Subject: + mm-ignore-vm_softdirty-on-vma-merging.patch added to -mm tree To: gorcunov@xxxxxxxxx,gnome@xxxxxxxx,gorcunov@xxxxxxxxxx,mgorman@xxxxxxx,stable@xxxxxxxxxxxxxxx,xemul@xxxxxxxxxxxxx From: akpm@xxxxxxxxxxxxxxxxxxxx Date: Thu, 23 Jan 2014 13:01:33 -0800 The patch titled Subject: mm: ignore VM_SOFTDIRTY on VMA merging has been added to the -mm tree. Its filename is mm-ignore-vm_softdirty-on-vma-merging.patch This patch should soon appear at http://ozlabs.org/~akpm/mmots/broken-out/mm-ignore-vm_softdirty-on-vma-merging.patch and later at http://ozlabs.org/~akpm/mmotm/broken-out/mm-ignore-vm_softdirty-on-vma-merging.patch Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/SubmitChecklist when testing your code *** The -mm tree is included into linux-next and is updated there every 3-4 working days ------------------------------------------------------ From: Cyrill Gorcunov <gorcunov@xxxxxxxxx> Subject: mm: ignore VM_SOFTDIRTY on VMA merging The VM_SOFTDIRTY bit affects vma merge routine: if two VMAs has all bits in vm_flags matched except dirty bit the kernel can't longer merge them and this forces the kernel to generate new VMAs instead. It finally may lead to the situation when userspace application reaches vm.max_map_count limit and get crashed in worse case | (gimp:11768): GLib-ERROR **: gmem.c:110: failed to allocate 4096 bytes | | (file-tiff-load:12038): LibGimpBase-WARNING **: file-tiff-load: gimp_wire_read(): error | xinit: connection to X server lost | | waiting for X server to shut down | /usr/lib64/gimp/2.0/plug-ins/file-tiff-load terminated: Hangup | /usr/lib64/gimp/2.0/plug-ins/script-fu terminated: Hangup | /usr/lib64/gimp/2.0/plug-ins/script-fu terminated: Hangup https://bugzilla.kernel.org/show_bug.cgi?id=67651 https://bugzilla.gnome.org/show_bug.cgi?id=719619#c0 Initial problem came from missed VM_SOFTDIRTY in do_brk() routine but even if we would set up VM_SOFTDIRTY here, there is still a way to prevent VMAs from merging: one can call | echo 4 > /proc/$PID/clear_refs and clear all VM_SOFTDIRTY over all VMAs presented in memory map, then new do_brk() will try to extend old VMA and finds that dirty bit doesn't match thus new VMA will be generated. As discussed with Pavel, the right approach should be to ignore VM_SOFTDIRTY bit when we're trying to merge VMAs and if merge successed we mark extended VMA with dirty bit where needed. Signed-off-by: Cyrill Gorcunov <gorcunov@xxxxxxxxxx> Reported-by: Bastian Hougaard <gnome@xxxxxxxx> Reported-by: Mel Gorman <mgorman@xxxxxxx> Cc: Pavel Emelyanov <xemul@xxxxxxxxxxxxx> Cc: <stable@xxxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/mmap.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) diff -puN mm/mmap.c~mm-ignore-vm_softdirty-on-vma-merging mm/mmap.c --- a/mm/mmap.c~mm-ignore-vm_softdirty-on-vma-merging +++ a/mm/mmap.c @@ -894,7 +894,15 @@ again: remove_next = 1 + (end > next-> static inline int is_mergeable_vma(struct vm_area_struct *vma, struct file *file, unsigned long vm_flags) { - if (vma->vm_flags ^ vm_flags) + /* + * VM_SOFTDIRTY should not prevent from VMA merging, if we + * match the flags but dirty bit -- the caller should mark + * merged VMA as dirty. If dirty bit won't be excluded from + * comparison, we increase pressue on the memory system forcing + * the kernel to generate new VMAs when old one could be + * extended instead. + */ + if ((vma->vm_flags ^ vm_flags) & ~VM_SOFTDIRTY) return 0; if (vma->vm_file != file) return 0; @@ -1083,7 +1091,7 @@ static int anon_vma_compatible(struct vm return a->vm_end == b->vm_start && mpol_equal(vma_policy(a), vma_policy(b)) && a->vm_file == b->vm_file && - !((a->vm_flags ^ b->vm_flags) & ~(VM_READ|VM_WRITE|VM_EXEC)) && + !((a->vm_flags ^ b->vm_flags) & ~(VM_READ|VM_WRITE|VM_EXEC|VM_SOFTDIRTY)) && b->vm_pgoff == a->vm_pgoff + ((b->vm_start - a->vm_start) >> PAGE_SHIFT); } _ Patches currently in -mm which might be from gorcunov@xxxxxxxxx are origin.patch mm-ignore-vm_softdirty-on-vma-merging.patch -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html