On Tue 22-08-17 18:17:10, Christoph Hellwig wrote:
> From: Milosz Tanski <milosz@xxxxxxxxx>
>
> Allow generic_file_buffered_read to bail out early instead of waiting for
> the page lock or reading a page if IOCB_NOWAIT is specified.
>
> Signed-off-by: Milosz Tanski <milosz@xxxxxxxxx>
> Reviewed-by: Christoph Hellwig <hch@xxxxxx>
> Reviewed-by: Jeff Moyer <jmoyer@xxxxxxxxxx>
> Acked-by: Sage Weil <sage@xxxxxxxxxx>
> ---
> mm/filemap.c | 15 +++++++++++++++
> 1 file changed, 15 insertions(+)
>
> diff --git a/mm/filemap.c b/mm/filemap.c
> index 4bcfa74ad802..9f60255fb7bb 100644
> --- a/mm/filemap.c
> +++ b/mm/filemap.c
> @@ -1937,6 +1937,8 @@ static ssize_t generic_file_buffered_read(struct kiocb *iocb,
>
> page = find_get_page(mapping, index);
> if (!page) {
> + if (iocb->ki_flags & IOCB_NOWAIT)
> + goto would_block;
> page_cache_sync_readahead(mapping,
> ra, filp,
> index, last_index - index);
Hum, we have:
if (!PageUptodate(page)) {
/*
* See comment in do_read_cache_page on why
* wait_on_page_locked is used to avoid
* unnecessarily
* serialisations and why it's safe.
*/
error = wait_on_page_locked_killable(page);
if (unlikely(error))
goto readpage_error;
if (PageUptodate(page))
goto page_ok;
And wait_on_page_locked_killable() above does not seem to be handled in
your patch. I would just check IOCB_NOWAIT in !PageUptodate(page) branch
above and bail - which also removes the need for the two checks below...
Honza
--
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR
