This adds a new helper btrfs_bio_clone_partial, it'll allocate a cloned
bio that only owns a part of the original bio's data.
Signed-off-by: Liu Bo <bo.li.liu@xxxxxxxxxx>
---
fs/btrfs/extent_io.c | 18 ++++++++++++++++++
fs/btrfs/extent_io.h | 2 ++
2 files changed, 20 insertions(+)
diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index 0d4aea4..47c0ee2 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -2726,6 +2726,24 @@ struct bio *btrfs_io_bio_alloc(gfp_t gfp_mask, unsigned int nr_iovecs)
return bio;
}
+struct bio *btrfs_bio_clone_partial(struct bio *orig, gfp_t gfp_mask,
+ int offset, int size)
+{
+ struct bio *bio;
+ struct btrfs_io_bio *btrfs_bio;
+
+ /* this will never fail when it's backed by a bioset */
+ bio = bio_clone_fast(orig, gfp_mask, btrfs_bioset);
+ ASSERT(bio);
+
+ btrfs_bio = btrfs_io_bio(bio);
+ btrfs_bio->csum = NULL;
+ btrfs_bio->csum_allocated = NULL;
+ btrfs_bio->end_io = NULL;
+
+ bio_trim(bio, offset >> 9, size >> 9);
+ return bio;
+}
static int __must_check submit_one_bio(struct bio *bio, int mirror_num,
unsigned long bio_flags)
diff --git a/fs/btrfs/extent_io.h b/fs/btrfs/extent_io.h
index 3e4fad4..b2235b5 100644
--- a/fs/btrfs/extent_io.h
+++ b/fs/btrfs/extent_io.h
@@ -460,6 +460,8 @@ btrfs_bio_alloc(struct block_device *bdev, u64 first_sector, int nr_vecs,
gfp_t gfp_flags);
struct bio *btrfs_io_bio_alloc(gfp_t gfp_mask, unsigned int nr_iovecs);
struct bio *btrfs_bio_clone(struct bio *bio, gfp_t gfp_mask);
+struct bio *btrfs_bio_clone_partial(struct bio *orig, gfp_t gfp_mask,
+ int offset, int size);
struct btrfs_fs_info;
struct btrfs_inode;
--
2.9.4
--
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