On Mon, Jun 08, 2009 at 12:55:18PM +0800, KOSAKI Motohiro wrote:
> 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)
No, kswapd also sets the PF_MEMALLOC flag. It looks like btrfs_writepage()
is trying to avoid inefficient page outs at the cost of pinning dirty
pages in memory (even when we really want free pages).
Thanks,
Fengguang
> Can't nfs does similar hack?
>
>
> I'm not net nor nfs expert. perhaps I'm wrong :-)
>
>
> Thanks.
>
>
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