Markus Stockhausen cf12d0f9c0 readahead: stricter check for bdi io_pages
commit dc30b96ab6d569060741572cf30517d3179429a8 upstream.

ondemand_readahead() checks bdi->io_pages to cap the maximum pages
that need to be processed. This works until the readit section. If
we would do an async only readahead (async size = sync size) and
target is at beginning of window we expand the pages by another
get_next_ra_size() pages. Btrace for large reads shows that kernel
always issues a doubled size read at the beginning of processing.
Add an additional check for io_pages in the lower part of the func.
The fix helps devices that hard limit bio pages and rely on proper
handling of max_hw_read_sectors (e.g. older FusionIO cards). For
that reason it could qualify for stable.

Fixes: 9491ae4a ("mm: don't cap request size based on read-ahead setting")
Cc: stable@vger.kernel.org
Signed-off-by: Markus Stockhausen stockhausen@collogia.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2018-09-09 19:55:53 +02:00
..
2017-06-05 16:59:12 +02:00
2017-02-27 18:43:47 -08:00
2018-02-22 15:42:24 +01:00
2018-02-22 15:42:24 +01:00
2018-04-24 09:36:39 +02:00
2018-05-30 07:52:23 +02:00