autofs4: fix pending checks (26e81b31) · Commits · 戴 / test

There are two cases for which a dentry that has a pending mount request does not wait for completion. One is via autofs4_revalidate() and the other via autofs4_follow_link(). In revalidate, after the mount point directory is created, but before the mount is done, the check in try_to_fill_dentry() can can fail to send the dentry to the wait queue since the dentry is positive and the lookup flags may contain only LOOKUP_FOLLOW. Although we don't trigger a mount for the LOOKUP_FOLLOW flag, if ther's one pending we might as well wait and use the mounted dentry for the lookup. In autofs4_follow_link() the dentry is not checked to see if it is pending so it may fail to call try_to_fill_dentry() and not wait for mount completion. A dentry that is pending must always be sent to the wait queue. Signed-off-by:

Ian Kent <raven@themaw.net> Reviewed-by:

Jeff Moyer <jmoyer@redhat.com> Signed-off-by:

Andrew Morton <akpm@linux-foundation.org> Signed-off-by:

Linus Torvalds <torvalds@linux-foundation.org>

fs/autofs4/root.c

+6 −3

Original line number	Diff line number	Diff line
		@@ -177,7 +177,8 @@ static int try_to_fill_dentry(struct dentry *dentry, int flags)
		return status;
		}
		/* Trigger mount for path component or follow link */
		} else if (flags & (TRIGGER_FLAGS \| TRIGGER_INTENTS) \|\|
		} else if (dentry->d_flags & DCACHE_AUTOFS_PENDING \|\|
		flags & (TRIGGER_FLAGS \| TRIGGER_INTENTS) \|\|
		current->link_count) {
		DPRINTK("waiting for mount name=%.*s",
		dentry->d_name.len, dentry->d_name.name);
		@@ -223,7 +224,8 @@ static void autofs4_follow_link(struct dentry dentry, struct nameidata *nd)

		/* If it's our master or we shouldn't trigger a mount we're done */
		lookup_type = nd->flags & (TRIGGER_FLAGS \| TRIGGER_INTENTS);
		if (oz_mode \|\| !lookup_type)
		if (oz_mode \|\|
		!(lookup_type \|\| dentry->d_flags & DCACHE_AUTOFS_PENDING))
		goto done;

		/* If an expire request is pending wait for it. */
		@@ -242,7 +244,8 @@ static void autofs4_follow_link(struct dentry dentry, struct nameidata *nd)
		* don't try to mount it again.
		*/
		spin_lock(&dcache_lock);
		if (!d_mountpoint(dentry) && __simple_empty(dentry)) {
		if (dentry->d_flags & DCACHE_AUTOFS_PENDING \|\|
		(!d_mountpoint(dentry) && __simple_empty(dentry))) {
		spin_unlock(&dcache_lock);

		status = try_to_fill_dentry(dentry, 0);

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