Miklos Szeredi <miklos@xxxxxxxxxx> writes:
> On Thu, 03 Dec 2009, Eric W. Biederman wrote:
>> > The only worry I have is that this adds an extra branch in a very hot
>> > codepath (do_lookup). An error can't be returned, as you note, and
>> > for bind mounted directories d_invalidate() will not succeed: the
>> > directory is busy, it's referenced by the mount.
>>
>> Not true. d_mountpoint is false, so d_invalidate can succeed.
>
> Have a look at the code. d_invalidate() doesn't check for a
> mountpoint, it checks the refcount. It needs to keep the directory
> dentry hashed if it's in any way reachable other than from the cache
> (file descriptor, cwd, mount, etc).
Ah. I thought you were thinking about the mandatory have_submounts()
check in dentry->d_op->d_revalidate().
I expect the generic d_invalidate will simply hit the:
spin_lock(&dcache_lock);
if (d_unhashed(dentry)) {
spin_unlock(&dcache_lock);
return 0;
}
After the distributed filesystem has called d_drop in
dentry->d_op->d_revalidate (when appropriate.
Eric
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