Re: Checking page_count(page) in invalidate_complete_page

[Chuck Lever <chuck.lever@oracle.com>]

Hi Nick-

Nick Piggin wrote:
>> The page references I'm noting are:
>>
>> 1.  add_to_page_cache_lru  1 -> 2
>>
>> 2.  do_generic_mapping_read, released in nfs_do_filldir
>>
>> 3.  read_cache_page, released in nfs_readdir
>>
>> 4.  pagevec_lookup (from invalidate_inode_pages2_range)  2 -> 3
>>
>> The odd thing is some of the pages for the directory are released, so 
>> they must have a ref count of 2 *after* the pagevec_lookup.  Looks 
>> like more investigation is needed.
> 
> 
> Well they could get flushed out of the lru add pagevecs which drops 
> their count. Just to
> test that theory you could run lru_add_drain_all() at the start of the 
> invalidate function.
> That's not going to actually fix the problem, but it might help 2.6.18 
> limp along when
> combined with some other work.

I've verified that the pages that fail to be invalidated are indeed 
languishing in the per-CPU lru-add pagevec.  Adding a call to 
lru_add_drain_all() to the invalidate_inode_pages2() path does fix the 
NFS readdir problem.

I think a call to lru_add_drain_all() belongs in both the 
invalidate_inode_pages() and the invalidate_inode_pages2() path.  Do you 
agree?

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