Btrfs: only cow in get_block when create==1

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

1 files changed, 3 insertions, 2 deletions

diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index 91aa1b4c50af..a3183972f310 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, 1);
+                                       iblock << inode->i_blkbits, create);
         if (ret < 0) {
                 err = ret;
                 goto out;
@@ -1046,7 +1046,8 @@ static int btrfs_get_block_lock(struct inode *inode, sector_t iblock,
         if (ret == 0) {
                 err = 0;
                 BUG_ON(btrfs_file_extent_disk_num_blocks(item) != 1);
-                if (btrfs_file_extent_generation(item) != trans->transid) {
+                if (create &&
+                    btrfs_file_extent_generation(item) != trans->transid) {
                         struct btrfs_key ins;
                         ret = btrfs_alloc_extent(trans, root, 1,
                                                  blocknr, (u64)-1, &ins);