Re: [Ocfs2-devel] [RFC PATCH 02/34] block: introduce and use bio_new

[Chaitanya Kulkarni <Chaitanya.Kulkarni@wdc.com>]

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On 1/27/21 11:21 PM, Damien Le Moal wrote:

On 2021/01/28 16:12, Chaitanya Kulkarni wrote:


Introduce bio_new() helper and use it in blk-lib.c to allocate and
initialize various non-optional or semi-optional members of the bio
along with bio allocation done with bio_alloc(). Here we also calmp the
max_bvecs for bio with BIO_MAX_PAGES before we pass to bio_alloc().

Signed-off-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com><mailto:chaitanya.kulkarni@wdc.com>
---
 block/blk-lib.c     |  6 +-----
 include/linux/bio.h | 25 +++++++++++++++++++++++++
 2 files changed, 26 insertions(+), 5 deletions(-)

diff --git a/block/blk-lib.c b/block/blk-lib.c
index fb486a0bdb58..ec29415f00dd 100644
--- a/block/blk-lib.c
+++ b/block/blk-lib.c
@@ -14,17 +14,13 @@ struct bio *blk_next_bio(struct bio *bio, struct block_device *bdev,
                        sector_t sect, unsigned op, unsigned opf,
                        unsigned int nr_pages, gfp_t gfp)
 {
-       struct bio *new = bio_alloc(gfp, nr_pages);
+       struct bio *new = bio_new(bdev, sect, op, opf, gfp, nr_pages);

        if (bio) {
                bio_chain(bio, new);
                submit_bio(bio);
        }

-       new->bi_iter.bi_sector = sect;
-       bio_set_dev(new, bdev);
-       bio_set_op_attrs(new, op, opf);
-
        return new;
 }

diff --git a/include/linux/bio.h b/include/linux/bio.h
index c74857cf1252..2a09ba100546 100644
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -826,5 +826,30 @@ static inline void bio_set_polled(struct bio *bio, struct kiocb *kiocb)
        if (!is_sync_kiocb(kiocb))
                bio->bi_opf |= REQ_NOWAIT;
 }
+/**
+ * bio_new -   allcate and initialize new bio
+ * @bdev:      blockdev to issue discard for
+ * @sector:    start sector
+ * @op:                REQ_OP_XXX from enum req_opf
+ * @op_flags:  REQ_XXX from enum req_flag_bits
+ * @max_bvecs: maximum bvec to be allocated for this bio
+ * @gfp_mask:  memory allocation flags (for bio_alloc)
+ *
+ * Description:
+ *    Allocates, initializes common members, and returns a new bio.
+ */
+static inline struct bio *bio_new(struct block_device *bdev, sector_t sector,
+                                 unsigned int op, unsigned int op_flags,
+                                 unsigned int max_bvecs, gfp_t gfp_mask)
+{
+       unsigned nr_bvec = clamp_t(unsigned int, max_bvecs, 0, BIO_MAX_PAGES);
+       struct bio *bio = bio_alloc(gfp_mask, nr_bvec);


I think that depending on the gfp_mask passed, bio can be NULL. So this should
be checked.


true, I'll add that check.




+
+       bio_set_dev(bio, bdev);
+       bio->bi_iter.bi_sector = sector;
+       bio_set_op_attrs(bio, op, op_flags);


This function is obsolete. Open code this.


true, will do.




+
+       return bio;
+}

 #endif /* __LINUX_BIO_H */



Thanks for the comments Damien.

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