cc libfuse maintainer On Thu, May 22, 2025 at 4:30 PM André Almeida <andrealmeid@xxxxxxxxxx> wrote: > > Em 22/05/2025 06:52, Amir Goldstein escreveu: > > On Thu, May 22, 2025 at 8:20 AM André Almeida <andrealmeid@xxxxxxxxxx> wrote: > >> > >> Hi Christian, Amir, > >> > >> Thanks for the feedback :) > >> > >> Em 21/05/2025 08:20, Christian Brauner escreveu: > >>> On Wed, May 21, 2025 at 12:35:57PM +0200, Amir Goldstein wrote: > >>>> On Wed, May 21, 2025 at 8:45 AM André Almeida <andrealmeid@xxxxxxxxxx> wrote: > >>>>> > >> > >> [...] > >> > >>>> > >>>> I see the test generic/623 failure - this test needs to be fixed for overlay > >>>> or not run on overlayfs. > >>>> > >>>> I do not see those other 5 failures although before running the test I did: > >>>> export LIBMOUNT_FORCE_MOUNT2=always > >>>> > >>>> Not sure what I am doing differently. > >>>> > >> > >> I have created a smaller reproducer for this, have a look: > >> > >> mkdir -p ovl/lower ovl/upper ovl/merge ovl/work ovl/mnt > >> sudo mount -t overlay overlay -o lowerdir=ovl/lower,upperdir=ovl/ > >> upper,workdir=ovl/work ovl/mnt > >> sudo mount ovl/mnt -o remount,ro > >> > > > > Why would you use this command? > > Why would you want to re-specify the lower/upperdir when remounting ro? > > And more specifically, fstests does not use this command in the tests > > that you mention that they fail, so what am I missing? > > > > I've added "set -x" to tests/generic/294 to see exactly which mount > parameters were being used and I got this from the output: > > + _try_scratch_mount -o remount,ro > + local mount_ret > + '[' overlay == overlay ']' > + _overlay_scratch_mount -o remount,ro > + echo '-o remount,ro' > + grep -q remount > + /usr/bin/mount /tmp/dir2/ovl-mnt -o remount,ro > mount: /tmp/dir2/ovl-mnt: fsconfig() failed: ... > > So, from what I can see, fstests is using this command. Not sure if I > did something wrong when setting up fstests. > No you are right, I misread your reproducer. The problem is that my test machine has older libmount 2.38.1 without the new mount API. > >> And this returns: > >> > >> mount: /tmp/ovl/mnt: fsconfig() failed: overlay: No changes allowed in > >> reconfigure. > >> dmesg(1) may have more information after failed mount system call. > >> > >> However, when I use mount like this: > >> > >> sudo mount -t overlay overlay -o remount,ro ovl/mnt > >> > >> mount succeeds. Having a look at strace, I found out that the first > >> mount command tries to set lowerdir to "ovl/lower" again, which will to > >> return -EINVAL from ovl_parse_param(): > >> > >> fspick(3, "", FSPICK_NO_AUTOMOUNT|FSPICK_EMPTY_PATH) = 4 > >> fsconfig(4, FSCONFIG_SET_STRING, "lowerdir", "/tmp/ovl/lower", 0) = > >> -1 EINVAL (Invalid argument) > >> > >> Now, the second mount command sets just the "ro" flag, which will return > >> after vfs_parse_sb_flag(), before getting to ovl_parse_param(): > >> > >> fspick(3, "", FSPICK_NO_AUTOMOUNT|FSPICK_EMPTY_PATH) = 4 > >> fsconfig(4, FSCONFIG_SET_FLAG, "ro", NULL, 0) = 0 > >> > >> After applying my patch and running the first mount command again, we > >> can set that this flag is set only after setting all the strings: > >> > >> fsconfig(4, FSCONFIG_SET_STRING, "lowerdir", "/tmp/ovl/lower", 0) = 0 > >> fsconfig(4, FSCONFIG_SET_STRING, "upperdir", "/tmp/ovl/upper", 0) = 0 > >> fsconfig(4, FSCONFIG_SET_STRING, "workdir", "/tmp/ovl/work", 0) = 0 > >> fsconfig(4, FSCONFIG_SET_STRING, "uuid", "on", 0) = 0 > >> fsconfig(4, FSCONFIG_SET_FLAG, "ro", NULL, 0) = 0 > >> > >> I understood that the patch that I proposed is wrong, and now I wonder > >> if the kernel needs to be fixed at all, or if the bug is how mount is > >> using fsconfig() in the first mount command? > > If you ask me, when a user does: /usr/bin/mount /tmp/dir2/ovl-mnt -o remount,ro The library only needs to do the FSCONFIG_SET_FLAG command and has no business re-sending the other config commands, but that's just me. BTW, which version of libmount (mount --version) are you using? I think there were a few problematic versions when the new mount api was first introduced. Thanks, Amir.
