Re: [PATCH v2] cifs: report error instead of invalid when revalidating a dentry fails

[Shyam Prasad N <nspmangalore@gmail.com>]

What does cifs_revalidate_dentry return when the dentry is no longer exists?
I'm guessing that it'll return some error (ENOENT?). Do we need to
treat that as a special case and return 0 (invalid)?

Regards,
Shyam

On Tue, Feb 2, 2021 at 4:46 PM Aurélien Aptel <aaptel@suse.com> wrote:
>
> From: Aurelien Aptel <aaptel@suse.com>
>
> Assuming
> - //HOST/a is mounted on /mnt
> - //HOST/b is mounted on /mnt/b
>
> On a slow connection, running 'df' and killing it while it's
> processing /mnt/b can make cifs_get_inode_info() returns -ERESTARTSYS.
>
> This triggers the following chain of events:
> => the dentry revalidation fail
> => dentry is put and released
> => superblock associated with the dentry is put
> => /mnt/b is unmounted
>
> This patch makes cifs_d_revalidate() return the error instead of
> 0 (invalid) when cifs_revalidate_dentry() fails.
>
> Signed-off-by: Aurelien Aptel <aaptel@suse.com>
> Suggested-by: Shyam Prasad N <nspmangalore@gmail.com>
> ---
>  fs/cifs/dir.c | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/fs/cifs/dir.c b/fs/cifs/dir.c
> index 68900f1629bff..4174f35590e62 100644
> --- a/fs/cifs/dir.c
> +++ b/fs/cifs/dir.c
> @@ -737,6 +737,7 @@ static int
>  cifs_d_revalidate(struct dentry *direntry, unsigned int flags)
>  {
>         struct inode *inode;
> +       int rc;
>
>         if (flags & LOOKUP_RCU)
>                 return -ECHILD;
> @@ -746,8 +747,11 @@ cifs_d_revalidate(struct dentry *direntry, unsigned int flags)
>                 if ((flags & LOOKUP_REVAL) && !CIFS_CACHE_READ(CIFS_I(inode)))
>                         CIFS_I(inode)->time = 0; /* force reval */
>
> -               if (cifs_revalidate_dentry(direntry))
> -                       return 0;
> +               rc = cifs_revalidate_dentry(direntry);
> +               if (rc) {
> +                       cifs_dbg(FYI, "cifs_revalidate_dentry failed with rc=%d", rc);
> +                       return rc;
> +               }
>                 else {
>                         /*
>                          * If the inode wasn't known to be a dfs entry when
> --
> 2.29.2
>


-- 
Regards,
Shyam