nfs mount disappears due to inode revalidate failure

[Sylvain Menu <sylvain.menu@xxxxxxxxx>]

Hello,

I am writing to report an issue on a nfs mount that disappears due to
an inode revalide failure (already sent in January but probably banned
with html format...).
This very old commit
(https://github.com/torvalds/linux/commit/cc89684c9a265828ce061037f1f79f4a68ccd3f7)
exactly show the problem I have and this old resolved issue
(https://bugzilla.kernel.org/show_bug.cgi?id=117651) is probably
failing again today

To sum up, I have a NFS mount inside another NFS mount (for example:
/opt/nfs/mount1 & /opt/nfs/mount1/mount2).
If I kill a task trying to get a file descriptor on
/opt/nfs/mount1/mount2 then it will be unmounted. My simple test code
to reproduce very easily:

int main(int argc, char *argv[]) {
    while (1) {
        close(open(argv[1], O_RDONLY));
    }
}

In logs, I have: "nfs_revalidate_inode: (0:62/845965) getattr failed,
error=-512"

Tested on 5.19 and 6.1 kernel

Best regards,
Sylvain Menu