Re: [PATCH v4 03/12] block: Add bio_reset()
From: Kent Overstreet <hidden>
Date: 2012-07-25 22:56:27
Also in:
dm-devel, lkml
Subsystem:
block layer, filesystems (vfs and infrastructure), the rest · Maintainers:
Jens Axboe, Alexander Viro, Christian Brauner, Linus Torvalds
On Wed, Jul 25, 2012 at 02:19:27PM +0300, Boaz Harrosh wrote:
On 07/24/2012 11:11 PM, Kent Overstreet wrote:quoted
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.
Yeah, that's a much better idea. Do you think this is clear enough?
diff --git a/fs/bio.c b/fs/bio.c
index 1c6c8b7..c7f3442 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 293547e..769799f 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 +114,9 @@ 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 */ + +#define BIO_RESET_BITS 12 /* Flags starting here get preserved by bio_reset() */ + #define bio_flagged(bio, flag) ((bio)->bi_flags & (1 << (flag))) /*