linux-kernel - [PATCH 3/7] autofs4

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Date:	Fri, 18 Jul 2008 10:37:10 +0800
From:	Ian Kent <raven@...maw.net>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	autofs mailing list <autofs@...ux.kernel.org>,
	Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linux-fsdevel <linux-fsdevel@...r.kernel.org>,
	Al Viro <viro@...IV.linux.org.uk>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: [PATCH 3/7] 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@...maw.net>

---

 fs/autofs4/root.c |    9 ++++++---
 1 files changed, 6 insertions(+), 3 deletions(-)


diff --git a/fs/autofs4/root.c b/fs/autofs4/root.c
index e842b0a..2944b28 100644
--- a/fs/autofs4/root.c
+++ b/fs/autofs4/root.c
@@ -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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