Prev: [PATCH 1/2] Revert "rt: trivial fix to REMINDER block in init/main.c"
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From: Dmitry Monakhov on 24 Mar 2010 13:40
Not all implementations require discard bio to be filled with one-sector
sized payload. Let's allocate payload only when necessary.

Signed-off-by: Dmitry Monakhov <dmonakhov(a)openvz.org>
---
block/blk-lib.c | 24 +++++++++++++-----------
drivers/scsi/sd.c | 1 +
include/linux/blkdev.h | 5 ++++-
3 files changed, 18 insertions(+), 12 deletions(-)

diff --git a/block/blk-lib.c b/block/blk-lib.c
index 67b641e..321d150 100644
--- a/block/blk-lib.c
+++ b/block/blk-lib.c
@@ -184,17 +184,19 @@ int blkdev_issue_discard(struct block_device *bdev, sector_t sector,
if (flags & BLKDEV_IFL_BARRIER)
bio->bi_private = &wait;

- /*
- * Add a zeroed one-sector payload as that's what
- * our current implementations need. If we'll ever need
- * more the interface will need revisiting.
- */
- page = alloc_page(gfp_mask | __GFP_ZERO);
- if (!page)
- goto out_free_bio;
- if (bio_add_pc_page(q, bio, page, sector_size, 0) < sector_size)
- goto out_free_page;
-
+ if (blk_queue_discard_mem(q)) {
+ /*
+ * Add a zeroed one-sector payload as that's what
+ * our current implementations need. If we'll ever
+ * need more the interface will need revisiting.
+ */
+ page = alloc_page(gfp_mask | __GFP_ZERO);
+ if (!page)
+ goto out_free_bio;
+ if (bio_add_pc_page(q, bio, page, sector_size, 0) <
+ sector_size)
+ goto out_free_page;
+ }
/*
* And override the bio size - the way discard works we
* touch many more blocks on disk than the actual payload
diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index 1dd4d84..9994977 100644
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -1513,6 +1513,7 @@ static int read_capacity_16(struct scsi_disk *sdkp, struct scsi_device *sdp,
q->limits.discard_zeroes_data = 1;

queue_flag_set_unlocked(QUEUE_FLAG_DISCARD, q);
+ queue_flag_set_unlocked(QUEUE_FLAG_DISCARD_MEM, q);
}

sdkp->capacity = lba + 1;
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 78180b7..e232a0d 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -461,7 +461,8 @@ struct request_queue
#define QUEUE_FLAG_VIRT QUEUE_FLAG_NONROT /* paravirt device */
#define QUEUE_FLAG_IO_STAT 15 /* do IO stats */
#define QUEUE_FLAG_DISCARD 16 /* supports DISCARD */
-#define QUEUE_FLAG_NOXMERGES 17 /* No extended merges */
+#define QUEUE_FLAG_DISCARD_MEM 17 /* require memory in DISCARD request*/
+#define QUEUE_FLAG_NOXMERGES 18 /* No extended merges */

#define QUEUE_FLAG_DEFAULT ((1 << QUEUE_FLAG_IO_STAT) | \
(1 << QUEUE_FLAG_CLUSTER) | \
@@ -595,6 +596,8 @@ enum {
#define blk_queue_stackable(q) \
test_bit(QUEUE_FLAG_STACKABLE, &(q)->queue_flags)
#define blk_queue_discard(q) test_bit(QUEUE_FLAG_DISCARD, &(q)->queue_flags)
+#define blk_queue_discard_mem(q) \
+ test_bit(QUEUE_FLAG_DISCARD_MEM, &(q)->queue_flags)

#define blk_fs_request(rq) ((rq)->cmd_type == REQ_TYPE_FS)
#define blk_pc_request(rq) ((rq)->cmd_type == REQ_TYPE_BLOCK_PC)
--
1.6.6.1

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Prev: [PATCH 1/2] Revert "rt: trivial fix to REMINDER block in init/main.c"
Next: [git pull] drm-intel fixes for 2.6.34-rc1