6.10-stable review patch. If anyone has any objections, please let me know.
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From: David Hildenbrand david@redhat.com
[ Upstream commit da7f31ed0f4df8f61e8195e527aa83dd54896ba3 ]
Relying on the mapcount for non-present PTEs that reference pages doesn't make any sense: they are not accounted in the mapcount, so page_mapcount() == 1 won't return the result we actually want to know.
While we don't check the mapcount for migration entries already, we could end up checking it for swap, hwpoison, device exclusive, ... entries, which we really shouldn't.
There is one exception: device private entries, which we consider fake-present (e.g., incremented the mapcount). But we won't care about that for now for PM_MMAP_EXCLUSIVE, because indicating PM_SWAP for them although they are fake-present already sounds suspiciously wrong.
Let's never indicate PM_MMAP_EXCLUSIVE without PM_PRESENT.
Link: https://lkml.kernel.org/r/20240607122357.115423-3-david@redhat.com Signed-off-by: David Hildenbrand david@redhat.com Reviewed-by: Oscar Salvador osalvador@suse.de Cc: Alexey Dobriyan adobriyan@gmail.com Cc: Jonathan Corbet corbet@lwn.net Cc: Kirill A. Shutemov kirill.shutemov@linux.intel.com Cc: Lance Yang ioworker0@gmail.com Signed-off-by: Andrew Morton akpm@linux-foundation.org Stable-dep-of: 2c1f057e5be6 ("fs/proc/task_mmu: properly detect PM_MMAP_EXCLUSIVE per page of PMD-mapped THPs") Signed-off-by: Sasha Levin sashal@kernel.org --- fs/proc/task_mmu.c | 8 ++------ 1 file changed, 2 insertions(+), 6 deletions(-)
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c index 76ad35df3b1ee..22892cdb74cef 100644 --- a/fs/proc/task_mmu.c +++ b/fs/proc/task_mmu.c @@ -1418,7 +1418,6 @@ static pagemap_entry_t pte_to_pagemap_entry(struct pagemapread *pm, { u64 frame = 0, flags = 0; struct page *page = NULL; - bool migration = false;
if (pte_present(pte)) { if (pm->show_pfn) @@ -1450,7 +1449,6 @@ static pagemap_entry_t pte_to_pagemap_entry(struct pagemapread *pm, (offset << MAX_SWAPFILES_SHIFT); } flags |= PM_SWAP; - migration = is_migration_entry(entry); if (is_pfn_swap_entry(entry)) page = pfn_swap_entry_to_page(entry); if (pte_marker_entry_uffd_wp(entry)) @@ -1459,7 +1457,7 @@ static pagemap_entry_t pte_to_pagemap_entry(struct pagemapread *pm,
if (page && !PageAnon(page)) flags |= PM_FILE; - if (page && !migration && page_mapcount(page) == 1) + if (page && (flags & PM_PRESENT) && page_mapcount(page) == 1) flags |= PM_MMAP_EXCLUSIVE; if (vma->vm_flags & VM_SOFTDIRTY) flags |= PM_SOFT_DIRTY; @@ -1476,7 +1474,6 @@ static int pagemap_pmd_range(pmd_t *pmdp, unsigned long addr, unsigned long end, pte_t *pte, *orig_pte; int err = 0; #ifdef CONFIG_TRANSPARENT_HUGEPAGE - bool migration = false;
ptl = pmd_trans_huge_lock(pmdp, vma); if (ptl) { @@ -1520,14 +1517,13 @@ static int pagemap_pmd_range(pmd_t *pmdp, unsigned long addr, unsigned long end, if (pmd_swp_uffd_wp(pmd)) flags |= PM_UFFD_WP; VM_BUG_ON(!is_pmd_migration_entry(pmd)); - migration = is_migration_entry(entry); page = pfn_swap_entry_to_page(entry); } #endif
if (page && !PageAnon(page)) flags |= PM_FILE; - if (page && !migration && page_mapcount(page) == 1) + if (page && (flags & PM_PRESENT) && page_mapcount(page) == 1) flags |= PM_MMAP_EXCLUSIVE;
for (; addr != end; addr += PAGE_SIZE) {