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authorMing Lin <ming.l@ssi.samsung.com>2015-05-06 22:51:24 -0700
committerJens Axboe <axboe@fb.com>2015-08-13 12:31:51 -0600
commit7ef6b12a1966f273afb750e19e1e8129bea48fec (patch)
treeb55c76f78bfe553966c2a07fe47ef8f0e94c4f77 /drivers/md
parentb49a0871be31a745b2ef7912653683a1876ff701 (diff)
downloadlinux-7ef6b12a1966f273afb750e19e1e8129bea48fec.tar.bz2
md/raid5: split bio for chunk_aligned_read
If a read request fits entirely in a chunk, it will be passed directly to the underlying device (providing it hasn't failed of course). If it doesn't fit, the slightly less efficient path that uses the stripe_cache is used. Requests that get to the stripe cache are always completely split up as necessary. So with RAID5, ripping out the merge_bvec_fn doesn't cause it to stop work, but could cause it to take the less efficient path more often. All that is needed to manage this is for 'chunk_aligned_read' do some bio splitting, much like the RAID0 code does. Cc: Neil Brown <neilb@suse.de> Cc: linux-raid@vger.kernel.org Acked-by: NeilBrown <neilb@suse.de> Signed-off-by: Ming Lin <ming.l@ssi.samsung.com> Signed-off-by: Jens Axboe <axboe@fb.com>
Diffstat (limited to 'drivers/md')
-rw-r--r--drivers/md/raid5.c37
1 files changed, 32 insertions, 5 deletions
diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 085db931aafc..256cc07f0874 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -4800,7 +4800,7 @@ static int bio_fits_rdev(struct bio *bi)
return 1;
}
-static int chunk_aligned_read(struct mddev *mddev, struct bio * raid_bio)
+static int raid5_read_one_chunk(struct mddev *mddev, struct bio *raid_bio)
{
struct r5conf *conf = mddev->private;
int dd_idx;
@@ -4809,7 +4809,7 @@ static int chunk_aligned_read(struct mddev *mddev, struct bio * raid_bio)
sector_t end_sector;
if (!in_chunk_boundary(mddev, raid_bio)) {
- pr_debug("chunk_aligned_read : non aligned\n");
+ pr_debug("%s: non aligned\n", __func__);
return 0;
}
/*
@@ -4886,6 +4886,31 @@ static int chunk_aligned_read(struct mddev *mddev, struct bio * raid_bio)
}
}
+static struct bio *chunk_aligned_read(struct mddev *mddev, struct bio *raid_bio)
+{
+ struct bio *split;
+
+ do {
+ sector_t sector = raid_bio->bi_iter.bi_sector;
+ unsigned chunk_sects = mddev->chunk_sectors;
+ unsigned sectors = chunk_sects - (sector & (chunk_sects-1));
+
+ if (sectors < bio_sectors(raid_bio)) {
+ split = bio_split(raid_bio, sectors, GFP_NOIO, fs_bio_set);
+ bio_chain(split, raid_bio);
+ } else
+ split = raid_bio;
+
+ if (!raid5_read_one_chunk(mddev, split)) {
+ if (split != raid_bio)
+ generic_make_request(raid_bio);
+ return split;
+ }
+ } while (split != raid_bio);
+
+ return NULL;
+}
+
/* __get_priority_stripe - get the next stripe to process
*
* Full stripe writes are allowed to pass preread active stripes up until
@@ -5163,9 +5188,11 @@ static void make_request(struct mddev *mddev, struct bio * bi)
* data on failed drives.
*/
if (rw == READ && mddev->degraded == 0 &&
- mddev->reshape_position == MaxSector &&
- chunk_aligned_read(mddev,bi))
- return;
+ mddev->reshape_position == MaxSector) {
+ bi = chunk_aligned_read(mddev, bi);
+ if (!bi)
+ return;
+ }
if (unlikely(bi->bi_rw & REQ_DISCARD)) {
make_discard_request(mddev, bi);