| From affc0ff902d539ebe9bba405d330410314f46e9f Mon Sep 17 00:00:00 2001 |
| From: Filipe Manana <fdmanana@suse.com> |
| Date: Wed, 24 Feb 2016 07:35:05 +0000 |
| Subject: Btrfs: fix race when checking if we can skip fsync'ing an inode |
| |
| From: Filipe Manana <fdmanana@suse.com> |
| |
| commit affc0ff902d539ebe9bba405d330410314f46e9f upstream. |
| |
| 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 <fdmanana@suse.com> |
| Signed-off-by: Chris Mason <clm@fb.com> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| |
| --- |
| fs/btrfs/file.c | 9 +++++---- |
| 1 file changed, 5 insertions(+), 4 deletions(-) |
| |
| --- a/fs/btrfs/file.c |
| +++ b/fs/btrfs/file.c |
| @@ -1996,10 +1996,11 @@ int btrfs_sync_file(struct file *file, l |
| */ |
| 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 |
