Am curious how you noticed this problem?  Did you have a test case?

On Tue, Nov 27, 2012 at 12:50 AM, Pavel Shilovsky <[email protected]> wrote:
> If we have a read oplock and set a read lock in it, we can't write to the
> locked area - so, filemap_fdatawrite may fail with a no information for a
> userspace application even if we request a write to non-locked area. Fix
> this by replacing it with filemap_write_and_wait call and sending non-page
> write in a error case.
>
> While this may end up with two write requests to the server, we can be sure
> that our data will be the same at the server and the page cache - the next 
> read
> on this file gets the valid data.
>
> Signed-off-by: Pavel Shilovsky <[email protected]>
> ---
>  fs/cifs/file.c |   10 ++++------
>  1 file changed, 4 insertions(+), 6 deletions(-)
>
> diff --git a/fs/cifs/file.c b/fs/cifs/file.c
> index f8fe1bd..89efd85 100644
> --- a/fs/cifs/file.c
> +++ b/fs/cifs/file.c
> @@ -2511,14 +2511,12 @@ cifs_strict_writev(struct kiocb *iocb, const struct 
> iovec *iov,
>          */
>         if (!cinode->clientCanCacheAll && cinode->clientCanCacheRead) {
>                 ssize_t written;
> -               int rc;
>
>                 written = generic_file_aio_write(iocb, iov, nr_segs, pos);
> -               rc = filemap_fdatawrite(inode->i_mapping);
> -               if (rc)
> -                       return (ssize_t)rc;
> -
> -               return written;
> +               /* try page write at first */
> +               if (!filemap_write_and_wait(inode->i_mapping))
> +                       return written;
> +               /* page write failed - try from pos to pos+len-1 */
>         }
>  #endif
>
> --
> 1.7.10.4
>
> --
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-- 
Thanks,

Steve
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