Commit f44b48c7 authored by Kent Overstreet's avatar Kent Overstreet Committed by Jens Axboe
Browse files

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: default avatarKent Overstreet <koverstreet@google.com>
CC: Jens Axboe <axboe@kernel.dk>
Acked-by: default avatarTejun Heo <tj@kernel.org>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 94818742

fs/bio.c

+24 −0
Original line number Diff line number Diff line
@@ -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

include/linux/bio.h

+1 −0
Original line number Diff line number Diff line
@@ -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 *,

include/linux/blk_types.h

+19 −6
Original line number Diff line number Diff line
@@ -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)))



/*

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