[autofs] [PATCH] VFS: Fix automount for negative autofs dentries

[David Howells]

Autofs may set the DCACHE_NEED_AUTOMOUNT flag on negative dentries.  These
need attention from the automounter daemon regardless of the LOOKUP_FOLLOW flag.

Signed-off-by: David Howells dhowe...@redhat.com
Acked-by: Ian Kent ra...@themaw.net
---

 fs/namei.c |   27 +++
 1 files changed, 19 insertions(+), 8 deletions(-)

diff --git a/fs/namei.c b/fs/namei.c
index 0223c41..93e221e 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -777,18 +777,29 @@ static int follow_automount(struct path *path, unsigned 
flags,
if ((flags  LOOKUP_NO_AUTOMOUNT)  !(flags  LOOKUP_CONTINUE))
return -EISDIR; /* we actually want to stop here */
 
-   /* We want to mount if someone is trying to open/create a file of any
-* type under the mountpoint, wants to traverse through the mountpoint
-* or wants to open the mounted directory.
-*
-* We don't want to mount if someone's just doing a stat and they've
+   /* We don't want to mount if someone's just doing a stat and they've
 * set AT_SYMLINK_NOFOLLOW - unless they're stat'ing a directory and
 * appended a '/' to the name.
 */
-   if (!(flags  LOOKUP_FOLLOW) 
-   !(flags  (LOOKUP_CONTINUE | LOOKUP_DIRECTORY |
-  LOOKUP_OPEN | LOOKUP_CREATE)))
+   if (!(flags  LOOKUP_FOLLOW)) {
+   /* We do, however, want to mount if someone wants to open or
+* create a file of any type under the mountpoint, wants to
+* traverse through the mountpoint or wants to open the mounted
+* directory.
+*/
+   if (flags  (LOOKUP_CONTINUE | LOOKUP_DIRECTORY |
+LOOKUP_OPEN | LOOKUP_CREATE))
+   goto need_automount;
+
+   /* Also, autofs may mark negative dentries as being automount
+* points.  These will need the attentions of the daemon to
+* instantiate them before they can be used.
+*/
+   if (!path-dentry-d_inode)
+   goto need_automount;
return -EISDIR;
+   }
+need_automount:
 
current-total_link_count++;
if (current-total_link_count = 40)

___
autofs mailing list
autofs@linux.kernel.org
http://linux.kernel.org/mailman/listinfo/autofs

Re: [autofs] [PATCH] VFS: Fix automount for negative autofs dentries

[David Howells]

Christoph Hellwig h...@infradead.org wrote:

 would do the same.

But is much less obvious.  The LOOKUP_FOLLOW flag is the primary reason for
this statement.  The rest are subordinate and would be wholly irrelevant if
LOOKUP_FOLLOW was to be removed from the list.

David

___
autofs mailing list
autofs@linux.kernel.org
http://linux.kernel.org/mailman/listinfo/autofs

Re: [autofs] [PATCH] VFS: Fix automount for negative autofs dentries

[Christoph Hellwig]

On Mon, Jul 11, 2011 at 03:13:41PM +0100, David Howells wrote:
 Christoph Hellwig h...@infradead.org wrote:
 
  would do the same.
 
 But is much less obvious.  The LOOKUP_FOLLOW flag is the primary reason for
 this statement.  The rest are subordinate and would be wholly irrelevant if
 LOOKUP_FOLLOW was to be removed from the list.

Then keep the LOOKUP_FOLLOW semi-separate as in the original code.
But there's absolutely no reason for the goto spaghetti.

___
autofs mailing list
autofs@linux.kernel.org
http://linux.kernel.org/mailman/listinfo/autofs