Hi Georges,

Thanks for the fix, LGTM, ack.

Thanks,
Tao Liu

On Fri, Sep 26, 2025 at 11:26 AM Aureau, Georges (Kernel Tools ERT)
<[email protected]> wrote:
>
> Should read "mount | grep tmpfs"  (and not "grep /tmp/test"):
>
> crash> mount | grep tmpfs
> ffff9648e7febc00 ffff9648d91ac800 tmpfs  tmpfs     /tmp/test
> ffff9648c9281380 ffff9648d91ac800 tmpfs  tmpfs     /tmp/test/
> ffff9648c8e9a700 ffff9648d91ac800 tmpfs  tmpfs     /
>
> |-----Original Message-----
> |From: Aureau, Georges (Kernel Tools ERT)
> |Sent: Tuesday, September 23, 2025 10:08 AM
> |To: [email protected]
> |Subject: [PATCH] Fix get_pathname() not handling stacked mounts
> |
> |[PATCH] Fix get_pathname() not handling stacked mounts
> |
> |This get_pathname() issue can be duplicated as follow:
> |
> |sudo mkdir -p /tmp/test
> |sudo mount -t tmpfs tmpfs /tmp/test
> |sudo mount --make-private /tmp/test
> |sudo mount --bind /tmp/test /tmp/test
> |sudo mount --bind /tmp/test /tmp/test
> |sudo mount -o remount,ro /tmp/test
> |
> |$ sudo crash /usr/lib/debug/boot/vmlinux-$(uname -r)
> |crash> mount | grep /tmp/test
> |ffff9648e7febc00 ffff9648d91ac800 tmpfs  tmpfs     /tmp/test
> |ffff9648c9281380 ffff9648d91ac800 tmpfs  tmpfs     /tmp/test/
> |ffff9648c8e9a700 ffff9648d91ac800 tmpfs  tmpfs     /
> |
> |The last mount is not printed properly, and this is impacting diagnostic
> |when looking at vmcore from complex containers mount environments.
> |
> |Signed-off-by: Georges Aureau <[email protected]>
> |--
> |diff --git a/filesys.c b/filesys.c
> |index 8d13807..af6d616 100644
> |--- a/filesys.c
> |+++ b/filesys.c
> |@@ -3140,6 +3154,7 @@ get_pathname(ulong dentry, char *pathname, int
> |length, int full, ulong vfsmnt)
> |       tmp_vfsmnt = vfsmnt;
> |
> |       do {
> |+      more_vfsmnt:
> |               tmp_dentry = parent;
> |
> |               dentry_buf = fill_dentry_cache(tmp_dentry);
> |@@ -3195,6 +3210,7 @@ get_pathname(ulong dentry, char *pathname, int
> |length, int full, ulong vfsmnt)
> |                                               break;
> |                                       else
> |                                               tmp_vfsmnt = mnt_parent;
> |+                                      goto more_vfsmnt;
> |                               }
> |                       } else if (VALID_STRUCT(mount)) {
> |                               if (tmp_vfsmnt) {
> |@@ -3213,6 +3229,7 @@ get_pathname(ulong dentry, char *pathname, int
> |length, int full, ulong vfsmnt)
> |                                               break;
> |                                       else
> |                                               tmp_vfsmnt = mnt_parent +
> |OFFSET(mount_mnt);
> |+                                      goto more_vfsmnt;
> |                               }
> |                       }
> |                       else {
> |@@ -3222,6 +3239,9 @@ get_pathname(ulong dentry, char *pathname, int
> |length, int full, ulong vfsmnt)
> |               }
> |
> |       } while (tmp_dentry != parent && parent);
> |+      if (!STREQ(pathname, "/") && LASTCHAR(pathname) == '/') {
> |+              LASTCHAR(pathname) = '\0';
> |+      }
> |
> |       if (mnt_buf)
> |               FREEBUF(mnt_buf);
> --
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