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Message-Id: <20251010214735.22683-1-dave.dykstra@cern.ch>
Date: Fri, 10 Oct 2025 16:47:35 -0500
From: Dave Dykstra <dave.dykstra@...n.ch>
To: linux-ext4@...r.kernel.org
Cc: Dave Dykstra <dave.dykstra@...n.ch>,
Dave Dykstra <2129743+DrDaveD@...rs.noreply.github.com>
Subject: [PATCH] fuse2fs: reopen filesystem read-write for read-only journal recovery
This changes the strategy added in c7f2688540d95e7f2cbcd178f8ff62ebe079faf7
for recovery of journals when read-only is requested. That strategy always
opened the filesystem file read-write first, in case there was a journal to
recover. A big problem with that strategy was that the user might not have
write access to the file. The new strategy with read-only mounts is to
open the filesystem read-only first, then if there is a journal that needs
recovery, attempt to reopen it read-write. If that works and the journal
is recovered, reopen it again read-only.
- Fixes https://github.com/tytso/e2fsprogs/issues/244
Signed-off-by: Dave Dykstra <2129743+DrDaveD@...rs.noreply.github.com>
---
misc/fuse2fs.c | 62 ++++++++++++++++++++++++++++++++++++++++++++------
1 file changed, 55 insertions(+), 7 deletions(-)
diff --git a/misc/fuse2fs.c b/misc/fuse2fs.c
index cb5620c7..30a46976 100644
--- a/misc/fuse2fs.c
+++ b/misc/fuse2fs.c
@@ -4607,8 +4607,7 @@ int main(int argc, char *argv[])
FILE *orig_stderr = stderr;
char extra_args[BUFSIZ];
int ret;
- int flags = EXT2_FLAG_64BITS | EXT2_FLAG_THREADS | EXT2_FLAG_EXCLUSIVE |
- EXT2_FLAG_RW;
+ int flags = EXT2_FLAG_64BITS | EXT2_FLAG_THREADS | EXT2_FLAG_EXCLUSIVE;
memset(&fctx, 0, sizeof(fctx));
fctx.magic = FUSE2FS_MAGIC;
@@ -4689,6 +4688,8 @@ int main(int argc, char *argv[])
/* Start up the fs (while we still can use stdout) */
ret = 2;
+ if (!fctx.ro)
+ flags |= EXT2_FLAG_RW;
char options[50];
sprintf(options, "offset=%lu", fctx.offset);
if (fctx.directio)
@@ -4751,8 +4752,12 @@ int main(int argc, char *argv[])
* ext4 can't do COW of shared blocks, so if the feature is enabled,
* we must force ro mode.
*/
- if (ext2fs_has_feature_shared_blocks(global_fs->super))
+ if (ext2fs_has_feature_shared_blocks(global_fs->super) && !fctx.ro) {
+ log_printf(&fctx, "%s\n",
+ _("Mounting read-only because shared blocks feature is enabled."));
fctx.ro = 1;
+ /* Note that EXT2_FLAG_RW is left set */
+ }
if (ext2fs_has_feature_journal_needs_recovery(global_fs->super)) {
if (fctx.norecovery) {
@@ -4761,6 +4766,27 @@ int main(int argc, char *argv[])
fctx.ro = 1;
global_fs->flags &= ~EXT2_FLAG_RW;
} else {
+ if (!(flags & EXT2_FLAG_RW)) {
+ /* Attempt to re-open read-write */
+ err = ext2fs_close(global_fs);
+ if (err)
+ com_err(argv[0], err,
+ "while closing filesystem");
+ global_fs = NULL;
+ 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",
+ _("Journal needs recovery but filesystem cannot be reopened read-write."));
+ err_printf(&fctx, "%s\n",
+ _("Please run e2fsck -fy."));
+ goto out;
+ }
+ }
log_printf(&fctx, "%s\n", _("Recovering journal."));
err = ext2fs_run_ext3_journal(&global_fs);
if (err) {
@@ -4772,12 +4798,32 @@ int main(int argc, char *argv[])
ext2fs_clear_feature_journal_needs_recovery(global_fs->super);
ext2fs_mark_super_dirty(global_fs);
}
+ } else if (fctx.ro && !(flags & EXT2_FLAG_RW)) {
+ log_printf(&fctx, "%s\n", _("Mounting read-only."));
}
- if (global_fs->flags & EXT2_FLAG_RW) {
+ if (fctx.ro && (flags & EXT2_FLAG_RW)) {
+ /* Re-open read-only */
+ err = ext2fs_close(global_fs);
+ if (err)
+ com_err(argv[0], err, "while closing filesystem");
+ global_fs = NULL;
+ 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",
+ _("Failed to remount read-only."));
+ goto out;
+ }
+ log_printf(&fctx, "%s\n", _("Remounted read-only."));
+ }
+
+ if (!fctx.ro) {
if (ext2fs_has_feature_journal(global_fs->super))
log_printf(&fctx, "%s",
- _("Warning: fuse2fs does not support using the journal.\n"
+ _("Warning: fuse2fs does not support writing the journal.\n"
"There may be file system corruption or data loss if\n"
"the file system is not gracefully unmounted.\n"));
err = ext2fs_read_inode_bitmap(global_fs);
@@ -4833,8 +4879,10 @@ 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
@@ -4892,7 +4940,6 @@ int main(int argc, char *argv[])
ret = 0;
break;
}
-out:
if (ret & 1) {
fprintf(orig_stderr, "%s\n",
_("Mount failed due to unrecognized options. Check dmesg(1) for details."));
@@ -4903,6 +4950,7 @@ out:
_("Mount failed while opening filesystem. Check dmesg(1) for details."));
fflush(orig_stderr);
}
+out:
if (global_fs) {
err = ext2fs_close(global_fs);
if (err)
--
2.43.5
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