Re: [PATCH v4 03/12] block: Add bio_reset()
From: Boaz Harrosh <hidden>
Date: 2012-07-25 11:19:56
Also in:
dm-devel, lkml
On 07/24/2012 11:11 PM, Kent Overstreet wrote:
quoted hunk ↗ jump to hunk
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. Signed-off-by: Kent Overstreet <redacted> --- fs/bio.c | 10 ++++++++++ include/linux/bio.h | 1 + include/linux/blk_types.h | 6 ++++++ 3 files changed, 17 insertions(+), 0 deletions(-)diff --git a/fs/bio.c b/fs/bio.c index 1c6c8b7..252e253 100644 --- a/fs/bio.c +++ b/fs/bio.c@@ -261,6 +261,16 @@ void bio_init(struct bio *bio) } EXPORT_SYMBOL(bio_init); +void bio_reset(struct bio *bio) +{ + /* Clear all flags below BIO_OWNS_VEC */ + unsigned long flags = bio->bi_flags & (~0UL << BIO_OWNS_VEC); +
Hey I have not seen these FLAGS thing before. Are these new? Anyway. Please NO!!! for one you need to put a big fat comment over at flags definitions. And two what happens when one adds a new flag. Is it reset or not reset? I'd rather you define a flags mask for those that need to be preserved, at header, plus a comment that any needed-to-be-preserved cross init flags, must be added to the mask. Never, ever, hide such crap so deep in the code. Boaz
quoted hunk ↗ jump to hunk
+ 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 allocatordiff --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 293547e..40411e2 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 */