From f44b48c7691be7643877d1f881b5eeace654d05d Mon Sep 17 00:00:00 2001 From: Kent Overstreet Date: Thu, 6 Sep 2012 15:34:58 -0700 Subject: [PATCH 4/8] 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 CC: Jens Axboe Acked-by: Tejun Heo Signed-off-by: Jens Axboe --- fs/bio.c | 24 ++++++++++++++++++++++++ include/linux/bio.h | 1 + include/linux/blk_types.h | 25 +++++++++++++++++++------ 3 files changed, 44 insertions(+), 6 deletions(-) diff --git a/fs/bio.c b/fs/bio.c index b14f71a..919ee9a 100644 --- a/fs/bio.c +++ b/fs/bio.c @@ -263,6 +263,30 @@ 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 * @nr_iovecs: number of iovecs to pre-allocate 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 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..1b607c2 100644 --- a/include/linux/blk_types.h +++ b/include/linux/blk_types.h @@ -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))) /* -- 1.7.4.4