[PATCH] CIFS: use the correct length when pinning memory for direct I/O for write

[Steve French]

merged into cifs-2.6.git for-next

On Sun, Dec 16, 2018 at 5:18 PM Long Li <longli at linuxonhyperv.com> wrote:
>
> From: Long Li <longli at microsoft.com>
>
> The current code attempts to pin memory using the largest possible wsize
> based on the currect SMB credits. This doesn't cause kernel oops but this is
> not optimal as we may pin more pages then actually needed.
>
> Fix this by only pinning what are needed for doing this write I/O.
>
> Signed-off-by: Long Li <longli at microsoft.com>
> Cc: stable at vger.kernel.org
> ---
>  fs/cifs/file.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/fs/cifs/file.c b/fs/cifs/file.c
> index 3467351..c23bf9d 100644
> --- a/fs/cifs/file.c
> +++ b/fs/cifs/file.c
> @@ -2617,11 +2617,13 @@ cifs_write_from_iter(loff_t offset, size_t len, struct iov_iter *from,
>                 if (rc)
>                         break;
>
> +               cur_len = min_t(const size_t, len, wsize);
> +
>                 if (ctx->direct_io) {
>                         ssize_t result;
>
>                         result = iov_iter_get_pages_alloc(
> -                               from, &pagevec, wsize, &start);
> +                               from, &pagevec, cur_len, &start);
>                         if (result < 0) {
>                                 cifs_dbg(VFS,
>                                         "direct_writev couldn't get user pages "
> --
> 2.7.4
>


-- 
Thanks,

Steve