Btrfs: cow file extents before writing

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

1 files changed, 18 insertions, 2 deletions

diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index 3e8bfb0e5d7e..91aa1b4c50af 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -1020,7 +1020,7 @@ static int btrfs_get_block_lock(struct inode *inode, sector_t iblock,
 
         ret = btrfs_lookup_file_extent(trans, root, path,
                                        inode->i_ino,
-                                       iblock << inode->i_blkbits, 0);
+                                       iblock << inode->i_blkbits, 1);
         if (ret < 0) {
                 err = ret;
                 goto out;
@@ -1040,9 +1040,25 @@ static int btrfs_get_block_lock(struct inode *inode, sector_t iblock,
         blocknr = btrfs_file_extent_disk_blocknr(item);
         blocknr += btrfs_file_extent_offset(item);
 
-        /* exact match found, use it */
+        /* exact match found, use it, FIXME, deal with extents
+         * other than the page size
+         */
         if (ret == 0) {
                 err = 0;
+                BUG_ON(btrfs_file_extent_disk_num_blocks(item) != 1);
+                if (btrfs_file_extent_generation(item) != trans->transid) {
+                        struct btrfs_key ins;
+                        ret = btrfs_alloc_extent(trans, root, 1,
+                                                 blocknr, (u64)-1, &ins);
+                        BUG_ON(ret);
+                        btrfs_set_file_extent_disk_blocknr(item, ins.objectid);
+                        mark_buffer_dirty(path->nodes[0]);
+                        ret = btrfs_free_extent(trans, root,
+                                                blocknr, 1, 0);
+                        BUG_ON(ret);
+                        blocknr = ins.objectid;
+
+                }
                 map_bh(result, inode->i_sb, blocknr);
                 goto out;
         }