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>

diff --git a/arch/um/kernel/mem.c b/arch/um/kernel/mem.c
index 1067469..2da2096 100644 (file)
--- 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 2637ff0..168fa27 100644 (file)
--- 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;
        }
 

diff --git a/drivers/hv/hv_balloon.c b/drivers/hv/hv_balloon.c
index 4163151..f3e7da9 100644 (file)
--- a/drivers/hv/hv_balloon.c
+++ b/drivers/hv/hv_balloon.c
@@ -1090,6 +1090,7 @@ static void process_info(struct hv_dynmem_device *dm, struct dm_info_msg *msg)
 static unsigned long compute_balloon_floor(void)
 {
        unsigned long min_pages;
+       unsigned long nr_pages = totalram_pages;
 #define MB2PAGES(mb) ((mb) << (20 - PAGE_SHIFT))
        /* Simple continuous piecewiese linear function:
         *  max MiB -> min MiB  gradient
@@ -1102,16 +1103,16 @@ static unsigned long compute_balloon_floor(void)
         *    8192       744    (1/16)
         *   32768      1512    (1/32)
         */
-       if (totalram_pages < MB2PAGES(128))
-               min_pages = MB2PAGES(8) + (totalram_pages >> 1);
-       else if (totalram_pages < MB2PAGES(512))
-               min_pages = MB2PAGES(40) + (totalram_pages >> 2);
-       else if (totalram_pages < MB2PAGES(2048))
-               min_pages = MB2PAGES(104) + (totalram_pages >> 3);
-       else if (totalram_pages < MB2PAGES(8192))
-               min_pages = MB2PAGES(232) + (totalram_pages >> 4);
+       if (nr_pages < MB2PAGES(128))
+               min_pages = MB2PAGES(8) + (nr_pages >> 1);
+       else if (nr_pages < MB2PAGES(512))
+               min_pages = MB2PAGES(40) + (nr_pages >> 2);
+       else if (nr_pages < MB2PAGES(2048))
+               min_pages = MB2PAGES(104) + (nr_pages >> 3);
+       else if (nr_pages < MB2PAGES(8192))
+               min_pages = MB2PAGES(232) + (nr_pages >> 4);
        else
-               min_pages = MB2PAGES(488) + (totalram_pages >> 5);
+               min_pages = MB2PAGES(488) + (nr_pages >> 5);
 #undef MB2PAGES
        return min_pages;
 }

diff --git a/fs/file_table.c b/fs/file_table.c
index e49af4c..b6e9587 100644 (file)
--- a/fs/file_table.c
+++ b/fs/file_table.c
@@ -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);
 }

diff --git a/kernel/fork.c b/kernel/fork.c
index e2a5156..8617a32 100644 (file)
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -744,15 +744,16 @@ void __init __weak arch_task_cache_init(void) { }
 static void set_max_threads(unsigned int max_threads_suggested)
 {
        u64 threads;
+       unsigned long nr_pages = totalram_pages;
 
        /*
         * The number of threads shall be limited such that the thread
         * structures may only consume a small part of the available memory.
         */
-       if (fls64(totalram_pages) + fls64(PAGE_SIZE) > 64)
+       if (fls64(nr_pages) + fls64(PAGE_SIZE) > 64)
                threads = MAX_THREADS;
        else
-               threads = div64_u64((u64) totalram_pages * (u64) PAGE_SIZE,
+               threads = div64_u64((u64) nr_pages * (u64) PAGE_SIZE,
                                    (u64) THREAD_SIZE * 8UL);
 
        if (threads > max_threads_suggested)

diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c
index 86ef06d..7e967ca 100644 (file)
--- a/kernel/kexec_core.c
+++ b/kernel/kexec_core.c
@@ -152,6 +152,7 @@ int sanity_check_segment_list(struct kimage *image)
        int i;
        unsigned long nr_segments = image->nr_segments;
        unsigned long total_pages = 0;
+       unsigned long nr_pages = totalram_pages;
 
        /*
         * Verify we have good destination addresses.  The caller is
@@ -217,13 +218,13 @@ int sanity_check_segment_list(struct kimage *image)
         * wasted allocating pages, which can cause a soft lockup.
         */
        for (i = 0; i < nr_segments; i++) {
-               if (PAGE_COUNT(image->segment[i].memsz) > totalram_pages / 2)
+               if (PAGE_COUNT(image->segment[i].memsz) > nr_pages / 2)
                        return -EINVAL;
 
                total_pages += PAGE_COUNT(image->segment[i].memsz);
        }
 
-       if (total_pages > totalram_pages / 2)
+       if (total_pages > nr_pages / 2)
                return -EINVAL;
 
        /*

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index c82c41e..b79e79c 100644 (file)
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -7257,6 +7257,7 @@ static void calculate_totalreserve_pages(void)
                for (i = 0; i < MAX_NR_ZONES; i++) {
                        struct zone *zone = pgdat->node_zones + i;
                        long max = 0;
+                       unsigned long managed_pages = zone->managed_pages;
 
                        /* Find valid and maximum lowmem_reserve in the zone */
                        for (j = i; j < MAX_NR_ZONES; j++) {
@@ -7267,8 +7268,8 @@ static void calculate_totalreserve_pages(void)
                        /* we treat the high watermark as reserved pages. */
                        max += high_wmark_pages(zone);
 
-                       if (max > zone->managed_pages)
-                               max = zone->managed_pages;
+                       if (max > managed_pages)
+                               max = managed_pages;
 
                        pgdat->totalreserve_pages += max;
 

diff --git a/mm/shmem.c b/mm/shmem.c
index 375f3ac..b1f0f54 100644 (file)
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -114,7 +114,8 @@ static unsigned long shmem_default_max_blocks(void)
 
 static unsigned long shmem_default_max_inodes(void)
 {
-       return min(totalram_pages - totalhigh_pages, totalram_pages / 2);
+       unsigned long nr_pages = totalram_pages;
+       return min(nr_pages - totalhigh_pages, nr_pages / 2);
 }
 #endif
 

diff --git a/net/dccp/proto.c b/net/dccp/proto.c
index 2cc5fbb..ff727ff 100644 (file)
--- a/net/dccp/proto.c
+++ b/net/dccp/proto.c
@@ -1131,6 +1131,7 @@ EXPORT_SYMBOL_GPL(dccp_debug);
 static int __init dccp_init(void)
 {
        unsigned long goal;
+       unsigned long nr_pages = totalram_pages;
        int ehash_order, bhash_order, i;
        int rc;
 
@@ -1157,10 +1158,10 @@ static int __init dccp_init(void)
         *
         * The methodology is similar to that of the buffer cache.
         */
-       if (totalram_pages >= (128 * 1024))
-               goal = totalram_pages >> (21 - PAGE_SHIFT);
+       if (nr_pages >= (128 * 1024))
+               goal = nr_pages >> (21 - PAGE_SHIFT);
        else
-               goal = totalram_pages >> (23 - PAGE_SHIFT);
+               goal = nr_pages >> (23 - PAGE_SHIFT);
 
        if (thash_entries)
                goal = (thash_entries *

diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c
index e87c21e..5eb9908 100644 (file)
--- a/net/netfilter/nf_conntrack_core.c
+++ b/net/netfilter/nf_conntrack_core.c
@@ -2248,6 +2248,7 @@ static __always_inline unsigned int total_extension_size(void)
 
 int nf_conntrack_init_start(void)
 {
+       unsigned long nr_pages = totalram_pages;
        int max_factor = 8;
        int ret = -ENOMEM;
        int i;
@@ -2267,11 +2268,11 @@ int nf_conntrack_init_start(void)
                 * >= 4GB machines have 65536 buckets.
                 */
                nf_conntrack_htable_size
-                       = (((totalram_pages << PAGE_SHIFT) / 16384)
+                       = (((nr_pages << PAGE_SHIFT) / 16384)
                           / sizeof(struct hlist_head));
-               if (totalram_pages > (4 * (1024 * 1024 * 1024 / PAGE_SIZE)))
+               if (nr_pages > (4 * (1024 * 1024 * 1024 / PAGE_SIZE)))
                        nf_conntrack_htable_size = 65536;
-               else if (totalram_pages > (1024 * 1024 * 1024 / PAGE_SIZE))
+               else if (nr_pages > (1024 * 1024 * 1024 / PAGE_SIZE))
                        nf_conntrack_htable_size = 16384;
                if (nf_conntrack_htable_size < 32)
                        nf_conntrack_htable_size = 32;

diff --git a/net/netfilter/xt_hashlimit.c b/net/netfilter/xt_hashlimit.c
index 28e27a3..88b520b 100644 (file)
--- a/net/netfilter/xt_hashlimit.c
+++ b/net/netfilter/xt_hashlimit.c
@@ -274,14 +274,15 @@ static int htable_create(struct net *net, struct hashlimit_cfg3 *cfg,
        struct xt_hashlimit_htable *hinfo;
        const struct seq_operations *ops;
        unsigned int size, i;
+       unsigned long nr_pages = totalram_pages;
        int ret;
 
        if (cfg->size) {
                size = cfg->size;
        } else {
-               size = (totalram_pages << PAGE_SHIFT) / 16384 /
+               size = (nr_pages << PAGE_SHIFT) / 16384 /
                       sizeof(struct hlist_head);
-               if (totalram_pages > 1024 * 1024 * 1024 / PAGE_SIZE)
+               if (nr_pages > 1024 * 1024 * 1024 / PAGE_SIZE)
                        size = 8192;
                if (size < 16)
                        size = 16;

diff --git a/net/sctp/protocol.c b/net/sctp/protocol.c
index 9b277bd..a5b2418 100644 (file)
--- a/net/sctp/protocol.c
+++ b/net/sctp/protocol.c
@@ -1368,6 +1368,7 @@ static __init int sctp_init(void)
        int status = -EINVAL;
        unsigned long goal;
        unsigned long limit;
+       unsigned long nr_pages = totalram_pages;
        int max_share;
        int order;
        int num_entries;
@@ -1426,10 +1427,10 @@ static __init int sctp_init(void)
         * The methodology is similar to that of the tcp hash tables.
         * Though not identical.  Start by getting a goal size
         */
-       if (totalram_pages >= (128 * 1024))
-               goal = totalram_pages >> (22 - PAGE_SHIFT);
+       if (nr_pages >= (128 * 1024))
+               goal = nr_pages >> (22 - PAGE_SHIFT);
        else
-               goal = totalram_pages >> (24 - PAGE_SHIFT);
+               goal = nr_pages >> (24 - PAGE_SHIFT);
 
        /* Then compute the page order for said goal */
        order = get_order(goal);