fs/btrfs/bio.c - kernel/common - Git at Google

 // SPDX-License-Identifier: GPL-2.0
 /*
  * Copyright (C) 2007 Oracle.  All rights reserved.
  * Copyright (C) 2022 Christoph Hellwig.
  */

 #include <linux/bio.h>
 #include "bio.h"
 #include "ctree.h"
 #include "volumes.h"
 #include "raid56.h"
 #include "async-thread.h"
 #include "check-integrity.h"
 #include "dev-replace.h"
 #include "rcu-string.h"
 #include "zoned.h"

 static struct bio_set btrfs_bioset;

 /*
  * Initialize a btrfs_bio structure.  This skips the embedded bio itself as it
  * is already initialized by the block layer.
  */
 static inline void btrfs_bio_init(struct btrfs_bio *bbio,
 				  btrfs_bio_end_io_t end_io, void *private)
 {
 	memset(bbio, 0, offsetof(struct btrfs_bio, bio));
 	bbio->end_io = end_io;
 	bbio->private = private;
 }

 /*
  * Allocate a btrfs_bio structure.  The btrfs_bio is the main I/O container for
  * btrfs, and is used for all I/O submitted through btrfs_submit_bio.
  *
  * Just like the underlying bio_alloc_bioset it will not fail as it is backed by
  * a mempool.
  */
 struct bio *btrfs_bio_alloc(unsigned int nr_vecs, blk_opf_t opf,
 			    btrfs_bio_end_io_t end_io, void *private)
 {
 	struct bio *bio;

 	bio = bio_alloc_bioset(NULL, nr_vecs, opf, GFP_NOFS, &btrfs_bioset);
 	btrfs_bio_init(btrfs_bio(bio), end_io, private);
 	return bio;
 }

 struct bio *btrfs_bio_clone_partial(struct bio *orig, u64 offset, u64 size,
 				    btrfs_bio_end_io_t end_io, void *private)
 {
 	struct bio *bio;
 	struct btrfs_bio *bbio;

 	ASSERT(offset <= UINT_MAX && size <= UINT_MAX);

 	bio = bio_alloc_clone(orig->bi_bdev, orig, GFP_NOFS, &btrfs_bioset);
 	bbio = btrfs_bio(bio);
 	btrfs_bio_init(bbio, end_io, private);

 	bio_trim(bio, offset >> 9, size >> 9);
 	bbio->iter = bio->bi_iter;
 	return bio;
 }

 static void btrfs_log_dev_io_error(struct bio *bio, struct btrfs_device *dev)
 {
 	if (!dev || !dev->bdev)
 		return;
 	if (bio->bi_status != BLK_STS_IOERR && bio->bi_status != BLK_STS_TARGET)
 		return;

 	if (btrfs_op(bio) == BTRFS_MAP_WRITE)
 		btrfs_dev_stat_inc_and_print(dev, BTRFS_DEV_STAT_WRITE_ERRS);
 	if (!(bio->bi_opf & REQ_RAHEAD))
 		btrfs_dev_stat_inc_and_print(dev, BTRFS_DEV_STAT_READ_ERRS);
 	if (bio->bi_opf & REQ_PREFLUSH)
 		btrfs_dev_stat_inc_and_print(dev, BTRFS_DEV_STAT_FLUSH_ERRS);
 }

 static struct workqueue_struct *btrfs_end_io_wq(struct btrfs_fs_info *fs_info,
 						struct bio *bio)
 {
 	if (bio->bi_opf & REQ_META)
 		return fs_info->endio_meta_workers;
 	return fs_info->endio_workers;
 }

 static void btrfs_end_bio_work(struct work_struct *work)
 {
 	struct btrfs_bio *bbio = container_of(work, struct btrfs_bio, end_io_work);

 	bbio->end_io(bbio);
 }

 static void btrfs_simple_end_io(struct bio *bio)
 {
 	struct btrfs_fs_info *fs_info = bio->bi_private;
 	struct btrfs_bio *bbio = btrfs_bio(bio);

 	btrfs_bio_counter_dec(fs_info);

 	if (bio->bi_status)
 		btrfs_log_dev_io_error(bio, bbio->device);

 	if (bio_op(bio) == REQ_OP_READ) {
 		INIT_WORK(&bbio->end_io_work, btrfs_end_bio_work);
 		queue_work(btrfs_end_io_wq(fs_info, bio), &bbio->end_io_work);
 	} else {
 		bbio->end_io(bbio);
 	}
 }

 static void btrfs_raid56_end_io(struct bio *bio)
 {
 	struct btrfs_io_context *bioc = bio->bi_private;
 	struct btrfs_bio *bbio = btrfs_bio(bio);

 	btrfs_bio_counter_dec(bioc->fs_info);
 	bbio->mirror_num = bioc->mirror_num;
 	bbio->end_io(bbio);

 	btrfs_put_bioc(bioc);
 }

 static void btrfs_orig_write_end_io(struct bio *bio)
 {
 	struct btrfs_io_stripe *stripe = bio->bi_private;
 	struct btrfs_io_context *bioc = stripe->bioc;
 	struct btrfs_bio *bbio = btrfs_bio(bio);

 	btrfs_bio_counter_dec(bioc->fs_info);

 	if (bio->bi_status) {
 		atomic_inc(&bioc->error);
 		btrfs_log_dev_io_error(bio, stripe->dev);
 	}

 	/*
 	 * Only send an error to the higher layers if it is beyond the tolerance
 	 * threshold.
 	 */
 	if (atomic_read(&bioc->error) > bioc->max_errors)
 		bio->bi_status = BLK_STS_IOERR;
 	else
 		bio->bi_status = BLK_STS_OK;

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

 static void btrfs_clone_write_end_io(struct bio *bio)
 {
 	struct btrfs_io_stripe *stripe = bio->bi_private;

 	if (bio->bi_status) {
 		atomic_inc(&stripe->bioc->error);
 		btrfs_log_dev_io_error(bio, stripe->dev);
 	}

 	/* Pass on control to the original bio this one was cloned from */
 	bio_endio(stripe->bioc->orig_bio);
 	bio_put(bio);
 }

 static void btrfs_submit_dev_bio(struct btrfs_device *dev, struct bio *bio)
 {
 	if (!dev || !dev->bdev ||
 	    test_bit(BTRFS_DEV_STATE_MISSING, &dev->dev_state) ||
 	    (btrfs_op(bio) == BTRFS_MAP_WRITE &&
 	     !test_bit(BTRFS_DEV_STATE_WRITEABLE, &dev->dev_state))) {
 		bio_io_error(bio);
 		return;
 	}

 	bio_set_dev(bio, dev->bdev);

 	/*
 	 * For zone append writing, bi_sector must point the beginning of the
 	 * zone
 	 */
 	if (bio_op(bio) == REQ_OP_ZONE_APPEND) {
 		u64 physical = bio->bi_iter.bi_sector << SECTOR_SHIFT;

 		if (btrfs_dev_is_sequential(dev, physical)) {
 			u64 zone_start = round_down(physical,
 						    dev->fs_info->zone_size);

 			bio->bi_iter.bi_sector = zone_start >> SECTOR_SHIFT;
 		} else {
 			bio->bi_opf &= ~REQ_OP_ZONE_APPEND;
 			bio->bi_opf |= REQ_OP_WRITE;
 		}
 	}
 	btrfs_debug_in_rcu(dev->fs_info,
 	"%s: rw %d 0x%x, sector=%llu, dev=%lu (%s id %llu), size=%u",
 		__func__, bio_op(bio), bio->bi_opf, bio->bi_iter.bi_sector,
 		(unsigned long)dev->bdev->bd_dev, btrfs_dev_name(dev),
 		dev->devid, bio->bi_iter.bi_size);

 	btrfsic_check_bio(bio);
 	submit_bio(bio);
 }

 static void btrfs_submit_mirrored_bio(struct btrfs_io_context *bioc, int dev_nr)
 {
 	struct bio *orig_bio = bioc->orig_bio, *bio;

 	ASSERT(bio_op(orig_bio) != REQ_OP_READ);

 	/* Reuse the bio embedded into the btrfs_bio for the last mirror */
 	if (dev_nr == bioc->num_stripes - 1) {
 		bio = orig_bio;
 		bio->bi_end_io = btrfs_orig_write_end_io;
 	} else {
 		bio = bio_alloc_clone(NULL, orig_bio, GFP_NOFS, &fs_bio_set);
 		bio_inc_remaining(orig_bio);
 		bio->bi_end_io = btrfs_clone_write_end_io;
 	}

 	bio->bi_private = &bioc->stripes[dev_nr];
 	bio->bi_iter.bi_sector = bioc->stripes[dev_nr].physical >> SECTOR_SHIFT;
 	bioc->stripes[dev_nr].bioc = bioc;
 	btrfs_submit_dev_bio(bioc->stripes[dev_nr].dev, bio);
 }

 void btrfs_submit_bio(struct btrfs_fs_info *fs_info, struct bio *bio, int mirror_num)
 {
 	u64 logical = bio->bi_iter.bi_sector << 9;
 	u64 length = bio->bi_iter.bi_size;
 	u64 map_length = length;
 	struct btrfs_io_context *bioc = NULL;
 	struct btrfs_io_stripe smap;
 	int ret;

 	btrfs_bio_counter_inc_blocked(fs_info);
 	ret = __btrfs_map_block(fs_info, btrfs_op(bio), logical, &map_length,
 				&bioc, &smap, &mirror_num, 1);
 	if (ret) {
 		btrfs_bio_counter_dec(fs_info);
 		btrfs_bio_end_io(btrfs_bio(bio), errno_to_blk_status(ret));
 		return;
 	}

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

 	if (!bioc) {
 		/* Single mirror read/write fast path */
 		btrfs_bio(bio)->mirror_num = mirror_num;
 		btrfs_bio(bio)->device = smap.dev;
 		bio->bi_iter.bi_sector = smap.physical >> SECTOR_SHIFT;
 		bio->bi_private = fs_info;
 		bio->bi_end_io = btrfs_simple_end_io;
 		btrfs_submit_dev_bio(smap.dev, bio);
 	} else if (bioc->map_type & BTRFS_BLOCK_GROUP_RAID56_MASK) {
 		/* Parity RAID write or read recovery */
 		bio->bi_private = bioc;
 		bio->bi_end_io = btrfs_raid56_end_io;
 		if (bio_op(bio) == REQ_OP_READ)
 			raid56_parity_recover(bio, bioc, mirror_num);
 		else
 			raid56_parity_write(bio, bioc);
 	} else {
 		/* Write to multiple mirrors */
 		int total_devs = bioc->num_stripes;
 		int dev_nr;

 		bioc->orig_bio = bio;
 		for (dev_nr = 0; dev_nr < total_devs; dev_nr++)
 			btrfs_submit_mirrored_bio(bioc, dev_nr);
 	}
 }

 /*
  * Submit a repair write.
  *
  * This bypasses btrfs_submit_bio deliberately, as that writes all copies in a
  * RAID setup.  Here we only want to write the one bad copy, so we do the
  * mapping ourselves and submit the bio directly.
  *
  * The I/O is issued sychronously to block the repair read completion from
  * freeing the bio.
  */
 int btrfs_repair_io_failure(struct btrfs_fs_info *fs_info, u64 ino, u64 start,
 			    u64 length, u64 logical, struct page *page,
 			    unsigned int pg_offset, int mirror_num)
 {
 	struct btrfs_device *dev;
 	struct bio_vec bvec;
 	struct bio bio;
 	u64 map_length = 0;
 	u64 sector;
 	struct btrfs_io_context *bioc = NULL;
 	int ret = 0;

 	ASSERT(!(fs_info->sb->s_flags & SB_RDONLY));
 	BUG_ON(!mirror_num);

 	if (btrfs_repair_one_zone(fs_info, logical))
 		return 0;

 	map_length = length;

 	/*
 	 * Avoid races with device replace and make sure our bioc has devices
 	 * associated to its stripes that don't go away while we are doing the
 	 * read repair operation.
 	 */
 	btrfs_bio_counter_inc_blocked(fs_info);
 	if (btrfs_is_parity_mirror(fs_info, logical, length)) {
 		/*
 		 * Note that we don't use BTRFS_MAP_WRITE because it's supposed
 		 * to update all raid stripes, but here we just want to correct
 		 * bad stripe, thus BTRFS_MAP_READ is abused to only get the bad
 		 * stripe's dev and sector.
 		 */
 		ret = btrfs_map_block(fs_info, BTRFS_MAP_READ, logical,
 				      &map_length, &bioc, 0);
 		if (ret)
 			goto out_counter_dec;
 		ASSERT(bioc->mirror_num == 1);
 	} else {
 		ret = btrfs_map_block(fs_info, BTRFS_MAP_WRITE, logical,
 				      &map_length, &bioc, mirror_num);
 		if (ret)
 			goto out_counter_dec;
 		BUG_ON(mirror_num != bioc->mirror_num);
 	}

 	sector = bioc->stripes[bioc->mirror_num - 1].physical >> 9;
 	dev = bioc->stripes[bioc->mirror_num - 1].dev;
 	btrfs_put_bioc(bioc);

 	if (!dev || !dev->bdev ||
 	    !test_bit(BTRFS_DEV_STATE_WRITEABLE, &dev->dev_state)) {
 		ret = -EIO;
 		goto out_counter_dec;
 	}

 	bio_init(&bio, dev->bdev, &bvec, 1, REQ_OP_WRITE | REQ_SYNC);
 	bio.bi_iter.bi_sector = sector;
 	__bio_add_page(&bio, page, length, pg_offset);

 	btrfsic_check_bio(&bio);
 	ret = submit_bio_wait(&bio);
 	if (ret) {
 		/* try to remap that extent elsewhere? */
 		btrfs_dev_stat_inc_and_print(dev, BTRFS_DEV_STAT_WRITE_ERRS);
 		goto out_bio_uninit;
 	}

 	btrfs_info_rl_in_rcu(fs_info,
 		"read error corrected: ino %llu off %llu (dev %s sector %llu)",
 			     ino, start, btrfs_dev_name(dev), sector);
 	ret = 0;

 out_bio_uninit:
 	bio_uninit(&bio);
 out_counter_dec:
 	btrfs_bio_counter_dec(fs_info);
 	return ret;
 }

 int __init btrfs_bioset_init(void)
 {
 	if (bioset_init(&btrfs_bioset, BIO_POOL_SIZE,
 			offsetof(struct btrfs_bio, bio),
 			BIOSET_NEED_BVECS))
 		return -ENOMEM;
 	return 0;
 }

 void __cold btrfs_bioset_exit(void)
 {
 	bioset_exit(&btrfs_bioset);
 }
	// SPDX-License-Identifier: GPL-2.0
	/*
	* Copyright (C) 2007 Oracle. All rights reserved.
	* Copyright (C) 2022 Christoph Hellwig.
	*/

	#include <linux/bio.h>
	#include "bio.h"
	#include "ctree.h"
	#include "volumes.h"
	#include "raid56.h"
	#include "async-thread.h"
	#include "check-integrity.h"
	#include "dev-replace.h"
	#include "rcu-string.h"
	#include "zoned.h"

	static struct bio_set btrfs_bioset;

	/*
	* Initialize a btrfs_bio structure. This skips the embedded bio itself as it
	* is already initialized by the block layer.
	*/
	static inline void btrfs_bio_init(struct btrfs_bio *bbio,
	btrfs_bio_end_io_t end_io, void *private)
	{
	memset(bbio, 0, offsetof(struct btrfs_bio, bio));
	bbio->end_io = end_io;
	bbio->private = private;
	}

	/*
	* Allocate a btrfs_bio structure. The btrfs_bio is the main I/O container for
	* btrfs, and is used for all I/O submitted through btrfs_submit_bio.
	*
	* Just like the underlying bio_alloc_bioset it will not fail as it is backed by
	* a mempool.
	*/
	struct bio *btrfs_bio_alloc(unsigned int nr_vecs, blk_opf_t opf,
	btrfs_bio_end_io_t end_io, void *private)
	{
	struct bio *bio;

	bio = bio_alloc_bioset(NULL, nr_vecs, opf, GFP_NOFS, &btrfs_bioset);
	btrfs_bio_init(btrfs_bio(bio), end_io, private);
	return bio;
	}

	struct bio btrfs_bio_clone_partial(struct bio orig, u64 offset, u64 size,
	btrfs_bio_end_io_t end_io, void *private)
	{
	struct bio *bio;
	struct btrfs_bio *bbio;

	ASSERT(offset <= UINT_MAX && size <= UINT_MAX);

	bio = bio_alloc_clone(orig->bi_bdev, orig, GFP_NOFS, &btrfs_bioset);
	bbio = btrfs_bio(bio);
	btrfs_bio_init(bbio, end_io, private);

	bio_trim(bio, offset >> 9, size >> 9);
	bbio->iter = bio->bi_iter;
	return bio;
	}

	static void btrfs_log_dev_io_error(struct bio bio, struct btrfs_device dev)
	{
	if (!dev \|\| !dev->bdev)
	return;
	if (bio->bi_status != BLK_STS_IOERR && bio->bi_status != BLK_STS_TARGET)
	return;

	if (btrfs_op(bio) == BTRFS_MAP_WRITE)
	btrfs_dev_stat_inc_and_print(dev, BTRFS_DEV_STAT_WRITE_ERRS);
	if (!(bio->bi_opf & REQ_RAHEAD))
	btrfs_dev_stat_inc_and_print(dev, BTRFS_DEV_STAT_READ_ERRS);
	if (bio->bi_opf & REQ_PREFLUSH)
	btrfs_dev_stat_inc_and_print(dev, BTRFS_DEV_STAT_FLUSH_ERRS);
	}

	static struct workqueue_struct btrfs_end_io_wq(struct btrfs_fs_info fs_info,
	struct bio *bio)
	{
	if (bio->bi_opf & REQ_META)
	return fs_info->endio_meta_workers;
	return fs_info->endio_workers;
	}

	static void btrfs_end_bio_work(struct work_struct *work)
	{
	struct btrfs_bio *bbio = container_of(work, struct btrfs_bio, end_io_work);

	bbio->end_io(bbio);
	}

	static void btrfs_simple_end_io(struct bio *bio)
	{
	struct btrfs_fs_info *fs_info = bio->bi_private;
	struct btrfs_bio *bbio = btrfs_bio(bio);

	btrfs_bio_counter_dec(fs_info);

	if (bio->bi_status)
	btrfs_log_dev_io_error(bio, bbio->device);

	if (bio_op(bio) == REQ_OP_READ) {
	INIT_WORK(&bbio->end_io_work, btrfs_end_bio_work);
	queue_work(btrfs_end_io_wq(fs_info, bio), &bbio->end_io_work);
	} else {
	bbio->end_io(bbio);
	}
	}

	static void btrfs_raid56_end_io(struct bio *bio)
	{
	struct btrfs_io_context *bioc = bio->bi_private;
	struct btrfs_bio *bbio = btrfs_bio(bio);

	btrfs_bio_counter_dec(bioc->fs_info);
	bbio->mirror_num = bioc->mirror_num;
	bbio->end_io(bbio);

	btrfs_put_bioc(bioc);
	}

	static void btrfs_orig_write_end_io(struct bio *bio)
	{
	struct btrfs_io_stripe *stripe = bio->bi_private;
	struct btrfs_io_context *bioc = stripe->bioc;
	struct btrfs_bio *bbio = btrfs_bio(bio);

	btrfs_bio_counter_dec(bioc->fs_info);

	if (bio->bi_status) {
	atomic_inc(&bioc->error);
	btrfs_log_dev_io_error(bio, stripe->dev);
	}

	/*
	* Only send an error to the higher layers if it is beyond the tolerance
	* threshold.
	*/
	if (atomic_read(&bioc->error) > bioc->max_errors)
	bio->bi_status = BLK_STS_IOERR;
	else
	bio->bi_status = BLK_STS_OK;

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

	static void btrfs_clone_write_end_io(struct bio *bio)
	{
	struct btrfs_io_stripe *stripe = bio->bi_private;

	if (bio->bi_status) {
	atomic_inc(&stripe->bioc->error);
	btrfs_log_dev_io_error(bio, stripe->dev);
	}

	/* Pass on control to the original bio this one was cloned from */
	bio_endio(stripe->bioc->orig_bio);
	bio_put(bio);
	}

	static void btrfs_submit_dev_bio(struct btrfs_device dev, struct bio bio)
	{
	if (!dev \|\| !dev->bdev \|\|
	test_bit(BTRFS_DEV_STATE_MISSING, &dev->dev_state) \|\|
	(btrfs_op(bio) == BTRFS_MAP_WRITE &&
	!test_bit(BTRFS_DEV_STATE_WRITEABLE, &dev->dev_state))) {
	bio_io_error(bio);
	return;
	}

	bio_set_dev(bio, dev->bdev);

	/*
	* For zone append writing, bi_sector must point the beginning of the
	* zone
	*/
	if (bio_op(bio) == REQ_OP_ZONE_APPEND) {
	u64 physical = bio->bi_iter.bi_sector << SECTOR_SHIFT;

	if (btrfs_dev_is_sequential(dev, physical)) {
	u64 zone_start = round_down(physical,
	dev->fs_info->zone_size);

	bio->bi_iter.bi_sector = zone_start >> SECTOR_SHIFT;
	} else {
	bio->bi_opf &= ~REQ_OP_ZONE_APPEND;
	bio->bi_opf \|= REQ_OP_WRITE;
	}
	}
	btrfs_debug_in_rcu(dev->fs_info,
	"%s: rw %d 0x%x, sector=%llu, dev=%lu (%s id %llu), size=%u",
	__func__, bio_op(bio), bio->bi_opf, bio->bi_iter.bi_sector,
	(unsigned long)dev->bdev->bd_dev, btrfs_dev_name(dev),
	dev->devid, bio->bi_iter.bi_size);

	btrfsic_check_bio(bio);
	submit_bio(bio);
	}

	static void btrfs_submit_mirrored_bio(struct btrfs_io_context *bioc, int dev_nr)
	{
	struct bio orig_bio = bioc->orig_bio, bio;

	ASSERT(bio_op(orig_bio) != REQ_OP_READ);

	/* Reuse the bio embedded into the btrfs_bio for the last mirror */
	if (dev_nr == bioc->num_stripes - 1) {
	bio = orig_bio;
	bio->bi_end_io = btrfs_orig_write_end_io;
	} else {
	bio = bio_alloc_clone(NULL, orig_bio, GFP_NOFS, &fs_bio_set);
	bio_inc_remaining(orig_bio);
	bio->bi_end_io = btrfs_clone_write_end_io;
	}

	bio->bi_private = &bioc->stripes[dev_nr];
	bio->bi_iter.bi_sector = bioc->stripes[dev_nr].physical >> SECTOR_SHIFT;
	bioc->stripes[dev_nr].bioc = bioc;
	btrfs_submit_dev_bio(bioc->stripes[dev_nr].dev, bio);
	}

	void btrfs_submit_bio(struct btrfs_fs_info fs_info, struct bio bio, int mirror_num)
	{
	u64 logical = bio->bi_iter.bi_sector << 9;
	u64 length = bio->bi_iter.bi_size;
	u64 map_length = length;
	struct btrfs_io_context *bioc = NULL;
	struct btrfs_io_stripe smap;
	int ret;

	btrfs_bio_counter_inc_blocked(fs_info);
	ret = __btrfs_map_block(fs_info, btrfs_op(bio), logical, &map_length,
	&bioc, &smap, &mirror_num, 1);
	if (ret) {
	btrfs_bio_counter_dec(fs_info);
	btrfs_bio_end_io(btrfs_bio(bio), errno_to_blk_status(ret));
	return;
	}

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

	if (!bioc) {
	/* Single mirror read/write fast path */
	btrfs_bio(bio)->mirror_num = mirror_num;
	btrfs_bio(bio)->device = smap.dev;
	bio->bi_iter.bi_sector = smap.physical >> SECTOR_SHIFT;
	bio->bi_private = fs_info;
	bio->bi_end_io = btrfs_simple_end_io;
	btrfs_submit_dev_bio(smap.dev, bio);
	} else if (bioc->map_type & BTRFS_BLOCK_GROUP_RAID56_MASK) {
	/* Parity RAID write or read recovery */
	bio->bi_private = bioc;
	bio->bi_end_io = btrfs_raid56_end_io;
	if (bio_op(bio) == REQ_OP_READ)
	raid56_parity_recover(bio, bioc, mirror_num);
	else
	raid56_parity_write(bio, bioc);
	} else {
	/* Write to multiple mirrors */
	int total_devs = bioc->num_stripes;
	int dev_nr;

	bioc->orig_bio = bio;
	for (dev_nr = 0; dev_nr < total_devs; dev_nr++)
	btrfs_submit_mirrored_bio(bioc, dev_nr);
	}
	}

	/*
	* Submit a repair write.
	*
	* This bypasses btrfs_submit_bio deliberately, as that writes all copies in a
	* RAID setup. Here we only want to write the one bad copy, so we do the
	* mapping ourselves and submit the bio directly.
	*
	* The I/O is issued sychronously to block the repair read completion from
	* freeing the bio.
	*/
	int btrfs_repair_io_failure(struct btrfs_fs_info *fs_info, u64 ino, u64 start,
	u64 length, u64 logical, struct page *page,
	unsigned int pg_offset, int mirror_num)
	{
	struct btrfs_device *dev;
	struct bio_vec bvec;
	struct bio bio;
	u64 map_length = 0;
	u64 sector;
	struct btrfs_io_context *bioc = NULL;
	int ret = 0;

	ASSERT(!(fs_info->sb->s_flags & SB_RDONLY));
	BUG_ON(!mirror_num);

	if (btrfs_repair_one_zone(fs_info, logical))
	return 0;

	map_length = length;

	/*
	* Avoid races with device replace and make sure our bioc has devices
	* associated to its stripes that don't go away while we are doing the
	* read repair operation.
	*/
	btrfs_bio_counter_inc_blocked(fs_info);
	if (btrfs_is_parity_mirror(fs_info, logical, length)) {
	/*
	* Note that we don't use BTRFS_MAP_WRITE because it's supposed
	* to update all raid stripes, but here we just want to correct
	* bad stripe, thus BTRFS_MAP_READ is abused to only get the bad
	* stripe's dev and sector.
	*/
	ret = btrfs_map_block(fs_info, BTRFS_MAP_READ, logical,
	&map_length, &bioc, 0);
	if (ret)
	goto out_counter_dec;
	ASSERT(bioc->mirror_num == 1);
	} else {
	ret = btrfs_map_block(fs_info, BTRFS_MAP_WRITE, logical,
	&map_length, &bioc, mirror_num);
	if (ret)
	goto out_counter_dec;
	BUG_ON(mirror_num != bioc->mirror_num);
	}

	sector = bioc->stripes[bioc->mirror_num - 1].physical >> 9;
	dev = bioc->stripes[bioc->mirror_num - 1].dev;
	btrfs_put_bioc(bioc);

	if (!dev \|\| !dev->bdev \|\|
	!test_bit(BTRFS_DEV_STATE_WRITEABLE, &dev->dev_state)) {
	ret = -EIO;
	goto out_counter_dec;
	}

	bio_init(&bio, dev->bdev, &bvec, 1, REQ_OP_WRITE \| REQ_SYNC);
	bio.bi_iter.bi_sector = sector;
	__bio_add_page(&bio, page, length, pg_offset);

	btrfsic_check_bio(&bio);
	ret = submit_bio_wait(&bio);
	if (ret) {
	/* try to remap that extent elsewhere? */
	btrfs_dev_stat_inc_and_print(dev, BTRFS_DEV_STAT_WRITE_ERRS);
	goto out_bio_uninit;
	}

	btrfs_info_rl_in_rcu(fs_info,
	"read error corrected: ino %llu off %llu (dev %s sector %llu)",
	ino, start, btrfs_dev_name(dev), sector);
	ret = 0;

	out_bio_uninit:
	bio_uninit(&bio);
	out_counter_dec:
	btrfs_bio_counter_dec(fs_info);
	return ret;
	}

	int __init btrfs_bioset_init(void)
	{
	if (bioset_init(&btrfs_bioset, BIO_POOL_SIZE,
	offsetof(struct btrfs_bio, bio),
	BIOSET_NEED_BVECS))
	return -ENOMEM;
	return 0;
	}

	void __cold btrfs_bioset_exit(void)
	{
	bioset_exit(&btrfs_bioset);
	}