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From: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
To: Wu Fengguang <fengguang.wu@intel.com>
Subject: Re: sk_lock: inconsistent {RECLAIM_FS-ON-W} -> {IN-RECLAIM_FS-W} usage
Cc: kosaki.motohiro@jp.fujitsu.com, LKML <linux-kernel@vger.kernel.org>,
       linux-nfs@vger.kernel.org, netdev@vger.kernel.org
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Date: Mon,  8 Jun 2009 13:55:18 +0900 (JST)
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Hi

> Hi,
> 
> This lockdep warning appears when doing stress memory tests over NFS.
> 
> page reclaim => nfs_writepage => tcp_sendmsg => lock sk_lock
> 
> tcp_close => lock sk_lock => tcp_send_fin => alloc_skb_fclone => page reclaim
> 
> Any ideas?

AFAIK, btrfs has re-dirty hack. 

------------------------------------------------------------------
static int btrfs_writepage(struct page *page, struct writeback_control *wbc)
{
        struct extent_io_tree *tree;


        if (current->flags & PF_MEMALLOC) {
                redirty_page_for_writepage(wbc, page);
                unlock_page(page);
                return 0;
        }
        tree = &BTRFS_I(page->mapping->host)->io_tree;
        return extent_write_full_page(tree, page, btrfs_get_extent, wbc);
}
---------------------------------------------------------------

PF_MEMALLOC mean caller is try_to_free_pages(). (not normal write nor kswapd)
Can't nfs does similar hack? 


I'm not net nor nfs expert. perhaps I'm wrong :-)


Thanks.