3.16.51-rc1 review patch. If anyone has any objections, please let me know.
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From: Tang Junhui tang.junhui@zte.com.cn
commit c81ffa32a214c84b08900fbc9d432187bd948eba upstream.
Sequential write IOs were tested with bs=1M by FIO in writeback cache mode, these IOs were expected to be bypassed, but actually they did not. We debug the code, and find in check_should_bypass(): if (!congested && mode == CACHE_MODE_WRITEBACK && op_is_write(bio_op(bio)) && (bio-＞bi_opf & REQ_SYNC)) goto rescale that means, If in writeback mode, a write IO with REQ_SYNC flag will not be bypassed though it is a sequential large IO, It's not a correct thing to do actually, so this patch remove these codes.
Signed-off-by: tang.junhui tang.junhui@zte.com.cn Reviewed-by: Kent Overstreet kent.overstreet@gmail.com Reviewed-by: Eric Wheeler bcache@linux.ewheeler.net Signed-off-by: Jens Axboe axboe@kernel.dk [bwh: Backported to 3.16: deleted code is slightly different] Signed-off-by: Ben Hutchings ben@decadent.org.uk --- drivers/md/bcache/request.c | 6 ------ 1 file changed, 6 deletions(-)
--- a/drivers/md/bcache/request.c +++ b/drivers/md/bcache/request.c @@ -395,12 +395,6 @@ static bool check_should_bypass(struct c if (!congested && !dc->sequential_cutoff) goto rescale;
- if (!congested && - mode == CACHE_MODE_WRITEBACK && - (bio->bi_rw & REQ_WRITE) && - (bio->bi_rw & REQ_SYNC)) - goto rescale; - spin_lock(&dc->io_lock);
hlist_for_each_entry(i, iohash(dc, bio->bi_iter.bi_sector), hash)