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block: Add bio_reset()

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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>
This commit is contained in:
Kent Overstreet 2012-09-06 15:34:58 -07:00 committed by Jens Axboe
parent 9481874231
commit f44b48c769
3 changed files with 44 additions and 6 deletions
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24
fs/bio.c
View File

@ -262,6 +262,30 @@ void bio_init(struct bio *bio)
}
EXPORT_SYMBOL(bio_init);
/**
* bio_reset - reinitialize a bio
* @bio: bio to reset
*
* Description:
* After calling bio_reset(), @bio will be in the same state as a freshly
* allocated bio returned bio bio_alloc_bioset() - the only fields that are
* preserved are the ones that are initialized by bio_alloc_bioset(). See
* comment in struct bio.
*/
void bio_reset(struct bio *bio)
{
unsigned long flags = bio->bi_flags & (~0UL << BIO_RESET_BITS);
if (bio_integrity(bio))
bio_integrity_free(bio);
bio_disassociate_task(bio);
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

1
include/linux/bio.h
View File

@ -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 *,

25
include/linux/blk_types.h
View File

@ -59,12 +59,6 @@ struct bio {
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 {
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 {
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)))
/*