Re: [PATCH] mmc: core: don't set limits.discard_granularity as 0
From: Adrian Hunter <adrian.hunter@intel.com>
Date: 2020-09-30 17:23:58
Also in:
linux-mmc, lkml
On 30/09/20 7:08 pm, Coly Li wrote:
In mmc_queue_setup_discard() the mmc driver queue's discard_granularity
might be set as 0 (when card->pref_erase > max_discard) while the mmc
device still declares to support discard operation. This is buggy and
triggered the following kernel warning message,
WARNING: CPU: 0 PID: 135 at __blkdev_issue_discard+0x200/0x294
CPU: 0 PID: 135 Comm: f2fs_discard-17 Not tainted 5.9.0-rc6 #1
Hardware name: Google Kevin (DT)
pstate: 00000005 (nzcv daif -PAN -UAO BTYPE=--)
pc : __blkdev_issue_discard+0x200/0x294
lr : __blkdev_issue_discard+0x54/0x294
sp : ffff800011dd3b10
x29: ffff800011dd3b10 x28: 0000000000000000 x27: ffff800011dd3cc4 x26: ffff800011dd3e18 x25: 000000000004e69b x24: 0000000000000c40 x23: ffff0000f1deaaf0 x22: ffff0000f2849200 x21: 00000000002734d8 x20: 0000000000000008 x19: 0000000000000000 x18: 0000000000000000 x17: 0000000000000000 x16: 0000000000000000 x15: 0000000000000000 x14: 0000000000000394 x13: 0000000000000000 x12: 0000000000000000 x11: 0000000000000000 x10: 00000000000008b0 x9 : ffff800011dd3cb0 x8 : 000000000004e69b x7 : 0000000000000000 x6 : ffff0000f1926400 x5 : ffff0000f1940800 x4 : 0000000000000000 x3 : 0000000000000c40 x2 : 0000000000000008 x1 : 00000000002734d8 x0 : 0000000000000000 Call trace:
__blkdev_issue_discard+0x200/0x294
__submit_discard_cmd+0x128/0x374
__issue_discard_cmd_orderly+0x188/0x244
__issue_discard_cmd+0x2e8/0x33c
issue_discard_thread+0xe8/0x2f0
kthread+0x11c/0x120
ret_from_fork+0x10/0x1c
---[ end trace e4c8023d33dfe77a ]---
This patch fixes the issue by setting discard_granularity as SECTOR_SIZE
instead of 0 when (card->pref_erase > max_discard) is true. Now no more
complain from __blkdev_issue_discard() for the improper value of discard
granularity.
Fixes: commit e056a1b5b67b ("mmc: queue: let host controllers specify maximum discard timeout")
That "Fixes" tag is a bit misleading. For some time, the block layer had
no problem with discard_granularity of zero, and blk_bio_discard_split()
still doesn't (see below).
static struct bio *blk_bio_discard_split(struct request_queue *q,
struct bio *bio,
struct bio_set *bs,
unsigned *nsegs)
{
unsigned int max_discard_sectors, granularity;
int alignment;
sector_t tmp;
unsigned split_sectors;
*nsegs = 1;
/* Zero-sector (unknown) and one-sector granularities are the same. */
granularity = max(q->limits.discard_granularity >> 9, 1U);
quoted hunk ↗ jump to hunk
Reported-by: Vicente Bergas <redacted> Signed-off-by: Coly Li <redacted> Cc: Adrian Hunter <adrian.hunter@intel.com> Cc: Ulf Hansson <redacted> --- drivers/mmc/core/queue.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)diff --git a/drivers/mmc/core/queue.c b/drivers/mmc/core/queue.c index 6c022ef0f84d..350d0cc4ee62 100644 --- a/drivers/mmc/core/queue.c +++ b/drivers/mmc/core/queue.c@@ -190,7 +190,7 @@ static void mmc_queue_setup_discard(struct request_queue *q, q->limits.discard_granularity = card->pref_erase << 9; /* granularity must not be greater than max. discard */ if (card->pref_erase > max_discard) - q->limits.discard_granularity = 0; + q->limits.discard_granularity = SECTOR_SIZE; if (mmc_can_secure_erase_trim(card)) blk_queue_flag_set(QUEUE_FLAG_SECERASE, q); }