Btrfs: Init address_space->writeback_index properly

The writeback_index field is used by write_cache_pages to pick up where
writeback on a given inode left off.  But, it is never set to a sane
value, so writeback can often start at a random offset in the file.

Kernels 2.6.28 and higher will have this fixed, but for everyone else,
we also fill in the value in btrfs.

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

1 files changed, 4 insertions, 0 deletions

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index a26d365111e5..33b990878d84 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -1833,6 +1833,7 @@ static int btrfs_init_locked_inode(struct inode *inode, void *p)
         inode->i_ino = args->ino;
         BTRFS_I(inode)->root = args->root;
         BTRFS_I(inode)->delalloc_bytes = 0;
+        inode->i_mapping->writeback_index = 0;
         BTRFS_I(inode)->disk_i_size = 0;
         BTRFS_I(inode)->index_cnt = (u64)-1;
         extent_map_tree_init(&BTRFS_I(inode)->extent_tree, GFP_NOFS);
@@ -2239,6 +2240,7 @@ static struct inode *btrfs_new_inode(struct btrfs_trans_handle *trans,
         mutex_init(&BTRFS_I(inode)->csum_mutex);
         mutex_init(&BTRFS_I(inode)->extent_mutex);
         BTRFS_I(inode)->delalloc_bytes = 0;
+        inode->i_mapping->writeback_index = 0;
         BTRFS_I(inode)->disk_i_size = 0;
         BTRFS_I(inode)->root = root;
 
@@ -2486,6 +2488,7 @@ static int btrfs_create(struct inode *dir, struct dentry *dentry,
                 mutex_init(&BTRFS_I(inode)->extent_mutex);
                 BTRFS_I(inode)->delalloc_bytes = 0;
                 BTRFS_I(inode)->disk_i_size = 0;
+                inode->i_mapping->writeback_index = 0;
                 BTRFS_I(inode)->io_tree.ops = &btrfs_extent_io_ops;
                 btrfs_ordered_inode_tree_init(&BTRFS_I(inode)->ordered_tree);
         }
@@ -3549,6 +3552,7 @@ static int btrfs_symlink(struct inode *dir, struct dentry *dentry,
                 mutex_init(&BTRFS_I(inode)->extent_mutex);
                 BTRFS_I(inode)->delalloc_bytes = 0;
                 BTRFS_I(inode)->disk_i_size = 0;
+                inode->i_mapping->writeback_index = 0;
                 BTRFS_I(inode)->io_tree.ops = &btrfs_extent_io_ops;
                 btrfs_ordered_inode_tree_init(&BTRFS_I(inode)->ordered_tree);
         }