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dm io: discards don't take a payload 

Fix up do_region to not allocate a bio_vec for discards.  We've
got rid of the discard payload allocated by the caller years ago.

Obviously this wasn't actually harmful given how long it's been
there, but it's still good to avoid the pointless allocation.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
This commit is contained in:
Christoph Hellwig 2017-04-05 19:21:04 +02:00 committed by Jens Axboe
parent 3deff1a70d
commit 0f5d690f7b
1 changed files with 8 additions and 2 deletions
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10
drivers/md/dm-io.c
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@ -328,11 +328,17 @@ static void do_region(int op, int op_flags, unsigned region,
/*
* Allocate a suitably sized-bio.
*/
if ((op == REQ_OP_DISCARD) || (op == REQ_OP_WRITE_SAME))
switch (op) {
case REQ_OP_DISCARD:
num_bvecs = 0;
break;
case REQ_OP_WRITE_SAME:
num_bvecs = 1;
else
break;
default:
num_bvecs = min_t(int, BIO_MAX_PAGES,
dm_sector_div_up(remaining, (PAGE_SIZE >> SECTOR_SHIFT)));
}
bio = bio_alloc_bioset(GFP_NOIO, num_bvecs, io->client->bios);
bio->bi_iter.bi_sector = where->sector + (where->count - remaining);