[LU-1234] Executing binary stored on Lustre results in " (deleted)" appended to /proc/self/exec

• Type: Bug
• Resolution: Fixed
• Priority: Minor
• Severity: 3
• Assignee: Lai Siyao
• Reporter: Prakash Surya (Inactive)

Description

We have reports that when running an executable stored on Lustre, the symlink /proc/self/exec will have " (deleted)" appended to it. This can be normal behavior under Linux, if the executable has in fact been overwritten or deleted. But I have been told this is not the case, and I would not be surprised if there is a Lustre bug here. Digging into the kernel sources, it appears the following snippets are relevant:

__d_path

 if (d_unlinked(dentry) &&
         (prepend(&end, &buflen, " (deleted)", 10) != 0))
                 goto Elong;

static inline int d_unhashed(struct dentry *dentry)
{
        return (dentry->d_flags & DCACHE_UNHASHED);
}

static inline int d_unlinked(struct dentry *dentry)
{
        return d_unhashed(dentry) && !IS_ROOT(dentry);
}

So, the string " (deleted)" is appended when the dentry in question has the DCACHE_UNHASHED flag set. Perhaps there's a situation where Lustre fails to take a reference on the dentry, allowing it to be dropped from the cache when it shouldn't be?

Also note, I haven't been able to reproduce this issue so it's been difficult to debug, or even determine exactly where the issue lies.