All submounts share the same virtio-fs device instance as the root
mount. If the same virtiofs filesystem is mounted again, sget_fc()
is likely to pick up any of these submounts and reuse it instead of
the root mount.
On the server side:
# mkdir ${some_dir}
# mkdir ${some_dir}/mnt1
# mount -t tmpfs none ${some_dir}/mnt1
# touch ${some_dir}/mnt1/THIS_IS_MNT1
# mkdir ${some_dir}/mnt2
# mount -t tmpfs none ${some_dir}/mnt2
# touch ${some_dir}/mnt2/THIS_IS_MNT2
On the client side:
# mkdir /mnt/virtiofs1
# mount -t virtiofs myfs /mnt/virtiofs1
# ls /mnt/virtiofs1
mnt1 mnt2
# grep virtiofs /proc/mounts
myfs /mnt/virtiofs1 virtiofs rw,seclabel,relatime 0 0
none on /mnt/mnt1 type virtiofs (rw,relatime,seclabel)
none on /mnt/mnt2 type virtiofs (rw,relatime,seclabel)
And now remount it again:
# mount -t virtiofs myfs /mnt/virtiofs2
# grep virtiofs /proc/mounts
myfs /mnt/virtiofs1 virtiofs rw,seclabel,relatime 0 0
none on /mnt/mnt1 type virtiofs (rw,relatime,seclabel)
none on /mnt/mnt2 type virtiofs (rw,relatime,seclabel)
myfs /mnt/virtiofs2 virtiofs rw,seclabel,relatime 0 0
# ls /mnt/virtiofs2
THIS_IS_MNT2
Submount mnt2 was picked-up instead of the root mount.
Just skip submounts in virtio_fs_test_super().
Signed-off-by: Greg Kurz <groug@xxxxxxxx>
---
fs/fuse/virtio_fs.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/fs/fuse/virtio_fs.c b/fs/fuse/virtio_fs.c
index e12e5190352c..8962cd033016 100644
--- a/fs/fuse/virtio_fs.c
+++ b/fs/fuse/virtio_fs.c
@@ -1408,6 +1408,11 @@ static int virtio_fs_test_super(struct super_block *sb,
struct fuse_mount *fsc_fm = fsc->s_fs_info;
struct fuse_mount *sb_fm = get_fuse_mount_super(sb);
+
+ /* Skip submounts */
+ if (!list_is_first(&sb_fm->fc_entry, &sb_fm->fc->mounts))
+ return 0;
+
return fsc_fm->fc->iq.priv == sb_fm->fc->iq.priv;
}
--
2.26.3
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