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Subject[PATCH v4 03/12] block: Add bio_reset()
Date
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@google.com>
---
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);
+
+ 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..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
*/
--
1.7.7.3


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