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dm thin: split discards on block boundary

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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>
This commit is contained in:
Mikulas Patocka 2012-07-27 15:08:03 +01:00 committed by Alasdair G Kergon
parent 7acf0277ce
commit 4929630901
1 changed files with 7 additions and 9 deletions
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16
drivers/md/dm-thin.c
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@ -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);