linux-ext4 - [PATCH 19/16] fuse2fs: mount norecovery if main block device is readonly

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Message-ID: <20251020202756.GO6170@frogsfrogsfrogs>
Date: Mon, 20 Oct 2025 13:27:56 -0700
From: "Darrick J. Wong" <djwong@...nel.org>
To: tytso@....edu
Cc: linux-ext4@...r.kernel.org
Subject: [PATCH 19/16] fuse2fs: mount norecovery if main block device is
 readonly

From: Darrick J. Wong <djwong@...nel.org>

If the main block device is read-only, downgrade the mount to an ro
norecovery mount to match what the kernel does.  This will make
generic/050 somewhat less grouchy.

Signed-off-by: "Darrick J. Wong" <djwong@...nel.org>
---
 misc/fuse2fs.c |   13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/misc/fuse2fs.c b/misc/fuse2fs.c
index 9922747728a438..83886faf2eada8 100644
--- a/misc/fuse2fs.c
+++ b/misc/fuse2fs.c
@@ -4773,6 +4773,19 @@ int main(int argc, char *argv[])
 		flags |= EXT2_FLAG_DIRECT_IO;
 	err = ext2fs_open2(fctx.device, options, flags, 0, 0, unix_io_manager,
 			   &global_fs);
+	if (err == EPERM || err == EACCES) {
+		/*
+		 * Source device cannot be opened for write.  Under these
+		 * circumstances, mount(8) will try again with a ro mount,
+		 * and the kernel will open the block device readonly.
+		 */
+		log_printf(&fctx, "%s\n",
+ _("WARNING: source write-protected, mounted read-only."));
+		flags &= ~EXT2_FLAG_RW;
+		fctx.ro = 1;
+		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."));