Hi, Jens,

I sent you a patch for review about a week ago.  Here is that same
patch, applied to the latest bk kernel.  Thanks in advance for the review

Dave Olien


===== drivers/md/dm.c 1.61 vs edited =====
--- 1.61/drivers/md/dm.c        2005-01-25 13:50:21 -08:00
+++ edited/drivers/md/dm.c      2005-01-31 11:37:27 -08:00
@@ -96,10 +96,16 @@ struct mapped_device {
 static kmem_cache_t *_io_cache;
 static kmem_cache_t *_tio_cache;
 
+static struct bio_set *dm_set;
+
 static int __init local_init(void)
 {
        int r;
 
+       dm_set = bioset_create(512, 512, 1);
+       if (!dm_set)
+               return -ENOMEM;
+
        /* allocate a slab for the dm_ios */
        _io_cache = kmem_cache_create("dm_io",
                                      sizeof(struct dm_io), 0, 0, NULL, NULL);
@@ -133,6 +139,8 @@ static void local_exit(void)
        kmem_cache_destroy(_tio_cache);
        kmem_cache_destroy(_io_cache);
 
+       bioset_free(dm_set);
+       
        if (unregister_blkdev(_major, _name) < 0)
                DMERR("devfs_unregister_blkdev failed");
 
@@ -393,7 +401,7 @@ static struct bio *split_bvec(struct bio
        struct bio *clone;
        struct bio_vec *bv = bio->bi_io_vec + idx;
 
-       clone = bio_alloc(GFP_NOIO, 1);
+       clone = bio_alloc_bs(GFP_NOIO, 1, dm_set);
        *clone->bi_io_vec = *bv;
 
        clone->bi_sector = sector;
===== drivers/md/dm-io.c 1.4 vs edited =====
--- 1.4/drivers/md/dm-io.c      2005-01-25 13:50:21 -08:00
+++ edited/drivers/md/dm-io.c   2005-01-31 11:45:42 -08:00
@@ -12,191 +12,7 @@
 #include <linux/sched.h>
 #include <linux/slab.h>
 
-#define BIO_POOL_SIZE 256
-
-
-/*-----------------------------------------------------------------
- * Bio set, move this to bio.c
- *---------------------------------------------------------------*/
-#define BV_NAME_SIZE 16
-struct biovec_pool {
-       int nr_vecs;
-       char name[BV_NAME_SIZE];
-       kmem_cache_t *slab;
-       mempool_t *pool;
-       atomic_t allocated;     /* FIXME: debug */
-};
-
-#define BIOVEC_NR_POOLS 6
-struct bio_set {
-       char name[BV_NAME_SIZE];
-       kmem_cache_t *bio_slab;
-       mempool_t *bio_pool;
-       struct biovec_pool pools[BIOVEC_NR_POOLS];
-};
-
-static void bio_set_exit(struct bio_set *bs)
-{
-       unsigned i;
-       struct biovec_pool *bp;
-
-       if (bs->bio_pool)
-               mempool_destroy(bs->bio_pool);
-
-       if (bs->bio_slab)
-               kmem_cache_destroy(bs->bio_slab);
-
-       for (i = 0; i < BIOVEC_NR_POOLS; i++) {
-               bp = bs->pools + i;
-               if (bp->pool)
-                       mempool_destroy(bp->pool);
-
-               if (bp->slab)
-                       kmem_cache_destroy(bp->slab);
-       }
-}
-
-static void mk_name(char *str, size_t len, const char *prefix, unsigned count)
-{
-       snprintf(str, len, "%s-%u", prefix, count);
-}
-
-static int bio_set_init(struct bio_set *bs, const char *slab_prefix,
-                        unsigned pool_entries, unsigned scale)
-{
-       /* FIXME: this must match bvec_index(), why not go the
-        * whole hog and have a pool per power of 2 ? */
-       static unsigned _vec_lengths[BIOVEC_NR_POOLS] = {
-               1, 4, 16, 64, 128, BIO_MAX_PAGES
-       };
-
-
-       unsigned i, size;
-       struct biovec_pool *bp;
-
-       /* zero the bs so we can tear down properly on error */
-       memset(bs, 0, sizeof(*bs));
-
-       /*
-        * Set up the bio pool.
-        */
-       snprintf(bs->name, sizeof(bs->name), "%s-bio", slab_prefix);
-
-       bs->bio_slab = kmem_cache_create(bs->name, sizeof(struct bio), 0,
-                                        SLAB_HWCACHE_ALIGN, NULL, NULL);
-       if (!bs->bio_slab) {
-               DMWARN("can't init bio slab");
-               goto bad;
-       }
-
-       bs->bio_pool = mempool_create(pool_entries, mempool_alloc_slab,
-                                     mempool_free_slab, bs->bio_slab);
-       if (!bs->bio_pool) {
-               DMWARN("can't init bio pool");
-               goto bad;
-       }
-
-       /*
-        * Set up the biovec pools.
-        */
-       for (i = 0; i < BIOVEC_NR_POOLS; i++) {
-               bp = bs->pools + i;
-               bp->nr_vecs = _vec_lengths[i];
-               atomic_set(&bp->allocated, 1); /* FIXME: debug */
-
-
-               size = bp->nr_vecs * sizeof(struct bio_vec);
-
-               mk_name(bp->name, sizeof(bp->name), slab_prefix, i);
-               bp->slab = kmem_cache_create(bp->name, size, 0,
-                                            SLAB_HWCACHE_ALIGN, NULL, NULL);
-               if (!bp->slab) {
-                       DMWARN("can't init biovec slab cache");
-                       goto bad;
-               }
-
-               if (i >= scale)
-                       pool_entries >>= 1;
-
-               bp->pool = mempool_create(pool_entries, mempool_alloc_slab,
-                                         mempool_free_slab, bp->slab);
-               if (!bp->pool) {
-                       DMWARN("can't init biovec mempool");
-                       goto bad;
-               }
-       }
-
-       return 0;
-
- bad:
-       bio_set_exit(bs);
-       return -ENOMEM;
-}
-
-/* FIXME: blech */
-static inline unsigned bvec_index(unsigned nr)
-{
-       switch (nr) {
-       case 1:         return 0;
-       case 2 ... 4:   return 1;
-       case 5 ... 16:  return 2;
-       case 17 ... 64: return 3;
-       case 65 ... 128:return 4;
-       case 129 ... BIO_MAX_PAGES: return 5;
-       }
-
-       BUG();
-       return 0;
-}
-
-static unsigned _bio_count = 0;
-struct bio *bio_set_alloc(struct bio_set *bs, int gfp_mask, int nr_iovecs)
-{
-       struct biovec_pool *bp;
-       struct bio_vec *bv = NULL;
-       unsigned long idx;
-       struct bio *bio;
-
-       bio = mempool_alloc(bs->bio_pool, gfp_mask);
-       if (unlikely(!bio))
-               return NULL;
-
-       bio_init(bio);
-
-       if (likely(nr_iovecs)) {
-               idx = bvec_index(nr_iovecs);
-               bp = bs->pools + idx;
-               bv = mempool_alloc(bp->pool, gfp_mask);
-               if (!bv) {
-                       mempool_free(bio, bs->bio_pool);
-                       return NULL;
-               }
-
-               memset(bv, 0, bp->nr_vecs * sizeof(*bv));
-               bio->bi_flags |= idx << BIO_POOL_OFFSET;
-               bio->bi_max_vecs = bp->nr_vecs;
-               atomic_inc(&bp->allocated);
-       }
-
-       bio->bi_io_vec = bv;
-       return bio;
-}
-
-static void bio_set_free(struct bio_set *bs, struct bio *bio)
-{
-       struct biovec_pool *bp = bs->pools + BIO_POOL_IDX(bio);
-
-       if (atomic_dec_and_test(&bp->allocated))
-               BUG();
-
-       mempool_free(bio->bi_io_vec, bp->pool);
-       mempool_free(bio, bs->bio_pool);
-}
-
-/*-----------------------------------------------------------------
- * dm-io proper
- *---------------------------------------------------------------*/
-static struct bio_set _bios;
+static struct bio_set *_bios;
 
 /* FIXME: can we shrink this ? */
 struct io {
@@ -240,7 +56,8 @@ static int resize_pool(unsigned int new_
                        /* free off the pool */
                        mempool_destroy(_io_pool);
                        _io_pool = NULL;
-                       bio_set_exit(&_bios);
+                       /*bio_set_exit(&_bios); XXX */
+                       bioset_free(_bios);
 
                } else {
                        /* resize the pool */
@@ -253,10 +70,11 @@ static int resize_pool(unsigned int new_
                if (!_io_pool)
                        return -ENOMEM;
 
-               r = bio_set_init(&_bios, "dm-io", 512, 1);
-               if (r) {
+               _bios = bioset_create(512, 512, 1);
+               if (!_bios) {
                        mempool_destroy(_io_pool);
                        _io_pool = NULL;
+                       return -ENOMEM;
                }
        }
 
@@ -280,6 +98,7 @@ void dm_io_put(unsigned int num_pages)
  * We need to keep track of which region a bio is doing io for.
  * In order to save a memory allocation we store this the last
  * bvec which we know is unused (blech).
+ * XXX This is ugly and can OOPS with some configs... find another way.
  *---------------------------------------------------------------*/
 static inline void bio_set_region(struct bio *bio, unsigned region)
 {
@@ -315,21 +134,6 @@ static void dec_count(struct io *io, uns
        }
 }
 
-/* FIXME Move this to bio.h? */
-static void zero_fill_bio(struct bio *bio)
-{
-       unsigned long flags;
-       struct bio_vec *bv;
-       int i;
-
-       bio_for_each_segment(bv, bio, i) {
-               char *data = bvec_kmap_irq(bv, &flags);
-               memset(data, 0, bv->bv_len);
-               flush_dcache_page(bv->bv_page);
-               bvec_kunmap_irq(data, &flags);
-       }
-}
-
 static int endio(struct bio *bio, unsigned int done, int error)
 {
        struct io *io = (struct io *) bio->bi_private;
@@ -347,12 +151,6 @@ static int endio(struct bio *bio, unsign
        return 0;
 }
 
-static void bio_dtr(struct bio *bio)
-{
-       _bio_count--;
-       bio_set_free(&_bios, bio);
-}
-
 /*-----------------------------------------------------------------
  * These little objects provide an abstraction for getting a new
  * destination page for io.
@@ -461,13 +259,12 @@ static void do_region(int rw, unsigned i
                 * bvec for bio_get/set_region().
                 */
                num_bvecs = (remaining / (PAGE_SIZE >> 9)) + 2;
-               _bio_count++;
-               bio = bio_set_alloc(&_bios, GFP_NOIO, num_bvecs);
+               bio = bio_alloc_bs(GFP_NOIO, num_bvecs, _bios);
                bio->bi_sector = where->sector + (where->count - remaining);
                bio->bi_bdev = where->bdev;
                bio->bi_end_io = endio;
                bio->bi_private = io;
-               bio->bi_destructor = bio_dtr;
+               /* bio->bi_destructor = bio_dtr; XXX */
                bio_set_region(bio, region);
 
                /*
===== drivers/md/dm-zero.c 1.3 vs edited =====
--- 1.3/drivers/md/dm-zero.c    2004-06-17 23:53:43 -07:00
+++ edited/drivers/md/dm-zero.c 2005-01-31 11:37:27 -08:00
@@ -24,23 +24,6 @@ static int zero_ctr(struct dm_target *ti
 }
 
 /*
- * Fills the bio pages with zeros
- */
-static void zero_fill_bio(struct bio *bio)
-{
-       unsigned long flags;
-       struct bio_vec *bv;
-       int i;
-
-       bio_for_each_segment(bv, bio, i) {
-               char *data = bvec_kmap_irq(bv, &flags);
-               memset(data, 0, bv->bv_len);
-               flush_dcache_page(bv->bv_page);
-               bvec_kunmap_irq(data, &flags);
-       }
-}
-
-/*
  * Return zeros only on reads
  */
 static int zero_map(struct dm_target *ti, struct bio *bio,
===== fs/bio.c 1.73 vs edited =====
--- 1.73/fs/bio.c       2005-01-20 21:02:13 -08:00
+++ edited/fs/bio.c     2005-01-31 14:50:37 -08:00
@@ -28,7 +28,6 @@
 
 #define BIO_POOL_SIZE 256
 
-static mempool_t *bio_pool;
 static kmem_cache_t *bio_slab;
 
 #define BIOVEC_NR_POOLS 6
@@ -40,11 +39,10 @@ static kmem_cache_t *bio_slab;
 #define BIO_SPLIT_ENTRIES 8    
 mempool_t *bio_split_pool;
 
-struct biovec_pool {
+struct biovec_slab {
        int nr_vecs;
        char *name; 
        kmem_cache_t *slab;
-       mempool_t *pool;
 };
 
 /*
@@ -54,15 +52,32 @@ struct biovec_pool {
  */
 
 #define BV(x) { .nr_vecs = x, .name = "biovec-"__stringify(x) }
-static struct biovec_pool bvec_array[BIOVEC_NR_POOLS] = {
+static struct biovec_slab bvec_slabs[BIOVEC_NR_POOLS] = {
        BV(1), BV(4), BV(16), BV(64), BV(128), BV(BIO_MAX_PAGES),
 };
 #undef BV
 
-static inline struct bio_vec *bvec_alloc(int gfp_mask, int nr, unsigned long 
*idx)
+/*
+ * bio_set is used to allow other portions of the IO system to
+ * allocate their own private memory pools for bio and iovec structures.
+ * These memory pools in turn all allocate from the bio_slab
+ * and the bvec_slabs[].
+ */
+struct bio_set {
+       mempool_t *bio_pool;
+       mempool_t *bvec_pools[BIOVEC_NR_POOLS];
+};
+
+/*
+ * fs_bio_set is the bio_set containing bio and iovec memory pools used by
+ * IO code that does not need private memory pools.
+ */
+static struct bio_set *fs_bio_set;
+
+static inline struct bio_vec *bvec_alloc_bs(int gfp_mask, int nr, unsigned 
long *idx, struct bio_set *bs)
 {
-       struct biovec_pool *bp;
        struct bio_vec *bvl;
+       struct biovec_slab *bp;
 
        /*
         * see comment near bvec_array define!
@@ -80,26 +95,27 @@ static inline struct bio_vec *bvec_alloc
        /*
         * idx now points to the pool we want to allocate from
         */
-       bp = bvec_array + *idx;
 
-       bvl = mempool_alloc(bp->pool, gfp_mask);
+       bp = bvec_slabs + *idx;
+       bvl = mempool_alloc(bs->bvec_pools[*idx], gfp_mask);
        if (bvl)
                memset(bvl, 0, bp->nr_vecs * sizeof(struct bio_vec));
+
        return bvl;
 }
 
 /*
- * default destructor for a bio allocated with bio_alloc()
+ * default destructor for a bio allocated with bio_alloc_bs()
  */
 static void bio_destructor(struct bio *bio)
 {
        const int pool_idx = BIO_POOL_IDX(bio);
-       struct biovec_pool *bp = bvec_array + pool_idx;
+       struct bio_set *bs = bio->bi_set;
 
        BIO_BUG_ON(pool_idx >= BIOVEC_NR_POOLS);
 
-       mempool_free(bio->bi_io_vec, bp->pool);
-       mempool_free(bio, bio_pool);
+       mempool_free(bio->bi_io_vec, bs->bvec_pools[pool_idx]);
+       mempool_free(bio, bs->bio_pool);
 }
 
 inline void bio_init(struct bio *bio)
@@ -121,18 +137,21 @@ inline void bio_init(struct bio *bio)
 }
 
 /**
- * bio_alloc - allocate a bio for I/O
+ * bio_alloc_bs - allocate a bio for I/O
  * @gfp_mask:   the GFP_ mask given to the slab allocator
  * @nr_iovecs: number of iovecs to pre-allocate
  *
  * Description:
- *   bio_alloc will first try it's on mempool to satisfy the allocation.
+ *   bio_alloc_bs will first try it's on mempool to satisfy the allocation.
  *   If %__GFP_WAIT is set then we will block on the internal pool waiting
  *   for a &struct bio to become free.
+ *
+ *   allocate bio and iovecs from the memory pools specified by the
+ *   bio_set structure.
  **/
-struct bio *bio_alloc(int gfp_mask, int nr_iovecs)
+struct bio *bio_alloc_bs(int gfp_mask, int nr_iovecs, struct bio_set *bs)
 {
-       struct bio *bio = mempool_alloc(bio_pool, gfp_mask);
+       struct bio *bio = mempool_alloc(bs->bio_pool, gfp_mask);
 
        if (likely(bio)) {
                struct bio_vec *bvl = NULL;
@@ -141,22 +160,28 @@ struct bio *bio_alloc(int gfp_mask, int 
                if (likely(nr_iovecs)) {
                        unsigned long idx;
 
-                       bvl = bvec_alloc(gfp_mask, nr_iovecs, &idx);
+                       bvl = bvec_alloc_bs(gfp_mask, nr_iovecs, &idx, bs);
                        if (unlikely(!bvl)) {
-                               mempool_free(bio, bio_pool);
+                               mempool_free(bio, bs->bio_pool);
                                bio = NULL;
                                goto out;
                        }
                        bio->bi_flags |= idx << BIO_POOL_OFFSET;
-                       bio->bi_max_vecs = bvec_array[idx].nr_vecs;
+                       bio->bi_max_vecs = bvec_slabs[idx].nr_vecs;
                }
                bio->bi_io_vec = bvl;
                bio->bi_destructor = bio_destructor;
+               bio->bi_set = bs;
        }
 out:
        return bio;
 }
 
+struct bio *bio_alloc(int gfp_mask, int nr_iovecs)
+{
+       return bio_alloc_bs(gfp_mask, nr_iovecs, fs_bio_set);
+}
+
 /**
  * bio_put - release a reference to a bio
  * @bio:   bio to release reference to
@@ -233,7 +258,7 @@ inline void __bio_clone(struct bio *bio,
  */
 struct bio *bio_clone(struct bio *bio, int gfp_mask)
 {
-       struct bio *b = bio_alloc(gfp_mask, bio->bi_max_vecs);
+       struct bio *b = bio_alloc_bs(gfp_mask, bio->bi_max_vecs, bio->bi_set);
 
        if (b)
                __bio_clone(b, bio);
@@ -904,11 +929,101 @@ static void bio_pair_free(void *bp, void
        kfree(bp);
 }
 
-static void __init biovec_init_pools(void)
+
+/*
+ * create memory pools for biovec's in a bio_set.
+ * use the global biovec slabs created for general use.
+ */
+static int biovec_create_pools(struct bio_set *bs, int pool_entries, int scale)
+{
+       int i;
+
+       for (i = 0; i < BIOVEC_NR_POOLS; i++) {
+               struct biovec_slab *bp = bvec_slabs + i;
+               mempool_t **bvp = bs->bvec_pools + i;
+
+               if (i >= scale)
+                       pool_entries >>= 1;
+
+               *bvp = mempool_create(pool_entries, mempool_alloc_slab,
+                                       mempool_free_slab, bp->slab);
+               if (!*bvp)
+                       return -ENOMEM;
+       }
+       return 0;
+}
+
+static void biovec_free_pools(struct bio_set *bs)
 {
-       int i, size, megabytes, pool_entries = BIO_POOL_SIZE;
+       int i;
+
+       for (i = 0; i < BIOVEC_NR_POOLS; i++) {
+               mempool_t *bvp = bs->bvec_pools[i];
+
+               if (bvp)
+                       mempool_destroy(bvp);
+       }
+       
+}
+
+void bioset_free(struct bio_set *bs)
+{
+       if (!bs->bio_pool)
+               mempool_destroy(bs->bio_pool);
+
+       biovec_free_pools(bs);
+
+       kfree(bs);
+}
+
+struct bio_set *bioset_create(int bio_pool_size, int bvec_pool_size, int scale)
+{
+       struct bio_set *bs = kmalloc(sizeof(*bs), GFP_KERNEL);
+
+       if (!bs)
+               return NULL;
+
+       memset(bs, 0, sizeof(*bs));
+       bs->bio_pool = mempool_create(bio_pool_size, mempool_alloc_slab,
+                       mempool_free_slab, bio_slab);
+
+       if (!bs->bio_pool) 
+               goto bad;
+       
+       if (biovec_create_pools(bs, bvec_pool_size, scale))
+               goto bad;
+
+       return bs;
+
+bad:
+       bioset_free(bs);
+       return NULL;
+}
+
+static void __init biovec_init_slabs(void)
+{
+       int i;
+
+       for (i = 0; i < BIOVEC_NR_POOLS; i++) {
+               int size;
+               struct biovec_slab *bvs = bvec_slabs + i;
+
+               size = bvs->nr_vecs * sizeof(struct bio_vec);
+               bvs->slab = kmem_cache_create(bvs->name, size, 0,
+                                SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL);
+       }
+}
+
+static int __init init_bio(void)
+{
+       int megabytes, bvec_pool_entries;
        int scale = BIOVEC_NR_POOLS;
 
+       bio_slab = kmem_cache_create("bio", sizeof(struct bio), 0,
+                               SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL);
+
+       biovec_init_slabs();
+
        megabytes = nr_free_pages() >> (20 - PAGE_SHIFT);
 
        /*
@@ -928,38 +1043,13 @@ static void __init biovec_init_pools(voi
        /*
         * scale number of entries
         */
-       pool_entries = megabytes * 2;
-       if (pool_entries > 256)
-               pool_entries = 256;
-
-       for (i = 0; i < BIOVEC_NR_POOLS; i++) {
-               struct biovec_pool *bp = bvec_array + i;
-
-               size = bp->nr_vecs * sizeof(struct bio_vec);
-
-               bp->slab = kmem_cache_create(bp->name, size, 0,
-                               SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL);
-
-               if (i >= scale)
-                       pool_entries >>= 1;
-
-               bp->pool = mempool_create(pool_entries, mempool_alloc_slab,
-                                       mempool_free_slab, bp->slab);
-               if (!bp->pool)
-                       panic("biovec: can't init mempool\n");
-       }
-}
-
-static int __init init_bio(void)
-{
-       bio_slab = kmem_cache_create("bio", sizeof(struct bio), 0,
-                               SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL);
-       bio_pool = mempool_create(BIO_POOL_SIZE, mempool_alloc_slab,
-                               mempool_free_slab, bio_slab);
-       if (!bio_pool)
-               panic("bio: can't create mempool\n");
-
-       biovec_init_pools();
+       bvec_pool_entries = megabytes * 2;
+       if (bvec_pool_entries > 256)
+               bvec_pool_entries = 256;
+
+       fs_bio_set = bioset_create(BIO_POOL_SIZE, bvec_pool_entries, scale);
+       if (!fs_bio_set)
+               panic("bio: can't allocate bios\n");
 
        bio_split_pool = mempool_create(BIO_SPLIT_ENTRIES,
                                bio_pair_alloc, bio_pair_free, NULL);
@@ -988,3 +1078,6 @@ EXPORT_SYMBOL(bio_split);
 EXPORT_SYMBOL(bio_split_pool);
 EXPORT_SYMBOL(bio_copy_user);
 EXPORT_SYMBOL(bio_uncopy_user);
+EXPORT_SYMBOL(bioset_create);
+EXPORT_SYMBOL(bioset_free);
+EXPORT_SYMBOL(bio_alloc_bs);
===== include/linux/bio.h 1.43 vs edited =====
--- 1.43/include/linux/bio.h    2004-11-06 03:03:05 -08:00
+++ edited/include/linux/bio.h  2005-01-31 11:37:27 -08:00
@@ -59,6 +59,7 @@ struct bio_vec {
        unsigned int    bv_offset;
 };
 
+struct bio_set;
 struct bio;
 typedef int (bio_end_io_t) (struct bio *, unsigned int, int);
 typedef void (bio_destructor_t) (struct bio *);
@@ -109,6 +110,7 @@ struct bio {
        void                    *bi_private;
 
        bio_destructor_t        *bi_destructor; /* destructor */
+       struct bio_set          *bi_set;        /* memory pools set */
 };
 
 /*
@@ -258,7 +260,11 @@ extern struct bio_pair *bio_split(struct
 extern mempool_t *bio_split_pool;
 extern void bio_pair_release(struct bio_pair *dbio);
 
+extern struct bio_set *bioset_create(int, int, int);
+extern void bioset_free(struct bio_set *);
+
 extern struct bio *bio_alloc(int, int);
+extern struct bio *bio_alloc_bs(int, int, struct bio_set *);
 extern void bio_put(struct bio *);
 
 extern void bio_endio(struct bio *, unsigned int, int);
@@ -328,5 +334,19 @@ extern inline char *__bio_kmap_irq(struc
 #define bio_kmap_irq(bio, flags) \
        __bio_kmap_irq((bio), (bio)->bi_idx, (flags))
 #define bio_kunmap_irq(buf,flags)      __bio_kunmap_irq(buf, flags)
+
+extern inline void zero_fill_bio(struct bio *bio)
+{
+       unsigned long flags;
+       struct bio_vec *bv;
+       int i;
+
+       bio_for_each_segment(bv, bio, i) {
+               char *data = bvec_kmap_irq(bv, &flags);
+               memset(data, 0, bv->bv_len);
+               flush_dcache_page(bv->bv_page);
+               bvec_kunmap_irq(data, &flags);
+       }
+}
 
 #endif /* __LINUX_BIO_H */
-
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