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@suse.de>
Signed-off-by: Shaohua Li <shli@fusionio.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

2 files changed, 16 insertions, 13 deletions

diff --git a/block/blk-lib.c b/block/blk-lib.c
index 9373b58dfab1..5677fd33d7d2 100644
--- a/block/blk-lib.c
+++ b/block/blk-lib.c
@@ -43,8 +43,8 @@ int blkdev_issue_discard(struct block_device *bdev, sector_t sector,
         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_device *bdev, sector_t sector,
 
         /* 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_device *bdev, sector_t sector,
 
         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_device *bdev, sector_t sector,
                  * 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;
                 }
 
diff --git a/block/blk-settings.c b/block/blk-settings.c
index 779bb7646bcd..c50ecf0ea3b1 100644
--- a/block/blk-settings.c
+++ b/block/blk-settings.c
@@ -611,7 +611,7 @@ int blk_stack_limits(struct queue_limits *t, struct queue_limits *b,
                         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 *t, struct queue_limits *b,
                                                       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;