Re: mm: another VM_BUG_ON_PAGE(PageTail(page))
From: Dmitry Vyukov <dvyukov@google.com>
Date: 2016-02-01 10:48:52
Also in:
linux-scsi, lkml
On Fri, Jan 29, 2016 at 1:35 PM, Kirill A. Shutemov [off-list ref] wrote:
From 691a961bb401c5815ed741dac63591efbc6027e3 Mon Sep 17 00:00:00 2001 From: "Kirill A. Shutemov" <redacted> Date: Fri, 29 Jan 2016 15:06:17 +0300 Subject: [PATCH 2/2] mempolicy: do not try to queue pages from !vma_migratable() Maybe I miss some point, but I don't see a reason why we try to queue pages from non migratable VMAs. The only case when we can queue pages from such VMA is MPOL_MF_STRICT plus MPOL_MF_MOVE or MPOL_MF_MOVE_ALL for VMA which has pages on LRU, but gfp mask is not sutable for migaration (see mapping_gfp_mask() check in vma_migratable()). That's looks like a bug to me. Let's filter out non-migratable vma at start of queue_pages_test_walk() and go to queue_pages_pte_range() only if MPOL_MF_MOVE or MPOL_MF_MOVE_ALL flag is set.
I've run the fuzzer with these two patches for the weekend and seen no crashes. I guess we can consider this as fixed. Thanks!
quoted hunk ↗ jump to hunk
Signed-off-by: Kirill A. Shutemov <redacted> --- mm/mempolicy.c | 14 +++++--------- 1 file changed, 5 insertions(+), 9 deletions(-)diff --git a/mm/mempolicy.c b/mm/mempolicy.c index 27d135408a22..4c4187c0e1de 100644 --- a/mm/mempolicy.c +++ b/mm/mempolicy.c@@ -548,8 +548,7 @@ retry: goto retry; } - if (flags & (MPOL_MF_MOVE | MPOL_MF_MOVE_ALL)) - migrate_page_add(page, qp->pagelist, flags); + migrate_page_add(page, qp->pagelist, flags); } pte_unmap_unlock(pte - 1, ptl); cond_resched();@@ -625,7 +624,7 @@ static int queue_pages_test_walk(unsigned long start, unsigned long end, unsigned long endvma = vma->vm_end; unsigned long flags = qp->flags; - if (vma->vm_flags & VM_PFNMAP) + if (!vma_migratable(vma)) return 1; if (endvma > end)@@ -644,16 +643,13 @@ static int queue_pages_test_walk(unsigned long start, unsigned long end, if (flags & MPOL_MF_LAZY) { /* Similar to task_numa_work, skip inaccessible VMAs */ - if (vma_migratable(vma) && - vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)) + if (vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)) change_prot_numa(vma, start, endvma); return 1; } - if ((flags & MPOL_MF_STRICT) || - ((flags & (MPOL_MF_MOVE | MPOL_MF_MOVE_ALL)) && - vma_migratable(vma))) - /* queue pages from current vma */ + /* queue pages from current vma */ + if (flags & (MPOL_MF_MOVE | MPOL_MF_MOVE_ALL)) return 0; return 1; } --2.7.0.rc3 -- You received this message because you are subscribed to the Google Groups "syzkaller" group. To unsubscribe from this group and stop receiving emails from it, send an email to syzkaller+unsubscribe@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
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