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dm: Refactor for new bio cloning/splitting

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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, it's no longer necessary to save/restore the bvec array anymore -
driver conversions for immutable bvecs are done, so drivers should never
be modifying it.

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

Signed-off-by: Kent Overstreet <kmo@daterainc.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Alasdair Kergon <agk@redhat.com>
Cc: dm-devel@redhat.com
Reviewed-by: Mike Snitzer <snitzer@redhat.com>
This commit is contained in:
Kent Overstreet
2013-10-29 17:17:49 -07:00
parent 5341a6278b
commit 1c3b13e64c
4 changed files with 20 additions and 253 deletions
Download Patch File Download Diff File Expand all files Collapse all files

174
drivers/md/dm.c
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@@ -1155,7 +1155,6 @@ 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)
@@ -1164,68 +1163,24 @@ 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);
__bio_clone_fast(clone, bio);
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, to_bytes(sector - clone->bi_iter.bi_sector));
clone->bi_iter.bi_size = to_bytes(len);
if (bio_integrity(bio))
bio_integrity_trim(clone, 0, len);
}
static struct dm_target_io *alloc_tio(struct clone_info *ci,
@@ -1258,7 +1213,7 @@ static void __clone_and_map_simple_bio(struct clone_info *ci,
* ci->bio->bi_max_vecs is BIO_INLINE_VECS anyway, for both flush
* and discard, so no need for concern about wasted bvec allocations.
*/
__bio_clone(clone, ci->bio);
__bio_clone_fast(clone, ci->bio);
if (len)
bio_setup_sector(clone, ci->sector, len);
@@ -1287,10 +1242,7 @@ 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;
@@ -1304,11 +1256,8 @@ 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);
}
}
@@ -1379,60 +1328,6 @@ static int __send_write_same(struct clone_info *ci)
return __send_changing_extent_only(ci, get_num_write_same_bios, NULL);
}
/*
* 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.
*/
@@ -1440,8 +1335,7 @@ 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);
@@ -1452,41 +1346,14 @@ 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);
len = min_t(sector_t, max_io_len(ci->sector, ti), ci->sector_count);
/*
* 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;
}
__clone_and_map_data_bio(ci, ti, ci->sector, len);
/*
* 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);
ci->sector += len;
ci->sector_count -= len;
__clone_and_map_data_bio(ci, ti, ci->sector, bio->bi_max_vecs,
ci->idx, idx - ci->idx, 0, len, 0);
ci->sector += len;
ci->sector_count -= len;
ci->idx = idx;
return 0;
}
/*
* Handle a bvec that must be split between two or more targets.
*/
return __split_bvec_across_targets(ci, ti, max);
return 0;
}
/*
@@ -1512,7 +1379,6 @@ static void __split_and_process_bio(struct mapped_device *md,
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);