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autofs4: fix pending checks 

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>
This commit is contained in:
Ian Kent 2008-07-23 21:30:25 -07:00 committed by Linus Torvalds
parent ff9cd499d6
commit 26e81b3142
1 changed files with 6 additions and 3 deletions
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9
fs/autofs4/root.c
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@ -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);