4.16-stable review patch. If anyone has any objections, please let me know.
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From: Huang Ying ying.huang@intel.com
[ Upstream commit 88c28f2469151b031f8cea9b28ed5be1b74a4172 ]
The swap offset reported by /proc/<pid>/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/<pid>/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" ying.huang@intel.com Cc: Michal Hocko mhocko@suse.com Cc: "Kirill A. Shutemov" kirill.shutemov@linux.intel.com Cc: Andrei Vagin avagin@openvz.org Cc: Dan Williams dan.j.williams@intel.com Cc: "Jerome Glisse" jglisse@redhat.com Cc: Daniel Colascione dancol@google.com Cc: Zi Yan zi.yan@cs.rutgers.edu Cc: Naoya Horiguchi n-horiguchi@ah.jp.nec.com Cc: Alexey Dobriyan adobriyan@gmail.com Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Sasha Levin alexander.levin@microsoft.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/proc/task_mmu.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-)
--- a/fs/proc/task_mmu.c +++ b/fs/proc/task_mmu.c @@ -1329,9 +1329,11 @@ static int pagemap_pmd_range(pmd_t *pmdp #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; @@ -1351,6 +1353,8 @@ static int pagemap_pmd_range(pmd_t *pmdp break; if (pm->show_pfn && (flags & PM_PRESENT)) frame++; + else if (flags & PM_SWAP) + frame += (1 << MAX_SWAPFILES_SHIFT); } spin_unlock(ptl); return err;