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authorMikulas Patocka <mpatocka@redhat.com>2012-07-27 15:08:03 +0100
committerAlasdair G Kergon <agk@redhat.com>2012-07-27 15:08:03 +0100
commit4929630901100fdbfa19186ecf5ea2706f57719b (patch)
treed12aaec9ccae4fb91eb55271fc8f987db0bbce96 /drivers/md/dm-thin.c
parent7acf0277cea0f2da89ffffcc9892bea23f618e63 (diff)
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dm thin: split discards on block boundary
This patch sets the variable "ti->split_discard_requests" for the dm thin target so that device mapper core splits discard requests on a block boundary. Consequently, a discard request that spans multiple blocks is never sent to dm-thin. The patch also removes some code in process_discard that deals with discards that span multiple blocks. Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Diffstat (limited to 'drivers/md/dm-thin.c')
-rw-r--r--drivers/md/dm-thin.c16
1 files changed, 7 insertions, 9 deletions
diff --git a/drivers/md/dm-thin.c b/drivers/md/dm-thin.c
index f21d318d98f..82864925690 100644
--- a/drivers/md/dm-thin.c
+++ b/drivers/md/dm-thin.c
@@ -1238,15 +1238,10 @@ static void process_discard(struct thin_c *tc, struct bio *bio)
}
} else {
/*
- * This path is hit if people are ignoring
- * limits->discard_granularity. It ignores any
- * part of the discard that is in a subsequent
- * block.
+ * The DM core makes sure that the discard doesn't span
+ * a block boundary. So we submit the discard of a
+ * partial block appropriately.
*/
- sector_t offset = bio->bi_sector - (block * pool->sectors_per_block);
- unsigned remaining = (pool->sectors_per_block - offset) << SECTOR_SHIFT;
- bio->bi_size = min(bio->bi_size, remaining);
-
cell_release_singleton(cell, bio);
cell_release_singleton(cell2, bio);
if ((!lookup_result.shared) && pool->pf.discard_passdown)
@@ -2509,7 +2504,8 @@ static void set_discard_limits(struct pool *pool, struct queue_limits *limits)
/*
* This is just a hint, and not enforced. We have to cope with
- * bios that overlap 2 blocks.
+ * bios that cover a block partially. A discard that spans a block
+ * boundary is not sent to this target.
*/
limits->discard_granularity = pool->sectors_per_block << SECTOR_SHIFT;
limits->discard_zeroes_data = pool->pf.zero_new_blocks;
@@ -2652,6 +2648,8 @@ static int thin_ctr(struct dm_target *ti, unsigned argc, char **argv)
ti->discards_supported = 1;
ti->num_discard_requests = 1;
ti->discard_zeroes_data_unsupported = 1;
+ /* Discard requests must be split on a block boundary */
+ ti->split_discard_requests = 1;
}
dm_put(pool_md);