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bio.c

/*
 * Copyright (C) 2001 Jens Axboe <axboe@kernel.dk>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public Licens
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-
 *
 */
#include <linux/mm.h>
#include <linux/swap.h>
#include <linux/bio.h>
#include <linux/blkdev.h>
#include <linux/slab.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/mempool.h>
#include <linux/workqueue.h>
#include <linux/blktrace_api.h>
#include <scsi/sg.h>          /* for struct sg_iovec */

#define BIO_POOL_SIZE 2

static struct kmem_cache *bio_slab __read_mostly;

#define BIOVEC_NR_POOLS 6

/*
 * a small number of entries is fine, not going to be performance critical.
 * basically we just need to survive
 */
#define BIO_SPLIT_ENTRIES 2
mempool_t *bio_split_pool __read_mostly;

struct biovec_slab {
      int nr_vecs;
      char *name; 
      struct kmem_cache *slab;
};

/*
 * if you change this list, also change bvec_alloc or things will
 * 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 = {
      BV(1), BV(4), BV(16), BV(64), BV(128), BV(BIO_MAX_PAGES),
};
#undef BV

/*
 * 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(gfp_t gfp_mask, int nr, unsigned long *idx, struct bio_set *bs)
{
      struct bio_vec *bvl;

      /*
       * see comment near bvec_array define!
       */
      switch (nr) {
            case   1        : *idx = 0; break;
            case   2 ...   4: *idx = 1; break;
            case   5 ...  16: *idx = 2; break;
            case  17 ...  64: *idx = 3; break;
            case  65 ... 128: *idx = 4; break;
            case 129 ... BIO_MAX_PAGES: *idx = 5; break;
            default:
                  return NULL;
      }
      /*
       * idx now points to the pool we want to allocate from
       */

      bvl = mempool_alloc(bs->bvec_pools[*idx], gfp_mask);
      if (bvl) {
            struct biovec_slab *bp = bvec_slabs + *idx;

            memset(bvl, 0, bp->nr_vecs * sizeof(struct bio_vec));
      }

      return bvl;
}

void bio_free(struct bio *bio, struct bio_set *bio_set)
{
      if (bio->bi_io_vec) {
            const int pool_idx = BIO_POOL_IDX(bio);

            BIO_BUG_ON(pool_idx >= BIOVEC_NR_POOLS);

            mempool_free(bio->bi_io_vec, bio_set->bvec_pools[pool_idx]);
      }

      mempool_free(bio, bio_set->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);
}

void bio_init(struct bio *bio)
{
      memset(bio, 0, sizeof(*bio));
      bio->bi_flags = 1 << BIO_UPTODATE;
      atomic_set(&bio->bi_cnt, 1);
}

/**
 * bio_alloc_bioset - allocate a bio for I/O
 * @gfp_mask:   the GFP_ mask given to the slab allocator
 * @nr_iovecs:    number of iovecs to pre-allocate
 * @bs:           the bio_set to allocate from
 *
 * Description:
 *   bio_alloc_bioset 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_bioset(gfp_t gfp_mask, int nr_iovecs, struct bio_set *bs)
{
      struct bio *bio = mempool_alloc(bs->bio_pool, gfp_mask);

      if (likely(bio)) {
            struct bio_vec *bvl = NULL;

            bio_init(bio);
            if (likely(nr_iovecs)) {
                  unsigned long idx = 0; /* shut up gcc */

                  bvl = bvec_alloc_bs(gfp_mask, nr_iovecs, &idx, bs);
                  if (unlikely(!bvl)) {
                        mempool_free(bio, bs->bio_pool);
                        bio = NULL;
                        goto out;
                  }
                  bio->bi_flags |= idx << BIO_POOL_OFFSET;
                  bio->bi_max_vecs = bvec_slabs[idx].nr_vecs;
            }
            bio->bi_io_vec = bvl;
      }
out:
      return bio;
}

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;
}

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);
      }
}
EXPORT_SYMBOL(zero_fill_bio);

/**
 * bio_put - release a reference to a bio
 * @bio:   bio to release reference to
 *
 * Description:
 *   Put a reference to a &struct bio, either one you have gotten with
 *   bio_alloc or bio_get. The last put of a bio will free it.
 **/
void bio_put(struct bio *bio)
{
      BIO_BUG_ON(!atomic_read(&bio->bi_cnt));

      /*
       * last put frees it
       */
      if (atomic_dec_and_test(&bio->bi_cnt)) {
            bio->bi_next = NULL;
            bio->bi_destructor(bio);
      }
}

inline int bio_phys_segments(struct request_queue *q, struct bio *bio)
{
      if (unlikely(!bio_flagged(bio, BIO_SEG_VALID)))
            blk_recount_segments(q, bio);

      return bio->bi_phys_segments;
}

inline int bio_hw_segments(struct request_queue *q, struct bio *bio)
{
      if (unlikely(!bio_flagged(bio, BIO_SEG_VALID)))
            blk_recount_segments(q, bio);

      return bio->bi_hw_segments;
}

/**
 *    __bio_clone -     clone a bio
 *    @bio: destination bio
 *    @bio_src: bio to clone
 *
 *    Clone a &bio. Caller will own the returned bio, but not
 *    the actual data it points to. Reference count of returned
 *    bio will be one.
 */
void __bio_clone(struct bio *bio, struct bio *bio_src)
{
      struct request_queue *q = bdev_get_queue(bio_src->bi_bdev);

      memcpy(bio->bi_io_vec, bio_src->bi_io_vec,
            bio_src->bi_max_vecs * sizeof(struct bio_vec));

      bio->bi_sector = bio_src->bi_sector;
      bio->bi_bdev = bio_src->bi_bdev;
      bio->bi_flags |= 1 << BIO_CLONED;
      bio->bi_rw = bio_src->bi_rw;
      bio->bi_vcnt = bio_src->bi_vcnt;
      bio->bi_size = bio_src->bi_size;
      bio->bi_idx = bio_src->bi_idx;
      bio_phys_segments(q, bio);
      bio_hw_segments(q, bio);
}

/**
 *    bio_clone   -     clone a bio
 *    @bio: bio to clone
 *    @gfp_mask: allocation priority
 *
 *    Like __bio_clone, only also allocates the returned bio
 */
struct bio *bio_clone(struct bio *bio, gfp_t gfp_mask)
{
      struct bio *b = bio_alloc_bioset(gfp_mask, bio->bi_max_vecs, fs_bio_set);

      if (b) {
            b->bi_destructor = bio_fs_destructor;
            __bio_clone(b, bio);
      }

      return b;
}

/**
 *    bio_get_nr_vecs         - return approx number of vecs
 *    @bdev:  I/O target
 *
 *    Return the approximate number of pages we can send to this target.
 *    There's no guarantee that you will be able to fit this number of pages
 *    into a bio, it does not account for dynamic restrictions that vary
 *    on offset.
 */
int bio_get_nr_vecs(struct block_device *bdev)
{
      struct request_queue *q = bdev_get_queue(bdev);
      int nr_pages;

      nr_pages = ((q->max_sectors << 9) + PAGE_SIZE - 1) >> PAGE_SHIFT;
      if (nr_pages > q->max_phys_segments)
            nr_pages = q->max_phys_segments;
      if (nr_pages > q->max_hw_segments)
            nr_pages = q->max_hw_segments;

      return nr_pages;
}

static int __bio_add_page(struct request_queue *q, struct bio *bio, struct page
                    *page, unsigned int len, unsigned int offset,
                    unsigned short max_sectors)
{
      int retried_segments = 0;
      struct bio_vec *bvec;

      /*
       * cloned bio must not modify vec list
       */
      if (unlikely(bio_flagged(bio, BIO_CLONED)))
            return 0;

      if (((bio->bi_size + len) >> 9) > max_sectors)
            return 0;

      /*
       * For filesystems with a blocksize smaller than the pagesize
       * we will often be called with the same page as last time and
       * a consecutive offset.  Optimize this special case.
       */
      if (bio->bi_vcnt > 0) {
            struct bio_vec *prev = &bio->bi_io_vec[bio->bi_vcnt - 1];

            if (page == prev->bv_page &&
                offset == prev->bv_offset + prev->bv_len) {
                  prev->bv_len += len;
                  if (q->merge_bvec_fn &&
                      q->merge_bvec_fn(q, bio, prev) < len) {
                        prev->bv_len -= len;
                        return 0;
                  }

                  goto done;
            }
      }

      if (bio->bi_vcnt >= bio->bi_max_vecs)
            return 0;

      /*
       * we might lose a segment or two here, but rather that than
       * make this too complex.
       */

      while (bio->bi_phys_segments >= q->max_phys_segments
             || bio->bi_hw_segments >= q->max_hw_segments
             || BIOVEC_VIRT_OVERSIZE(bio->bi_size)) {

            if (retried_segments)
                  return 0;

            retried_segments = 1;
            blk_recount_segments(q, bio);
      }

      /*
       * setup the new entry, we might clear it again later if we
       * cannot add the page
       */
      bvec = &bio->bi_io_vec[bio->bi_vcnt];
      bvec->bv_page = page;
      bvec->bv_len = len;
      bvec->bv_offset = offset;

      /*
       * if queue has other restrictions (eg varying max sector size
       * depending on offset), it can specify a merge_bvec_fn in the
       * queue to get further control
       */
      if (q->merge_bvec_fn) {
            /*
             * merge_bvec_fn() returns number of bytes it can accept
             * at this offset
             */
            if (q->merge_bvec_fn(q, bio, bvec) < len) {
                  bvec->bv_page = NULL;
                  bvec->bv_len = 0;
                  bvec->bv_offset = 0;
                  return 0;
            }
      }

      /* If we may be able to merge these biovecs, force a recount */
      if (bio->bi_vcnt && (BIOVEC_PHYS_MERGEABLE(bvec-1, bvec) ||
          BIOVEC_VIRT_MERGEABLE(bvec-1, bvec)))
            bio->bi_flags &= ~(1 << BIO_SEG_VALID);

      bio->bi_vcnt++;
      bio->bi_phys_segments++;
      bio->bi_hw_segments++;
 done:
      bio->bi_size += len;
      return len;
}

/**
 *    bio_add_pc_page   -     attempt to add page to bio
 *    @q: the target queue
 *    @bio: destination bio
 *    @page: page to add
 *    @len: vec entry length
 *    @offset: vec entry offset
 *
 *    Attempt to add a page to the bio_vec maplist. This can fail for a
 *    number of reasons, such as the bio being full or target block
 *    device limitations. The target block device must allow bio's
 *      smaller than PAGE_SIZE, so it is always possible to add a single
 *      page to an empty bio. This should only be used by REQ_PC bios.
 */
int bio_add_pc_page(struct request_queue *q, struct bio *bio, struct page *page,
                unsigned int len, unsigned int offset)
{
      return __bio_add_page(q, bio, page, len, offset, q->max_hw_sectors);
}

/**
 *    bio_add_page      -     attempt to add page to bio
 *    @bio: destination bio
 *    @page: page to add
 *    @len: vec entry length
 *    @offset: vec entry offset
 *
 *    Attempt to add a page to the bio_vec maplist. This can fail for a
 *    number of reasons, such as the bio being full or target block
 *    device limitations. The target block device must allow bio's
 *      smaller than PAGE_SIZE, so it is always possible to add a single
 *      page to an empty bio.
 */
int bio_add_page(struct bio *bio, struct page *page, unsigned int len,
             unsigned int offset)
{
      struct request_queue *q = bdev_get_queue(bio->bi_bdev);
      return __bio_add_page(q, bio, page, len, offset, q->max_sectors);
}

struct bio_map_data {
      struct bio_vec *iovecs;
      void __user *userptr;
};

static void bio_set_map_data(struct bio_map_data *bmd, struct bio *bio)
{
      memcpy(bmd->iovecs, bio->bi_io_vec, sizeof(struct bio_vec) * bio->bi_vcnt);
      bio->bi_private = bmd;
}

static void bio_free_map_data(struct bio_map_data *bmd)
{
      kfree(bmd->iovecs);
      kfree(bmd);
}

static struct bio_map_data *bio_alloc_map_data(int nr_segs)
{
      struct bio_map_data *bmd = kmalloc(sizeof(*bmd), GFP_KERNEL);

      if (!bmd)
            return NULL;

      bmd->iovecs = kmalloc(sizeof(struct bio_vec) * nr_segs, GFP_KERNEL);
      if (bmd->iovecs)
            return bmd;

      kfree(bmd);
      return NULL;
}

/**
 *    bio_uncopy_user   -     finish previously mapped bio
 *    @bio: bio being terminated
 *
 *    Free pages allocated from bio_copy_user() and write back data
 *    to user space in case of a read.
 */
int bio_uncopy_user(struct bio *bio)
{
      struct bio_map_data *bmd = bio->bi_private;
      const int read = bio_data_dir(bio) == READ;
      struct bio_vec *bvec;
      int i, ret = 0;

      __bio_for_each_segment(bvec, bio, i, 0) {
            char *addr = page_address(bvec->bv_page);
            unsigned int len = bmd->iovecs[i].bv_len;

            if (read && !ret && copy_to_user(bmd->userptr, addr, len))
                  ret = -EFAULT;

            __free_page(bvec->bv_page);
            bmd->userptr += len;
      }
      bio_free_map_data(bmd);
      bio_put(bio);
      return ret;
}

/**
 *    bio_copy_user     -     copy user data to bio
 *    @q: destination block queue
 *    @uaddr: start of user address
 *    @len: length in bytes
 *    @write_to_vm: bool indicating writing to pages or not
 *
 *    Prepares and returns a bio for indirect user io, bouncing data
 *    to/from kernel pages as necessary. Must be paired with
 *    call bio_uncopy_user() on io completion.
 */
struct bio *bio_copy_user(struct request_queue *q, unsigned long uaddr,
                    unsigned int len, int write_to_vm)
{
      unsigned long end = (uaddr + len + PAGE_SIZE - 1) >> PAGE_SHIFT;
      unsigned long start = uaddr >> PAGE_SHIFT;
      struct bio_map_data *bmd;
      struct bio_vec *bvec;
      struct page *page;
      struct bio *bio;
      int i, ret;

      bmd = bio_alloc_map_data(end - start);
      if (!bmd)
            return ERR_PTR(-ENOMEM);

      bmd->userptr = (void __user *) uaddr;

      ret = -ENOMEM;
      bio = bio_alloc(GFP_KERNEL, end - start);
      if (!bio)
            goto out_bmd;

      bio->bi_rw |= (!write_to_vm << BIO_RW);

      ret = 0;
      while (len) {
            unsigned int bytes = PAGE_SIZE;

            if (bytes > len)
                  bytes = len;

            page = alloc_page(q->bounce_gfp | GFP_KERNEL);
            if (!page) {
                  ret = -ENOMEM;
                  break;
            }

            if (bio_add_pc_page(q, bio, page, bytes, 0) < bytes)
                  break;

            len -= bytes;
      }

      if (ret)
            goto cleanup;

      /*
       * success
       */
      if (!write_to_vm) {
            char __user *p = (char __user *) uaddr;

            /*
             * for a write, copy in data to kernel pages
             */
            ret = -EFAULT;
            bio_for_each_segment(bvec, bio, i) {
                  char *addr = page_address(bvec->bv_page);

                  if (copy_from_user(addr, p, bvec->bv_len))
                        goto cleanup;
                  p += bvec->bv_len;
            }
      }

      bio_set_map_data(bmd, bio);
      return bio;
cleanup:
      bio_for_each_segment(bvec, bio, i)
            __free_page(bvec->bv_page);

      bio_put(bio);
out_bmd:
      bio_free_map_data(bmd);
      return ERR_PTR(ret);
}

static struct bio *__bio_map_user_iov(struct request_queue *q,
                              struct block_device *bdev,
                              struct sg_iovec *iov, int iov_count,
                              int write_to_vm)
{
      int i, j;
      int nr_pages = 0;
      struct page **pages;
      struct bio *bio;
      int cur_page = 0;
      int ret, offset;

      for (i = 0; i < iov_count; i++) {
            unsigned long uaddr = (unsigned long)iov[i].iov_base;
            unsigned long len = iov[i].iov_len;
            unsigned long end = (uaddr + len + PAGE_SIZE - 1) >> PAGE_SHIFT;
            unsigned long start = uaddr >> PAGE_SHIFT;

            nr_pages += end - start;
            /*
             * buffer must be aligned to at least hardsector size for now
             */
            if (uaddr & queue_dma_alignment(q))
                  return ERR_PTR(-EINVAL);
      }

      if (!nr_pages)
            return ERR_PTR(-EINVAL);

      bio = bio_alloc(GFP_KERNEL, nr_pages);
      if (!bio)
            return ERR_PTR(-ENOMEM);

      ret = -ENOMEM;
      pages = kcalloc(nr_pages, sizeof(struct page *), GFP_KERNEL);
      if (!pages)
            goto out;

      for (i = 0; i < iov_count; i++) {
            unsigned long uaddr = (unsigned long)iov[i].iov_base;
            unsigned long len = iov[i].iov_len;
            unsigned long end = (uaddr + len + PAGE_SIZE - 1) >> PAGE_SHIFT;
            unsigned long start = uaddr >> PAGE_SHIFT;
            const int local_nr_pages = end - start;
            const int page_limit = cur_page + local_nr_pages;
            
            down_read(&current->mm->mmap_sem);
            ret = get_user_pages(current, current->mm, uaddr,
                             local_nr_pages,
                             write_to_vm, 0, &pages[cur_page], NULL);
            up_read(&current->mm->mmap_sem);

            if (ret < local_nr_pages) {
                  ret = -EFAULT;
                  goto out_unmap;
            }

            offset = uaddr & ~PAGE_MASK;
            for (j = cur_page; j < page_limit; j++) {
                  unsigned int bytes = PAGE_SIZE - offset;

                  if (len <= 0)
                        break;
                  
                  if (bytes > len)
                        bytes = len;

                  /*
                   * sorry...
                   */
                  if (bio_add_pc_page(q, bio, pages[j], bytes, offset) <
                                  bytes)
                        break;

                  len -= bytes;
                  offset = 0;
            }

            cur_page = j;
            /*
             * release the pages we didn't map into the bio, if any
             */
            while (j < page_limit)
                  page_cache_release(pages[j++]);
      }

      kfree(pages);

      /*
       * set data direction, and check if mapped pages need bouncing
       */
      if (!write_to_vm)
            bio->bi_rw |= (1 << BIO_RW);

      bio->bi_bdev = bdev;
      bio->bi_flags |= (1 << BIO_USER_MAPPED);
      return bio;

 out_unmap:
      for (i = 0; i < nr_pages; i++) {
            if(!pages[i])
                  break;
            page_cache_release(pages[i]);
      }
 out:
      kfree(pages);
      bio_put(bio);
      return ERR_PTR(ret);
}

/**
 *    bio_map_user      -     map user address into bio
 *    @q: the struct request_queue for the bio
 *    @bdev: destination block device
 *    @uaddr: start of user address
 *    @len: length in bytes
 *    @write_to_vm: bool indicating writing to pages or not
 *
 *    Map the user space address into a bio suitable for io to a block
 *    device. Returns an error pointer in case of error.
 */
struct bio *bio_map_user(struct request_queue *q, struct block_device *bdev,
                   unsigned long uaddr, unsigned int len, int write_to_vm)
{
      struct sg_iovec iov;

      iov.iov_base = (void __user *)uaddr;
      iov.iov_len = len;

      return bio_map_user_iov(q, bdev, &iov, 1, write_to_vm);
}

/**
 *    bio_map_user_iov - map user sg_iovec table into bio
 *    @q: the struct request_queue for the bio
 *    @bdev: destination block device
 *    @iov: the iovec.
 *    @iov_count: number of elements in the iovec
 *    @write_to_vm: bool indicating writing to pages or not
 *
 *    Map the user space address into a bio suitable for io to a block
 *    device. Returns an error pointer in case of error.
 */
struct bio *bio_map_user_iov(struct request_queue *q, struct block_device *bdev,
                       struct sg_iovec *iov, int iov_count,
                       int write_to_vm)
{
      struct bio *bio;

      bio = __bio_map_user_iov(q, bdev, iov, iov_count, write_to_vm);

      if (IS_ERR(bio))
            return bio;

      /*
       * subtle -- if __bio_map_user() ended up bouncing a bio,
       * it would normally disappear when its bi_end_io is run.
       * however, we need it for the unmap, so grab an extra
       * reference to it
       */
      bio_get(bio);

      return bio;
}

static void __bio_unmap_user(struct bio *bio)
{
      struct bio_vec *bvec;
      int i;

      /*
       * make sure we dirty pages we wrote to
       */
      __bio_for_each_segment(bvec, bio, i, 0) {
            if (bio_data_dir(bio) == READ)
                  set_page_dirty_lock(bvec->bv_page);

            page_cache_release(bvec->bv_page);
      }

      bio_put(bio);
}

/**
 *    bio_unmap_user    -     unmap a bio
 *    @bio:       the bio being unmapped
 *
 *    Unmap a bio previously mapped by bio_map_user(). Must be called with
 *    a process context.
 *
 *    bio_unmap_user() may sleep.
 */
void bio_unmap_user(struct bio *bio)
{
      __bio_unmap_user(bio);
      bio_put(bio);
}

static void bio_map_kern_endio(struct bio *bio, int err)
{
      bio_put(bio);
}


static struct bio *__bio_map_kern(struct request_queue *q, void *data,
                          unsigned int len, gfp_t gfp_mask)
{
      unsigned long kaddr = (unsigned long)data;
      unsigned long end = (kaddr + len + PAGE_SIZE - 1) >> PAGE_SHIFT;
      unsigned long start = kaddr >> PAGE_SHIFT;
      const int nr_pages = end - start;
      int offset, i;
      struct bio *bio;

      bio = bio_alloc(gfp_mask, nr_pages);
      if (!bio)
            return ERR_PTR(-ENOMEM);

      offset = offset_in_page(kaddr);
      for (i = 0; i < nr_pages; i++) {
            unsigned int bytes = PAGE_SIZE - offset;

            if (len <= 0)
                  break;

            if (bytes > len)
                  bytes = len;

            if (bio_add_pc_page(q, bio, virt_to_page(data), bytes,
                            offset) < bytes)
                  break;

            data += bytes;
            len -= bytes;
            offset = 0;
      }

      bio->bi_end_io = bio_map_kern_endio;
      return bio;
}

/**
 *    bio_map_kern      -     map kernel address into bio
 *    @q: the struct request_queue for the bio
 *    @data: pointer to buffer to map
 *    @len: length in bytes
 *    @gfp_mask: allocation flags for bio allocation
 *
 *    Map the kernel address into a bio suitable for io to a block
 *    device. Returns an error pointer in case of error.
 */
struct bio *bio_map_kern(struct request_queue *q, void *data, unsigned int len,
                   gfp_t gfp_mask)
{
      struct bio *bio;

      bio = __bio_map_kern(q, data, len, gfp_mask);
      if (IS_ERR(bio))
            return bio;

      if (bio->bi_size == len)
            return bio;

      /*
       * Don't support partial mappings.
       */
      bio_put(bio);
      return ERR_PTR(-EINVAL);
}

/*
 * bio_set_pages_dirty() and bio_check_pages_dirty() are support functions
 * for performing direct-IO in BIOs.
 *
 * The problem is that we cannot run set_page_dirty() from interrupt context
 * because the required locks are not interrupt-safe.  So what we can do is to
 * mark the pages dirty _before_ performing IO.  And in interrupt context,
 * check that the pages are still dirty.   If so, fine.  If not, redirty them
 * in process context.
 *
 * We special-case compound pages here: normally this means reads into hugetlb
 * pages.  The logic in here doesn't really work right for compound pages
 * because the VM does not uniformly chase down the head page in all cases.
 * But dirtiness of compound pages is pretty meaningless anyway: the VM doesn't
 * handle them at all.  So we skip compound pages here at an early stage.
 *
 * Note that this code is very hard to test under normal circumstances because
 * direct-io pins the pages with get_user_pages().  This makes
 * is_page_cache_freeable return false, and the VM will not clean the pages.
 * But other code (eg, pdflush) could clean the pages if they are mapped
 * pagecache.
 *
 * Simply disabling the call to bio_set_pages_dirty() is a good way to test the
 * deferred bio dirtying paths.
 */

/*
 * bio_set_pages_dirty() will mark all the bio's pages as dirty.
 */
void bio_set_pages_dirty(struct bio *bio)
{
      struct bio_vec *bvec = bio->bi_io_vec;
      int i;

      for (i = 0; i < bio->bi_vcnt; i++) {
            struct page *page = bvec[i].bv_page;

            if (page && !PageCompound(page))
                  set_page_dirty_lock(page);
      }
}

void bio_release_pages(struct bio *bio)
{
      struct bio_vec *bvec = bio->bi_io_vec;
      int i;

      for (i = 0; i < bio->bi_vcnt; i++) {
            struct page *page = bvec[i].bv_page;

            if (page)
                  put_page(page);
      }
}

/*
 * bio_check_pages_dirty() will check that all the BIO's pages are still dirty.
 * If they are, then fine.  If, however, some pages are clean then they must
 * have been written out during the direct-IO read.  So we take another ref on
 * the BIO and the offending pages and re-dirty the pages in process context.
 *
 * It is expected that bio_check_pages_dirty() will wholly own the BIO from
 * here on.  It will run one page_cache_release() against each page and will
 * run one bio_put() against the BIO.
 */

static void bio_dirty_fn(struct work_struct *work);

static DECLARE_WORK(bio_dirty_work, bio_dirty_fn);
static DEFINE_SPINLOCK(bio_dirty_lock);
static struct bio *bio_dirty_list;

/*
 * This runs in process context
 */
static void bio_dirty_fn(struct work_struct *work)
{
      unsigned long flags;
      struct bio *bio;

      spin_lock_irqsave(&bio_dirty_lock, flags);
      bio = bio_dirty_list;
      bio_dirty_list = NULL;
      spin_unlock_irqrestore(&bio_dirty_lock, flags);

      while (bio) {
            struct bio *next = bio->bi_private;

            bio_set_pages_dirty(bio);
            bio_release_pages(bio);
            bio_put(bio);
            bio = next;
      }
}

void bio_check_pages_dirty(struct bio *bio)
{
      struct bio_vec *bvec = bio->bi_io_vec;
      int nr_clean_pages = 0;
      int i;

      for (i = 0; i < bio->bi_vcnt; i++) {
            struct page *page = bvec[i].bv_page;

            if (PageDirty(page) || PageCompound(page)) {
                  page_cache_release(page);
                  bvec[i].bv_page = NULL;
            } else {
                  nr_clean_pages++;
            }
      }

      if (nr_clean_pages) {
            unsigned long flags;

            spin_lock_irqsave(&bio_dirty_lock, flags);
            bio->bi_private = bio_dirty_list;
            bio_dirty_list = bio;
            spin_unlock_irqrestore(&bio_dirty_lock, flags);
            schedule_work(&bio_dirty_work);
      } else {
            bio_put(bio);
      }
}

/**
 * bio_endio - end I/O on a bio
 * @bio:    bio
 * @error:  error, if any
 *
 * Description:
 *   bio_endio() will end I/O on the whole bio. bio_endio() is the
 *   preferred way to end I/O on a bio, it takes care of clearing
 *   BIO_UPTODATE on error. @error is 0 on success, and and one of the
 *   established -Exxxx (-EIO, for instance) error values in case
 *   something went wrong. Noone should call bi_end_io() directly on a
 *   bio unless they own it and thus know that it has an end_io
 *   function.
 **/
void bio_endio(struct bio *bio, int error)
{
      if (error)
            clear_bit(BIO_UPTODATE, &bio->bi_flags);
      else if (!test_bit(BIO_UPTODATE, &bio->bi_flags))
            error = -EIO;

      if (bio->bi_end_io)
            bio->bi_end_io(bio, error);
}

void bio_pair_release(struct bio_pair *bp)
{
      if (atomic_dec_and_test(&bp->cnt)) {
            struct bio *master = bp->bio1.bi_private;

            bio_endio(master, bp->error);
            mempool_free(bp, bp->bio2.bi_private);
      }
}

static void bio_pair_end_1(struct bio *bi, int err)
{
      struct bio_pair *bp = container_of(bi, struct bio_pair, bio1);

      if (err)
            bp->error = err;

      bio_pair_release(bp);
}

static void bio_pair_end_2(struct bio *bi, int err)
{
      struct bio_pair *bp = container_of(bi, struct bio_pair, bio2);

      if (err)
            bp->error = err;

      bio_pair_release(bp);
}

/*
 * split a bio - only worry about a bio with a single page
 * in it's iovec
 */
struct bio_pair *bio_split(struct bio *bi, mempool_t *pool, int first_sectors)
{
      struct bio_pair *bp = mempool_alloc(pool, GFP_NOIO);

      if (!bp)
            return bp;

      blk_add_trace_pdu_int(bdev_get_queue(bi->bi_bdev), BLK_TA_SPLIT, bi,
                        bi->bi_sector + first_sectors);

      BUG_ON(bi->bi_vcnt != 1);
      BUG_ON(bi->bi_idx != 0);
      atomic_set(&bp->cnt, 3);
      bp->error = 0;
      bp->bio1 = *bi;
      bp->bio2 = *bi;
      bp->bio2.bi_sector += first_sectors;
      bp->bio2.bi_size -= first_sectors << 9;
      bp->bio1.bi_size = first_sectors << 9;

      bp->bv1 = bi->bi_io_vec[0];
      bp->bv2 = bi->bi_io_vec[0];
      bp->bv2.bv_offset += first_sectors << 9;
      bp->bv2.bv_len -= first_sectors << 9;
      bp->bv1.bv_len = first_sectors << 9;

      bp->bio1.bi_io_vec = &bp->bv1;
      bp->bio2.bi_io_vec = &bp->bv2;

      bp->bio1.bi_max_vecs = 1;
      bp->bio2.bi_max_vecs = 1;

      bp->bio1.bi_end_io = bio_pair_end_1;
      bp->bio2.bi_end_io = bio_pair_end_2;

      bp->bio1.bi_private = bi;
      bp->bio2.bi_private = pool;

      return bp;
}


/*
 * 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 i;

      for (i = 0; i < BIOVEC_NR_POOLS; i++) {
            struct biovec_slab *bp = bvec_slabs + i;
            mempool_t **bvp = bs->bvec_pools + i;

            *bvp = mempool_create_slab_pool(pool_entries, bp->slab);
            if (!*bvp)
                  return -ENOMEM;
      }
      return 0;
}

static void biovec_free_pools(struct bio_set *bs)
{
      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)
{
      struct bio_set *bs = kzalloc(sizeof(*bs), GFP_KERNEL);

      if (!bs)
            return NULL;

      bs->bio_pool = mempool_create_slab_pool(bio_pool_size, bio_slab);
      if (!bs->bio_pool)
            goto bad;

      if (!biovec_create_pools(bs, bvec_pool_size))
            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);
      }
}

static int __init init_bio(void)
{
      bio_slab = KMEM_CACHE(bio, SLAB_HWCACHE_ALIGN|SLAB_PANIC);

      biovec_init_slabs();

      fs_bio_set = bioset_create(BIO_POOL_SIZE, 2);
      if (!fs_bio_set)
            panic("bio: can't allocate bios\n");

      bio_split_pool = mempool_create_kmalloc_pool(BIO_SPLIT_ENTRIES,
                                         sizeof(struct bio_pair));
      if (!bio_split_pool)
            panic("bio: can't create split pool\n");

      return 0;
}

subsys_initcall(init_bio);

EXPORT_SYMBOL(bio_alloc);
EXPORT_SYMBOL(bio_put);
EXPORT_SYMBOL(bio_free);
EXPORT_SYMBOL(bio_endio);
EXPORT_SYMBOL(bio_init);
EXPORT_SYMBOL(__bio_clone);
EXPORT_SYMBOL(bio_clone);
EXPORT_SYMBOL(bio_phys_segments);
EXPORT_SYMBOL(bio_hw_segments);
EXPORT_SYMBOL(bio_add_page);
EXPORT_SYMBOL(bio_add_pc_page);
EXPORT_SYMBOL(bio_get_nr_vecs);
EXPORT_SYMBOL(bio_map_kern);
EXPORT_SYMBOL(bio_pair_release);
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_bioset);

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