1 files changed, 161 insertions, 30 deletions

diff --git a/fs/bio.c b/fs/bio.c
index 1ab8986b0411..0146f80789e9 100644
--- a/fs/bio.c
+++ b/fs/bio.c
@@ -31,8 +31,6 @@
 
 DEFINE_TRACE(block_split);
 
-static struct kmem_cache *bio_slab __read_mostly;
-
 static mempool_t *bio_split_pool __read_mostly;
 
 /*
@@ -40,9 +38,8 @@ static mempool_t *bio_split_pool __read_mostly;
  * break badly! cannot be bigger than what you can fit into an
  * unsigned short
  */
-
 #define BV(x) { .nr_vecs = x, .name = "biovec-"__stringify(x) }
-static struct biovec_slab bvec_slabs[BIOVEC_NR_POOLS] __read_mostly = {
+struct biovec_slab bvec_slabs[BIOVEC_NR_POOLS] __read_mostly = {
         BV(1), BV(4), BV(16), BV(64), BV(128), BV(BIO_MAX_PAGES),
 };
 #undef BV
@@ -53,11 +50,119 @@ static struct biovec_slab bvec_slabs[BIOVEC_NR_POOLS] __read_mostly = {
  */
 struct bio_set *fs_bio_set;
 
+/*
+ * Our slab pool management
+ */
+struct bio_slab {
+        struct kmem_cache *slab;
+        unsigned int slab_ref;
+        unsigned int slab_size;
+        char name[8];
+};
+static DEFINE_MUTEX(bio_slab_lock);
+static struct bio_slab *bio_slabs;
+static unsigned int bio_slab_nr, bio_slab_max;
+
+static struct kmem_cache *bio_find_or_create_slab(unsigned int extra_size)
+{
+        unsigned int sz = sizeof(struct bio) + extra_size;
+        struct kmem_cache *slab = NULL;
+        struct bio_slab *bslab;
+        unsigned int i, entry = -1;
+
+        mutex_lock(&bio_slab_lock);
+
+        i = 0;
+        while (i < bio_slab_nr) {
+                struct bio_slab *bslab = &bio_slabs[i];
+
+                if (!bslab->slab && entry == -1)
+                        entry = i;
+                else if (bslab->slab_size == sz) {
+                        slab = bslab->slab;
+                        bslab->slab_ref++;
+                        break;
+                }
+                i++;
+        }
+
+        if (slab)
+                goto out_unlock;
+
+        if (bio_slab_nr == bio_slab_max && entry == -1) {
+                bio_slab_max <<= 1;
+                bio_slabs = krealloc(bio_slabs,
+                                     bio_slab_max * sizeof(struct bio_slab),
+                                     GFP_KERNEL);
+                if (!bio_slabs)
+                        goto out_unlock;
+        }
+        if (entry == -1)
+                entry = bio_slab_nr++;
+
+        bslab = &bio_slabs[entry];
+
+        snprintf(bslab->name, sizeof(bslab->name), "bio-%d", entry);
+        slab = kmem_cache_create(bslab->name, sz, 0, SLAB_HWCACHE_ALIGN, NULL);
+        if (!slab)
+                goto out_unlock;
+
+        printk("bio: create slab <%s> at %d\n", bslab->name, entry);
+        bslab->slab = slab;
+        bslab->slab_ref = 1;
+        bslab->slab_size = sz;
+out_unlock:
+        mutex_unlock(&bio_slab_lock);
+        return slab;
+}
+
+static void bio_put_slab(struct bio_set *bs)
+{
+        struct bio_slab *bslab = NULL;
+        unsigned int i;
+
+        mutex_lock(&bio_slab_lock);
+
+        for (i = 0; i < bio_slab_nr; i++) {
+                if (bs->bio_slab == bio_slabs[i].slab) {
+                        bslab = &bio_slabs[i];
+                        break;
+                }
+        }
+
+        if (WARN(!bslab, KERN_ERR "bio: unable to find slab!\n"))
+                goto out;
+
+        WARN_ON(!bslab->slab_ref);
+
+        if (--bslab->slab_ref)
+                goto out;
+
+        kmem_cache_destroy(bslab->slab);
+        bslab->slab = NULL;
+
+out:
+        mutex_unlock(&bio_slab_lock);
+}
+
 unsigned int bvec_nr_vecs(unsigned short idx)
 {
         return bvec_slabs[idx].nr_vecs;
 }
 
+void bvec_free_bs(struct bio_set *bs, struct bio_vec *bv, unsigned int idx)
+{
+        BIO_BUG_ON(idx >= BIOVEC_NR_POOLS);
+
+        if (idx == BIOVEC_MAX_IDX)
+                mempool_free(bv, bs->bvec_pool);
+        else {
+                struct biovec_slab *bvs = bvec_slabs + idx;
+
+                kmem_cache_free(bvs->slab, bv);
+        }
+}
+
 struct bio_vec *bvec_alloc_bs(gfp_t gfp_mask, int nr, unsigned long *idx,
                               struct bio_set *bs)
 {
@@ -134,24 +239,22 @@ fallback:
 
 void bio_free(struct bio *bio, struct bio_set *bs)
 {
-        if (bio->bi_io_vec) {
-                const int pool_idx = BIO_POOL_IDX(bio);
+        void *p;
 
-                BIO_BUG_ON(pool_idx >= BIOVEC_NR_POOLS);
-
-                if (pool_idx == BIOVEC_MAX_IDX)
-                        mempool_free(bio->bi_io_vec, bs->bvec_pool);
-                else {
-                        struct biovec_slab *bvs = bvec_slabs + pool_idx;
-
-                        kmem_cache_free(bvs->slab, bio->bi_io_vec);
-                }
-        }
+        if (bio->bi_io_vec)
+                bvec_free_bs(bs, bio->bi_io_vec, BIO_POOL_IDX(bio));
 
         if (bio_integrity(bio))
                 bio_integrity_free(bio, bs);
 
-        mempool_free(bio, bs->bio_pool);
+        /*
+         * If we have front padding, adjust the bio pointer before freeing
+         */
+        p = bio;
+        if (bs->front_pad)
+                p -= bs->front_pad;
+
+        mempool_free(p, bs->bio_pool);
 }
 
 /*
@@ -188,16 +291,20 @@ void bio_init(struct bio *bio)
  *   for a &struct bio to become free. If a %NULL @bs is passed in, we will
  *   fall back to just using @kmalloc to allocate the required memory.
  *
- *   allocate bio and iovecs from the memory pools specified by the
- *   bio_set structure, or @kmalloc if none given.
+ *   Note that the caller must set ->bi_destructor on succesful return
+ *   of a bio, to do the appropriate freeing of the bio once the reference
+ *   count drops to zero.
  **/
 struct bio *bio_alloc_bioset(gfp_t gfp_mask, int nr_iovecs, struct bio_set *bs)
 {
-        struct bio *bio;
+        struct bio *bio = NULL;
+
+        if (bs) {
+                void *p = mempool_alloc(bs->bio_pool, gfp_mask);
 
-        if (bs)
-                bio = mempool_alloc(bs->bio_pool, gfp_mask);
-        else
+                if (p)
+                        bio = p + bs->front_pad;
+        } else
                 bio = kmalloc(sizeof(*bio), gfp_mask);
 
         if (likely(bio)) {
@@ -1398,11 +1505,25 @@ void bioset_free(struct bio_set *bs)
 
         bioset_integrity_free(bs);
         biovec_free_pools(bs);
+        bio_put_slab(bs);
 
         kfree(bs);
 }
 
-struct bio_set *bioset_create(int bio_pool_size, int bvec_pool_size)
+/**
+ * bioset_create  - Create a bio_set
+ * @pool_size:  Number of bio and bio_vecs to cache in the mempool
+ * @front_pad:  Number of bytes to allocate in front of the returned bio
+ *
+ * Description:
+ *    Set up a bio_set to be used with @bio_alloc_bioset. Allows the caller
+ *    to ask for a number of bytes to be allocated in front of the bio.
+ *    Front pad allocation is useful for embedding the bio inside
+ *    another structure, to avoid allocating extra data to go with the bio.
+ *    Note that the bio must be embedded at the END of that structure always,
+ *    or things will break badly.
+ */
+struct bio_set *bioset_create(unsigned int pool_size, unsigned int front_pad)
 {
         struct bio_set *bs;
 
@@ -1410,16 +1531,22 @@ struct bio_set *bioset_create(int bio_pool_size, int bvec_pool_size)
         if (!bs)
                 return NULL;
 
-        bs->bio_slab = bio_slab;
+        bs->front_pad = front_pad;
 
-        bs->bio_pool = mempool_create_slab_pool(bio_pool_size, bs->bio_slab);
+        bs->bio_slab = bio_find_or_create_slab(front_pad);
+        if (!bs->bio_slab) {
+                kfree(bs);
+                return NULL;
+        }
+
+        bs->bio_pool = mempool_create_slab_pool(pool_size, bs->bio_slab);
         if (!bs->bio_pool)
                 goto bad;
 
-        if (bioset_integrity_create(bs, bio_pool_size))
+        if (bioset_integrity_create(bs, pool_size))
                 goto bad;
 
-        if (!biovec_create_pools(bs, bvec_pool_size))
+        if (!biovec_create_pools(bs, pool_size))
                 return bs;
 
 bad:
@@ -1443,12 +1570,16 @@ static void __init biovec_init_slabs(void)
 
 static int __init init_bio(void)
 {
-        bio_slab = KMEM_CACHE(bio, SLAB_HWCACHE_ALIGN|SLAB_PANIC);
+        bio_slab_max = 2;
+        bio_slab_nr = 0;
+        bio_slabs = kzalloc(bio_slab_max * sizeof(struct bio_slab), GFP_KERNEL);
+        if (!bio_slabs)
+                panic("bio: can't allocate bios\n");
 
         bio_integrity_init_slab();
         biovec_init_slabs();
 
-        fs_bio_set = bioset_create(BIO_POOL_SIZE, 2);
+        fs_bio_set = bioset_create(BIO_POOL_SIZE, 0);
         if (!fs_bio_set)
                 panic("bio: can't allocate bios\n");