bio: fix bio_kmalloc()

Impact: fix bio_kmalloc() and its destruction path

bio_kmalloc() was broken in two ways.

* bvec_alloc_bs() first allocates bvec using kmalloc() and then
  ignores it and allocates again like non-kmalloc bvecs.

* bio_kmalloc_destructor() didn't check for and free bio integrity
  data.

This patch fixes the above problems.  kmalloc patch is separated out
from bio_alloc_bioset() and allocates the requested number of bvecs as
inline bvecs.

* bio_alloc_bioset() no longer takes NULL @bs.  None other than
  bio_kmalloc() used it and outside users can't know how it was
  allocated anyway.

* Define and use BIO_POOL_NONE so that pool index check in
  bvec_free_bs() triggers if inline or kmalloc allocated bvec gets
  there.

* Relocate destructors on top of each allocation function so that how
  they're used is more clear.

Jens Axboe suggested allocating bvecs inline.

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

diff --git a/fs/bio.c b/fs/bio.c
index cd42bb8..d35588f 100644 (file)
--- a/fs/bio.c
+++ b/fs/bio.c
@@ -175,14 +175,6 @@ struct bio_vec *bvec_alloc_bs(gfp_t gfp_mask, int nr, unsigned long *idx,
        struct bio_vec *bvl;
 
        /*
-        * If 'bs' is given, lookup the pool and do the mempool alloc.
-        * If not, this is a bio_kmalloc() allocation and just do a
-        * kzalloc() for the exact number of vecs right away.
-        */
-       if (!bs)
-               bvl = kmalloc(nr * sizeof(struct bio_vec), gfp_mask);
-
-       /*
         * see comment near bvec_array define!
         */
        switch (nr) {
@@ -260,21 +252,6 @@ void bio_free(struct bio *bio, struct bio_set *bs)
        mempool_free(p, bs->bio_pool);
 }
 
-/*
- * default destructor for a bio allocated with bio_alloc_bioset()
- */
-static void bio_fs_destructor(struct bio *bio)
-{
-       bio_free(bio, fs_bio_set);
-}
-
-static void bio_kmalloc_destructor(struct bio *bio)
-{
-       if (bio_has_allocated_vec(bio))
-               kfree(bio->bi_io_vec);
-       kfree(bio);
-}
-
 void bio_init(struct bio *bio)
 {
        memset(bio, 0, sizeof(*bio));
@@ -301,21 +278,15 @@ void bio_init(struct bio *bio)
  **/
 struct bio *bio_alloc_bioset(gfp_t gfp_mask, int nr_iovecs, struct bio_set *bs)
 {
+       unsigned long idx = BIO_POOL_NONE;
        struct bio_vec *bvl = NULL;
-       struct bio *bio = NULL;
-       unsigned long idx = 0;
-       void *p = NULL;
-
-       if (bs) {
-               p = mempool_alloc(bs->bio_pool, gfp_mask);
-               if (!p)
-                       goto err;
-               bio = p + bs->front_pad;
-       } else {
-               bio = kmalloc(sizeof(*bio), gfp_mask);
-               if (!bio)
-                       goto err;
-       }
+       struct bio *bio;
+       void *p;
+
+       p = mempool_alloc(bs->bio_pool, gfp_mask);
+       if (unlikely(!p))
+               return NULL;
+       bio = p + bs->front_pad;
 
        bio_init(bio);
 
@@ -332,22 +303,50 @@ struct bio *bio_alloc_bioset(gfp_t gfp_mask, int nr_iovecs, struct bio_set *bs)
 
                nr_iovecs = bvec_nr_vecs(idx);
        }
+out_set:
        bio->bi_flags |= idx << BIO_POOL_OFFSET;
        bio->bi_max_vecs = nr_iovecs;
-out_set:
        bio->bi_io_vec = bvl;
-
        return bio;
 
 err_free:
-       if (bs)
-               mempool_free(p, bs->bio_pool);
-       else
-               kfree(bio);
-err:
+       mempool_free(p, bs->bio_pool);
        return NULL;
 }
 
+static void bio_fs_destructor(struct bio *bio)
+{
+       bio_free(bio, fs_bio_set);
+}
+
+/**
+ *     bio_alloc - allocate a new bio, memory pool backed
+ *     @gfp_mask: allocation mask to use
+ *     @nr_iovecs: number of iovecs
+ *
+ *     Allocate a new bio with @nr_iovecs bvecs.  If @gfp_mask
+ *     contains __GFP_WAIT, the allocation is guaranteed to succeed.
+ *
+ *     RETURNS:
+ *     Pointer to new bio on success, NULL on failure.
+ */
+struct bio *bio_alloc(gfp_t gfp_mask, int nr_iovecs)
+{
+       struct bio *bio = bio_alloc_bioset(gfp_mask, nr_iovecs, fs_bio_set);
+
+       if (bio)
+               bio->bi_destructor = bio_fs_destructor;
+
+       return bio;
+}
+
+static void bio_kmalloc_destructor(struct bio *bio)
+{
+       if (bio_integrity(bio))
+               bio_integrity_free(bio);
+       kfree(bio);
+}
+
 /**
  * bio_alloc - allocate a bio for I/O
  * @gfp_mask:   the GFP_ mask given to the slab allocator
@@ -366,29 +365,20 @@ err:
  *   do so can cause livelocks under memory pressure.
  *
  **/
-struct bio *bio_alloc(gfp_t gfp_mask, int nr_iovecs)
-{
-       struct bio *bio = bio_alloc_bioset(gfp_mask, nr_iovecs, fs_bio_set);
-
-       if (bio)
-               bio->bi_destructor = bio_fs_destructor;
-
-       return bio;
-}
-
-/*
- * Like bio_alloc(), but doesn't use a mempool backing. This means that
- * it CAN fail, but while bio_alloc() can only be used for allocations
- * that have a short (finite) life span, bio_kmalloc() should be used
- * for more permanent bio allocations (like allocating some bio's for
- * initalization or setup purposes).
- */
 struct bio *bio_kmalloc(gfp_t gfp_mask, int nr_iovecs)
 {
-       struct bio *bio = bio_alloc_bioset(gfp_mask, nr_iovecs, NULL);
+       struct bio *bio;
 
-       if (bio)
-               bio->bi_destructor = bio_kmalloc_destructor;
+       bio = kmalloc(sizeof(struct bio) + nr_iovecs * sizeof(struct bio_vec),
+                     gfp_mask);
+       if (unlikely(!bio))
+               return NULL;
+
+       bio_init(bio);
+       bio->bi_flags |= BIO_POOL_NONE << BIO_POOL_OFFSET;
+       bio->bi_max_vecs = nr_iovecs;
+       bio->bi_io_vec = bio->bi_inline_vecs;
+       bio->bi_destructor = bio_kmalloc_destructor;
 
        return bio;
 }

diff --git a/include/linux/bio.h b/include/linux/bio.h
index b89cf2d..7b214fd 100644 (file)
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -132,6 +132,7 @@ struct bio {
  * top 4 bits of bio flags indicate the pool this bio came from
  */
 #define BIO_POOL_BITS          (4)
+#define BIO_POOL_NONE          ((1UL << BIO_POOL_BITS) - 1)
 #define BIO_POOL_OFFSET                (BITS_PER_LONG - BIO_POOL_BITS)
 #define BIO_POOL_MASK          (1UL << BIO_POOL_OFFSET)
 #define BIO_POOL_IDX(bio)      ((bio)->bi_flags >> BIO_POOL_OFFSET)