David Sterba wrote:
On Wed, Jul 01, 2020 at 10:44:38AM -0400, Josef Bacik wrote:
One of the things that came up consistently in talking with Fedora about
switching to btrfs as default is that btrfs is particularly vulnerable
to metadata corruption. If any of the core global roots are corrupted,
the fs is unmountable and fsck can't usually do anything for you without
some special options.
Qu addressed this sort of with rescue=skipbg, but that's poorly named as
what it really does is just allow you to operate without an extent root.
However there are a lot of other roots, and I'd rather not have to do
mount -o rescue=skipbg,rescue=nocsum,rescue=nofreespacetree,rescue=blah
Instead take his original idea and modify it so it just works for
everything. Turn it into rescue=onlyfs, and then any major root we fail
to read just gets left empty and we carry on.
Obviously if the fs roots are screwed then the user is in trouble, but
otherwise this makes it much easier to pull stuff off the disk without
needing our special rescue tools. I tested this with my TEST_DEV that
had a bunch of data on it by corrupting the csum tree and then reading
files off the disk.
Signed-off-by: Josef Bacik <josef@xxxxxxxxxxxxxx>
---
I'm not married to the rescue=onlyfs name, if we can think of something better
I'm good.
Also rescue=skipbg is currently only sitting in misc-next, which is why I'm
killing it with this patch, we haven't sent it upstream so we're good to change
it now before it lands.
Right now we don't seem to have a consensus what rescue= should or
should not do and given that the patch is not in any released branch I
can keep it in for-next topic branch. We'll have something to test but
unless the final semantics is agreed on, I don't want to keep the patch
in misc-next to avoid dealing with the fallouts.
To be specific:
- patch "btrfs: introduce "rescue=" mount option" only wraps existing
options so that one is probably ok to stay in misc-next
- rescue=skipbg would go to topic branch
How about calling it recoverylevel=xyz or recoverymask=this,or,that
perhaps be a better with a conservative settings as the default?!
