From affc0ff902d539ebe9bba405d330410314f46e9f Mon Sep 17 00:00:00 2001 From: Filipe Manana Date: Wed, 24 Feb 2016 07:35:05 +0000 Subject: [PATCH] Btrfs: fix race when checking if we can skip fsync'ing an inode If we're about to do a fast fsync for an inode and btrfs_inode_in_log() returns false, it's possible that we had an ordered extent in progress (btrfs_finish_ordered_io() not run yet) when we noticed that the inode's last_trans field was not greater than the id of the last committed transaction, but shortly after, before we checked if there were any ongoing ordered extents, the ordered extent had just completed and removed itself from the inode's ordered tree, in which case we end up not logging the inode, losing some data if a power failure or crash happens after the fsync handler returns and before the transaction is committed. Fix this by checking first if there are any ongoing ordered extents before comparing the inode's last_trans with the id of the last committed transaction - when it completes, an ordered extent always updates the inode's last_trans before it removes itself from the inode's ordered tree (at btrfs_finish_ordered_io()). Signed-off-by: Filipe Manana Signed-off-by: Chris Mason --- fs/btrfs/file.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c index 03de2466db23..d23d10024cf0 100644 --- a/fs/btrfs/file.c +++ b/fs/btrfs/file.c @@ -2017,10 +2017,11 @@ int btrfs_sync_file(struct file *file, loff_t start, loff_t end, int datasync) */ smp_mb(); if (btrfs_inode_in_log(inode, root->fs_info->generation) || - (BTRFS_I(inode)->last_trans <= - root->fs_info->last_trans_committed && - (full_sync || - !btrfs_have_ordered_extents_in_range(inode, start, len)))) { + (full_sync && BTRFS_I(inode)->last_trans <= + root->fs_info->last_trans_committed) || + (!btrfs_have_ordered_extents_in_range(inode, start, len) && + BTRFS_I(inode)->last_trans + <= root->fs_info->last_trans_committed)) { /* * We'v had everything committed since the last time we were * modified so clear this flag in case it was set for whatever -- 2.20.1