From 663dfbb07774e0fe1049e8db3054a08500122f18 Mon Sep 17 00:00:00 2001 From: Filipe Manana Date: Mon, 13 Oct 2014 12:28:37 +0100 Subject: Btrfs: deal with convert_extent_bit errors to avoid fs corruption When committing a transaction or a log, we look for btree extents that need to be durably persisted by searching for ranges in a io tree that have some bits set (EXTENT_DIRTY or EXTENT_NEW). We then attempt to clear those bits and set the EXTENT_NEED_WAIT bit, with calls to the function convert_extent_bit, and then start writeback for the extents. That function however can return an error (at the moment only -ENOMEM is possible, specially when it does GFP_ATOMIC allocation requests through alloc_extent_state_atomic) - that means the ranges didn't got the EXTENT_NEED_WAIT bit set (or at least not for the whole range), which in turn means a call to btrfs_wait_marked_extents() won't find those ranges for which we started writeback, causing a transaction commit or a log commit to persist a new superblock without waiting for the writeback of extents in that range to finish first. Therefore if a crash happens after persisting the new superblock and before writeback finishes, we have a superblock pointing to roots that weren't fully persisted or roots that point to nodes or leafs that weren't fully persisted, causing all sorts of unexpected/bad behaviour as we endup reading garbage from disk or the content of some node/leaf from a past generation that got cowed or deleted and is no longer valid (for this later case we end up getting error messages like "parent transid verify failed on X wanted Y found Z" when reading btree nodes/leafs from disk). Signed-off-by: Filipe Manana Signed-off-by: Chris Mason --- fs/btrfs/transaction.h | 2 -- 1 file changed, 2 deletions(-) (limited to 'fs/btrfs/transaction.h') diff --git a/fs/btrfs/transaction.h b/fs/btrfs/transaction.h index d8f40e1a5d2d..b3f5b40aab22 100644 --- a/fs/btrfs/transaction.h +++ b/fs/btrfs/transaction.h @@ -145,8 +145,6 @@ struct btrfs_trans_handle *btrfs_attach_transaction_barrier( struct btrfs_root *root); struct btrfs_trans_handle *btrfs_start_ioctl_transaction(struct btrfs_root *root); int btrfs_wait_for_commit(struct btrfs_root *root, u64 transid); -int btrfs_write_and_wait_transaction(struct btrfs_trans_handle *trans, - struct btrfs_root *root); void btrfs_add_dead_root(struct btrfs_root *root); int btrfs_defrag_root(struct btrfs_root *root); -- cgit v1.2.3