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block: reorganize rounding of max_discard_sectors 

Mostly a preparation for the next patch.

In principle this fixes an infinite loop if max_discard_sectors < granularity,
but that really shouldn't happen.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Tested-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Paolo Bonzini 2012-08-02 09:48:49 +02:00 committed by Jens Axboe
parent 1a9b4993b7
commit f6ff53d361
1 changed files with 5 additions and 4 deletions
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9
block/blk-lib.c
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@ -44,6 +44,7 @@ int blkdev_issue_discard(struct block_device *bdev, sector_t sector,
struct request_queue *q = bdev_get_queue(bdev);
int type = REQ_WRITE | REQ_DISCARD;
unsigned int max_discard_sectors;
unsigned int granularity;
struct bio_batch bb;
struct bio *bio;
int ret = 0;
@ -54,18 +55,18 @@ int blkdev_issue_discard(struct block_device *bdev, sector_t sector,
if (!blk_queue_discard(q))
return -EOPNOTSUPP;
/* Zero-sector (unknown) and one-sector granularities are the same. */
granularity = max(q->limits.discard_granularity >> 9, 1U);
/*
* Ensure that max_discard_sectors is of the proper
* granularity
*/
max_discard_sectors = min(q->limits.max_discard_sectors, UINT_MAX >> 9);
max_discard_sectors = round_down(max_discard_sectors, granularity);
if (unlikely(!max_discard_sectors)) {
/* Avoid infinite loop below. Being cautious never hurts. */
return -EOPNOTSUPP;
} else if (q->limits.discard_granularity) {
unsigned int disc_sects = q->limits.discard_granularity >> 9;
max_discard_sectors &= ~(disc_sects - 1);
}
if (flags & BLKDEV_DISCARD_SECURE) {