From: Ming Lei <ming.lei@xxxxxxxxxxxxx>
This patch has been added to the 3.18 stable tree. If you have any
objections, please let us know.
===============
[ Upstream commit 7bcd79ac50d9d83350a835bdb91c04ac9e098412 ]
The bio passed to bio_will_gap() may be fast cloned from upper
layer(dm, md, bcache, fs, ...), or from bio splitting in block
core.
Unfortunately bio_will_gap() just figures out the last bvec via
'bi_io_vec[prev->bi_vcnt - 1]' directly, and this way is obviously
wrong.
This patch introduces two helpers for getting the first and last
bvec of one bio for fixing the issue.
Cc: stable@xxxxxxxxxxxxxxx
Reported-by: Sagi Grimberg <sagig@xxxxxxxxxxxxxxxxxx>
Reviewed-by: Sagi Grimberg <sagig@xxxxxxxxxxxx>
Reviewed-by: Christoph Hellwig <hch@xxxxxx>
Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxxxxx>
Signed-off-by: Jens Axboe <axboe@xxxxxx>
Signed-off-by: Sasha Levin <sasha.levin@xxxxxxxxxx>
---
include/linux/bio.h | 37 +++++++++++++++++++++++++++++++++++++
1 file changed, 37 insertions(+)
diff --git a/include/linux/bio.h b/include/linux/bio.h
index 7347f48..08ce93e 100644
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -292,6 +292,43 @@ static inline unsigned bio_segments(struct bio *bio)
*/
#define bio_get(bio) atomic_inc(&(bio)->bi_cnt)
+static inline void bio_get_first_bvec(struct bio *bio, struct bio_vec *bv)
+{
+ *bv = bio_iovec(bio);
+}
+
+static inline void bio_get_last_bvec(struct bio *bio, struct bio_vec *bv)
+{
+ struct bvec_iter iter = bio->bi_iter;
+ int idx;
+
+ if (!bio_flagged(bio, BIO_CLONED)) {
+ *bv = bio->bi_io_vec[bio->bi_vcnt - 1];
+ return;
+ }
+
+ if (unlikely(!bio_multiple_segments(bio))) {
+ *bv = bio_iovec(bio);
+ return;
+ }
+
+ bio_advance_iter(bio, &iter, iter.bi_size);
+
+ if (!iter.bi_bvec_done)
+ idx = iter.bi_idx - 1;
+ else /* in the middle of bvec */
+ idx = iter.bi_idx;
+
+ *bv = bio->bi_io_vec[idx];
+
+ /*
+ * iter.bi_bvec_done records actual length of the last bvec
+ * if this bio ends in the middle of one io vector
+ */
+ if (iter.bi_bvec_done)
+ bv->bv_len = iter.bi_bvec_done;
+}
+
enum bip_flags {
BIP_BLOCK_INTEGRITY = 1 << 0, /* block layer owns integrity data */
BIP_MAPPED_INTEGRITY = 1 << 1, /* ref tag has been remapped */
--
2.5.0
--
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