wait on a new mount if the expire

	 * succeeds or return here if it doesn't (since there's no

	 * mount to follow with a rootless multi-mount).

	 */

	if (!(ino->flags & AUTOFS_INF_EXPIRING)) {

		/*

		 * Any needed mounting has been completed and the path

		 * updated so check if this is a rootless multi-mount so

		 * we can avoid needless calls ->d_automount() and avoid

		 * an incorrect ELOOP error return.

		 */

		if ((!d_mountpoint(dentry) && !simple_empty(dentry)) ||

		    (dentry->d_inode && S_ISLNK(dentry->d_inode->i_mode)))

			status = -EISDIR;

	}

	spin_unlock(&sbi->fs_lock);



	return status;

}



/* Lookups in the root directory */