On Mon, May 07, 2018 at 10:13:32AM -0600, Jens Axboe wrote:
> Don't build discards bigger than what the user asked for, if the
> user decided to limit the size by writing to 'discard_max_bytes'.
>
> Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
> ---
> block/blk-lib.c | 7 ++++---
> 1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/block/blk-lib.c b/block/blk-lib.c
> index a676084d4740..7417d617091b 100644
> --- a/block/blk-lib.c
> +++ b/block/blk-lib.c
> @@ -62,10 +62,11 @@ int __blkdev_issue_discard(struct block_device *bdev, sector_t sector,
> unsigned int req_sects;
> sector_t end_sect, tmp;
>
> - /* Make sure bi_size doesn't overflow */
> - req_sects = min_t(sector_t, nr_sects, UINT_MAX >> 9);
> + /* Issue in chunks of the user defined max discard setting */
> + req_sects = min_t(sector_t, nr_sects,
> + q->limits.max_discard_sectors);
>
Some drivers, including nvme, do
blk_queue_max_discard_sectors(q, UINT_MAX)
That means q->limits.max_discard_sectors can be UINT_MAX, and
bio->bi_iter.bi_size = req_sects << 9;
will overflow. We should probably cap max_discard_sectors at
UINT_MAX >> 9 in a prep patch.
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