On 26.03.19 г. 12:49 ч., fdman...@kernel.org wrote:
> From: Filipe Manana <fdman...@suse.com>
>
> Whan a filesystem is mounted with the nologreplay mount option, which
> requires it to be mounted in RO mode as well, we can not allow discard on
> free space inside block groups, because log trees refer to extents that
> are not pinned in a block group's free space cache (pinning the extents is
> precisely the first phase of replaying a log tree).
>
> So do not allow the fitrim ioctl to do anything when the filesystem is
> mounted with the nologreplay option, because later it can be mounted RW
> without that option, which causes log replay to happen and result in
> either a failure to replay the log trees (leading to a mount failure), a
> crash or some silent corruption.
>
> Reported-by: Darrick J. Wong <darrick.w...@oracle.com>
> Signed-off-by: Filipe Manana <fdman...@suse.com>
Does it make sense to make the check a bit more specific and only return
EROFS when NOLOGREPLAY and the log tree has non-null generation?
In any case:
Reviewed-by: Nikolay Borisov <nbori...@suse.com>
> ---
> fs/btrfs/ioctl.c | 10 ++++++++++
> 1 file changed, 10 insertions(+)
>
> diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
> index 494f0f10d70e..01808934d21f 100644
> --- a/fs/btrfs/ioctl.c
> +++ b/fs/btrfs/ioctl.c
> @@ -501,6 +501,16 @@ static noinline int btrfs_ioctl_fitrim(struct file
> *file, void __user *arg)
> if (!capable(CAP_SYS_ADMIN))
> return -EPERM;
>
> + /*
> + * If the fs is mounted with nologreplay, which requires it to be
> + * mounted in RO mode as well, we can not allow discard on free space
> + * inside block groups, because log trees refer to extents that are not
> + * pinned in a block group's free space cache (pinning the extents is
> + * precisely the first phase of replaying a log tree).
> + */
> + if (btrfs_test_opt(fs_info, NOLOGREPLAY))
> + return -EROFS;
> +
> rcu_read_lock();
> list_for_each_entry_rcu(device, &fs_info->fs_devices->devices,
> dev_list) {
>
