Messages in this thread | | | From | Segher Boessenkool <> | Subject | Re: [PATCH] mm: fix page_mkclean_one | Date | Fri, 29 Dec 2006 03:50:50 +0100 |
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> I think what might be happening is that pdflush writes them out fine, > however we don't trap writes by the application _during_ that writeout.
Yeah. I believe that more exactly it happens if the very last write to the page causes a writeback (due to dirty balancing) while another writeback for the page is already happening.
As usual in these cases, I have zero proof.
> It's something that will only occur with writeback and MAP_SHARED > writable access to the file pages.
It's the do_wp_page -> balance_dirty_pages -> generic_writepages path for sure. Maybe it's enough to change
if (wbc->sync_mode != WB_SYNC_NONE) wait_on_page_writeback(page);
if (PageWriteback(page) || !clear_page_dirty_for_io(page)) { unlock_page(page); continue; }
to
if (wbc->sync_mode != WB_SYNC_NONE) wait_on_page_writeback(page);
if (PageWriteback(page)) { redirty_page_for_writepage(wbc, page); unlock_page(page); continue; }
if (!clear_page_dirty_for_io(page)) { unlock_page(page); continue; }
or something along those lines. Completely untested of course :-)
Segher
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