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mm: reference totalram_pages and managed_pages once per function

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Patch series "mm: convert totalram_pages, totalhigh_pages and managed
pages to atomic", v5.

This series converts totalram_pages, totalhigh_pages and
zone->managed_pages to atomic variables.

totalram_pages, zone->managed_pages and totalhigh_pages updates are
protected by managed_page_count_lock, but readers never care about it.
Convert these variables to atomic to avoid readers potentially seeing a
store tear.

Main motivation was that managed_page_count_lock handling was complicating
things.  It was discussed in length here,
https://lore.kernel.org/patchwork/patch/995739/#1181785 It seemes better
to remove the lock and convert variables to atomic.  With the change,
preventing poteintial store-to-read tearing comes as a bonus.

This patch (of 4):

This is in preparation to a later patch which converts totalram_pages and
zone->managed_pages to atomic variables.  Please note that re-reading the
value might lead to a different value and as such it could lead to
unexpected behavior.  There are no known bugs as a result of the current
code but it is better to prevent from them in principle.

Link: http://lkml.kernel.org/r/1542090790-21750-2-git-send-email-arunks@codeaurora.org
Signed-off-by: Arun KS <arunks@codeaurora.org>
Reviewed-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Reviewed-by: David Hildenbrand <david@redhat.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Pavel Tatashin <pasha.tatashin@soleen.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Arun KS
2018-12-28 00:34:20 -08:00
committed by Linus Torvalds
parent fecd4a50ba
commit 3d6357de8a
12 changed files with 44 additions and 33 deletions
Download Patch File Download Diff File Expand all files Collapse all files

7
fs/file_table.c
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@@ -380,10 +380,11 @@ void __init files_init(void)
void __init files_maxfiles_init(void)
{
unsigned long n;
unsigned long memreserve = (totalram_pages - nr_free_pages()) * 3/2;
unsigned long nr_pages = totalram_pages;
unsigned long memreserve = (nr_pages - nr_free_pages()) * 3/2;
memreserve = min(memreserve, totalram_pages - 1);
n = ((totalram_pages - memreserve) * (PAGE_SIZE / 1024)) / 10;
memreserve = min(memreserve, nr_pages - 1);
n = ((nr_pages - memreserve) * (PAGE_SIZE / 1024)) / 10;
files_stat.max_files = max_t(unsigned long, n, NR_FILE);
}