On 2021/12/30 14:55, Greg KH wrote:

On Thu, Dec 30, 2021 at 08:06:49AM +0800, Qu Wenruo wrote:

...

Hi,

Since v5.10 is an LTS release, I'm wondering should we backport write time tree-checker feature to v5.10?

There are already some reports of runtime memory bitflip get written to disk and causing problems.

Unfortunately write-time tree-checker is only introduced in v5.11, one version late.

Considering how many bitflips write-time tree-checker has caught (and prevented corrupted data reaching disk), I think it's definitely worthy to backport it to an LTS kernel.

Or is there any special requirement for LTS kernel to reject certain features?

Stable/LTS kernels do not get new features, sorry.

OK, sorry to hear that.

If someone wants this feature, why not just use 5.15?

One thing is, this is not really a feature, but more like an extra safenet to catch hardware problems.

In fact, just according to the reports in btrfs mail list, memory bitflip is not that rare in the real world.

And any undetected bitflip reached disk will be later rejected by the read time sanity check, causing a possibly unmountable fs. (even we output exactly the reason why we reject the metadata, and with those error messages, one can easily know it's a bitflip, it's still way worse than rejecting the corrupted data at write time).

So I guess the only way to get full runtime sanity check is waiting for the next LTS.

Thanks, Qu

thanks,

greg k-h

On 2021/12/30 15:32, Greg KH wrote:

On Thu, Dec 30, 2021 at 03:10:13PM +0800, Qu Wenruo wrote:

...

On 2021/12/30 14:55, Greg KH wrote:

...

On Thu, Dec 30, 2021 at 08:06:49AM +0800, Qu Wenruo wrote:

...

Hi,

Since v5.10 is an LTS release, I'm wondering should we backport write time tree-checker feature to v5.10?

There are already some reports of runtime memory bitflip get written to disk and causing problems.

Unfortunately write-time tree-checker is only introduced in v5.11, one version late.

Considering how many bitflips write-time tree-checker has caught (and prevented corrupted data reaching disk), I think it's definitely worthy to backport it to an LTS kernel.

Or is there any special requirement for LTS kernel to reject certain features?

Stable/LTS kernels do not get new features, sorry.

OK, sorry to hear that.

...

If someone wants this feature, why not just use 5.15?

One thing is, this is not really a feature, but more like an extra safenet to catch hardware problems.

In fact, just according to the reports in btrfs mail list, memory bitflip is not that rare in the real world.

And any undetected bitflip reached disk will be later rejected by the read time sanity check, causing a possibly unmountable fs. (even we output exactly the reason why we reject the metadata, and with those error messages, one can easily know it's a bitflip, it's still way worse than rejecting the corrupted data at write time).

So I guess the only way to get full runtime sanity check is waiting for the next LTS.

What exactly does the patches look like to backport this?

All my bad, the upstream commit is 8d47a0d8f794 ("btrfs: Do mandatory tree block check before submitting bio") which is already in v5.2, not v5.11.

So all these features are already in lts.

Really sorry for the noise. Qu

And what prevents people from using the 5.15 LTS kernel instead of 5.10 if they wish to have this additional protection?

thanks,

greg k-h