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Commit ef16cc59 authored by NeilBrown's avatar NeilBrown Committed by Linus Torvalds
Browse files

autofs4: d_manage() should return -EISDIR when appropriate in rcu-walk mode. 



If rcu-walk mode we don't *have* to return -EISDIR for non-mount-traps
as we will simply drop into REF-walk and handling DCACHE_NEED_AUTOMOUNT
dentrys the slow way.  But it is better if we do when possible.

In 'oz_mode', use the same condition as ref-walk: if not a mountpoint,
then it must be -EISDIR.

In regular mode there are most tests needed.  Most of them can be
performed without taking any spinlocks.  If we find a directory that
isn't obviously empty, and isn't mounted on, we need to call
'simple_empty()' which does take a spinlock.  If this turned out to hurt
performance, some other approach could be found to signal when a
directory is known to be empty.

Signed-off-by: default avatarNeilBrown <neilb@suse.de>
Reviewed-by: default avatarIan Kent <raven@themaw.net>
Tested-by: default avatarIan Kent <raven@themaw.net>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 4d885f90

fs/autofs4/root.c

+20 −6
Original line number Diff line number Diff line
@@ -433,8 +433,6 @@ static int autofs4_d_manage(struct dentry *dentry, bool rcu_walk) 


	/* The daemon never waits. */

	if (autofs4_oz_mode(sbi)) {

		if (rcu_walk)

			return 0;

		if (!d_mountpoint(dentry))

			return -EISDIR;

		return 0;
@@ -452,12 +450,28 @@ static int autofs4_d_manage(struct dentry *dentry, bool rcu_walk) 
	if (status)

		return status;



	if (rcu_walk)

		/* it is always safe to return 0 as the worst that

		 * will happen is we retry in REF-walk mode.

		 * Better than always taking a lock.

	if (rcu_walk) {

		/* We don't need fs_lock in rcu_walk mode,

		 * just testing 'AUTOFS_INFO_NO_RCU' is enough.

		 * simple_empty() takes a spinlock, so leave it

		 * to last.

		 * We only return -EISDIR when certain this isn't

		 * a mount-trap.

		 */

		struct inode *inode;

		if (ino->flags & (AUTOFS_INF_EXPIRING | AUTOFS_INF_NO_RCU))

			return 0;

		if (d_mountpoint(dentry))

			return 0;

		inode = ACCESS_ONCE(dentry->d_inode);

		if (inode && S_ISLNK(inode->i_mode))

			return -EISDIR;

		if (list_empty(&dentry->d_subdirs))

			return 0;

		if (!simple_empty(dentry))

			return -EISDIR;

		return 0;

	}



	spin_lock(&sbi->fs_lock);

	/*