The patch titled
mm: add comment why mark_page_accessed() would be better than pte_mkyoung() in follow_page()
has been removed from the -mm tree. Its filename was
mm-add-comment-why-mark_page_accessed-would-be-better-than-pte_mkyoung-in-follow_page.patch
This patch was dropped because it was merged into mainline or a subsystem tree
The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/
------------------------------------------------------
Subject: mm: add comment why mark_page_accessed() would be better than pte_mkyoung() in follow_page()
From: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx>
At first look, mark_page_accessed() in follow_page() seems a bit strange.
It seems pte_mkyoung() would be better consistent with other kernel code.
However, it is intentional. The commit log said:
------------------------------------------------
commit 9e45f61d69be9024a2e6bef3831fb04d90fac7a8
Author: akpm <akpm>
Date: Fri Aug 15 07:24:59 2003 +0000
[PATCH] Use mark_page_accessed() in follow_page()
Touching a page via follow_page() counts as a reference so we should be
either setting the referenced bit in the pte or running mark_page_accessed().
Altering the pte is tricky because we haven't implemented an atomic
pte_mkyoung(). And mark_page_accessed() is better anyway because it has more
aging state: it can move the page onto the active list.
BKrev: 3f3c8acbplT8FbwBVGtth7QmnqWkIw
------------------------------------------------
The atomic issue is still true nowadays. adding comment help to understand
code intention and it would be better.
[akpm@xxxxxxxxxxxxxxxxxxxx: clarify text]
Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx>
Signed-off-by: Hugh Dickins <hugh@xxxxxxxxxxx>
Cc: Nick Piggin <npiggin@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/memory.c | 5 +++++
1 file changed, 5 insertions(+)
diff -puN mm/memory.c~mm-add-comment-why-mark_page_accessed-would-be-better-than-pte_mkyoung-in-follow_page mm/memory.c
--- a/mm/memory.c~mm-add-comment-why-mark_page_accessed-would-be-better-than-pte_mkyoung-in-follow_page
+++ a/mm/memory.c
@@ -1151,6 +1151,11 @@ struct page *follow_page(struct vm_area_
if ((flags & FOLL_WRITE) &&
!pte_dirty(pte) && !PageDirty(page))
set_page_dirty(page);
+ /*
+ * pte_mkyoung() would be more correct here, but atomic care
+ * is needed to avoid losing the dirty bit: it is easier to use
+ * mark_page_accessed().
+ */
mark_page_accessed(page);
}
unlock:
_
Patches currently in -mm which might be from kosaki.motohiro@xxxxxxxxxxxxxx are
origin.patch
linux-next.patch
mm-update_page_reclaim_stat-is-called-from-page-fault-path.patch
getrusage-fill-ru_maxrss-value.patch
softirq-introduce-statistics-for-softirq.patch
proc-export-statistics-for-softirq-to-proc.patch
proc-export-statistics-for-softirq-to-proc-fix.patch
proc-update-document-for-proc-softirqs-and-proc-stat.patch
memcg-remove-mem_cgroup_calc_mapped_ratio-take2.patch
memcg-remove-mem_cgroup_reclaim_imbalance-remnants.patch
ia64-implement-interrupt-enabling-rwlocks.patch
fs-symlink-write_begin-allocation-context-fix-reiser4-fix.patch
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