Re: [PATCH] ext4: properly check for dirty state in ext4_inode_datasync_dirty()

harshad shirwadkar
2020-10-26T22:28:58Z

Thanks Andrea for catching and sending out a fix for this.

On Sat, Oct 24, 2020 at 7:01 AM Andrea Righi <andrea.righi@canonical.com> wrote:
>
> ext4_inode_datasync_dirty() needs to return 'true' if the inode is
> dirty, 'false' otherwise, but the logic seems to be incorrectly changed
> by commit aa75f4d3daae ("ext4: main fast-commit commit path").
>
> This introduces a problem with swap files that are always failing to be
> activated, showing this error in dmesg:
>
> [ 34.406479] swapon: file is not committed
>
> Simple test case to reproduce the problem:
>
> # fallocate -l 8G swapfile
> # chmod 0600 swapfile
> # mkswap swapfile
> # swapon swapfile
>
> Fix the logic to return the proper state of the inode.
>
> Link: https://lore.kernel.org/lkml/20201024131333.GA32124@xps-13-7390
> Fixes: aa75f4d3daae ("ext4: main fast-commit commit path")
> Signed-off-by: Andrea Righi <andrea.righi@canonical.com>
> ---
> fs/ext4/inode.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index 03c2253005f0..a890a17ab7e1 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -3308,8 +3308,8 @@ static bool ext4_inode_datasync_dirty(struct inode *inode)
> if (journal) {
> if (jbd2_transaction_committed(journal,
> EXT4_I(inode)->i_datasync_tid))
> - return true;
> - return atomic_read(&EXT4_SB(inode->i_sb)->s_fc_subtid) >=
> + return false;
> + return atomic_read(&EXT4_SB(inode->i_sb)->s_fc_subtid) <
> EXT4_I(inode)->i_fc_committed_subtid;
In addition, the above condition should only be checked if fast
commits are enabled. So, in effect this overall condition will look
like this:

if (journal) {
if (jbd2_transaction_committed(journal, EXT4_I(inode)->i_datasync_tid))
return false;
if (test_opt2(sb, JOURNAL_FAST_COMMIT))
return atomic_read(&EXT4_SB(inode->i_sb)->s_fc_subtid) <
EXT4_I(inode)->i_fc_committed_subtid;
return true;
}

Thanks,
Harshad

> }
>
> --
> 2.27.0
>