linux-kernel - [Regression 5.17-rc2] Symlink on NFS mount to directory on other NFS mount not resolved on first access

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Date:   Tue, 8 Feb 2022 15:36:35 +0100
From:   Paul Menzel <pmenzel@...gen.mpg.de>
To:     Trond Myklebust <trond.myklebust@...merspace.com>,
        Anna Schumaker <Anna.Schumaker@...app.com>
Cc:     Lyu Tao <tao.lyu@...l.ch>, linux-nfs@...r.kernel.org,
        linux-kernel@...r.kernel.org, it+linux-nfs@...gen.mpg.de,
        regressions@...ts.linux.dev
Subject: [Regression 5.17-rc2] Symlink on NFS mount to directory on other NFS
 mount not resolved on first access

#regzbot introduced: ac795161c93699d600db16c1a8cc23a65a1eceaf


Dear Linux folks,


Commit ac795161c936 (NFSv4: Handle case where the lookup of a directory 
fails) [1], part of Linux since 5.17-rc2, introduced a regression, where 
a symbolic link on an NFS mount to a directory on another NFS does not 
resolve(?) the first time it is accessed:

```
$ ls -dl /src/mariux/beeroot/build-archives
lrwxrwxrwx 1 root root 39 May  5  2021 
/src/mariux/beeroot/build-archives -> 
/src/mariux_data/beeroot/build-archives
$ df /src/mariux{,_data}
Filesystem                                           1K-blocks 
Used   Available Use% Mounted on
macheteinfach:/amd/macheteinfach/1/src/mariux      17575970816 
2930189312 14645781504  17% /src/mariux
macheteinfach:/amd/macheteinfach/1/src/mariux_data 17575970816 
2930189312 14645781504  17% /src/mariux_data

$ sudo umount /src/mariux /src/mariux_data
$ echo /src/mariux/beeroot/build-archives/*5.17*
/src/mariux/beeroot/build-archives/*5.17*
$ strace -e openat echo /src/mariux/beeroot/build-archives/*5.17*
openat(AT_FDCWD, "/etc/ld.so.cache", O_RDONLY|O_CLOEXEC) = 3
openat(AT_FDCWD, "/lib/libc.so.6", O_RDONLY|O_CLOEXEC) = 3
openat(AT_FDCWD, "/usr/lib/locale/locale-archive", O_RDONLY|O_CLOEXEC) = 3
/src/mariux/beeroot/build-archives/*5.17*
+++ exited with 0 +++
$ echo /src/mariux/beeroot/build-archives/*5.17*
/src/mariux/beeroot/build-archives/linux-5.17_rc1-423.x86_64.beebuild.tar.bz2 
/src/mariux/beeroot/build-archives/linux-5.17_rc2-424.x86_64.beebuild.tar.bz2 
/src/mariux/beeroot/build-archives/linux-5.17_rc3-426.x86_64.beebuild.tar.bz2 
/src/mariux/beeroot/build-archives/mariux64-caret_R-3.0.2-5.17_7-0.x86_64.beebuild.tar.bz2

Using a dot in the path works around the issue:

```
$ sudo umount /src/mariux /src/mariux_data
$ strace -e openat echo /src/mariux/beeroot/build-archives/./*5.17*
openat(AT_FDCWD, "/etc/ld.so.cache", O_RDONLY|O_CLOEXEC) = 3
openat(AT_FDCWD, "/lib/libc.so.6", O_RDONLY|O_CLOEXEC) = 3
openat(AT_FDCWD, "/usr/lib/locale/locale-archive", O_RDONLY|O_CLOEXEC) = 3
/src/mariux/beeroot/build-archives/./linux-5.17_rc1-423.x86_64.beebuild.tar.bz2 
/src/mariux/beeroot/build-archives/./linux-5.17_rc2-424.x86_64.beebuild.tar.bz2 
/src/mariux/beeroot/build-archives/./linux-5.17_rc3-426.x86_64.beebuild.tar.bz2 
/src/mariux/beeroot/build-archives/./mariux64-caret_R-3.0.2-5.17_7-0.x86_64.beebuild.tar.bz2
+++ exited with 0 +++
```


Kind regards,

Paul


[1]: 
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=ac795161c93699d600db16c1a8cc23a65a1eceaf