From: Andrew Morton <akpm@linux-foundation.org>
To: David Hildenbrand <david@redhat.com>
Cc: Yang Shi <shy828301@gmail.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Hugh Dickins <hughd@google.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
David Rientjes <rientjes@google.com>,
Shakeel Butt <shakeelb@google.com>,
John Hubbard <jhubbard@nvidia.com>,
Jason Gunthorpe <jgg@nvidia.com>,
Mike Kravetz <mike.kravetz@oracle.com>,
Mike Rapoport <rppt@linux.ibm.com>,
"Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>,
Matthew Wilcox <willy@infradead.org>,
Vlastimil Babka <vbabka@suse.cz>, Jann Horn <jannh@google.com>,
Michal Hocko <mhocko@kernel.org>, Nadav Amit <namit@vmware.com>,
Rik van Riel <riel@surriel.com>, Roman Gushchin <guro@fb.com>,
Andrea Arcangeli <aarcange@redhat.com>,
Peter Xu <peterx@redhat.com>, Donald Dutile <ddutile@redhat.com>,
Christoph Hellwig <hch@lst.de>, Oleg Nesterov <oleg@redhat.com>,
Jan Kara <jack@suse.cz>, Liang Zhang <zhangliang5@huawei.com>,
Linux MM <linux-mm@kvack.org>
Subject: Re: [PATCH v3 3/9] mm: slightly clarify KSM logic in do_swap_page()
Date: Wed, 9 Mar 2022 12:50:45 -0800 [thread overview]
Message-ID: <20220309125045.b04d20235a7260afceaf04d6@linux-foundation.org> (raw)
In-Reply-To: <a01de28c-2195-eab3-fd3c-0e8ad3f58040@redhat.com>
On Wed, 9 Mar 2022 20:15:54 +0100 David Hildenbrand <david@redhat.com> wrote:
> On 09.03.22 19:48, Yang Shi wrote:
> > On Mon, Jan 31, 2022 at 8:33 AM David Hildenbrand <david@redhat.com> wrote:
> >>
> >> Let's make it clearer that KSM might only have to copy a page
> >> in case we have a page in the swapcache, not if we allocated a fresh
> >> page and bypassed the swapcache. While at it, add a comment why this is
> >> usually necessary and merge the two swapcache conditions.
> >>
> >> Signed-off-by: David Hildenbrand <david@redhat.com>
> >> ---
> >> mm/memory.c | 38 +++++++++++++++++++++++---------------
> >> 1 file changed, 23 insertions(+), 15 deletions(-)
> >>
> >> diff --git a/mm/memory.c b/mm/memory.c
> >> index 923165b4c27e..3c91294cca98 100644
> >> --- a/mm/memory.c
> >> +++ b/mm/memory.c
> >> @@ -3615,21 +3615,29 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
> >> goto out_release;
> >> }
> >>
> >> - /*
> >> - * Make sure try_to_free_swap or reuse_swap_page or swapoff did not
> >
> > We could remove the reference to "reuse_swap_page", right?
> >
> Yes, I noticed this a couple of days ago as well and already have a
> patch prepared for that ("mm: adjust stale comment in do_swap_page()
> mentioning reuse_swap_page()" at
> https://github.com/davidhildenbrand/linux/commits/cow_fixes_part_3)
>
> If Andrew wants, we can fix that up directly before sending upstream or
> I'll simply include that patch when sending out part2 v2.
>
> (I want to avoid sending another series just for this)
Thanks, I did this. The same change plus gratuitous comment reflowing.
--- a/mm/memory.c~mm-slightly-clarify-ksm-logic-in-do_swap_page-fix
+++ a/mm/memory.c
@@ -3609,11 +3609,11 @@ vm_fault_t do_swap_page(struct vm_fault
if (swapcache) {
/*
- * Make sure try_to_free_swap or reuse_swap_page or swapoff did
- * not release the swapcache from under us. The page pin, and
- * pte_same test below, are not enough to exclude that. Even if
- * it is still swapcache, we need to check that the page's swap
- * has not changed.
+ * Make sure try_to_free_swap or swapoff did not release the
+ * swapcache from under us. The page pin, and pte_same test
+ * below, are not enough to exclude that. Even if it is still
+ * swapcache, we need to check that the page's swap has not
+ * changed.
*/
if (unlikely(!PageSwapCache(page) ||
page_private(page) != entry.val))
_
next prev parent reply other threads:[~2022-03-09 20:50 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-01-31 16:29 [PATCH v3 0/9] mm: COW fixes part 1: fix the COW security issue for THP and swap David Hildenbrand
2022-01-31 16:29 ` [PATCH v3 1/9] mm: optimize do_wp_page() for exclusive pages in the swapcache David Hildenbrand
2022-01-31 16:29 ` [PATCH v3 2/9] mm: optimize do_wp_page() for fresh pages in local LRU pagevecs David Hildenbrand
2022-03-09 17:53 ` Vlastimil Babka
2022-01-31 16:29 ` [PATCH v3 3/9] mm: slightly clarify KSM logic in do_swap_page() David Hildenbrand
2022-03-09 18:03 ` Vlastimil Babka
2022-03-09 18:48 ` Yang Shi
2022-03-09 19:15 ` David Hildenbrand
2022-03-09 20:50 ` Andrew Morton [this message]
2022-01-31 16:29 ` [PATCH v3 4/9] mm: streamline COW " David Hildenbrand
2022-03-10 9:41 ` Vlastimil Babka
2022-01-31 16:29 ` [PATCH v3 5/9] mm/huge_memory: streamline COW logic in do_huge_pmd_wp_page() David Hildenbrand
2022-03-10 9:52 ` Vlastimil Babka
2022-01-31 16:29 ` [PATCH v3 6/9] mm/khugepaged: remove reuse_swap_page() usage David Hildenbrand
2022-02-01 21:31 ` Yang Shi
2022-03-10 10:37 ` Vlastimil Babka
2022-01-31 16:29 ` [PATCH v3 7/9] mm/swapfile: remove stale reuse_swap_page() David Hildenbrand
2022-02-02 14:35 ` Christoph Hellwig
2022-02-02 17:01 ` David Hildenbrand
2022-03-10 10:44 ` Vlastimil Babka
2022-01-31 16:29 ` [PATCH v3 8/9] mm/huge_memory: remove stale page_trans_huge_mapcount() David Hildenbrand
2022-03-10 10:50 ` Vlastimil Babka
2022-01-31 16:29 ` [PATCH v3 9/9] mm/huge_memory: remove stale locking logic from __split_huge_pmd() David Hildenbrand
2022-03-10 11:02 ` Vlastimil Babka
2022-02-01 18:59 ` [PATCH v3 0/9] mm: COW fixes part 1: fix the COW security issue for THP and swap Linus Torvalds
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