lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
Open Source and information security mailing list archives
| ||
|
Date: Fri, 25 Oct 2019 01:27:46 +0800 From: Yang Shi <yang.shi@...ux.alibaba.com> To: hughd@...gle.com, kirill.shutemov@...ux.intel.com, aarcange@...hat.com, akpm@...ux-foundation.org Cc: yang.shi@...ux.alibaba.com, linux-mm@...ck.org, linux-kernel@...r.kernel.org Subject: [PATCH] mm: thp: clear PageDoubleMap flag when the last PMD map gone File THP sets PageDoubleMap flag when the first it gets PTE mapped, but the flag is never cleared until the THP is freed. This result in unbalanced state although it is not a big deal. Clear the flag when the last compound_mapcount is gone. It should be cleared when all the PTE maps are gone (become PMD mapped only) as well, but this needs check all subpage's _mapcount every time any subpage's rmap is removed, the overhead may be not worth. The anonymous THP also just clears PageDoubleMap flag when the last PMD map is gone. Cc: Hugh Dickins <hughd@...gle.com> Cc: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com> Cc: Andrea Arcangeli <aarcange@...hat.com> Signed-off-by: Yang Shi <yang.shi@...ux.alibaba.com> --- Hugh thought it is unnecessary to fix it completely due to the overhead (https://lkml.org/lkml/2019/10/22/1011), but it sounds simple to achieve the similar balance as anonymous THP. mm/rmap.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/mm/rmap.c b/mm/rmap.c index 0c7b2a9..d17cbf3 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -1236,6 +1236,9 @@ static void page_remove_file_rmap(struct page *page, bool compound) __dec_node_page_state(page, NR_SHMEM_PMDMAPPED); else __dec_node_page_state(page, NR_FILE_PMDMAPPED); + + /* The last PMD map is gone */ + ClearPageDoubleMap(compound_head(page)); } else { if (!atomic_add_negative(-1, &page->_mapcount)) goto out; -- 1.8.3.1
Powered by blists - more mailing lists