[PATCH 3/9] btrfs: factor out a btrfs_map_repair_bio helper

[Christoph Hellwig <hch@lst.de>]

Factor out the guts of repair_io_failure so that we have a new helper
to submit synchronous I/O for repair.  Unlike repair_io_failure itself
this helper also handles reads.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 fs/btrfs/extent_io.c | 82 ++++++--------------------------------------
 fs/btrfs/volumes.c   | 69 +++++++++++++++++++++++++++++++++++++
 fs/btrfs/volumes.h   |  2 ++
 3 files changed, 81 insertions(+), 72 deletions(-)

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index 54a0ec62c7b0d..27775031ed2d4 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -2308,27 +2308,13 @@ int free_io_failure(struct extent_io_tree *failure_tree,
 	return err;
 }
 
-/*
- * this bypasses the standard btrfs submit functions deliberately, as
- * the standard behavior is to write all copies in a raid setup. here we only
- * want to write the one bad copy. so we do the mapping for ourselves and issue
- * submit_bio directly.
- * to avoid any synchronization issues, wait for the data after writing, which
- * actually prevents the read that triggered the error from finishing.
- * currently, there can be no more than two copies of every data bit. thus,
- * exactly one rewrite is required.
- */
 static int 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;
+	int ret;
 
 	ASSERT(!(fs_info->sb->s_flags & SB_RDONLY));
 	BUG_ON(!mirror_num);
@@ -2336,67 +2322,19 @@ static int repair_io_failure(struct btrfs_fs_info *fs_info, u64 ino, u64 start,
 	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_init(&bio, NULL, &bvec, 1, REQ_OP_WRITE | REQ_SYNC);
+	bio.bi_iter.bi_sector = logical >> 9;
 	__bio_add_page(&bio, page, length, pg_offset);
+	ret = btrfs_map_repair_bio(fs_info, &bio, mirror_num);
+	bio_uninit(&bio);
 
-	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;
-	}
+	if (ret)
+		return ret;
 
 	btrfs_info_rl_in_rcu(fs_info,
-		"read error corrected: ino %llu off %llu (dev %s sector %llu)",
-				  ino, start,
-				  rcu_str_deref(dev->name), sector);
-	ret = 0;
-
-out_bio_uninit:
-	bio_uninit(&bio);
-out_counter_dec:
-	btrfs_bio_counter_dec(fs_info);
-	return ret;
+		"read error corrected: ino %llu off %llu (logical %llu)",
+			  ino, start, logical);
+	return 0;
 }
 
 int btrfs_repair_eb_io_failure(const struct extent_buffer *eb, int mirror_num)
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 1954a3e1c93a9..515f5fccf3d17 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -6805,6 +6805,75 @@ blk_status_t btrfs_map_bio(struct btrfs_fs_info *fs_info, struct bio *bio,
 	return errno_to_blk_status(ret);
 }
 
+/*
+ * This bypasses the standard btrfs submit functions deliberately, as the
+ * standard behavior is to write all copies in a raid setup. Here we only want
+ * to write the one bad copy.  Sso do the mapping ourselves and submit directly
+ * and synchronously.
+ */
+int btrfs_map_repair_bio(struct btrfs_fs_info *fs_info, struct bio *bio,
+		int mirror_num)
+{
+	u64 logical = bio->bi_iter.bi_sector << 9;
+	u64 map_length = bio->bi_iter.bi_size;
+	struct btrfs_io_context *bioc = NULL;
+	struct btrfs_device *dev;
+	u64 sector;
+	int ret;
+
+	ASSERT(mirror_num);
+	ASSERT(bio_op(bio) == REQ_OP_WRITE);
+
+	/*
+	 * 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, map_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_set_dev(bio, dev->bdev);
+	bio->bi_iter.bi_sector = sector;
+
+	btrfsic_check_bio(bio);
+	submit_bio_wait(bio);
+
+	ret = blk_status_to_errno(bio->bi_status);
+	if (ret)
+		btrfs_dev_stat_inc_and_print(dev, BTRFS_DEV_STAT_WRITE_ERRS);
+out_counter_dec:
+	btrfs_bio_counter_dec(fs_info);
+	return ret;
+}
+
 static bool dev_args_match_fs_devices(const struct btrfs_dev_lookup_args *args,
 				      const struct btrfs_fs_devices *fs_devices)
 {
diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
index 517288d46ecf5..00c87833ce841 100644
--- a/fs/btrfs/volumes.h
+++ b/fs/btrfs/volumes.h
@@ -565,6 +565,8 @@ struct btrfs_block_group *btrfs_create_chunk(struct btrfs_trans_handle *trans,
 void btrfs_mapping_tree_free(struct extent_map_tree *tree);
 blk_status_t btrfs_map_bio(struct btrfs_fs_info *fs_info, struct bio *bio,
 			   int mirror_num);
+int btrfs_map_repair_bio(struct btrfs_fs_info *fs_info, struct bio *bio,
+		int mirror_num);
 int btrfs_open_devices(struct btrfs_fs_devices *fs_devices,
 		       fmode_t flags, void *holder);
 struct btrfs_device *btrfs_scan_one_device(const char *path,
-- 
2.30.2