Steve? I have a CIFS pull request from you now, and it doesn't contain
this one. I don't know the code well enough to say one way or the
other, so I haven't applied this. Pls Ack/Nak.
Linus
On Fri, Apr 27, 2012 at 1:18 AM, Ian Kent <raven@xxxxxxxxxx> wrote:
> 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@xxxxxxxxxx>
> Reviewed-by: Jeff Layton <jlayton@xxxxxxxxxx>
> Cc: Steve French <smfrench@xxxxxxxxx>
> Cc: linux-cifs@xxxxxxxxxxxxxxx
> ---
>
> fs/cifs/dir.c | 17 ++++++++++++-----
> 1 files changed, 12 insertions(+), 5 deletions(-)
>
> diff --git a/fs/cifs/dir.c b/fs/cifs/dir.c
> index d172c8e..ec4e9a2 100644
> --- a/fs/cifs/dir.c
> +++ b/fs/cifs/dir.c
> @@ -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;
> }
> }
>
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