On Wed, Mar 19, 2014 at 9:21 PM, Al Viro <v...@zeniv.linux.org.uk> wrote:
>
> Er... I have, actually, right in the part you've snipped ;-)
Heh. That's what I get for just reading the patch, and skimming the explanation.
> I would prefer to deal with (1) by turning mnt_hash into hlist; the problem
> with that is __lookup_mnt_last(). That sucker is only called under
> mount_lock, so RCU issues do not play there, but it's there and it
> complicates things. There might be a way to get rid of that thing for
> good, but that's more invasive than what I'd be happy with for backports.
Yeah. I see what you're saying. That said, if we expect the mnt_hash
queues to be short (and they really should be), that whole
__lookup_mnt_last() could just be
struct mount *p, *result = NULL;
hlist_for_each_entry(p, head, mnt_hash)
if (&p->mnt_parent->mnt == mnt && p->mnt_mountpoint == dentry)
result = p;
return result;
which is certainly simple.
Sure, it always walks the whole list, but as far as I can tell the
callers aren't exactly performance-critical, and we're talking about a
hlist that should be just a couple of entries in size..
So if that's the _only_ thing holding back using hlists, I'd say we
should just do the above trivial conversion.
Linus
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