From 88c28f2469151b031f8cea9b28ed5be1b74a4172 Mon Sep 17 00:00:00 2001 From: Huang Ying Date: Fri, 20 Apr 2018 14:55:38 -0700 Subject: [PATCH] mm, pagemap: fix swap offset value for PMD migration entry The swap offset reported by /proc//pagemap may be not correct for PMD migration entries. If addr passed into pagemap_pmd_range() isn't aligned with PMD start address, the swap offset reported doesn't reflect this. And in the loop to report information of each sub-page, the swap offset isn't increased accordingly as that for PFN. This may happen after opening /proc//pagemap and seeking to a page whose address doesn't align with a PMD start address. I have verified this with a simple test program. BTW: migration swap entries have PFN information, do we need to restrict whether to show them? [akpm@linux-foundation.org: fix typo, per Huang, Ying] Link: http://lkml.kernel.org/r/20180408033737.10897-1-ying.huang@intel.com Signed-off-by: "Huang, Ying" Cc: Michal Hocko Cc: "Kirill A. Shutemov" Cc: Andrei Vagin Cc: Dan Williams Cc: "Jerome Glisse" Cc: Daniel Colascione Cc: Zi Yan Cc: Naoya Horiguchi Cc: Alexey Dobriyan Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/proc/task_mmu.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c index 65ae54659833..c486ad4b43f0 100644 --- a/fs/proc/task_mmu.c +++ b/fs/proc/task_mmu.c @@ -1310,9 +1310,11 @@ static int pagemap_pmd_range(pmd_t *pmdp, unsigned long addr, unsigned long end, #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION else if (is_swap_pmd(pmd)) { swp_entry_t entry = pmd_to_swp_entry(pmd); + unsigned long offset = swp_offset(entry); + offset += (addr & ~PMD_MASK) >> PAGE_SHIFT; frame = swp_type(entry) | - (swp_offset(entry) << MAX_SWAPFILES_SHIFT); + (offset << MAX_SWAPFILES_SHIFT); flags |= PM_SWAP; if (pmd_swp_soft_dirty(pmd)) flags |= PM_SOFT_DIRTY; @@ -1332,6 +1334,8 @@ static int pagemap_pmd_range(pmd_t *pmdp, unsigned long addr, unsigned long end, break; if (pm->show_pfn && (flags & PM_PRESENT)) frame++; + else if (flags & PM_SWAP) + frame += (1 << MAX_SWAPFILES_SHIFT); } spin_unlock(ptl); return err; -- 2.20.1