On Wed, Apr 19, 2017 at 11:07:45PM +0200, Adam Borowski wrote:
> Too many people come complaining about losing their data -- and indeed,
> there's no warning outside a wiki and the mailing list tribal knowledge.
> Message severity chosen for consistency with XFS -- "alert" makes dmesg
> produce nice red background which should get the point across.
...
> I intend to ask for inclusion of this one (or an equivalent) in 4.9, either
> in Debian or via GregKH -- while for us kernels "that old" are history,
> regular users expect stable releases to be free of known serious data loss
> bugs.
Hi guys, could you please comment? While there's only relatively little
urgency for mainline (heck, it'd be best if the warning was not needed at
all!), there's a Debian release close by, and it's be grossly inresponsible
to not let people know that a feature advertised in the documentation is in
an unusable state (especially as of 4.9). For you, filesystem developers,
a way of thinking that "the user should do research" might be acceptable,
but once it filters down to a stable release, the user expects no known
serious bugs.
And here the severity is "critical -- causes serious data loss".
> diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
> index e54844767fe5..e7f91f70e149 100644
> --- a/fs/btrfs/disk-io.c
> +++ b/fs/btrfs/disk-io.c
> @@ -3083,6 +3083,14 @@ int open_ctree(struct super_block *sb,
> btrfs_set_opt(fs_info->mount_opt, SSD);
> }
>
> + if ((fs_info->avail_data_alloc_bits |
> + fs_info->avail_metadata_alloc_bits |
> + fs_info->avail_system_alloc_bits) &
> + BTRFS_BLOCK_GROUP_RAID56_MASK) {
> + btrfs_alert(fs_info,
> + "btrfs RAID5/6 is EXPERIMENTAL and has known data-loss bugs");
> + }
> +
> /*
> * Mount does not set all options immediately, we can do it now and do
> * not have to wait for transaction commit
> --
Doing this in the kernel should be better than in userspace (like
https://patchwork.kernel.org/patch/9450035/) as it can deal with a future
kernel with working RAID5/6 on old -progs; but if you prefer, I can finish
that patch and request its inclusion in Debian stretch -progs instead or in
addition to the above warning in the kernel.
ᛗᛖᛟᚹ!
--
⢀⣴⠾⠻⢶⣦⠀ Meow!
⣾⠁⢠⠒⠀⣿⡁
⢿⡄⠘⠷⠚⠋⠀ Collisions shmolisions, let's see them find a collision or second
⠈⠳⣄⠀⠀⠀⠀ preimage for double rot13!
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