On Sat, Feb 28, 2015 at 02:45:38PM -0800, [email protected] wrote: > > The patch below does not apply to the 3.14-stable tree. > If someone wants it applied there, or to any other stable or longterm > tree, then please email the backport, including the original git commit > id to <[email protected]>. > > thanks,
This patch depends on the following one: commit 81d0fa623c5b8dbd5279d9713094b0f9b0a00fb4 Author: Peter Feiner <[email protected]> Date: Thu Oct 9 15:28:32 2014 -0700 mm: softdirty: unmapped addresses between VMAs are clean Commit 81d0fa623c5b is cleanly applicable onto v3.14.34, so we can backport 05fbf357d941 with this patch. As for the change in 81d0fa623c5b, I think the fix looks clear and simple (contained in a single function,) so it's worth backporting as a stable fix too. Or is there any reason that this 81d0fa623c5b was not tagged for stable trees? Any idea, Peter? Thanks, Naoya Horiguchi > > greg k-h > > ------------------ original commit in Linus's tree ------------------ > > From 05fbf357d94152171bc50f8a369390f1f16efd89 Mon Sep 17 00:00:00 2001 > From: Konstantin Khlebnikov <[email protected]> > Date: Wed, 11 Feb 2015 15:27:31 -0800 > Subject: [PATCH] proc/pagemap: walk page tables under pte lock > > Lockless access to pte in pagemap_pte_range() might race with page > migration and trigger BUG_ON(!PageLocked()) in migration_entry_to_page(): > > CPU A (pagemap) CPU B (migration) > lock_page() > try_to_unmap(page, TTU_MIGRATION...) > make_migration_entry() > set_pte_at() > <read *pte> > pte_to_pagemap_entry() > remove_migration_ptes() > unlock_page() > if(is_migration_entry()) > migration_entry_to_page() > BUG_ON(!PageLocked(page)) > > Also lockless read might be non-atomic if pte is larger than wordsize. > Other pte walkers (smaps, numa_maps, clear_refs) already lock ptes. > > Fixes: 052fb0d635df ("proc: report file/anon bit in /proc/pid/pagemap") > Signed-off-by: Konstantin Khlebnikov <[email protected]> > Reported-by: Andrey Ryabinin <[email protected]> > Reviewed-by: Cyrill Gorcunov <[email protected]> > Acked-by: Naoya Horiguchi <[email protected]> > Acked-by: Kirill A. Shutemov <[email protected]> > Cc: <[email protected]> [3.5+] > Signed-off-by: Andrew Morton <[email protected]> > Signed-off-by: Linus Torvalds <[email protected]> > > diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c > index e6e0abeb5d12..eeab30fcffcc 100644 > --- a/fs/proc/task_mmu.c > +++ b/fs/proc/task_mmu.c > @@ -1056,7 +1056,7 @@ static int pagemap_pte_range(pmd_t *pmd, unsigned long > addr, unsigned long end, > struct vm_area_struct *vma; > struct pagemapread *pm = walk->private; > spinlock_t *ptl; > - pte_t *pte; > + pte_t *pte, *orig_pte; > int err = 0; > > /* find the first VMA at or above 'addr' */ > @@ -1117,15 +1117,19 @@ static int pagemap_pte_range(pmd_t *pmd, unsigned > long addr, unsigned long end, > BUG_ON(is_vm_hugetlb_page(vma)); > > /* Addresses in the VMA. */ > - for (; addr < min(end, vma->vm_end); addr += PAGE_SIZE) { > + orig_pte = pte = pte_offset_map_lock(walk->mm, pmd, addr, &ptl); > + for (; addr < min(end, vma->vm_end); pte++, addr += PAGE_SIZE) { > pagemap_entry_t pme; > - pte = pte_offset_map(pmd, addr); > + > pte_to_pagemap_entry(&pme, pm, vma, addr, *pte); > - pte_unmap(pte); > err = add_to_pagemap(addr, &pme, pm); > if (err) > - return err; > + break; > } > + pte_unmap_unlock(orig_pte, ptl); > + > + if (err) > + return err; > > if (addr == end) > break; > -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
