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Date: Fri, 14 Dec 2012 11:15:36 +0800
From: Shaohua Li <shli@...nel.org>
To: axboe@...nel.dk
Cc: neilb@...e.de, linux-kernel@...r.kernel.org
Subject: [patch 1/2]block: discard granularity might not be power of 2
In MD raid case, discard granularity might not be power of 2, for example, a
4-disk raid5 has 3*chunk_size discard granularity. Correct the calculation for
such cases.
Reported-by: Neil Brown <neilb@...e.de>
Signed-off-by: Shaohua Li <shli@...ionio.com>
---
block/blk-lib.c | 23 +++++++++++++----------
block/blk-settings.c | 6 +++---
include/linux/blkdev.h | 7 ++++---
3 files changed, 20 insertions(+), 16 deletions(-)
Index: linux/block/blk-lib.c
===================================================================
--- linux.orig/block/blk-lib.c 2012-10-15 10:01:52.763544641 +0800
+++ linux/block/blk-lib.c 2012-12-14 08:56:24.539932760 +0800
@@ -43,8 +43,8 @@ int blkdev_issue_discard(struct block_de
DECLARE_COMPLETION_ONSTACK(wait);
struct request_queue *q = bdev_get_queue(bdev);
int type = REQ_WRITE | REQ_DISCARD;
- unsigned int max_discard_sectors;
- unsigned int granularity, alignment, mask;
+ sector_t max_discard_sectors;
+ sector_t granularity, alignment;
struct bio_batch bb;
struct bio *bio;
int ret = 0;
@@ -57,15 +57,16 @@ int blkdev_issue_discard(struct block_de
/* Zero-sector (unknown) and one-sector granularities are the same. */
granularity = max(q->limits.discard_granularity >> 9, 1U);
- mask = granularity - 1;
- alignment = (bdev_discard_alignment(bdev) >> 9) & mask;
+ alignment = bdev_discard_alignment(bdev) >> 9;
+ alignment = sector_div(alignment, granularity);
/*
* Ensure that max_discard_sectors is of the proper
* granularity, so that requests stay aligned after a split.
*/
max_discard_sectors = min(q->limits.max_discard_sectors, UINT_MAX >> 9);
- max_discard_sectors = round_down(max_discard_sectors, granularity);
+ sector_div(max_discard_sectors, granularity);
+ max_discard_sectors *= granularity;
if (unlikely(!max_discard_sectors)) {
/* Avoid infinite loop below. Being cautious never hurts. */
return -EOPNOTSUPP;
@@ -83,7 +84,7 @@ int blkdev_issue_discard(struct block_de
while (nr_sects) {
unsigned int req_sects;
- sector_t end_sect;
+ sector_t end_sect, tmp;
bio = bio_alloc(gfp_mask, 1);
if (!bio) {
@@ -98,10 +99,12 @@ int blkdev_issue_discard(struct block_de
* misaligned, stop the discard at the previous aligned sector.
*/
end_sect = sector + req_sects;
- if (req_sects < nr_sects && (end_sect & mask) != alignment) {
- end_sect =
- round_down(end_sect - alignment, granularity)
- + alignment;
+ tmp = end_sect;
+ if (req_sects < nr_sects &&
+ sector_div(tmp, granularity) != alignment) {
+ end_sect = end_sect - alignment;
+ sector_div(end_sect, granularity);
+ end_sect = end_sect * granularity + alignment;
req_sects = end_sect - sector;
}
Index: linux/block/blk-settings.c
===================================================================
--- linux.orig/block/blk-settings.c 2012-10-15 10:01:52.763544641 +0800
+++ linux/block/blk-settings.c 2012-12-14 09:53:18.493013557 +0800
@@ -611,7 +611,7 @@ int blk_stack_limits(struct queue_limits
bottom = b->discard_granularity + alignment;
/* Verify that top and bottom intervals line up */
- if (max(top, bottom) & (min(top, bottom) - 1))
+ if ((max(top, bottom) % min(top, bottom)) != 0)
t->discard_misaligned = 1;
}
@@ -619,8 +619,8 @@ int blk_stack_limits(struct queue_limits
b->max_discard_sectors);
t->discard_granularity = max(t->discard_granularity,
b->discard_granularity);
- t->discard_alignment = lcm(t->discard_alignment, alignment) &
- (t->discard_granularity - 1);
+ t->discard_alignment = lcm(t->discard_alignment, alignment) %
+ t->discard_granularity;
}
return ret;
Index: linux/include/linux/blkdev.h
===================================================================
--- linux.orig/include/linux/blkdev.h 2012-10-15 10:01:52.999541673 +0800
+++ linux/include/linux/blkdev.h 2012-12-13 14:26:25.469877308 +0800
@@ -1180,13 +1180,14 @@ static inline int queue_discard_alignmen
static inline int queue_limit_discard_alignment(struct queue_limits *lim, sector_t sector)
{
- unsigned int alignment = (sector << 9) & (lim->discard_granularity - 1);
+ sector_t alignment = sector << 9;
+ alignment = sector_div(alignment, lim->discard_granularity);
if (!lim->max_discard_sectors)
return 0;
- return (lim->discard_granularity + lim->discard_alignment - alignment)
- & (lim->discard_granularity - 1);
+ alignment = lim->discard_granularity + lim->discard_alignment - alignment;
+ return sector_div(alignment, lim->discard_granularity);
}
static inline int bdev_discard_alignment(struct block_device *bdev)
--
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