Btrfs: Extent based page cache code. This uses an rbtree of extents and tests

instead of buffer heads.

Signed-off-by: Chris Mason <chris.mason@oracle.com>

1 files changed, 306 insertions, 510 deletions

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 504d37dfa6c9..fd4cb65fcf1f 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -121,6 +121,8 @@ void btrfs_read_locked_inode(struct inode *inode)
         switch (inode->i_mode & S_IFMT) {
         case S_IFREG:
                 inode->i_mapping->a_ops = &btrfs_aops;
+                extent_map_tree_init(&BTRFS_I(inode)->extent_tree,
+                                     inode->i_mapping, GFP_NOFS);
                 inode->i_fop = &btrfs_file_operations;
                 inode->i_op = &btrfs_file_inode_operations;
                 break;
@@ -169,7 +171,7 @@ static void fill_inode_item(struct btrfs_inode_item *item,
                                     BTRFS_I(inode)->block_group->key.objectid);
 }
 
-static int btrfs_update_inode(struct btrfs_trans_handle *trans,
+int btrfs_update_inode(struct btrfs_trans_handle *trans,
                               struct btrfs_root *root,
                               struct inode *inode)
 {
@@ -400,6 +402,7 @@ static int btrfs_truncate_in_trans(struct btrfs_trans_handle *trans,
         int found_extent;
         int del_item;
 
+        btrfs_drop_extent_cache(inode, inode->i_size, (u64)-1);
         path = btrfs_alloc_path();
         path->reada = -1;
         BUG_ON(!path);
@@ -511,6 +514,50 @@ error:
         return ret;
 }
 
+static int btrfs_cow_one_page(struct btrfs_trans_handle *trans,
+                              struct inode *inode, struct page *page,
+                              size_t zero_start)
+{
+        char *kaddr;
+        int ret = 0;
+        struct btrfs_root *root = BTRFS_I(inode)->root;
+        u64 alloc_hint = 0;
+        u64 page_start = page->index << PAGE_CACHE_SHIFT;
+        struct btrfs_key ins;
+
+        if (!PagePrivate(page)) {
+                SetPagePrivate(page);
+                set_page_private(page, 1);
+                page_cache_get(page);
+        }
+
+        btrfs_set_trans_block_group(trans, inode);
+
+        ret = btrfs_drop_extents(trans, root, inode,
+                                 page_start, page_start + PAGE_CACHE_SIZE,
+                                 &alloc_hint);
+        if (ret)
+                goto out;
+        ret = btrfs_alloc_extent(trans, root, inode->i_ino, 1, 0,
+                                 alloc_hint, (u64)-1, &ins, 1);
+        if (ret)
+                goto out;
+        ret = btrfs_insert_file_extent(trans, root, inode->i_ino,
+                                       page_start, ins.objectid, 1, 1);
+        if (ret)
+                goto out;
+        SetPageChecked(page);
+        kaddr = kmap(page);
+        if (zero_start != PAGE_CACHE_SIZE) {
+                memset(kaddr + zero_start, 0, PAGE_CACHE_SIZE - zero_start);
+                flush_dcache_page(page);
+        }
+        kunmap(page);
+
+out:
+        return ret;
+}
+
 /*
  * taken from block_truncate_page, but does cow as it zeros out
  * any bytes left in the last page in the file.
@@ -518,16 +565,14 @@ error:
 static int btrfs_truncate_page(struct address_space *mapping, loff_t from)
 {
         struct inode *inode = mapping->host;
+        struct btrfs_root *root = BTRFS_I(inode)->root;
+        struct btrfs_trans_handle *trans;
         unsigned blocksize = 1 << inode->i_blkbits;
         pgoff_t index = from >> PAGE_CACHE_SHIFT;
         unsigned offset = from & (PAGE_CACHE_SIZE-1);
         struct page *page;
-        char *kaddr;
         int ret = 0;
-        struct btrfs_root *root = BTRFS_I(inode)->root;
-        u64 alloc_hint = 0;
-        struct btrfs_key ins;
-        struct btrfs_trans_handle *trans;
+        u64 page_start;
 
         if ((offset & (blocksize - 1)) == 0)
                 goto out;
@@ -536,7 +581,6 @@ static int btrfs_truncate_page(struct address_space *mapping, loff_t from)
         page = grab_cache_page(mapping, index);
         if (!page)
                 goto out;
-
         if (!PageUptodate(page)) {
                 ret = btrfs_readpage(NULL, page);
                 lock_page(page);
@@ -545,37 +589,24 @@ static int btrfs_truncate_page(struct address_space *mapping, loff_t from)
                         goto out;
                 }
         }
+        page_start = page->index << PAGE_CACHE_SHIFT;
+
         mutex_lock(&root->fs_info->fs_mutex);
         trans = btrfs_start_transaction(root, 1);
-        btrfs_set_trans_block_group(trans, inode);
-
-        ret = btrfs_drop_extents(trans, root, inode,
-                                 page->index << PAGE_CACHE_SHIFT,
-                                 (page->index + 1) << PAGE_CACHE_SHIFT,
-                                 &alloc_hint);
-        if (ret)
-                goto out;
-        ret = btrfs_alloc_extent(trans, root, inode->i_ino, 1, 0,
-                                 alloc_hint, (u64)-1, &ins, 1);
-        if (ret)
-                goto out;
-        ret = btrfs_insert_file_extent(trans, root, inode->i_ino,
-                                       page->index << PAGE_CACHE_SHIFT,
-                                       ins.objectid, 1, 1);
-        if (ret)
-                goto out;
-        SetPageChecked(page);
-        kaddr = kmap(page);
-        memset(kaddr + offset, 0, PAGE_CACHE_SIZE - offset);
-        flush_dcache_page(page);
-        ret = btrfs_csum_file_block(trans, root, inode->i_ino,
-                              page->index << PAGE_CACHE_SHIFT,
-                              kaddr, PAGE_CACHE_SIZE);
-        kunmap(page);
+        ret = btrfs_cow_one_page(trans, inode, page, offset);
+        if (!ret) {
+                char *kaddr = kmap(page);
+                ret = btrfs_csum_file_block(trans, root, inode->i_ino,
+                                            page_start, kaddr, PAGE_CACHE_SIZE);
+                kunmap(page);
+        }
+        set_extent_dirty(&BTRFS_I(inode)->extent_tree,
+                         page_start, page_start + PAGE_CACHE_SIZE - 1,
+                         GFP_NOFS);
+        set_page_dirty(page);
         btrfs_end_transaction(trans, root);
         mutex_unlock(&root->fs_info->fs_mutex);
 
-        set_page_dirty(page);
         unlock_page(page);
         page_cache_release(page);
 out:
@@ -1095,6 +1126,8 @@ static int btrfs_create(struct inode *dir, struct dentry *dentry,
                 inode->i_mapping->a_ops = &btrfs_aops;
                 inode->i_fop = &btrfs_file_operations;
                 inode->i_op = &btrfs_file_inode_operations;
+                extent_map_tree_init(&BTRFS_I(inode)->extent_tree,
+                                     inode->i_mapping, GFP_NOFS);
         }
         dir->i_sb->s_dirt = 1;
         btrfs_update_inode_block_group(trans, inode);
@@ -1238,6 +1271,182 @@ out_unlock:
         return err;
 }
 
+struct extent_map *btrfs_get_extent(struct inode *inode, struct page *page,
+                                    size_t page_offset, u64 start, u64 end,
+                                    int create)
+{
+        int ret;
+        int err = 0;
+        u64 blocknr;
+        u64 extent_start = 0;
+        u64 extent_end = 0;
+        u64 objectid = inode->i_ino;
+        u32 found_type;
+        int failed_insert = 0;
+        struct btrfs_path *path;
+        struct btrfs_root *root = BTRFS_I(inode)->root;
+        struct btrfs_file_extent_item *item;
+        struct btrfs_leaf *leaf;
+        struct btrfs_disk_key *found_key;
+        struct extent_map *em = NULL;
+        struct extent_map_tree *em_tree = &BTRFS_I(inode)->extent_tree;
+        struct btrfs_trans_handle *trans = NULL;
+
+        path = btrfs_alloc_path();
+        BUG_ON(!path);
+        mutex_lock(&root->fs_info->fs_mutex);
+
+again:
+        em = lookup_extent_mapping(em_tree, start, end);
+        if (em) {
+                goto out;
+        }
+        if (!em) {
+                em = alloc_extent_map(GFP_NOFS);
+                if (!em) {
+                        err = -ENOMEM;
+                        goto out;
+                }
+                em->start = 0;
+                em->end = 0;
+        }
+        em->bdev = inode->i_sb->s_bdev;
+        ret = btrfs_lookup_file_extent(NULL, root, path,
+                                       objectid, start, 0);
+        if (ret < 0) {
+                err = ret;
+                goto out;
+        }
+
+        if (ret != 0) {
+                if (path->slots[0] == 0)
+                        goto not_found;
+                path->slots[0]--;
+        }
+
+        item = btrfs_item_ptr(btrfs_buffer_leaf(path->nodes[0]), path->slots[0],
+                              struct btrfs_file_extent_item);
+        leaf = btrfs_buffer_leaf(path->nodes[0]);
+        blocknr = btrfs_file_extent_disk_blocknr(item);
+        blocknr += btrfs_file_extent_offset(item);
+
+        /* are we inside the extent that was found? */
+        found_key = &leaf->items[path->slots[0]].key;
+        found_type = btrfs_disk_key_type(found_key);
+        if (btrfs_disk_key_objectid(found_key) != objectid ||
+            found_type != BTRFS_EXTENT_DATA_KEY) {
+                goto not_found;
+        }
+
+        found_type = btrfs_file_extent_type(item);
+        extent_start = btrfs_disk_key_offset(&leaf->items[path->slots[0]].key);
+        if (found_type == BTRFS_FILE_EXTENT_REG) {
+                extent_end = extent_start +
+                       (btrfs_file_extent_num_blocks(item) << inode->i_blkbits);
+                err = 0;
+                if (start < extent_start || start > extent_end) {
+                        em->start = start;
+                        if (start < extent_start) {
+                                em->end = extent_end - 1;
+                        } else {
+                                em->end = end;
+                        }
+                        goto not_found_em;
+                }
+                if (btrfs_file_extent_disk_blocknr(item) == 0) {
+                        em->start = extent_start;
+                        em->end = extent_end - 1;
+                        em->block_start = 0;
+                        em->block_end = 0;
+                        goto insert;
+                }
+                em->block_start = blocknr << inode->i_blkbits;
+                em->block_end = em->block_start +
+                        (btrfs_file_extent_num_blocks(item) <<
+                         inode->i_blkbits) - 1;
+                em->start = extent_start;
+                em->end = extent_end - 1;
+                goto insert;
+        } else if (found_type == BTRFS_FILE_EXTENT_INLINE) {
+                char *ptr;
+                char *map;
+                u32 size;
+
+                size = btrfs_file_extent_inline_len(leaf->items +
+                                                    path->slots[0]);
+                extent_end = extent_start + size;
+                if (start < extent_start || start > extent_end) {
+                        em->start = start;
+                        if (start < extent_start) {
+                                em->end = extent_end - 1;
+                        } else {
+                                em->end = end;
+                        }
+                        goto not_found_em;
+                }
+                em->block_start = EXTENT_MAP_INLINE;
+                em->block_end = EXTENT_MAP_INLINE;
+                em->start = extent_start;
+                em->end = extent_end - 1;
+                if (!page) {
+                        goto insert;
+                }
+                ptr = btrfs_file_extent_inline_start(item);
+                map = kmap(page);
+                memcpy(map + page_offset, ptr, size);
+                flush_dcache_page(result->b_page);
+                kunmap(page);
+                set_extent_uptodate(em_tree, extent_start,
+                                    extent_end, GFP_NOFS);
+                goto insert;
+        } else {
+                printk("unkknown found_type %d\n", found_type);
+                WARN_ON(1);
+        }
+not_found:
+        em->start = start;
+        em->end = end;
+not_found_em:
+        em->block_start = 0;
+        em->block_end = 0;
+insert:
+        btrfs_release_path(root, path);
+        if (em->start > start || em->end < start) {
+                printk("bad extent! %Lu %Lu start %Lu end %Lu\n", em->start, em->end, start, end);
+                WARN_ON(1);
+                err = -EIO;
+                goto out;
+        }
+        ret = add_extent_mapping(em_tree, em);
+        if (ret == -EEXIST) {
+                free_extent_map(em);
+                failed_insert++;
+                if (failed_insert > 5) {
+                        printk("failing to insert %Lu %Lu\n", start, end);
+                        err = -EIO;
+                        goto out;
+                }
+                em = NULL;
+                goto again;
+        }
+        err = 0;
+out:
+        btrfs_free_path(path);
+        if (trans) {
+                ret = btrfs_end_transaction(trans, root);
+                if (!err)
+                        err = ret;
+        }
+        mutex_unlock(&root->fs_info->fs_mutex);
+        if (err) {
+                free_extent_map(em);
+                WARN_ON(1);
+                return ERR_PTR(err);
+        }
+        return em;
+}
+
+
 /*
  * FIBMAP and others want to pass in a fake buffer head.  They need to
  * use BTRFS_GET_BLOCK_NO_DIRECT to make sure we don't try to memcpy
@@ -1398,46 +1607,22 @@ int btrfs_get_block(struct inode *inode, sector_t iblock,
         return err;
 }
 
-static int btrfs_get_block_csum(struct inode *inode, sector_t iblock,
-                                struct buffer_head *result, int create)
-{
-        int ret;
-        struct btrfs_root *root = BTRFS_I(inode)->root;
-        struct page *page = result->b_page;
-        u64 offset = (page->index << PAGE_CACHE_SHIFT) + bh_offset(result);
-        struct btrfs_csum_item *item;
-        struct btrfs_path *path = NULL;
-
-        mutex_lock(&root->fs_info->fs_mutex);
-        ret = btrfs_get_block_lock(inode, iblock, result, create);
-        if (ret)
-                goto out;
-
-        path = btrfs_alloc_path();
-        item = btrfs_lookup_csum(NULL, root, path, inode->i_ino, offset, 0);
-        if (IS_ERR(item)) {
-                ret = PTR_ERR(item);
-                /* a csum that isn't present is a preallocated region. */
-                if (ret == -ENOENT || ret == -EFBIG)
-                        ret = 0;
-                result->b_private = NULL;
-                goto out;
-        }
-        memcpy((char *)&result->b_private, &item->csum, BTRFS_CRC32_SIZE);
-out:
-        if (path)
-                btrfs_free_path(path);
-        mutex_unlock(&root->fs_info->fs_mutex);
-        return ret;
-}
-
 static int btrfs_get_block_bmap(struct inode *inode, sector_t iblock,
                            struct buffer_head *result, int create)
 {
         struct btrfs_root *root = BTRFS_I(inode)->root;
-        mutex_lock(&root->fs_info->fs_mutex);
-        btrfs_get_block_lock(inode, iblock, result, BTRFS_GET_BLOCK_NO_DIRECT);
-        mutex_unlock(&root->fs_info->fs_mutex);
+        u64 start = iblock << inode->i_blkbits;
+        u64 end = start + root->blocksize -1;
+        struct extent_map *em;
+
+        em = btrfs_get_extent(inode, NULL, 0, start, end, 0);
+        if (em && !IS_ERR(em) && em->block_start != EXTENT_MAP_INLINE &&
+            em->block_start != 0) {
+                u64 offset;
+                offset = start - em->start;
+                start = (em->block_start + offset) >> inode->i_blkbits;
+                btrfs_map_bh_to_logical(root, result, start);
+        }
         return 0;
 }
 
@@ -1449,442 +1634,50 @@ static sector_t btrfs_bmap(struct address_space *as, sector_t block)
 static int btrfs_prepare_write(struct file *file, struct page *page,
                                unsigned from, unsigned to)
 {
-        return block_prepare_write(page, from, to, btrfs_get_block);
+        return extent_prepare_write(&BTRFS_I(page->mapping->host)->extent_tree,
+                                    page->mapping->host, page, from, to,
+                                    btrfs_get_extent);
 }
 
-static void buffer_io_error(struct buffer_head *bh)
+int btrfs_readpage(struct file *file, struct page *page)
 {
-        char b[BDEVNAME_SIZE];
-
-        printk(KERN_ERR "Buffer I/O error on device %s, logical block %Lu\n",
-                        bdevname(bh->b_bdev, b),
-                        (unsigned long long)bh->b_blocknr);
+        struct extent_map_tree *tree;
+        tree = &BTRFS_I(page->mapping->host)->extent_tree;
+        return extent_read_full_page(tree, page, btrfs_get_extent);
 }
-
-/*
- * I/O completion handler for block_read_full_page() - pages
- * which come unlocked at the end of I/O.
- */
-static void btrfs_end_buffer_async_read(struct buffer_head *bh, int uptodate)
+static int btrfs_writepage(struct page *page, struct writeback_control *wbc)
 {
-        unsigned long flags;
-        struct buffer_head *first;
-        struct buffer_head *tmp;
-        struct page *page;
-        int page_uptodate = 1;
-        struct inode *inode;
-        int ret;
-
-        BUG_ON(!buffer_async_read(bh));
-
-        page = bh->b_page;
-        inode = page->mapping->host;
-        if (uptodate) {
-                void *kaddr;
-                struct btrfs_root *root = BTRFS_I(page->mapping->host)->root;
-                if (bh->b_private) {
-                        char csum[BTRFS_CRC32_SIZE];
-                        kaddr = kmap_atomic(page, KM_IRQ0);
-                        ret = btrfs_csum_data(root, kaddr + bh_offset(bh),
-                                              bh->b_size, csum);
-                        BUG_ON(ret);
-                        if (memcmp(csum, &bh->b_private, BTRFS_CRC32_SIZE)) {
-                                u64 offset;
-                                offset = (page->index << PAGE_CACHE_SHIFT) +
-                                        bh_offset(bh);
-                                printk("btrfs csum failed ino %lu off %llu\n",
-                                       page->mapping->host->i_ino,
-                                       (unsigned long long)offset);
-                                memset(kaddr + bh_offset(bh), 1, bh->b_size);
-                                flush_dcache_page(page);
-                        }
-                        kunmap_atomic(kaddr, KM_IRQ0);
-                }
-                set_buffer_uptodate(bh);
-        } else {
-                clear_buffer_uptodate(bh);
-                if (printk_ratelimit())
-                        buffer_io_error(bh);
-                SetPageError(page);
-        }
-
-        /*
-         * Be _very_ careful from here on. Bad things can happen if
-         * two buffer heads end IO at almost the same time and both
-         * decide that the page is now completely done.
-         */
-        first = page_buffers(page);
-        local_irq_save(flags);
-        bit_spin_lock(BH_Uptodate_Lock, &first->b_state);
-        clear_buffer_async_read(bh);
-        unlock_buffer(bh);
-        tmp = bh;
-        do {
-                if (!buffer_uptodate(tmp))
-                        page_uptodate = 0;
-                if (buffer_async_read(tmp)) {
-                        BUG_ON(!buffer_locked(tmp));
-                        goto still_busy;
-                }
-                tmp = tmp->b_this_page;
-        } while (tmp != bh);
-        bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
-        local_irq_restore(flags);
-
-        /*
-         * If none of the buffers had errors and they are all
-         * uptodate then we can set the page uptodate.
-         */
-        if (page_uptodate && !PageError(page))
-                SetPageUptodate(page);
-        unlock_page(page);
-        return;
-
-still_busy:
-        bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
-        local_irq_restore(flags);
-        return;
+        struct extent_map_tree *tree;
+        tree = &BTRFS_I(page->mapping->host)->extent_tree;
+        return extent_write_full_page(tree, page, btrfs_get_extent, wbc);
 }
 
-/*
- * Generic "read page" function for block devices that have the normal
- * get_block functionality. This is most of the block device filesystems.
- * Reads the page asynchronously --- the unlock_buffer() and
- * set/clear_buffer_uptodate() functions propagate buffer state into the
- * page struct once IO has completed.
- */
-int btrfs_readpage(struct file *file, struct page *page)
+static int btrfs_releasepage(struct page *page, gfp_t unused_gfp_flags)
 {
-        struct inode *inode = page->mapping->host;
-        sector_t iblock, lblock;
-        struct buffer_head *bh, *head, *arr[MAX_BUF_PER_PAGE];
-        unsigned int blocksize;
-        int nr, i;
-        int fully_mapped = 1;
-
-        BUG_ON(!PageLocked(page));
-        blocksize = 1 << inode->i_blkbits;
-        if (!page_has_buffers(page))
-                create_empty_buffers(page, blocksize, 0);
-        head = page_buffers(page);
-
-        iblock = (sector_t)page->index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
-        lblock = (i_size_read(inode)+blocksize-1) >> inode->i_blkbits;
-        bh = head;
-        nr = 0;
-        i = 0;
-
-        do {
-                if (buffer_uptodate(bh))
-                        continue;
-
-                if (!buffer_mapped(bh)) {
-                        int err = 0;
-
-                        fully_mapped = 0;
-                        if (iblock < lblock) {
-                                WARN_ON(bh->b_size != blocksize);
-                                err = btrfs_get_block_csum(inode, iblock,
-                                                           bh, 0);
-                                if (err)
-                                        SetPageError(page);
-                        }
-                        if (!buffer_mapped(bh)) {
-                                void *kaddr = kmap_atomic(page, KM_USER0);
-                                memset(kaddr + i * blocksize, 0, blocksize);
-                                flush_dcache_page(page);
-                                kunmap_atomic(kaddr, KM_USER0);
-                                if (!err)
-                                        set_buffer_uptodate(bh);
-                                continue;
-                        }
-                        /*
-                         * get_block() might have updated the buffer
-                         * synchronously
-                         */
-                        if (buffer_uptodate(bh))
-                                continue;
-                }
-                arr[nr++] = bh;
-        } while (i++, iblock++, (bh = bh->b_this_page) != head);
-
-        if (fully_mapped)
-                SetPageMappedToDisk(page);
-
-        if (!nr) {
-                /*
-                 * All buffers are uptodate - we can set the page uptodate
-                 * as well. But not if get_block() returned an error.
-                 */
-                if (!PageError(page))
-                        SetPageUptodate(page);
-                unlock_page(page);
-                return 0;
-        }
-
-        /* Stage two: lock the buffers */
-        for (i = 0; i < nr; i++) {
-                bh = arr[i];
-                lock_buffer(bh);
-                bh->b_end_io = btrfs_end_buffer_async_read;
-                set_buffer_async_read(bh);
-        }
-
-        /*
-         * Stage 3: start the IO.  Check for uptodateness
-         * inside the buffer lock in case another process reading
-         * the underlying blockdev brought it uptodate (the sct fix).
-         */
-        for (i = 0; i < nr; i++) {
-                bh = arr[i];
-                if (buffer_uptodate(bh))
-                        btrfs_end_buffer_async_read(bh, 1);
-                else
-                        submit_bh(READ, bh);
-        }
-        return 0;
-}
-
-/*
- * Aside from a tiny bit of packed file data handling, this is the
- * same as the generic code.
- *
- * While block_write_full_page is writing back the dirty buffers under
- * the page lock, whoever dirtied the buffers may decide to clean them
- * again at any time.  We handle that by only looking at the buffer
- * state inside lock_buffer().
- *
- * If block_write_full_page() is called for regular writeback
- * (wbc->sync_mode == WB_SYNC_NONE) then it will redirty a page which has a
- * locked buffer.   This only can happen if someone has written the buffer
- * directly, with submit_bh().  At the address_space level PageWriteback
- * prevents this contention from occurring.
- */
-static int __btrfs_write_full_page(struct inode *inode, struct page *page,
-                                   struct writeback_control *wbc)
-{
-        int err;
-        sector_t block;
-        sector_t last_block;
-        struct buffer_head *bh, *head;
-        const unsigned blocksize = 1 << inode->i_blkbits;
-        int nr_underway = 0;
-        struct btrfs_root *root = BTRFS_I(inode)->root;
-
-        BUG_ON(!PageLocked(page));
-
-        last_block = (i_size_read(inode) - 1) >> inode->i_blkbits;
-
-        /* no csumming allowed when from PF_MEMALLOC */
-        if (current->flags & PF_MEMALLOC) {
-                redirty_page_for_writepage(wbc, page);
-                unlock_page(page);
-                return 0;
-        }
+        struct extent_map_tree *tree;
+        int ret;
 
-        if (!page_has_buffers(page)) {
-                create_empty_buffers(page, blocksize,
-                                        (1 << BH_Dirty)|(1 << BH_Uptodate));
+        if (page->private != 1) {
+                WARN_ON(1);
+                return try_to_free_buffers(page);
         }
-
-        /*
-         * Be very careful.  We have no exclusion from __set_page_dirty_buffers
-         * here, and the (potentially unmapped) buffers may become dirty at
-         * any time.  If a buffer becomes dirty here after we've inspected it
-         * then we just miss that fact, and the page stays dirty.
-         *
-         * Buffers outside i_size may be dirtied by __set_page_dirty_buffers;
-         * handle that here by just cleaning them.
-         */
-
-        block = (sector_t)page->index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
-        head = page_buffers(page);
-        bh = head;
-
-        /*
-         * Get all the dirty buffers mapped to disk addresses and
-         * handle any aliases from the underlying blockdev's mapping.
-         */
-        do {
-                if (block > last_block) {
-                        /*
-                         * mapped buffers outside i_size will occur, because
-                         * this page can be outside i_size when there is a
-                         * truncate in progress.
-                         */
-                        /*
-                         * The buffer was zeroed by block_write_full_page()
-                         */
-                        clear_buffer_dirty(bh);
-                        set_buffer_uptodate(bh);
-                } else if (!buffer_mapped(bh) && buffer_dirty(bh)) {
-                        WARN_ON(bh->b_size != blocksize);
-                        err = btrfs_get_block(inode, block, bh, 0);
-                        if (err) {
-                                goto recover;
-                        }
-                        if (buffer_new(bh)) {
-                                /* blockdev mappings never come here */
-                                clear_buffer_new(bh);
-                        }
-                }
-                bh = bh->b_this_page;
-                block++;
-        } while (bh != head);
-
-        do {
-                if (!buffer_mapped(bh))
-                        continue;
-                /*
-                 * If it's a fully non-blocking write attempt and we cannot
-                 * lock the buffer then redirty the page.  Note that this can
-                 * potentially cause a busy-wait loop from pdflush and kswapd
-                 * activity, but those code paths have their own higher-level
-                 * throttling.
-                 */
-                if (wbc->sync_mode != WB_SYNC_NONE || !wbc->nonblocking) {
-                        lock_buffer(bh);
-                } else if (test_set_buffer_locked(bh)) {
-                        redirty_page_for_writepage(wbc, page);
-                        continue;
-                }
-                if (test_clear_buffer_dirty(bh) && bh->b_blocknr != 0) {
-                        struct btrfs_trans_handle *trans;
-                        int ret;
-                        u64 off = page->index << PAGE_CACHE_SHIFT;
-                        char *kaddr;
-
-                        off += bh_offset(bh);
-                        mutex_lock(&root->fs_info->fs_mutex);
-                        trans = btrfs_start_transaction(root, 1);
-                        btrfs_set_trans_block_group(trans, inode);
-                        kaddr = kmap(page);
-                        btrfs_csum_file_block(trans, root, inode->i_ino,
-                                                    off, kaddr + bh_offset(bh),
-                                                    bh->b_size);
-                        kunmap(page);
-                        ret = btrfs_end_transaction(trans, root);
-                        BUG_ON(ret);
-                        mutex_unlock(&root->fs_info->fs_mutex);
-                        mark_buffer_async_write(bh);
-                } else {
-                        unlock_buffer(bh);
-                }
-        } while ((bh = bh->b_this_page) != head);
-
-        /*
-         * The page and its buffers are protected by PageWriteback(), so we can
-         * drop the bh refcounts early.
-         */
-        BUG_ON(PageWriteback(page));
-        set_page_writeback(page);
-
-        do {
-                struct buffer_head *next = bh->b_this_page;
-                if (buffer_async_write(bh)) {
-                        submit_bh(WRITE, bh);
-                        nr_underway++;
-                }
-                bh = next;
-        } while (bh != head);
-        unlock_page(page);
-
-        err = 0;
-done:
-        if (nr_underway == 0) {
-                /*
-                 * The page was marked dirty, but the buffers were
-                 * clean.  Someone wrote them back by hand with
-                 * ll_rw_block/submit_bh.  A rare case.
-                 */
-                int uptodate = 1;
-                do {
-                        if (!buffer_uptodate(bh)) {
-                                uptodate = 0;
-                                break;
-                        }
-                        bh = bh->b_this_page;
-                } while (bh != head);
-                if (uptodate)
-                        SetPageUptodate(page);
-                end_page_writeback(page);
+        tree = &BTRFS_I(page->mapping->host)->extent_tree;
+        ret = try_release_extent_mapping(tree, page);
+        if (ret == 1) {
+                ClearPagePrivate(page);
+                set_page_private(page, 0);
+                page_cache_release(page);
         }
-        return err;
-
-recover:
-        /*
-         * ENOSPC, or some other error.  We may already have added some
-         * blocks to the file, so we need to write these out to avoid
-         * exposing stale data.
-         * The page is currently locked and not marked for writeback
-         */
-        bh = head;
-        /* Recovery: lock and submit the mapped buffers */
-        do {
-                if (buffer_mapped(bh) && buffer_dirty(bh)) {
-                        lock_buffer(bh);
-                        mark_buffer_async_write(bh);
-                } else {
-                        /*
-                         * The buffer may have been set dirty during
-                         * attachment to a dirty page.
-                         */
-                        clear_buffer_dirty(bh);
-                }
-        } while ((bh = bh->b_this_page) != head);
-        SetPageError(page);
-        BUG_ON(PageWriteback(page));
-        set_page_writeback(page);
-        do {
-                struct buffer_head *next = bh->b_this_page;
-                if (buffer_async_write(bh)) {
-                        clear_buffer_dirty(bh);
-                        submit_bh(WRITE, bh);
-                        nr_underway++;
-                }
-                bh = next;
-        } while (bh != head);
-        unlock_page(page);
-        goto done;
+        return ret;
 }
 
-static int btrfs_writepage(struct page *page, struct writeback_control *wbc)
+static void btrfs_invalidatepage(struct page *page, unsigned long offset)
 {
-        struct inode * const inode = page->mapping->host;
-        loff_t i_size = i_size_read(inode);
-        const pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT;
-        unsigned offset;
-        void *kaddr;
-
-        /* Is the page fully inside i_size? */
-        if (page->index < end_index)
-                return __btrfs_write_full_page(inode, page, wbc);
-
-        /* Is the page fully outside i_size? (truncate in progress) */
-        offset = i_size & (PAGE_CACHE_SIZE-1);
-        if (page->index >= end_index+1 || !offset) {
-                /*
-                 * The page may have dirty, unmapped buffers.  For example,
-                 * they may have been added in ext3_writepage().  Make them
-                 * freeable here, so the page does not leak.
-                 */
-                block_invalidatepage(page, 0);
-                unlock_page(page);
-                return 0; /* don't care */
-        }
+        struct extent_map_tree *tree;
 
-        /*
-         * The page straddles i_size.  It must be zeroed out on each and every
-         * writepage invokation because it may be mmapped.  "A file is mapped
-         * in multiples of the page size.  For a file that is not a multiple of
-         * the  page size, the remaining memory is zeroed when mapped, and
-         * writes to that region are not written out to the file."
-         */
-        kaddr = kmap_atomic(page, KM_USER0);
-        memset(kaddr + offset, 0, PAGE_CACHE_SIZE - offset);
-        flush_dcache_page(page);
-        kunmap_atomic(kaddr, KM_USER0);
-        return __btrfs_write_full_page(inode, page, wbc);
+        tree = &BTRFS_I(page->mapping->host)->extent_tree;
+        extent_invalidatepage(tree, page, offset);
+        btrfs_releasepage(page, GFP_NOFS);
 }
 
 /*
@@ -1905,28 +1698,39 @@ static int btrfs_writepage(struct page *page, struct writeback_control *wbc)
 int btrfs_page_mkwrite(struct vm_area_struct *vma, struct page *page)
 {
         struct inode *inode = vma->vm_file->f_path.dentry->d_inode;
+        struct btrfs_root *root = BTRFS_I(inode)->root;
+        struct btrfs_trans_handle *trans;
         unsigned long end;
         loff_t size;
         int ret = -EINVAL;
+        u64 page_start;
 
         lock_page(page);
         wait_on_page_writeback(page);
         size = i_size_read(inode);
+        page_start = page->index << PAGE_CACHE_SHIFT;
+
         if ((page->mapping != inode->i_mapping) ||
-            ((page->index << PAGE_CACHE_SHIFT) > size)) {
+            (page_start > size)) {
                 /* page got truncated out from underneath us */
                 goto out_unlock;
         }
 
         /* page is wholly or partially inside EOF */
-        if (((page->index + 1) << PAGE_CACHE_SHIFT) > size)
+        if (page_start + PAGE_CACHE_SIZE > size)
                 end = size & ~PAGE_CACHE_MASK;
         else
                 end = PAGE_CACHE_SIZE;
 
-        ret = btrfs_prepare_write(NULL, page, 0, end);
-        if (!ret)
-                ret = btrfs_commit_write(NULL, page, 0, end);
+        mutex_lock(&root->fs_info->fs_mutex);
+        trans = btrfs_start_transaction(root, 1);
+        ret = btrfs_cow_one_page(trans, inode, page, end);
+        btrfs_end_transaction(trans, root);
+        mutex_unlock(&root->fs_info->fs_mutex);
+        set_extent_dirty(&BTRFS_I(inode)->extent_tree,
+                         page_start, page_start + PAGE_CACHE_SIZE - 1,
+                         GFP_NOFS);
+        set_page_dirty(page);
 
 out_unlock:
         unlock_page(page);
@@ -1962,21 +1766,8 @@ static void btrfs_truncate(struct inode *inode)
 int btrfs_commit_write(struct file *file, struct page *page,
                        unsigned from, unsigned to)
 {
-        struct inode *inode = page->mapping->host;
-        struct buffer_head *bh;
-        loff_t pos = ((loff_t)page->index << PAGE_CACHE_SHIFT) + to;
-
-        SetPageUptodate(page);
-        bh = page_buffers(page);
-        set_buffer_uptodate(bh);
-        if (buffer_mapped(bh) && bh->b_blocknr != 0) {
-                set_page_dirty(page);
-        }
-        if (pos > inode->i_size) {
-                i_size_write(inode, pos);
-                mark_inode_dirty(inode);
-        }
-        return 0;
+        return extent_commit_write(&BTRFS_I(page->mapping->host)->extent_tree,
+                                   page->mapping->host, page, from, to);
 }
 
 static int create_subvol(struct btrfs_root *root, char *name, int namelen)
@@ -2471,6 +2262,8 @@ static int btrfs_symlink(struct inode *dir, struct dentry *dentry,
                 inode->i_mapping->a_ops = &btrfs_aops;
                 inode->i_fop = &btrfs_file_operations;
                 inode->i_op = &btrfs_file_inode_operations;
+                extent_map_tree_init(&BTRFS_I(inode)->extent_tree,
+                                     inode->i_mapping, GFP_NOFS);
         }
         dir->i_sb->s_dirt = 1;
         btrfs_update_inode_block_group(trans, inode);
@@ -2553,6 +2346,9 @@ static struct address_space_operations btrfs_aops = {
         .prepare_write  = btrfs_prepare_write,
         .commit_write   = btrfs_commit_write,
         .bmap           = btrfs_bmap,
+        .invalidatepage = btrfs_invalidatepage,
+        .releasepage    = btrfs_releasepage,
+        .set_page_dirty = __set_page_dirty_nobuffers,
 };
 
 static struct address_space_operations btrfs_symlink_aops = {