6.10-stable review patch. If anyone has any objections, please let me know.
------------------
From: David Hildenbrand david@redhat.com
[ Upstream commit 2c1f057e5be63e890f2dd89e4c25ab5eef084a91 ]
We added PM_MMAP_EXCLUSIVE in 2015 via commit 77bb499bb60f ("pagemap: add mmap-exclusive bit for marking pages mapped only here"), when THPs could not be partially mapped and page_mapcount() returned something that was true for all pages of the THP.
In 2016, we added support for partially mapping THPs via commit 53f9263baba6 ("mm: rework mapcount accounting to enable 4k mapping of THPs") but missed to determine PM_MMAP_EXCLUSIVE as well per page.
Checking page_mapcount() on the head page does not tell the whole story.
We should check each individual page. In a future without per-page mapcounts it will be different, but we'll change that to be consistent with PTE-mapped THPs once we deal with that.
Link: https://lkml.kernel.org/r/20240607122357.115423-4-david@redhat.com Fixes: 53f9263baba6 ("mm: rework mapcount accounting to enable 4k mapping of THPs") Signed-off-by: David Hildenbrand david@redhat.com Reviewed-by: Oscar Salvador osalvador@suse.de Cc: Kirill A. Shutemov kirill.shutemov@linux.intel.com Cc: Alexey Dobriyan adobriyan@gmail.com Cc: Jonathan Corbet corbet@lwn.net Cc: Lance Yang ioworker0@gmail.com Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Sasha Levin sashal@kernel.org --- fs/proc/task_mmu.c | 22 ++++++++++++---------- 1 file changed, 12 insertions(+), 10 deletions(-)
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c index 22892cdb74cef..a45f2da0ada0d 100644 --- a/fs/proc/task_mmu.c +++ b/fs/proc/task_mmu.c @@ -1477,6 +1477,7 @@ static int pagemap_pmd_range(pmd_t *pmdp, unsigned long addr, unsigned long end,
ptl = pmd_trans_huge_lock(pmdp, vma); if (ptl) { + unsigned int idx = (addr & ~PMD_MASK) >> PAGE_SHIFT; u64 flags = 0, frame = 0; pmd_t pmd = *pmdp; struct page *page = NULL; @@ -1493,8 +1494,7 @@ static int pagemap_pmd_range(pmd_t *pmdp, unsigned long addr, unsigned long end, if (pmd_uffd_wp(pmd)) flags |= PM_UFFD_WP; if (pm->show_pfn) - frame = pmd_pfn(pmd) + - ((addr & ~PMD_MASK) >> PAGE_SHIFT); + frame = pmd_pfn(pmd) + idx; } #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION else if (is_swap_pmd(pmd)) { @@ -1503,11 +1503,9 @@ static int pagemap_pmd_range(pmd_t *pmdp, unsigned long addr, unsigned long end,
if (pm->show_pfn) { if (is_pfn_swap_entry(entry)) - offset = swp_offset_pfn(entry); + offset = swp_offset_pfn(entry) + idx; else - offset = swp_offset(entry); - offset = offset + - ((addr & ~PMD_MASK) >> PAGE_SHIFT); + offset = swp_offset(entry) + idx; frame = swp_type(entry) | (offset << MAX_SWAPFILES_SHIFT); } @@ -1523,12 +1521,16 @@ static int pagemap_pmd_range(pmd_t *pmdp, unsigned long addr, unsigned long end,
if (page && !PageAnon(page)) flags |= PM_FILE; - if (page && (flags & PM_PRESENT) && page_mapcount(page) == 1) - flags |= PM_MMAP_EXCLUSIVE;
- for (; addr != end; addr += PAGE_SIZE) { - pagemap_entry_t pme = make_pme(frame, flags); + for (; addr != end; addr += PAGE_SIZE, idx++) { + unsigned long cur_flags = flags; + pagemap_entry_t pme; + + if (page && (flags & PM_PRESENT) && + page_mapcount(page + idx) == 1) + cur_flags |= PM_MMAP_EXCLUSIVE;
+ pme = make_pme(frame, cur_flags); err = add_to_pagemap(&pme, pm); if (err) break;