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>

1 files changed, 54 insertions, 64 deletions

diff --git a/fs/bio.c b/fs/bio.c
index cd42bb882f30..d35588fd6d57 100644
--- 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;
 }