On 2019/3/26 下午8:17, Nikolay Borisov wrote:
>
>
> 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?
To me fstrim is a WRITE operation, why it is allowed even in RO mount?
Thanks,
Qu
>
> 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) {
>>
