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.
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
Signed-off-by: Kent Overstreet <koverstreet@xxxxxxxxxx>
CC: Jens Axboe <axboe@xxxxxxxxx>
---
fs/bio.c | 9 +++++++++
include/linux/bio.h | 1 +
include/linux/blk_types.h | 13 +++++++++++++
3 files changed, 23 insertions(+)
diff --git a/fs/bio.c b/fs/bio.c
index 86e0534..81bdf4f 100644
--- a/fs/bio.c
+++ b/fs/bio.c
@@ -261,6 +261,15 @@ void bio_init(struct bio *bio)
}
EXPORT_SYMBOL(bio_init);
+void bio_reset(struct bio *bio)
+{
+ unsigned long flags = bio->bi_flags & (~0UL << BIO_RESET_BITS);
+
+ memset(bio, 0, BIO_RESET_BYTES);
+ bio->bi_flags = flags|(1 << BIO_UPTODATE);
+}
+EXPORT_SYMBOL(bio_reset);
+
/**
* bio_alloc_bioset - allocate a bio for I/O
* @gfp_mask: the GFP_ mask given to the slab allocator
diff --git a/include/linux/bio.h b/include/linux/bio.h
index 2643589..ba60319 100644
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -226,6 +226,7 @@ extern void __bio_clone(struct bio *, struct bio *);
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..4fe4984 100644
--- a/include/linux/blk_types.h
+++ b/include/linux/blk_types.h
@@ -59,6 +59,10 @@ struct bio {
unsigned int bi_seg_front_size;
unsigned int bi_seg_back_size;
+ /*
+ * 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 */
@@ -93,6 +97,8 @@ struct bio {
struct bio_vec bi_inline_vecs[0];
};
+#define BIO_RESET_BYTES offsetof(struct bio, bi_max_vecs)
+
/*
* bio flags
*/
@@ -108,6 +114,13 @@ struct bio {
#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)))
/*
--
1.7.12
--
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