On Wed, Jul 25, 2012 at 02:19:27PM +0300, Boaz Harrosh wrote:
> On 07/24/2012 11:11 PM, Kent Overstreet wrote:
>
> > 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 <koverstreet@xxxxxxxxxx>
> > ---
> > 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)))
/*
--
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