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authorArun KS <arunks@codeaurora.org>2018-12-28 00:34:20 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2018-12-28 12:11:47 -0800
commit3d6357de8aa09e1966770dc1171c72679946464f (patch)
treea24bb2f8795ea4927c1ff64d5f5f00398bee925d /arch
parentfecd4a50baaebf6bde7f9e0b88fef13ffe5d98a1 (diff)
downloadlinux-3d6357de8aa09e1966770dc1171c72679946464f.tar.gz
mm: reference totalram_pages and managed_pages once per function
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>
Diffstat (limited to 'arch')
-rw-r--r--arch/um/kernel/mem.c2
-rw-r--r--arch/x86/kernel/cpu/microcode/core.c5
2 files changed, 4 insertions, 3 deletions
diff --git a/arch/um/kernel/mem.c b/arch/um/kernel/mem.c
index 1067469ba2ea..2da209687a22 100644
--- a/arch/um/kernel/mem.c
+++ b/arch/um/kernel/mem.c
@@ -52,7 +52,7 @@ void __init mem_init(void)
/* this will put all low memory onto the freelists */
memblock_free_all();
max_low_pfn = totalram_pages;
- max_pfn = totalram_pages;
+ max_pfn = max_low_pfn;
mem_init_print_info(NULL);
kmalloc_ok = 1;
}
diff --git a/arch/x86/kernel/cpu/microcode/core.c b/arch/x86/kernel/cpu/microcode/core.c
index 2637ff09d6a0..168fa272cc3e 100644
--- a/arch/x86/kernel/cpu/microcode/core.c
+++ b/arch/x86/kernel/cpu/microcode/core.c
@@ -434,9 +434,10 @@ static ssize_t microcode_write(struct file *file, const char __user *buf,
size_t len, loff_t *ppos)
{
ssize_t ret = -EINVAL;
+ unsigned long nr_pages = totalram_pages;
- if ((len >> PAGE_SHIFT) > totalram_pages) {
- pr_err("too much data (max %ld pages)\n", totalram_pages);
+ if ((len >> PAGE_SHIFT) > nr_pages) {
+ pr_err("too much data (max %ld pages)\n", nr_pages);
return ret;
}