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author | Mike Snitzer <snitzer@redhat.com> | 2013-01-31 14:11:14 (GMT) |
---|---|---|
committer | Alasdair G Kergon <agk@redhat.com> | 2013-01-31 14:11:14 (GMT) |
commit | 0f640dca08330dfc7820d610578e5935b5e654b2 (patch) | |
tree | 47c201a750b6f405726ee6b66fba825b6475a6c7 /drivers | |
parent | 949db153b6466c6f7cad5a427ecea94985927311 (diff) | |
download | linux-fsl-qoriq-0f640dca08330dfc7820d610578e5935b5e654b2.tar.xz |
dm thin: fix queue limits stacking
thin_io_hints() is blindly copying the queue limits from the thin-pool
which can lead to incorrect limits being set. The fix here simply
deletes the thin_io_hints() hook which leaves the existing stacking
infrastructure to set the limits correctly.
When a thin-pool uses an MD device for the data device a thin device
from the thin-pool must respect MD's constraints about disallowing a bio
from spanning multiple chunks. Otherwise we can see problems. If the raid0
chunksize is 1152K and thin-pool chunksize is 256K I see the following
md/raid0 error (with extra debug tracing added to thin_endio) when
mkfs.xfs is executed against the thin device:
md/raid0:md99: make_request bug: can't convert block across chunks or bigger than 1152k 6688 127
device-mapper: thin: bio sector=2080 err=-5 bi_size=130560 bi_rw=17 bi_vcnt=32 bi_idx=0
This extra DM debugging shows that the failing bio is spanning across
the first and second logical 1152K chunk (sector 2080 + 255 takes the
bio beyond the first chunk's boundary of sector 2304). So the bio
splitting that DM is doing clearly isn't respecting the MD limits.
max_hw_sectors_kb is 127 for both the thin-pool and thin device
(queue_max_hw_sectors returns 255 so we'll excuse sysfs's lack of
precision). So this explains why bi_size is 130560.
But the thin device's max_hw_sectors_kb should be 4 (PAGE_SIZE) given
that it doesn't have a .merge function (for bio_add_page to consult
indirectly via dm_merge_bvec) yet the thin-pool does sit above an MD
device that has a compulsory merge_bvec_fn. This scenario is exactly
why DM must resort to sending single PAGE_SIZE bios to the underlying
layer. Some additional context for this is available in the header for
commit 8cbeb67a ("dm: avoid unsupported spanning of md stripe boundaries").
Long story short, the reason a thin device doesn't properly get
configured to have a max_hw_sectors_kb of 4 (PAGE_SIZE) is that
thin_io_hints() is blindly copying the queue limits from the thin-pool
device directly to the thin device's queue limits.
Fix this by eliminating thin_io_hints. Doing so is safe because the
block layer's queue limits stacking already enables the upper level thin
device to inherit the thin-pool device's discard and minimum_io_size and
optimal_io_size limits that get set in pool_io_hints. But avoiding the
queue limits copy allows the thin and thin-pool limits to be different
where it is important, namely max_hw_sectors_kb.
Reported-by: Daniel Browning <db@kavod.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Cc: stable@vger.kernel.org
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Diffstat (limited to 'drivers')
-rw-r--r-- | drivers/md/dm-thin.c | 13 |
1 files changed, 1 insertions, 12 deletions
diff --git a/drivers/md/dm-thin.c b/drivers/md/dm-thin.c index 675ae52..5409607 100644 --- a/drivers/md/dm-thin.c +++ b/drivers/md/dm-thin.c @@ -2746,19 +2746,9 @@ static int thin_iterate_devices(struct dm_target *ti, return 0; } -/* - * A thin device always inherits its queue limits from its pool. - */ -static void thin_io_hints(struct dm_target *ti, struct queue_limits *limits) -{ - struct thin_c *tc = ti->private; - - *limits = bdev_get_queue(tc->pool_dev->bdev)->limits; -} - static struct target_type thin_target = { .name = "thin", - .version = {1, 6, 0}, + .version = {1, 7, 0}, .module = THIS_MODULE, .ctr = thin_ctr, .dtr = thin_dtr, @@ -2767,7 +2757,6 @@ static struct target_type thin_target = { .postsuspend = thin_postsuspend, .status = thin_status, .iterate_devices = thin_iterate_devices, - .io_hints = thin_io_hints, }; /*----------------------------------------------------------------*/ |