block: Add bio_reset()
Reusing bios is something that's been highly frowned upon in the past,
but driver code keeps doing it anyways. If it's going to happen anyways,
we should provide a generic method.
This'll help with getting rid of bi_destructor - drivers/block/pktcdvd.c
was open coding it, by doing a bio_init() and resetting bi_destructor.
This required reordering struct bio, but the block layer is not yet
nearly fast enough for any cacheline effects to matter here.
v5: Add a define BIO_RESET_BITS, to be very explicit about what parts of
bio->bi_flags are saved.
v6: Further commenting verbosity, per Tejun
v9: Add a function comment
Signed-off-by: Kent Overstreet <koverstreet@google.com>
CC: Jens Axboe <axboe@kernel.dk>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/include/linux/bio.h b/include/linux/bio.h
index a11f74b..76f6c25 100644
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -226,6 +226,7 @@
extern struct bio *bio_clone(struct bio *, gfp_t);
extern void bio_init(struct bio *);
+extern void bio_reset(struct bio *);
extern int bio_add_page(struct bio *, struct page *, unsigned int,unsigned int);
extern int bio_add_pc_page(struct request_queue *, struct bio *, struct page *,
diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
index af9dd9d..1b607c2 100644
--- a/include/linux/blk_types.h
+++ b/include/linux/blk_types.h
@@ -59,12 +59,6 @@
unsigned int bi_seg_front_size;
unsigned int bi_seg_back_size;
- unsigned int bi_max_vecs; /* max bvl_vecs we can hold */
-
- atomic_t bi_cnt; /* pin count */
-
- struct bio_vec *bi_io_vec; /* the actual vec list */
-
bio_end_io_t *bi_end_io;
void *bi_private;
@@ -80,6 +74,16 @@
struct bio_integrity_payload *bi_integrity; /* data integrity */
#endif
+ /*
+ * Everything starting with bi_max_vecs will be preserved by bio_reset()
+ */
+
+ unsigned int bi_max_vecs; /* max bvl_vecs we can hold */
+
+ atomic_t bi_cnt; /* pin count */
+
+ struct bio_vec *bi_io_vec; /* the actual vec list */
+
/* If bi_pool is non NULL, bi_destructor is not called */
struct bio_set *bi_pool;
@@ -93,6 +97,8 @@
struct bio_vec bi_inline_vecs[0];
};
+#define BIO_RESET_BYTES offsetof(struct bio, bi_max_vecs)
+
/*
* bio flags
*/
@@ -108,6 +114,13 @@
#define BIO_FS_INTEGRITY 9 /* fs owns integrity data, not block layer */
#define BIO_QUIET 10 /* Make BIO Quiet */
#define BIO_MAPPED_INTEGRITY 11/* integrity metadata has been remapped */
+
+/*
+ * Flags starting here get preserved by bio_reset() - this includes
+ * BIO_POOL_IDX()
+ */
+#define BIO_RESET_BITS 12
+
#define bio_flagged(bio, flag) ((bio)->bi_flags & (1 << (flag)))
/*