Messages in this thread | | | Date | Tue, 20 Dec 2022 20:53:06 +0100 | From | David Sterba <> | Subject | Re: [PATCH] btrfs: refuse to remount read-write with unsupported compat-ro features |
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On Tue, Dec 06, 2022 at 11:14:56AM +0000, Filipe Manana wrote: > On Tue, Dec 6, 2022 at 2:42 AM Chung-Chiang Cheng <shepjeng@gmail.com> wrote: > > > > On Mon, Dec 5, 2022 at 6:45 PM Filipe Manana <fdmanana@kernel.org> wrote: > > > > > > Wasn't this already done by the following commit? > > > > > > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=81d5d61454c365718655cfc87d8200c84e25d596 > > > > > > Thanks. > > > > > > > Wow. I did not notice this commit doing the same job by Qu. But I have > > tested the latest linux-6.1 rc-7, and it's still able to mount a unsupported > > comat-ro btrfs as read-write via remount. > > > > It's caused by the follow-up commit d7f67ac9a928 ("btrfs: relax > > block-group-tree feature dependency checks"). This commit checks read- > > only with the current superblock, which will always pass in the situation > > remounting from read-only to read-write. It seems `btrfs_check_features()` > > cannot cover this scenario. > > > > if (compat_ro_unsupp && !sb_rdonly(sb)) { > > ^^^^^^^^^^^^^^ > > Yep, that's a bug. > btrfs_check_features() is called before the read only flag is updated > in the super block. > > So the condition should be: > > if (compat_ro_unsupp && sb_rdonly(sb) && we_want_to_transition_to_rw) > > We need to pass the flags passed to btrfs_remount() to > btrfs_check_features() for that "we_want_to_transition_to_rw" check. > > That seems to be what needs to be fixed.
Qu, can you please have a look, it's caused by commit 81d5d61454c365718655cfc87d8200c84e25d596 that's also in stable kernels so this should be fixed quickly.
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