Re: [PATCH][RFC]fix soft lock up at NFS mount by per-SB LRU-listof unused dentries

From: Kentaro Makita
Date: Thu May 22 2008 - 22:15:36 EST

Hi, David

Thank you for reviewing the patch.
I'd fix coding style issues at next post. And,...

David Chinner wrote:
> On Thu, May 22, 2008 at 11:22:18AM +0900, Kentaro Makita wrote:
>> + }
>> + }
>> + }
> I'm wondering if this loop is an excessively long time to be holding the
> dcache_lock. I guess the hol dtime is limited by the size of *count being
> passed in. I think we could also do a:
> cond_resched_lock(&dcache_lock);
> in the loop here to prevent this from occurring....
Did you mean:
- scan sb->s_dentry_lru and move dentries to temporary list
with lock held
- cond_resched_lock(&dcache_lock);
- prune dentries on temporary list
Is that right?

>> + spin_lock(&sb_lock);
>> + list_for_each_entry(sb, &super_blocks, s_list) {
> Question on lock ordering of sb_lock vs dcache_lock - which is the inner
> lock? Are the two of them held together anywhere else? (/me doesn't
> have time to searchthe code right now).
The sb_lock is inner lock. And I searched the whole code and found only
prune_dcache() held both sb_lock and dcache_lock.

Best Regards,
Kentaro Makita
> Otherwise it's looking good.
> Cheers,
> Dave.
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