Re: [PATCH 1/2] block: fix leaks associated with discard requestpayload

From: FUJITA Tomonori
Date: Sun Jun 27 2010 - 04:50:34 EST

On Sat, 26 Jun 2010 15:56:50 -0400
Mike Snitzer <snitzer@xxxxxxxxxx> wrote:

> Fix leaks introduced via "block: don't allocate a payload for discard
> request" commit a1d949f5f44.
> sd_done() is not called for REQ_TYPE_BLOCK_PC commands so cleanup
> discard request's payload directly in scsi_finish_command().

Instead of adding another discard hack to scsi_finish_command(), how
about converting discard to REQ_TYPE_FS request? discard is FS request
from the perspective of the block layer. It also fixes a problem that
discard isn't retried in the case of UNIT ATTENTION.

I think that we can get more cleaner code if we handle discard as
normal (fs) request in the block layer (and scsi-ml). We need more
changes but this patch is the first step.

This patch depends on the patchset to convert flush request to

The git tree is also available:

git:// flush

> Also cleanup page allocated for discard payload in
> scsi_setup_discard_cmnd's scsi_setup_blk_pc_cmnd error path.

This patch doesn't address on this (since it's a different problem). I
think that scsi_setup_discard_cmnd() sees if it already allocates a
page before allocating a page. That's similar to how other prep
functions work, I think.

From: FUJITA Tomonori <fujita.tomonori@xxxxxxxxxxxxx>
Subject: [PATCH] convert discard request to REQ_TYPE_FS instead of BLOCK_PC

Signed-off-by: FUJITA Tomonori <fujita.tomonori@xxxxxxxxxxxxx>
block/blk-lib.c | 4 ++++
drivers/scsi/sd.c | 11 +----------
2 files changed, 5 insertions(+), 10 deletions(-)

diff --git a/block/blk-lib.c b/block/blk-lib.c
index e16185b..9e15c46 100644
--- a/block/blk-lib.c
+++ b/block/blk-lib.c
@@ -20,6 +20,10 @@ static void blkdev_discard_end_io(struct bio *bio, int err)
if (bio->bi_private)

+ /* free the page that the lower layer allocated */
+ if (bio_page(bio))
+ __free_page(bio_page(bio));

diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index d447726..1b182de 100644
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -432,7 +432,7 @@ static int scsi_setup_discard_cmnd(struct scsi_device *sdp, struct request *rq)
nr_sectors >>= 3;

- rq->cmd_type = REQ_TYPE_BLOCK_PC;
+ rq->cmd_type = REQ_TYPE_FS;
rq->timeout = SD_TIMEOUT;

memset(rq->cmd, 0, rq->cmd_len);
@@ -1177,15 +1177,6 @@ static int sd_done(struct scsi_cmnd *SCpnt)
int sense_valid = 0;
int sense_deferred = 0;

- /*
- * If this is a discard request that originated from the kernel
- * we need to free our payload here. Note that we need to check
- * the request flag as the normal payload rules apply for
- * pass-through UNMAP / WRITE SAME requests.
- */
- if (SCpnt->request->cmd_flags & REQ_DISCARD)
- __free_page(bio_page(SCpnt->request->bio));
if (result) {
sense_valid = scsi_command_normalize_sense(SCpnt, &sshdr);
if (sense_valid)

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