block: remove split code in blkdev_issue_{discard,write_same}

The split code in blkdev_issue_{discard,write_same} can go away
now that any driver that cares does the split. We have to make
sure bio size doesn't overflow.

For discard, we set max discard sectors to (1<<31)>>9 to ensure
it doesn't overflow bi_size and hopefully it is of the proper
granularity as long as the granularity is a power of two.

Acked-by: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Ming Lin <ming.l@ssi.samsung.com>
Signed-off-by: Jens Axboe <axboe@fb.com>

diff --git a/block/blk-lib.c b/block/blk-lib.c
index 6dee17443f14dc8b8b5461c8076ddf2379a5363d..bd40292e5009675ef17d6914b67010834cf1beb6 100644 (file)
--- a/block/blk-lib.c
+++ b/block/blk-lib.c
@@ -26,6 +26,13 @@ static void bio_batch_end_io(struct bio *bio)
        bio_put(bio);
 }
 
+/*
+ * Ensure that max discard sectors doesn't overflow bi_size and hopefully
+ * it is of the proper granularity as long as the granularity is a power
+ * of two.
+ */
+#define MAX_BIO_SECTORS ((1U << 31) >> 9)
+
 /**
  * blkdev_issue_discard - queue a discard
  * @bdev:      blockdev to issue discard for
@@ -43,8 +50,6 @@ 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, granularity;
-       int alignment;
        struct bio_batch bb;
        struct bio *bio;
        int ret = 0;
@@ -56,21 +61,6 @@ int blkdev_issue_discard(struct block_device *bdev, sector_t sector,
        if (!blk_queue_discard(q))
                return -EOPNOTSUPP;
 
-       /* Zero-sector (unknown) and one-sector granularities are the same.  */
-       granularity = max(q->limits.discard_granularity >> 9, 1U);
-       alignment = (bdev_discard_alignment(bdev) >> 9) % 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 -= max_discard_sectors % granularity;
-       if (unlikely(!max_discard_sectors)) {
-               /* Avoid infinite loop below. Being cautious never hurts. */
-               return -EOPNOTSUPP;
-       }
-
        if (flags & BLKDEV_DISCARD_SECURE) {
                if (!blk_queue_secdiscard(q))
                        return -EOPNOTSUPP;
@@ -84,7 +74,7 @@ int blkdev_issue_discard(struct block_device *bdev, sector_t sector,
        blk_start_plug(&plug);
        while (nr_sects) {
                unsigned int req_sects;
-               sector_t end_sect, tmp;
+               sector_t end_sect;
 
                bio = bio_alloc(gfp_mask, 1);
                if (!bio) {
@@ -92,21 +82,8 @@ int blkdev_issue_discard(struct block_device *bdev, sector_t sector,
                        break;
                }
 
-               req_sects = min_t(sector_t, nr_sects, max_discard_sectors);
-
-               /*
-                * If splitting a request, and the next starting sector would be
-                * misaligned, stop the discard at the previous aligned sector.
-                */
+               req_sects = min_t(sector_t, nr_sects, MAX_BIO_SECTORS);
                end_sect = sector + req_sects;
-               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;
-               }
 
                bio->bi_iter.bi_sector = sector;
                bio->bi_end_io = bio_batch_end_io;
@@ -165,10 +142,8 @@ int blkdev_issue_write_same(struct block_device *bdev, sector_t sector,
        if (!q)
                return -ENXIO;
 
-       max_write_same_sectors = q->limits.max_write_same_sectors;
-
-       if (max_write_same_sectors == 0)
-               return -EOPNOTSUPP;
+       /* Ensure that max_write_same_sectors doesn't overflow bi_size */
+       max_write_same_sectors = UINT_MAX >> 9;
 
        atomic_set(&bb.done, 1);
        bb.error = 0;