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
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?
Thanks,
André
