diff options
author | Hugh Dickins <hughd@google.com> | 2021-07-11 20:10:49 -0700 |
---|---|---|
committer | Linus Torvalds <torvalds@linux-foundation.org> | 2021-07-12 11:30:56 -0700 |
commit | efdb6720b44b2f016d2a04b2c84e577e57ed84bd (patch) | |
tree | 8839da504223a882c72890dde4d56c9c44d5e6a4 | |
parent | e73f0f0ee7541171d89f2e2491130c7771ba58d3 (diff) | |
download | linux-efdb6720b44b2f016d2a04b2c84e577e57ed84bd.tar.gz linux-efdb6720b44b2f016d2a04b2c84e577e57ed84bd.tar.bz2 linux-efdb6720b44b2f016d2a04b2c84e577e57ed84bd.zip |
mm/rmap: fix munlocking Anon THP with mlocked ptes
Many thanks to Kirill for reminding that PageDoubleMap cannot be relied on
to warn of pte mappings in the Anon THP case; and a scan of subpages does
not seem appropriate here. Note how follow_trans_huge_pmd() does not even
mark an Anon THP as mlocked when compound_mapcount != 1: multiple mlocking
of Anon THP is avoided, so simply return from page_mlock() in this case.
Link: https://lore.kernel.org/lkml/cfa154c-d595-406-eb7d-eb9df730f944@google.com/
Fixes: d9770fcc1c0c ("mm/rmap: fix old bug: munlocking THP missed other mlocks")
Reported-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Hugh Dickins <hughd@google.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: Ralph Campbell <rcampbell@nvidia.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Shakeel Butt <shakeelb@google.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r-- | mm/rmap.c | 39 |
1 files changed, 22 insertions, 17 deletions
diff --git a/mm/rmap.c b/mm/rmap.c index 795f9d5f8386..b9eb5c12f3fe 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -1440,21 +1440,20 @@ static bool try_to_unmap_one(struct page *page, struct vm_area_struct *vma, /* * If the page is mlock()d, we cannot swap it out. */ - if (!(flags & TTU_IGNORE_MLOCK)) { - if (vma->vm_flags & VM_LOCKED) { - /* PTE-mapped THP are never marked as mlocked */ - if (!PageTransCompound(page) || - (PageHead(page) && !PageDoubleMap(page))) { - /* - * Holding pte lock, we do *not* need - * mmap_lock here - */ - mlock_vma_page(page); - } - ret = false; - page_vma_mapped_walk_done(&pvmw); - break; - } + if (!(flags & TTU_IGNORE_MLOCK) && + (vma->vm_flags & VM_LOCKED)) { + /* + * PTE-mapped THP are never marked as mlocked: so do + * not set it on a DoubleMap THP, nor on an Anon THP + * (which may still be PTE-mapped after DoubleMap was + * cleared). But stop unmapping even in those cases. + */ + if (!PageTransCompound(page) || (PageHead(page) && + !PageDoubleMap(page) && !PageAnon(page))) + mlock_vma_page(page); + page_vma_mapped_walk_done(&pvmw); + ret = false; + break; } /* Unexpected PMD-mapped THP? */ @@ -1986,8 +1985,10 @@ static bool page_mlock_one(struct page *page, struct vm_area_struct *vma, */ if (vma->vm_flags & VM_LOCKED) { /* - * PTE-mapped THP are never marked as mlocked, but - * this function is never called when PageDoubleMap(). + * PTE-mapped THP are never marked as mlocked; but + * this function is never called on a DoubleMap THP, + * nor on an Anon THP (which may still be PTE-mapped + * after DoubleMap was cleared). */ mlock_vma_page(page); /* @@ -2022,6 +2023,10 @@ void page_mlock(struct page *page) VM_BUG_ON_PAGE(!PageLocked(page) || PageLRU(page), page); VM_BUG_ON_PAGE(PageCompound(page) && PageDoubleMap(page), page); + /* Anon THP are only marked as mlocked when singly mapped */ + if (PageTransCompound(page) && PageAnon(page)) + return; + rmap_walk(page, &rwc); } |