Messages in this thread | | | Date | Thu, 1 Jan 2004 23:31:48 -0800 | From | Andrew Morton <> | Subject | Re: [PATCH linux-2.6.0-test10-mm1] filemap_fdatawait.patch |
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Suparna Bhattacharya <suparna@in.ibm.com> wrote: > > On Wed, Dec 31, 2003 at 03:17:36AM -0800, Andrew Morton wrote: > > Andrew Morton <akpm@osdl.org> wrote: > > > > > > Let me actually think about this a bit. > > > > Nasty. The same race is present in 2.4.x... > > > > How's about we start new I/O in filemap_fdatawait() if the page is dirty? > > > > Makes sense to me. > There's a chance that this could explain why Daniel saw exposures even > with his fix. > > Would be interesting to see his results with your patch. > > Though we might as well plug this anyway ?
Yes, we should. I'm not dreadfully keen on starting I/O from within filemap_fdatawait() though - it seems "wrong" somehow.
> > > > diff -puN mm/filemap.c~a mm/filemap.c > > --- 25/mm/filemap.c~a 2003-12-31 03:10:29.000000000 -0800 > > +++ 25-akpm/mm/filemap.c 2003-12-31 03:17:05.000000000 -0800 > > @@ -206,7 +206,13 @@ restart: > > page_cache_get(page); > > spin_unlock(&mapping->page_lock); > > > > - wait_on_page_writeback(page); > > + lock_page(page); > > + if (PageDirty(page) && mapping->a_ops->writepage) { > > + write_one_page(page, 1); > > + } else { > > + wait_on_page_writeback(page); > > + unlock_page(page); > > Would we lose anything if we unlock_page() before wait_on_page_writeback() ?
No, that should be OK.
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