From f9d03f96b988002027d4b28ea1b7a24729a4c9b5 Mon Sep 17 00:00:00 2001 From: Christoph Hellwig Date: Thu, 8 Dec 2016 15:20:32 -0700 Subject: block: improve handling of the magic discard payload Instead of allocating a single unused biovec for discard requests, send them down without any payload. Instead we allow the driver to add a "special" payload using a biovec embedded into struct request (unioned over other fields never used while in the driver), and overloading the number of segments for this case. This has a couple of advantages: - we don't have to allocate the bio_vec - the amount of special casing for discard requests in the block layer is significantly reduced - using this same scheme for other request types is trivial, which will be important for implementing the new WRITE_ZEROES op on devices where it actually requires a payload (e.g. SCSI) - we can get rid of playing games with the request length, as we'll never touch it and completions will work just fine - it will allow us to support ranged discard operations in the future by merging non-contiguous discard bios into a single request - last but not least it removes a lot of code This patch is the common base for my WIP series for ranges discards and to remove discard_zeroes_data in favor of always using REQ_OP_WRITE_ZEROES, so it would be good to get it in quickly. Signed-off-by: Christoph Hellwig Signed-off-by: Jens Axboe --- block/blk-lib.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'block/blk-lib.c') diff --git a/block/blk-lib.c b/block/blk-lib.c index 510a6fb15318..ed89c8f4b2a0 100644 --- a/block/blk-lib.c +++ b/block/blk-lib.c @@ -80,7 +80,7 @@ int __blkdev_issue_discard(struct block_device *bdev, sector_t sector, req_sects = end_sect - sector; } - bio = next_bio(bio, 1, gfp_mask); + bio = next_bio(bio, 0, gfp_mask); bio->bi_iter.bi_sector = sector; bio->bi_bdev = bdev; bio_set_op_attrs(bio, op, 0); -- cgit v1.2.3-58-ga151