linux-ext4 - Re: [PATCH] fuse2fs: reopen filesystem read-write for read-only journal recovery

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Message-ID: <aO--1J4bOVMYgbBt@cern.ch>
Date: Wed, 15 Oct 2025 10:33:40 -0500
From: Dave Dykstra <dwd@...n.ch>
To: "Darrick J. Wong" <djwong@...nel.org>
Cc: linux-ext4@...r.kernel.org
Subject: Re: [PATCH] fuse2fs: reopen filesystem read-write for read-only
 journal recovery

On Tue, Oct 14, 2025 at 06:15:05PM -0700, Darrick J. Wong wrote:
> On Fri, Oct 10, 2025 at 04:47:35PM -0500, Dave Dykstra wrote:
> > This changes the strategy added in c7f2688540d95e7f2cbcd178f8ff62ebe079faf7
> > for recovery of journals when read-only is requested.
...
> ro and EXT2_FLAG_RW are not the same thing!

I understand that.

...
> I don't like this, because we should open the filesystem with
> EXT2_FLAG_RW set by default and only downgrade to !EXT2_FLAG_RW if we
> can't open it...

I was following the suggestion of tytso at
    https://github.com/tytso/e2fsprogs/issues/244#issuecomment-3390084495

However, I think your suggestion might be better.  I will try that.

...

> ...if the close fails, you just leaked the old global_fs context.
> ext2fs_close_free is what you want (and yes that's a bug in fuse2fs).

Ok, thanks, I'll use that.

...
> ...and also, if you re-do ext2fs_open2(), you then have to re-check all
> the feature support bits above because we unlocked the filesystem
> device, which means its contents could have been replaced completely
> in the interim.

I'm not convinced that's something to worry about, but in any case
your suggestion of only opening ro if rw fails should avoid it.

> Also note that I have a /very large/ pile of fuse2fs improvements and
> rewrites and cleanups that are out for review on the list; you might
> want to look at those first.

I do appreciate your efforts.  Unfortunately I have too many other
priorities to have enough bandwidth to take on general responsibility
for reviewing fuse2fs patches.  I also don't have much experience with
filesystems.  I'm only trying to help here because it is impacting a
case that I support.  I was very happy when I found that the fuse2fs in
v1.47.3 of e2fsprogs fixed another user-reported problem, but the new
version ended up causing a couple of new problems.

Having said that, if there are particular patches that you think are
important bug fixes that you would like to call my attention to, please
send me a direct message. I could test them and respond.

Dave