"Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx> writes: > On Tue, Jun 27, 2017 at 09:18:15AM +0200, Vlastimil Babka wrote: >> On 06/24/2017 05:08 PM, Andrei Vagin wrote: >> > On Fri, Jun 23, 2017 at 05:17:44PM -0700, Andrei Vagin wrote: >> >> On Thu, Jun 22, 2017 at 11:21:03PM -0700, Andrei Vagin wrote: >> >>> Hello, >> >>> >> >>> We run CRIU tests for linux-next and today they triggered a kernel >> >>> bug. I want to mention that this kernel is built with kasan. This bug >> >>> was triggered in travis-ci. I can't reproduce it on my host. Without >> >>> kasan, kernel crashed but it is impossible to get a kernel log for >> >>> this case. >> >> >> >> We use this tree >> >> https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/ >> >> >> >> This issue isn't reproduced on the akpm-base branch and >> >> it is reproduced each time on the akpm branch. I didn't >> >> have time today to bisect it, will do on Monday. >> > >> > c3aab7b2d4e8434d53bc81770442c14ccf0794a8 is the first bad commit >> > >> > commit c3aab7b2d4e8434d53bc81770442c14ccf0794a8 >> > Merge: 849c34f 93a7379 >> > Author: Stephen Rothwell >> > Date: Fri Jun 23 16:40:07 2017 +1000 >> > >> > Merge branch 'akpm-current/current' >> >> Hm is it really the merge of mmotm itself and not one of the patches in >> mmotm? >> Anyway smells like THP, adding Kirill. > > Okay, it took a while to figure it out. I'm sorry you had to go chasing for this one again. I'd found the same issue while investigating an ltp failure on arm64[0] and sent a fix[1]. The fix is effectively the same as your patch below. Andrew picked up the patch from v5 posting and I can see it in today's next[2]. [0] http://lists.infradead.org/pipermail/linux-arm-kernel/2017-June/510318.html [1] https://patchwork.kernel.org/patch/9766193/ [2] https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/mm/gup.c?h=next-20170627&id=d31945b5d4ab4490fb5f961dd5b066cc9f560eb3 > > The bug is in patch "mm, gup: ensure real head page is ref-counted when > using hugepages". We should look for a head *before* the loop. Otherwise > 'page' may point to the first page beyond the compound page. > > The patch below should help. > > If no objections, Andrew, could you fold it into the problematic patch? > > diff --git a/mm/gup.c b/mm/gup.c > index d8db6e5016a8..6f9ca86b3d03 100644 > --- a/mm/gup.c > +++ b/mm/gup.c > @@ -1424,6 +1424,7 @@ static int gup_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr, > > refs = 0; > page = pmd_page(orig) + ((addr & ~PMD_MASK) >> PAGE_SHIFT); > + head = compound_head(page); > do { > pages[*nr] = page; > (*nr)++; > @@ -1431,7 +1432,6 @@ static int gup_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr, > refs++; > } while (addr += PAGE_SIZE, addr != end); > > - head = compound_head(page); > if (!page_cache_add_speculative(head, refs)) { > *nr -= refs; > return 0; > @@ -1462,6 +1462,7 @@ static int gup_huge_pud(pud_t orig, pud_t *pudp, unsigned long addr, > > refs = 0; > page = pud_page(orig) + ((addr & ~PUD_MASK) >> PAGE_SHIFT); > + head = compound_head(page); > do { > pages[*nr] = page; > (*nr)++; > @@ -1469,7 +1470,6 @@ static int gup_huge_pud(pud_t orig, pud_t *pudp, unsigned long addr, > refs++; > } while (addr += PAGE_SIZE, addr != end); > > - head = compound_head(page); > if (!page_cache_add_speculative(head, refs)) { > *nr -= refs; > return 0; > @@ -1499,6 +1499,7 @@ static int gup_huge_pgd(pgd_t orig, pgd_t *pgdp, unsigned long addr, > BUILD_BUG_ON(pgd_devmap(orig)); > refs = 0; > page = pgd_page(orig) + ((addr & ~PGDIR_MASK) >> PAGE_SHIFT); > + head = compound_head(page); > do { > pages[*nr] = page; > (*nr)++; > @@ -1506,7 +1507,6 @@ static int gup_huge_pgd(pgd_t orig, pgd_t *pgdp, unsigned long addr, > refs++; > } while (addr += PAGE_SIZE, addr != end); > > - head = compound_head(page); > if (!page_cache_add_speculative(head, refs)) { > *nr -= refs; > return 0; -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
