Re: [PATCH 4/8] scsi: stop passing a gfp_mask argument down the command setup path

[Bart Van Assche]

On 09/07/14 18:31, Christoph Hellwig wrote:

There is no reason for ULDs to pass in a flag on how to allocate the S/G
lists.  While we don't need GFP_ATOMIC for the blk-mq case because we
don't hold locks, that decision can be made way down the chain without
having to pass a pointless gfp_mask argument.


Reviewed-by: Bart Van Assche 

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[PATCH 4/8] scsi: stop passing a gfp_mask argument down the command setup path

[Christoph Hellwig]

There is no reason for ULDs to pass in a flag on how to allocate the S/G
lists.  While we don't need GFP_ATOMIC for the blk-mq case because we
don't hold locks, that decision can be made way down the chain without
having to pass a pointless gfp_mask argument.

Signed-off-by: Christoph Hellwig 
---
 drivers/scsi/scsi_lib.c  | 20 +---
 drivers/scsi/sd.c|  6 +++---
 drivers/scsi/sr.c|  2 +-
 include/scsi/scsi_cmnd.h |  2 +-
 4 files changed, 14 insertions(+), 16 deletions(-)

diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 0062865..877ea3d 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -587,10 +587,10 @@ static void scsi_free_sgtable(struct scsi_data_buffer 
*sdb, bool mq)
__sg_free_table(&sdb->table, SCSI_MAX_SG_SEGMENTS, mq, scsi_sg_free);
 }
 
-static int scsi_alloc_sgtable(struct scsi_data_buffer *sdb, int nents,
- gfp_t gfp_mask, bool mq)
+static int scsi_alloc_sgtable(struct scsi_data_buffer *sdb, int nents, bool mq)
 {
struct scatterlist *first_chunk = NULL;
+   gfp_t gfp_mask = mq ? GFP_NOIO : GFP_ATOMIC;
int ret;
 
BUG_ON(!nents);
@@ -1017,8 +1017,7 @@ void scsi_io_completion(struct scsi_cmnd *cmd, unsigned 
int good_bytes)
}
 }
 
-static int scsi_init_sgtable(struct request *req, struct scsi_data_buffer *sdb,
-gfp_t gfp_mask)
+static int scsi_init_sgtable(struct request *req, struct scsi_data_buffer *sdb)
 {
int count;
 
@@ -1026,7 +1025,7 @@ static int scsi_init_sgtable(struct request *req, struct 
scsi_data_buffer *sdb,
 * If sg table allocation fails, requeue request later.
 */
if (unlikely(scsi_alloc_sgtable(sdb, req->nr_phys_segments,
-   gfp_mask, req->mq_ctx != NULL)))
+   req->mq_ctx != NULL)))
return BLKPREP_DEFER;
 
/* 
@@ -1051,7 +1050,7 @@ static int scsi_init_sgtable(struct request *req, struct 
scsi_data_buffer *sdb,
  * BLKPREP_DEFER if the failure is retryable
  * BLKPREP_KILL if the failure is fatal
  */
-int scsi_init_io(struct scsi_cmnd *cmd, gfp_t gfp_mask)
+int scsi_init_io(struct scsi_cmnd *cmd)
 {
struct scsi_device *sdev = cmd->device;
struct request *rq = cmd->request;
@@ -1060,7 +1059,7 @@ int scsi_init_io(struct scsi_cmnd *cmd, gfp_t gfp_mask)
 
BUG_ON(!rq->nr_phys_segments);
 
-   error = scsi_init_sgtable(rq, &cmd->sdb, gfp_mask);
+   error = scsi_init_sgtable(rq, &cmd->sdb);
if (error)
goto err_exit;
 
@@ -1076,8 +1075,7 @@ int scsi_init_io(struct scsi_cmnd *cmd, gfp_t gfp_mask)
rq->next_rq->special = bidi_sdb;
}
 
-   error = scsi_init_sgtable(rq->next_rq, rq->next_rq->special,
- GFP_ATOMIC);
+   error = scsi_init_sgtable(rq->next_rq, rq->next_rq->special);
if (error)
goto err_exit;
}
@@ -1089,7 +1087,7 @@ int scsi_init_io(struct scsi_cmnd *cmd, gfp_t gfp_mask)
BUG_ON(prot_sdb == NULL);
ivecs = blk_rq_count_integrity_sg(rq->q, rq->bio);
 
-   if (scsi_alloc_sgtable(prot_sdb, ivecs, gfp_mask, is_mq)) {
+   if (scsi_alloc_sgtable(prot_sdb, ivecs, is_mq)) {
error = BLKPREP_DEFER;
goto err_exit;
}
@@ -1156,7 +1154,7 @@ static int scsi_setup_blk_pc_cmnd(struct scsi_device 
*sdev, struct request *req)
 * submit a request without an attached bio.
 */
if (req->bio) {
-   int ret = scsi_init_io(cmd, GFP_ATOMIC);
+   int ret = scsi_init_io(cmd);
if (unlikely(ret))
return ret;
} else {
diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index aa43496..6f7588d 100644
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -769,7 +769,7 @@ static int sd_setup_discard_cmnd(struct scsi_cmnd *cmd)
 * amount of blocks described by the request.
 */
blk_add_request_payload(rq, page, len);
-   ret = scsi_init_io(cmd, GFP_ATOMIC);
+   ret = scsi_init_io(cmd);
rq->__data_len = nr_bytes;
 
 out:
@@ -863,7 +863,7 @@ static int sd_setup_write_same_cmnd(struct scsi_cmnd *cmd)
 * knows how much to actually write.
 */
rq->__data_len = sdp->sector_size;
-   ret = scsi_init_io(cmd, GFP_ATOMIC);
+   ret = scsi_init_io(cmd);
rq->__data_len = nr_bytes;
return ret;
 }
@@ -896,7 +896,7 @@ static int sd_setup_read_write_cmnd(struct scsi_cmnd *SCpnt)
int ret, host_dif;
unsigned char protect;
 
-   ret = scsi_init_io(SCpnt, GFP_ATOMIC);
+   ret = scsi_init_io(SCpnt);
if (ret != BLKPREP_OK)
goto out;
SCpnt = rq->special;
diff --git a/