Commit 936ad909 authored May 02, 2012 by Ian Kent Committed by Steve French May 03, 2012

cifs - check S_AUTOMOUNT in revalidate



When revalidating a dentry, if the inode wasn't known to be a dfs
entry when the dentry was instantiated, such as when created via
->readdir(), the DCACHE_NEED_AUTOMOUNT flag needs to be set on the
dentry in ->d_revalidate().

The false return from cifs_d_revalidate(), due to the inode now
being marked with the S_AUTOMOUNT flag, might not invalidate the
dentry if there is a concurrent unlazy path walk. This is because
the dentry reference count will be at least 2 in this case causing
d_invalidate() to return EBUSY. So the asumption that the dentry
will be discarded then correctly instantiated via ->lookup() might
not hold.

Signed-off-by: Ian Kent <raven@themaw.net>
Reviewed-by: Jeff Layton <jlayton@redhat.com>
Cc: Steve French <smfrench@gmail.com>
Cc: linux-cifs@vger.kernel.org
Signed-off-by: Steve French <sfrench@us.ibm.com>

parent 58fa015f

fs/cifs/dir.c

+12 −5

Original line number	Diff line number	Diff line
		@@ -668,12 +668,19 @@ cifs_d_revalidate(struct dentry direntry, struct nameidata nd)
		return 0;
		else {
		/*
		* Forcibly invalidate automounting directory inodes
		* (remote DFS directories) so to have them
		* instantiated again for automount
		* If the inode wasn't known to be a dfs entry when
		* the dentry was instantiated, such as when created
		* via ->readdir(), it needs to be set now since the
		* attributes will have been updated by
		* cifs_revalidate_dentry().
		*/
		if (IS_AUTOMOUNT(direntry->d_inode))
		return 0;
		if (IS_AUTOMOUNT(direntry->d_inode) &&
		!(direntry->d_flags & DCACHE_NEED_AUTOMOUNT)) {
		spin_lock(&direntry->d_lock);
		direntry->d_flags \|= DCACHE_NEED_AUTOMOUNT;
		spin_unlock(&direntry->d_lock);
		}

		return 1;
		}
		}