[PATCH 13/26] dm: Refactor for new bio cloning/splitting

From: Kent Overstreet
Date: Sat Jun 08 2013 - 22:23:23 EST

We need to convert the dm code to the new bvec_iter primitives which
respect bi_bvec_done; they also allow us to drastically simplify dm's
bio splitting code.

Also kill bio_sector_offset(), dm was the only user and it doesn't make
much sense anymore.

Signed-off-by: Kent Overstreet <koverstreet@xxxxxxxxxx>
Cc: Jens Axboe <axboe@xxxxxxxxx>
Cc: Alasdair Kergon <agk@xxxxxxxxxx>
Cc: dm-devel@xxxxxxxxxx
---
drivers/md/dm.c | 170 ++++++----------------------------------------------
fs/bio.c | 38 ------------
include/linux/bio.h | 1 -
3 files changed, 18 insertions(+), 191 deletions(-)

diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index d67c6a9..8aac97b 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -1013,7 +1013,6 @@ struct clone_info {
struct dm_io *io;
sector_t sector;
sector_t sector_count;
- unsigned short idx;
};

static void bio_setup_sector(struct bio *bio, sector_t sector, sector_t len)
@@ -1022,68 +1021,24 @@ static void bio_setup_sector(struct bio *bio, sector_t sector, sector_t len)
bio->bi_iter.bi_size = to_bytes(len);
}

-static void bio_setup_bv(struct bio *bio, unsigned short idx, unsigned short bv_count)
-{
- bio->bi_iter.bi_idx = idx;
- bio->bi_vcnt = idx + bv_count;
- bio->bi_flags &= ~(1 << BIO_SEG_VALID);
-}
-
-static void clone_bio_integrity(struct bio *bio, struct bio *clone,
- unsigned short idx, unsigned len, unsigned offset,
- unsigned trim)
-{
- if (!bio_integrity(bio))
- return;
-
- bio_integrity_clone(clone, bio, GFP_NOIO);
-
- if (trim)
- bio_integrity_trim(clone, bio_sector_offset(bio, idx, offset), len);
-}
-
-/*
- * Creates a little bio that just does part of a bvec.
- */
-static void clone_split_bio(struct dm_target_io *tio, struct bio *bio,
- sector_t sector, unsigned short idx,
- unsigned offset, unsigned len)
-{
- struct bio *clone = &tio->clone;
- struct bio_vec *bv = bio->bi_io_vec + idx;
-
- *clone->bi_io_vec = *bv;
-
- bio_setup_sector(clone, sector, len);
-
- clone->bi_bdev = bio->bi_bdev;
- clone->bi_rw = bio->bi_rw;
- clone->bi_vcnt = 1;
- clone->bi_io_vec->bv_offset = offset;
- clone->bi_io_vec->bv_len = clone->bi_iter.bi_size;
- clone->bi_flags |= 1 << BIO_CLONED;
-
- clone_bio_integrity(bio, clone, idx, len, offset, 1);
-}
-
/*
* Creates a bio that consists of range of complete bvecs.
*/
static void clone_bio(struct dm_target_io *tio, struct bio *bio,
- sector_t sector, unsigned short idx,
- unsigned short bv_count, unsigned len)
+ sector_t sector, unsigned len)
{
struct bio *clone = &tio->clone;
- unsigned trim = 0;

__bio_clone(clone, bio);
- bio_setup_sector(clone, sector, len);
- bio_setup_bv(clone, idx, bv_count);

- if (idx != bio->bi_iter.bi_idx ||
- clone->bi_iter.bi_size < bio->bi_iter.bi_size)
- trim = 1;
- clone_bio_integrity(bio, clone, idx, len, 0, trim);
+ if (bio_integrity(bio))
+ bio_integrity_clone(clone, bio, GFP_NOIO);
+
+ bio_advance(clone, (sector - clone->bi_iter.bi_sector) << 9);
+ bio->bi_iter.bi_size = len << 9;
+
+ if (bio_integrity(bio))
+ bio_integrity_trim(clone, 0, len);
}

static struct dm_target_io *alloc_tio(struct clone_info *ci,
@@ -1145,10 +1100,7 @@ static int __send_empty_flush(struct clone_info *ci)
}

static void __clone_and_map_data_bio(struct clone_info *ci, struct dm_target *ti,
- sector_t sector, int nr_iovecs,
- unsigned short idx, unsigned short bv_count,
- unsigned offset, unsigned len,
- unsigned split_bvec)
+ sector_t sector, unsigned len)
{
struct bio *bio = ci->bio;
struct dm_target_io *tio;
@@ -1162,11 +1114,8 @@ static void __clone_and_map_data_bio(struct clone_info *ci, struct dm_target *ti
num_target_bios = ti->num_write_bios(ti, bio);

for (target_bio_nr = 0; target_bio_nr < num_target_bios; target_bio_nr++) {
- tio = alloc_tio(ci, ti, nr_iovecs, target_bio_nr);
- if (split_bvec)
- clone_split_bio(tio, bio, sector, idx, offset, len);
- else
- clone_bio(tio, bio, sector, idx, bv_count, len);
+ tio = alloc_tio(ci, ti, 0, target_bio_nr);
+ clone_bio(tio, bio, sector, len);
__map_bio(tio);
}
}
@@ -1238,68 +1187,13 @@ static int __send_write_same(struct clone_info *ci)
}

/*
- * Find maximum number of sectors / bvecs we can process with a single bio.
- */
-static sector_t __len_within_target(struct clone_info *ci, sector_t max, int *idx)
-{
- struct bio *bio = ci->bio;
- sector_t bv_len, total_len = 0;
-
- for (*idx = ci->idx; max && (*idx < bio->bi_vcnt); (*idx)++) {
- bv_len = to_sector(bio->bi_io_vec[*idx].bv_len);
-
- if (bv_len > max)
- break;
-
- max -= bv_len;
- total_len += bv_len;
- }
-
- return total_len;
-}
-
-static int __split_bvec_across_targets(struct clone_info *ci,
- struct dm_target *ti, sector_t max)
-{
- struct bio *bio = ci->bio;
- struct bio_vec *bv = bio->bi_io_vec + ci->idx;
- sector_t remaining = to_sector(bv->bv_len);
- unsigned offset = 0;
- sector_t len;
-
- do {
- if (offset) {
- ti = dm_table_find_target(ci->map, ci->sector);
- if (!dm_target_is_valid(ti))
- return -EIO;
-
- max = max_io_len(ci->sector, ti);
- }
-
- len = min(remaining, max);
-
- __clone_and_map_data_bio(ci, ti, ci->sector, 1, ci->idx, 0,
- bv->bv_offset + offset, len, 1);
-
- ci->sector += len;
- ci->sector_count -= len;
- offset += to_bytes(len);
- } while (remaining -= len);
-
- ci->idx++;
-
- return 0;
-}
-
-/*
* Select the correct strategy for processing a non-flush bio.
*/
static int __split_and_process_non_flush(struct clone_info *ci)
{
struct bio *bio = ci->bio;
struct dm_target *ti;
- sector_t len, max;
- int idx;
+ unsigned len;

if (unlikely(bio->bi_rw & REQ_DISCARD))
return __send_discard(ci);
@@ -1310,41 +1204,14 @@ static int __split_and_process_non_flush(struct clone_info *ci)
if (!dm_target_is_valid(ti))
return -EIO;

- max = max_io_len(ci->sector, ti);
-
- /*
- * Optimise for the simple case where we can do all of
- * the remaining io with a single clone.
- */
- if (ci->sector_count <= max) {
- __clone_and_map_data_bio(ci, ti, ci->sector, bio->bi_max_vecs,
- ci->idx, bio->bi_vcnt - ci->idx, 0,
- ci->sector_count, 0);
- ci->sector_count = 0;
- return 0;
- }
-
- /*
- * There are some bvecs that don't span targets.
- * Do as many of these as possible.
- */
- if (to_sector(bio->bi_io_vec[ci->idx].bv_len) <= max) {
- len = __len_within_target(ci, max, &idx);
-
- __clone_and_map_data_bio(ci, ti, ci->sector, bio->bi_max_vecs,
- ci->idx, idx - ci->idx, 0, len, 0);
+ len = min_t(unsigned, max_io_len(ci->sector, ti), bio_sectors(bio));

- ci->sector += len;
- ci->sector_count -= len;
- ci->idx = idx;
+ __clone_and_map_data_bio(ci, ti, ci->sector, len);

- return 0;
- }
+ ci->sector += len;
+ ci->sector_count -= len;

- /*
- * Handle a bvec that must be split between two or more targets.
- */
- return __split_bvec_across_targets(ci, ti, max);
+ return 0;
}

/*
@@ -1369,7 +1236,6 @@ static void __split_and_process_bio(struct mapped_device *md, struct bio *bio)
ci.io->md = md;
spin_lock_init(&ci.io->endio_lock);
ci.sector = bio->bi_iter.bi_sector;
- ci.idx = bio->bi_iter.bi_idx;

start_io_acct(ci.io);

diff --git a/fs/bio.c b/fs/bio.c
index d4200f4..24271ce 100644
--- a/fs/bio.c
+++ b/fs/bio.c
@@ -1762,44 +1762,6 @@ struct bio_pair *bio_split(struct bio *bi, int first_sectors)
}
EXPORT_SYMBOL(bio_split);

-/**
- * bio_sector_offset - Find hardware sector offset in bio
- * @bio: bio to inspect
- * @index: bio_vec index
- * @offset: offset in bv_page
- *
- * Return the number of hardware sectors between beginning of bio
- * and an end point indicated by a bio_vec index and an offset
- * within that vector's page.
- */
-sector_t bio_sector_offset(struct bio *bio, unsigned short index,
- unsigned int offset)
-{
- unsigned int sector_sz;
- struct bio_vec *bv;
- sector_t sectors;
- int i;
-
- sector_sz = queue_logical_block_size(bio->bi_bdev->bd_disk->queue);
- sectors = 0;
-
- if (index >= bio->bi_iter.bi_idx)
- index = bio->bi_vcnt - 1;
-
- bio_for_each_segment_all(bv, bio, i) {
- if (i == index) {
- if (offset > bv->bv_offset)
- sectors += (offset - bv->bv_offset) / sector_sz;
- break;
- }
-
- sectors += bv->bv_len / sector_sz;
- }
-
- return sectors;
-}
-EXPORT_SYMBOL(bio_sector_offset);
-
/*
* create memory pools for biovec's in a bio_set.
* use the global biovec slabs created for general use.
diff --git a/include/linux/bio.h b/include/linux/bio.h
index 1967b64..80ffe15 100644
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -331,7 +331,6 @@ extern int bio_add_page(struct bio *, struct page *, unsigned int,unsigned int);
extern int bio_add_pc_page(struct request_queue *, struct bio *, struct page *,
unsigned int, unsigned int);
extern int bio_get_nr_vecs(struct block_device *);
-extern sector_t bio_sector_offset(struct bio *, unsigned short, unsigned int);
extern struct bio *bio_map_user(struct request_queue *, struct block_device *,
unsigned long, unsigned int, int, gfp_t);
struct sg_iovec;
--
1.8.3.rc1

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