From c36047d729a3fa080dd194b20b684cc9fe73e90c Mon Sep 17 00:00:00 2001 From: Yan Zheng Date: Wed, 12 Nov 2008 14:19:50 -0500 Subject: Btrfs: Fix race in btrfs_mark_extent_written When extent needs to be split, btrfs_mark_extent_written truncates the extent first, then inserts a new extent and increases the reference count. The race happens if someone else deletes the old extent before the new extent is inserted. The fix here is increase the reference count in advance. This race is similar to the race in btrfs_drop_extents that was recently fixed. Signed-off-by: Yan Zheng --- fs/btrfs/file.c | 18 ++++++++++++++---- 1 file changed, 14 insertions(+), 4 deletions(-) (limited to 'fs') diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c index 934bc094bf1..1e8c024c69c 100644 --- a/fs/btrfs/file.c +++ b/fs/btrfs/file.c @@ -746,6 +746,7 @@ int btrfs_mark_extent_written(struct btrfs_trans_handle *trans, u64 other_end; u64 split = start; u64 locked_end = end; + u64 orig_parent; int extent_type; int split_end = 1; int ret; @@ -890,6 +891,12 @@ again: } btrfs_mark_buffer_dirty(leaf); + + orig_parent = leaf->start; + ret = btrfs_inc_extent_ref(trans, root, bytenr, num_bytes, + orig_parent, root->root_key.objectid, + trans->transid, inode->i_ino); + BUG_ON(ret); btrfs_release_path(root, path); key.offset = start; @@ -910,10 +917,13 @@ again: btrfs_set_file_extent_encryption(leaf, fi, 0); btrfs_set_file_extent_other_encoding(leaf, fi, 0); - ret = btrfs_inc_extent_ref(trans, root, bytenr, num_bytes, - leaf->start, root->root_key.objectid, - trans->transid, inode->i_ino); - BUG_ON(ret); + if (orig_parent != leaf->start) { + ret = btrfs_update_extent_ref(trans, root, bytenr, + orig_parent, leaf->start, + root->root_key.objectid, + trans->transid, inode->i_ino); + BUG_ON(ret); + } done: btrfs_mark_buffer_dirty(leaf); btrfs_release_path(root, path); -- cgit v1.2.3