diff options
| author | Mike Snitzer <snitzer@redhat.com> | 2011-08-02 12:32:08 +0100 |
|---|---|---|
| committer | Alasdair G Kergon <agk@redhat.com> | 2011-08-02 12:32:08 +0100 |
| commit | ed8b752bccf2560e305e25125721d2f0ac759e88 (patch) | |
| tree | b909fcf21ca7cdda3e7a680b37162212cce99586 | |
| parent | 772ae5f54d69c38a5e3c4352c5fdbdaff141af21 (diff) | |
dm table: set flush capability based on underlying devices
DM has always advertised both REQ_FLUSH and REQ_FUA flush capabilities
regardless of whether or not a given DM device's underlying devices
also advertised a need for them.
Block's flush-merge changes from 2.6.39 have proven to be more costly
for DM devices. Performance regressions have been reported even when
DM's underlying devices do not advertise that they have a write cache.
Fix the performance regressions by configuring a DM device's flushing
capabilities based on those of the underlying devices' capabilities.
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
| -rw-r--r-- | drivers/md/dm-table.c | 43 | ||||
| -rw-r--r-- | drivers/md/dm.c | 1 |
2 files changed, 43 insertions, 1 deletions
diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c index 259ce99302f..986b8754bb0 100644 --- a/drivers/md/dm-table.c +++ b/drivers/md/dm-table.c @@ -1248,9 +1248,45 @@ static void dm_table_set_integrity(struct dm_table *t) blk_get_integrity(template_disk)); } +static int device_flush_capable(struct dm_target *ti, struct dm_dev *dev, + sector_t start, sector_t len, void *data) +{ + unsigned flush = (*(unsigned *)data); + struct request_queue *q = bdev_get_queue(dev->bdev); + + return q && (q->flush_flags & flush); +} + +static bool dm_table_supports_flush(struct dm_table *t, unsigned flush) +{ + struct dm_target *ti; + unsigned i = 0; + + /* + * Require at least one underlying device to support flushes. + * t->devices includes internal dm devices such as mirror logs + * so we need to use iterate_devices here, which targets + * supporting flushes must provide. + */ + while (i < dm_table_get_num_targets(t)) { + ti = dm_table_get_target(t, i++); + + if (!ti->num_flush_requests) + continue; + + if (ti->type->iterate_devices && + ti->type->iterate_devices(ti, device_flush_capable, &flush)) + return 1; + } + + return 0; +} + void dm_table_set_restrictions(struct dm_table *t, struct request_queue *q, struct queue_limits *limits) { + unsigned flush = 0; + /* * Copy table's limits to the DM device's request_queue */ @@ -1261,6 +1297,13 @@ void dm_table_set_restrictions(struct dm_table *t, struct request_queue *q, else queue_flag_set_unlocked(QUEUE_FLAG_DISCARD, q); + if (dm_table_supports_flush(t, REQ_FLUSH)) { + flush |= REQ_FLUSH; + if (dm_table_supports_flush(t, REQ_FUA)) + flush |= REQ_FUA; + } + blk_queue_flush(q, flush); + dm_table_set_integrity(t); /* diff --git a/drivers/md/dm.c b/drivers/md/dm.c index 1000eaf984e..52b39f335bb 100644 --- a/drivers/md/dm.c +++ b/drivers/md/dm.c @@ -1808,7 +1808,6 @@ static void dm_init_md_queue(struct mapped_device *md) blk_queue_make_request(md->queue, dm_request); blk_queue_bounce_limit(md->queue, BLK_BOUNCE_ANY); blk_queue_merge_bvec(md->queue, dm_merge_bvec); - blk_queue_flush(md->queue, REQ_FLUSH | REQ_FUA); } /* |