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Subject[RFC PATCH 05/17] btrfs: remove bio splitting and merge_bvec_fn() calls
Date
From: Kent Overstreet <kmo@daterainc.com>

Btrfs has been doing bio splitting from btrfs_map_bio(), by checking
device limits as well as calling ->merge_bvec_fn() etc. That is not
necessary any more, because generic_make_request() is now able to
handle arbitrarily sized bios. So clean up unnecessary code paths.

Signed-off-by: Kent Overstreet <kmo@daterainc.com>
[dpark: add more description in commit message]
Signed-off-by: Dongsu Park <dongsu.park@profitbricks.com>
Cc: Chris Mason <clm@fb.com>
Cc: Josef Bacik <jbacik@fb.com>
Cc: linux-btrfs@vger.kernel.org
---
fs/btrfs/volumes.c | 73 ------------------------------------------------------
1 file changed, 73 deletions(-)

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 50c5a87..c627bf8 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -5691,34 +5691,6 @@ static noinline void btrfs_schedule_bio(struct btrfs_root *root,
&device->work);
}

-static int bio_size_ok(struct block_device *bdev, struct bio *bio,
- sector_t sector)
-{
- struct bio_vec *prev;
- struct request_queue *q = bdev_get_queue(bdev);
- unsigned int max_sectors = queue_max_sectors(q);
- struct bvec_merge_data bvm = {
- .bi_bdev = bdev,
- .bi_sector = sector,
- .bi_rw = bio->bi_rw,
- };
-
- if (WARN_ON(bio->bi_vcnt == 0))
- return 1;
-
- prev = &bio->bi_io_vec[bio->bi_vcnt - 1];
- if (bio_sectors(bio) > max_sectors)
- return 0;
-
- if (!q->merge_bvec_fn)
- return 1;
-
- bvm.bi_size = bio->bi_iter.bi_size - prev->bv_len;
- if (q->merge_bvec_fn(q, &bvm, prev) < prev->bv_len)
- return 0;
- return 1;
-}
-
static void submit_stripe_bio(struct btrfs_root *root, struct btrfs_bio *bbio,
struct bio *bio, u64 physical, int dev_nr,
int rw, int async)
@@ -5752,38 +5724,6 @@ static void submit_stripe_bio(struct btrfs_root *root, struct btrfs_bio *bbio,
btrfsic_submit_bio(rw, bio);
}

-static int breakup_stripe_bio(struct btrfs_root *root, struct btrfs_bio *bbio,
- struct bio *first_bio, struct btrfs_device *dev,
- int dev_nr, int rw, int async)
-{
- struct bio_vec *bvec = first_bio->bi_io_vec;
- struct bio *bio;
- int nr_vecs = bio_get_nr_vecs(dev->bdev);
- u64 physical = bbio->stripes[dev_nr].physical;
-
-again:
- bio = btrfs_bio_alloc(dev->bdev, physical >> 9, nr_vecs, GFP_NOFS);
- if (!bio)
- return -ENOMEM;
-
- while (bvec <= (first_bio->bi_io_vec + first_bio->bi_vcnt - 1)) {
- if (bio_add_page(bio, bvec->bv_page, bvec->bv_len,
- bvec->bv_offset) < bvec->bv_len) {
- u64 len = bio->bi_iter.bi_size;
-
- atomic_inc(&bbio->stripes_pending);
- submit_stripe_bio(root, bbio, bio, physical, dev_nr,
- rw, async);
- physical += len;
- goto again;
- }
- bvec++;
- }
-
- submit_stripe_bio(root, bbio, bio, physical, dev_nr, rw, async);
- return 0;
-}
-
static void bbio_error(struct btrfs_bio *bbio, struct bio *bio, u64 logical)
{
atomic_inc(&bbio->error);
@@ -5862,19 +5802,6 @@ int btrfs_map_bio(struct btrfs_root *root, int rw, struct bio *bio,
continue;
}

- /*
- * Check and see if we're ok with this bio based on it's size
- * and offset with the given device.
- */
- if (!bio_size_ok(dev->bdev, first_bio,
- bbio->stripes[dev_nr].physical >> 9)) {
- ret = breakup_stripe_bio(root, bbio, first_bio, dev,
- dev_nr, rw, async_submit);
- BUG_ON(ret);
- dev_nr++;
- continue;
- }
-
if (dev_nr < total_devs - 1) {
bio = btrfs_bio_clone(first_bio, GFP_NOFS);
BUG_ON(!bio); /* -ENOMEM */
--
2.1.0


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