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 --- drivers/scsi/scsi_lib.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) (limited to 'drivers/scsi/scsi_lib.c') diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c index 47a5c8783b89..9a8ccff1121f 100644 --- a/drivers/scsi/scsi_lib.c +++ b/drivers/scsi/scsi_lib.c @@ -1007,8 +1007,8 @@ static int scsi_init_sgtable(struct request *req, struct scsi_data_buffer *sdb) /* * If sg table allocation fails, requeue request later. */ - if (unlikely(sg_alloc_table_chained(&sdb->table, req->nr_phys_segments, - sdb->table.sgl))) + if (unlikely(sg_alloc_table_chained(&sdb->table, + blk_rq_nr_phys_segments(req), sdb->table.sgl))) return BLKPREP_DEFER; /* @@ -1040,7 +1040,7 @@ int scsi_init_io(struct scsi_cmnd *cmd) bool is_mq = (rq->mq_ctx != NULL); int error; - BUG_ON(!rq->nr_phys_segments); + BUG_ON(!blk_rq_nr_phys_segments(rq)); error = scsi_init_sgtable(rq, &cmd->sdb); if (error) -- cgit v1.2.3