Re: BTRFS error: bad tree block start 0 623771648

[Liu Bo <bo.li.liu@oracle.com>]

On Tue, Aug 01, 2017 at 11:04:10AM +0500, Roman Mamedov wrote:
> On Mon, 31 Jul 2017 11:12:01 -0700
> Liu Bo <bo.li.liu@oracle.com> wrote:
> 
> > Superblock and chunk tree root is OK, looks like the header part of
> > the tree root is now all-zero, but I'm unable to think of a btrfs bug
> > which can lead to that (if there is, it is a serious enough one)
> 
> I see that the FS is being mounted with "discard". So maybe it was a TRIM gone
> bad (wrong location or in a wrong sequence).
>

By checking discard path in btrfs, looks OK to me, more likely it's
caused by problems from underlying stuff.

Thanks,

-liubo

> Generally it appears to be not recommended to use "discard" by now (because of
> its performance impact, and maybe possible issues like this), instead schedule
> to call "fstrim <mountpoint>" once a day or so, and/or on boot-up.
> 
> > on ssd like disks, by default there is only one copy for metadata.
> 
> Time and time again, the default of "single" metadata for SSD is a terrible
> idea. Most likely DUP metadata would save the FS in this case.
> 
> -- 
> With respect,
> Roman
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