Messages in this thread | | | Subject | Re: [BUG] infinite loop in find_get_pages() | From | Shaohua Li <> | Date | Wed, 14 Sep 2011 16:55:19 +0800 |
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On Wed, 2011-09-14 at 16:43 +0800, Eric Dumazet wrote: > Le mercredi 14 septembre 2011 à 16:20 +0800, Shaohua Li a écrit : > > 2011/9/14 Shaohua Li <shli@kernel.org>: > > > it appears we didn't account skipped swap entry in find_get_pages(). > > > does the attached patch help? > > I can easily reproduce the issue. Just cp files in tmpfs, trigger swap and > > drop caches. The debug patch fixes it at my side. > > Eric, please try it. > > > > Hello Shaohua > > I tried it with added traces : > > > [ 277.077855] mv used greatest stack depth: 3336 bytes left > [ 310.558012] nr_found=2 nr_skip=2 > [ 310.558139] nr_found=14 nr_skip=14 > [ 332.195162] nr_found=2 nr_skip=2 > [ 332.195274] nr_found=14 nr_skip=14 > [ 352.315273] nr_found=14 nr_skip=14 > [ 372.673575] nr_found=14 nr_skip=14 > [ 397.115463] nr_found=14 nr_skip=14 > [ 403.391694] cc1 used greatest stack depth: 3184 bytes left > [ 404.761194] cc1 used greatest stack depth: 2640 bytes left > [ 417.306510] nr_found=14 nr_skip=14 > [ 440.198051] nr_found=14 nr_skip=14 > > I also used : > > - if (unlikely(!ret && nr_found)) > + if (unlikely(!ret && nr_found > nr_skip)) > goto restart; nr_found > nr_skip is better
> It seems to fix the bug. I suspect it also aborts > invalidate_mapping_pages() if we skip 14 pages, but existing comment > states its OK : > > /* > * Note: this function may get called on a shmem/tmpfs mapping: > * pagevec_lookup() might then return 0 prematurely (because it > * got a gangful of swap entries); but it's hardly worth worrying > * about - it can rarely have anything to free from such a mapping > * (most pages are dirty), and already skips over any difficulties. > */ that might be a problem, let Hugh answer if it is.
Thanks, Shaohua
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