linux-ext4 - Re: [PATCH] fuse2fs: open read-only when image is not writable

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Message-ID: <20251017233255.GL6170@frogsfrogsfrogs>
Date: Fri, 17 Oct 2025 16:32:55 -0700
From: "Darrick J. Wong" <djwong@...nel.org>
To: Dave Dykstra <dave.dykstra@...n.ch>, Theodore Ts'o <tytso@....edu>
Cc: linux-ext4@...r.kernel.org,
	Dave Dykstra <2129743+DrDaveD@...rs.noreply.github.com>
Subject: Re: [PATCH] fuse2fs: open read-only when image is not writable

On Fri, Oct 17, 2025 at 04:11:30PM -0500, Dave Dykstra wrote:
> This opens the image read-only when the image is not writable. If it is then found that a journal recovery is needed, an error is returned then.
> 
> The ret value is set to 2 after the option checks so that if there's an error resulting in "goto out" it won't print an error about unrecognized options.
> 
> Also submitted as PR https://github.com/tytso/e2fsprogs/pull/250
> for the issue https://github.com/tytso/e2fsprogs/issues/244.
> 
> Replaces 
>   https://lore.kernel.org/linux-ext4/20251016200206.3035-1-dave.dykstra@cern.ch/
>   https://lore.kernel.org/linux-ext4/175798064776.350013.6744611652039454651.stgit@frogsfrogsfrogs/
> 
> Signed-off-by: Dave Dykstra <2129743+DrDaveD@...rs.noreply.github.com>

Please slow down and give me a chance to reshuffle and QA my existing
fixes for the problems you've complained about.

--D

> ---
>  misc/fuse2fs.c | 32 ++++++++++++++++++++++++++++----
>  1 file changed, 28 insertions(+), 4 deletions(-)
> 
> diff --git a/misc/fuse2fs.c b/misc/fuse2fs.c
> index cb5620c7..6a107d2b 100644
> --- a/misc/fuse2fs.c
> +++ b/misc/fuse2fs.c
> @@ -4696,9 +4696,24 @@ int main(int argc, char *argv[])
>  	err = ext2fs_open2(fctx.device, options, flags, 0, 0, unix_io_manager,
>  			   &global_fs);
>  	if (err) {
> -		err_printf(&fctx, "%s.\n", error_message(err));
> -		err_printf(&fctx, "%s\n", _("Please run e2fsck -fy."));
> -		goto out;
> +		if ((err == EACCES) || (err == EPERM)) {
> +			if (fctx.ro) {
> +				dbg_printf(&fctx, "%s: %s\n", __func__,
> + _("Permission denied with writable, trying without.\n"));
> +			} else {
> +				dbg_printf(&fctx, "%s: %s\n", __func__,
> + _("No write access, opening read-only.\n"));
> +				fctx.ro = 1;
> +			}
> +			flags &= ~EXT2_FLAG_RW;
> +			err = ext2fs_open2(fctx.device, options, flags, 0, 0, 
> +					   unix_io_manager, &global_fs);
> +		}
> +		if (err) {
> +			err_printf(&fctx, "%s.\n", error_message(err));
> +			err_printf(&fctx, "%s\n", _("Please run e2fsck -fy."));
> +			goto out;
> +		}
>  	}
>  	fctx.fs = global_fs;
>  	global_fs->priv_data = &fctx;
> @@ -4741,6 +4756,8 @@ int main(int argc, char *argv[])
>  		goto out;
>  	}
>  
> +	ret = 2;
> +
>  	if (global_fs->super->s_state & EXT2_ERROR_FS) {
>  		err_printf(&fctx, "%s\n",
>   _("Errors detected; running e2fsck is required."));
> @@ -4760,6 +4777,11 @@ int main(int argc, char *argv[])
>   _("Mounting read-only without recovering journal."));
>  			fctx.ro = 1;
>  			global_fs->flags &= ~EXT2_FLAG_RW;
> +		} else if (fctx.ro && !(flags & EXT2_FLAG_RW)) {
> +			err_printf(&fctx, "%s\n",
> + _("Journal needs recovery but filesystem could not be opened read-write."));
> +			err_printf(&fctx, "%s\n", _("Please run e2fsck -fy."));
> +			goto out;
>  		} else {
>  			log_printf(&fctx, "%s\n", _("Recovering journal."));
>  			err = ext2fs_run_ext3_journal(&global_fs);
> @@ -4833,8 +4855,10 @@ int main(int argc, char *argv[])
>  	if (fctx.no_default_opts == 0)
>  		fuse_opt_add_arg(&args, extra_args);
>  
> -	if (fctx.ro)
> +	if (fctx.ro) {
> +		/* This is in case ro was implied above and not passed in */
>  		fuse_opt_add_arg(&args, "-oro");
> +	}
>  
>  	if (fctx.fakeroot) {
>  #ifdef HAVE_MOUNT_NODEV
> -- 
> 2.43.5
> 
>