diff options
| author | Mikulas Patocka <mpatocka@redhat.com> | 2010-08-03 11:30:37 +1000 |
|---|---|---|
| committer | Stephen Rothwell <sfr@canb.auug.org.au> | 2010-08-03 11:30:37 +1000 |
| commit | 99c068ab7beeb38fe2ba6ccb4cd6625962a50f90 (patch) | |
| tree | 2e03ad2c78672c1bc7147b4d2d0e1fa820c4f427 /drivers/md | |
| parent | efa4745d78c0ea25f021e84deb1a7655c2408528 (diff) | |
dm-skip-second-flush-on-bio-unsupported-error
When processing barriers, skip the second flush if processing the bio
failed with -EOPNOTSUPP. This can happen with discard+barrier requests.
If the device doesn't support discard, there would be two useless
SYNCHRONIZE CACHE commands. The first dm_flush cannot be so easily
optimized out, so we leave it there.
Previously, -EOPNOTSUPP could be received in dec_pending only with empty
barriers and we ignored that error, assuming the device not supporting
cache flushes has cache always consistent. With the addition of discard
barriers, this -EOPNOTSUPP can also be generated by discards and we
must record it in md->barrier_error for process_barrier.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Diffstat (limited to 'drivers/md')
| -rw-r--r-- | drivers/md/dm.c | 15 |
1 files changed, 13 insertions, 2 deletions
diff --git a/drivers/md/dm.c b/drivers/md/dm.c index 56d192dbe9f1..bd976bdb83cc 100644 --- a/drivers/md/dm.c +++ b/drivers/md/dm.c @@ -631,8 +631,14 @@ static void dec_pending(struct dm_io *io, int error) * There can be just one barrier request so we use * a per-device variable for error reporting. * Note that you can't touch the bio after end_io_acct + * + * We ignore -EOPNOTSUPP for empty flush reported by + * underlying devices. We assume that if the device + * doesn't support empty barriers, it doesn't need + * cache flushing commands. */ - if (!md->barrier_error && io_error != -EOPNOTSUPP) + if (!md->barrier_error && + !(bio_empty_barrier(bio) && io_error == -EOPNOTSUPP)) md->barrier_error = io_error; end_io_acct(io); free_io(md, io); @@ -2259,7 +2265,12 @@ static void process_barrier(struct mapped_device *md, struct bio *bio) if (!bio_empty_barrier(bio)) { __split_and_process_bio(md, bio); - dm_flush(md); + /* + * If the request isn't supported, don't waste time with + * the second flush. + */ + if (md->barrier_error != -EOPNOTSUPP) + dm_flush(md); } if (md->barrier_error != DM_ENDIO_REQUEUE) |