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btrfs: allow btrfs_submit_bio to split bios
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Currently the I/O submitters have to split bios according to the chunk
stripe boundaries.  This leads to extra lookups in the extent trees and
a lot of boilerplate code.

To drop this requirement, split the bio when __btrfs_map_block returns a
mapping that is smaller than the requested size and keep a count of
pending bios in the original btrfs_bio so that the upper level
completion is only invoked when all clones have completed.

Based on a patch from Qu Wenruo.

Reviewed-by: Josef Bacik <[email protected]>
Reviewed-by: Johannes Thumshirn <[email protected]>
Reviewed-by: Qu Wenruo <[email protected]>
Signed-off-by: Christoph Hellwig <[email protected]>
Signed-off-by: David Sterba <[email protected]>
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@kdave
Christoph Hellwig authored and kdave committed Feb 15, 2023
1 parent 542e300 commit 852eee6
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Showing 2 changed files with 93 additions and 18 deletions.
110 changes: 92 additions & 18 deletions fs/btrfs/bio.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -17,6 +17,7 @@
#include "file-item.h"

static struct bio_set btrfs_bioset;
static struct bio_set btrfs_clone_bioset;
static struct bio_set btrfs_repair_bioset;
static mempool_t btrfs_failed_bio_pool;

Expand All @@ -38,6 +39,7 @@ static inline void btrfs_bio_init(struct btrfs_bio *bbio,
bbio->inode = inode;
bbio->end_io = end_io;
bbio->private = private;
atomic_set(&bbio->pending_ios, 1);
}

/*
Expand Down Expand Up @@ -75,6 +77,59 @@ struct bio *btrfs_bio_clone_partial(struct bio *orig, u64 offset, u64 size,
return bio;
}

static struct bio *btrfs_split_bio(struct bio *orig, u64 map_length)
{
struct btrfs_bio *orig_bbio = btrfs_bio(orig);
struct bio *bio;

bio = bio_split(orig, map_length >> SECTOR_SHIFT, GFP_NOFS,
&btrfs_clone_bioset);
btrfs_bio_init(btrfs_bio(bio), orig_bbio->inode, NULL, orig_bbio);

btrfs_bio(bio)->file_offset = orig_bbio->file_offset;
if (!(orig->bi_opf & REQ_BTRFS_ONE_ORDERED))
orig_bbio->file_offset += map_length;

atomic_inc(&orig_bbio->pending_ios);
return bio;
}

static void btrfs_orig_write_end_io(struct bio *bio);

static void btrfs_bbio_propagate_error(struct btrfs_bio *bbio,
struct btrfs_bio *orig_bbio)
{
/*
* For writes we tolerate nr_mirrors - 1 write failures, so we can't
* just blindly propagate a write failure here. Instead increment the
* error count in the original I/O context so that it is guaranteed to
* be larger than the error tolerance.
*/
if (bbio->bio.bi_end_io == &btrfs_orig_write_end_io) {
struct btrfs_io_stripe *orig_stripe = orig_bbio->bio.bi_private;
struct btrfs_io_context *orig_bioc = orig_stripe->bioc;

atomic_add(orig_bioc->max_errors, &orig_bioc->error);
} else {
orig_bbio->bio.bi_status = bbio->bio.bi_status;
}
}

static void btrfs_orig_bbio_end_io(struct btrfs_bio *bbio)
{
if (bbio->bio.bi_pool == &btrfs_clone_bioset) {
struct btrfs_bio *orig_bbio = bbio->private;

if (bbio->bio.bi_status)
btrfs_bbio_propagate_error(bbio, orig_bbio);
bio_put(&bbio->bio);
bbio = orig_bbio;
}

if (atomic_dec_and_test(&bbio->pending_ios))
bbio->end_io(bbio);
}

static int next_repair_mirror(struct btrfs_failed_bio *fbio, int cur_mirror)
{
if (cur_mirror == fbio->num_copies)
Expand All @@ -92,7 +147,7 @@ static int prev_repair_mirror(struct btrfs_failed_bio *fbio, int cur_mirror)
static void btrfs_repair_done(struct btrfs_failed_bio *fbio)
{
if (atomic_dec_and_test(&fbio->repair_count)) {
fbio->bbio->end_io(fbio->bbio);
btrfs_orig_bbio_end_io(fbio->bbio);
mempool_free(fbio, &btrfs_failed_bio_pool);
}
}
Expand Down Expand Up @@ -229,7 +284,7 @@ static void btrfs_check_read_bio(struct btrfs_bio *bbio, struct btrfs_device *de
if (fbio)
btrfs_repair_done(fbio);
else
bbio->end_io(bbio);
btrfs_orig_bbio_end_io(bbio);
}

static void btrfs_log_dev_io_error(struct bio *bio, struct btrfs_device *dev)
Expand Down Expand Up @@ -283,7 +338,7 @@ static void btrfs_simple_end_io(struct bio *bio)
} else {
if (bio_op(bio) == REQ_OP_ZONE_APPEND)
btrfs_record_physical_zoned(bbio);
bbio->end_io(bbio);
btrfs_orig_bbio_end_io(bbio);
}
}

Expand All @@ -297,7 +352,7 @@ static void btrfs_raid56_end_io(struct bio *bio)
if (bio_op(bio) == REQ_OP_READ && !(bbio->bio.bi_opf & REQ_META))
btrfs_check_read_bio(bbio, NULL);
else
bbio->end_io(bbio);
btrfs_orig_bbio_end_io(bbio);

btrfs_put_bioc(bioc);
}
Expand All @@ -324,7 +379,7 @@ static void btrfs_orig_write_end_io(struct bio *bio)
else
bio->bi_status = BLK_STS_OK;

bbio->end_io(bbio);
btrfs_orig_bbio_end_io(bbio);
btrfs_put_bioc(bioc);
}

Expand Down Expand Up @@ -488,7 +543,7 @@ static void run_one_async_done(struct btrfs_work *work)

/* If an error occurred we just want to clean up the bio and move on. */
if (bio->bi_status) {
btrfs_bio_end_io(async->bbio, bio->bi_status);
btrfs_orig_bbio_end_io(async->bbio);
return;
}

Expand Down Expand Up @@ -563,9 +618,11 @@ static bool btrfs_wq_submit_bio(struct btrfs_bio *bbio,
return true;
}

void btrfs_submit_bio(struct btrfs_fs_info *fs_info, struct bio *bio, int mirror_num)
static bool btrfs_submit_chunk(struct btrfs_fs_info *fs_info, struct bio *bio,
int mirror_num)
{
struct btrfs_bio *bbio = btrfs_bio(bio);
struct btrfs_bio *orig_bbio = bbio;
u64 logical = bio->bi_iter.bi_sector << 9;
u64 length = bio->bi_iter.bi_size;
u64 map_length = length;
Expand All @@ -582,11 +639,10 @@ void btrfs_submit_bio(struct btrfs_fs_info *fs_info, struct bio *bio, int mirror
goto fail;
}

map_length = min(map_length, length);
if (map_length < length) {
btrfs_crit(fs_info,
"mapping failed logical %llu bio len %llu len %llu",
logical, length, map_length);
BUG();
bio = btrfs_split_bio(bio, map_length);
bbio = btrfs_bio(bio);
}

/*
Expand All @@ -597,14 +653,14 @@ void btrfs_submit_bio(struct btrfs_fs_info *fs_info, struct bio *bio, int mirror
bbio->saved_iter = bio->bi_iter;
ret = btrfs_lookup_bio_sums(bbio);
if (ret)
goto fail;
goto fail_put_bio;
}

if (btrfs_op(bio) == BTRFS_MAP_WRITE) {
if (bio_op(bio) == REQ_OP_ZONE_APPEND) {
ret = btrfs_extract_ordered_extent(btrfs_bio(bio));
if (ret)
goto fail;
goto fail_put_bio;
}

/*
Expand All @@ -616,20 +672,32 @@ void btrfs_submit_bio(struct btrfs_fs_info *fs_info, struct bio *bio, int mirror
!btrfs_is_data_reloc_root(bbio->inode->root)) {
if (should_async_write(bbio) &&
btrfs_wq_submit_bio(bbio, bioc, &smap, mirror_num))
return;
goto done;

ret = btrfs_bio_csum(bbio);
if (ret)
goto fail;
goto fail_put_bio;
}
}

__btrfs_submit_bio(bio, bioc, &smap, mirror_num);
return;
done:
return map_length == length;

fail_put_bio:
if (map_length < length)
bio_put(bio);
fail:
btrfs_bio_counter_dec(fs_info);
btrfs_bio_end_io(bbio, ret);
btrfs_bio_end_io(orig_bbio, ret);
/* Do not submit another chunk */
return true;
}

void btrfs_submit_bio(struct btrfs_fs_info *fs_info, struct bio *bio, int mirror_num)
{
while (!btrfs_submit_chunk(fs_info, bio, mirror_num))
;
}

/*
Expand Down Expand Up @@ -737,17 +805,22 @@ int __init btrfs_bioset_init(void)
offsetof(struct btrfs_bio, bio),
BIOSET_NEED_BVECS))
return -ENOMEM;
if (bioset_init(&btrfs_clone_bioset, BIO_POOL_SIZE,
offsetof(struct btrfs_bio, bio), 0))
goto out_free_bioset;
if (bioset_init(&btrfs_repair_bioset, BIO_POOL_SIZE,
offsetof(struct btrfs_bio, bio),
BIOSET_NEED_BVECS))
goto out_free_bioset;
goto out_free_clone_bioset;
if (mempool_init_kmalloc_pool(&btrfs_failed_bio_pool, BIO_POOL_SIZE,
sizeof(struct btrfs_failed_bio)))
goto out_free_repair_bioset;
return 0;

out_free_repair_bioset:
bioset_exit(&btrfs_repair_bioset);
out_free_clone_bioset:
bioset_exit(&btrfs_clone_bioset);
out_free_bioset:
bioset_exit(&btrfs_bioset);
return -ENOMEM;
Expand All @@ -757,5 +830,6 @@ void __cold btrfs_bioset_exit(void)
{
mempool_exit(&btrfs_failed_bio_pool);
bioset_exit(&btrfs_repair_bioset);
bioset_exit(&btrfs_clone_bioset);
bioset_exit(&btrfs_bioset);
}
1 change: 1 addition & 0 deletions fs/btrfs/bio.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -55,6 +55,7 @@ struct btrfs_bio {

/* For internal use in read end I/O handling */
unsigned int mirror_num;
atomic_t pending_ios;
struct work_struct end_io_work;

/*
Expand Down

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