> 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).
Sorry, I was confused ;)
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