mm, shmem: add internal shmem resident memory accounting

Currently looking at /proc/<pid>/status or statm, there is no way to
distinguish shmem pages from pages mapped to a regular file (shmem pages
are mapped to /dev/zero), even though their implication in actual memory
use is quite different.

The internal accounting currently counts shmem pages together with
regular files.  As a preparation to extend the userspace interfaces,
this patch adds MM_SHMEMPAGES counter to mm_rss_stat to account for
shmem pages separately from MM_FILEPAGES.  The next patch will expose it
to userspace - this patch doesn't change the exported values yet, by
adding up MM_SHMEMPAGES to MM_FILEPAGES at places where MM_FILEPAGES was
used before.  The only user-visible change after this patch is the OOM
killer message that separates the reported "shmem-rss" from "file-rss".

[vbabka@suse.cz: forward-porting, tweak changelog]
Signed-off-by: Jerome Marchand <jmarchan@redhat.com>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 10 insertions, 20 deletions

diff --git a/mm/memory.c b/mm/memory.c
index c387430f06c3..f7026c035940 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -832,10 +832,7 @@ copy_one_pte(struct mm_struct *dst_mm, struct mm_struct *src_mm,
                 } else if (is_migration_entry(entry)) {
                         page = migration_entry_to_page(entry);
 
-                        if (PageAnon(page))
-                                rss[MM_ANONPAGES]++;
-                        else
-                                rss[MM_FILEPAGES]++;
+                        rss[mm_counter(page)]++;
 
                         if (is_write_migration_entry(entry) &&
                                         is_cow_mapping(vm_flags)) {
@@ -874,10 +871,7 @@ copy_one_pte(struct mm_struct *dst_mm, struct mm_struct *src_mm,
         if (page) {
                 get_page(page);
                 page_dup_rmap(page);
-                if (PageAnon(page))
-                        rss[MM_ANONPAGES]++;
-                else
-                        rss[MM_FILEPAGES]++;
+                rss[mm_counter(page)]++;
         }
 
 out_set_pte:
@@ -1113,9 +1107,8 @@ again:
                         tlb_remove_tlb_entry(tlb, pte, addr);
                         if (unlikely(!page))
                                 continue;
-                        if (PageAnon(page))
-                                rss[MM_ANONPAGES]--;
-                        else {
+
+                        if (!PageAnon(page)) {
                                 if (pte_dirty(ptent)) {
                                         force_flush = 1;
                                         set_page_dirty(page);
@@ -1123,8 +1116,8 @@ again:
                                 if (pte_young(ptent) &&
                                     likely(!(vma->vm_flags & VM_SEQ_READ)))
                                         mark_page_accessed(page);
-                                rss[MM_FILEPAGES]--;
                         }
+                        rss[mm_counter(page)]--;
                         page_remove_rmap(page);
                         if (unlikely(page_mapcount(page) < 0))
                                 print_bad_pte(vma, addr, ptent, page);
@@ -1146,11 +1139,7 @@ again:
                         struct page *page;
 
                         page = migration_entry_to_page(entry);
-
-                        if (PageAnon(page))
-                                rss[MM_ANONPAGES]--;
-                        else
-                                rss[MM_FILEPAGES]--;
+                        rss[mm_counter(page)]--;
                 }
                 if (unlikely(!free_swap_and_cache(entry)))
                         print_bad_pte(vma, addr, ptent, NULL);
@@ -1460,7 +1449,7 @@ static int insert_page(struct vm_area_struct *vma, unsigned long addr,
 
         /* Ok, finally just insert the thing.. */
         get_page(page);
-        inc_mm_counter_fast(mm, MM_FILEPAGES);
+        inc_mm_counter_fast(mm, mm_counter_file(page));
         page_add_file_rmap(page);
         set_pte_at(mm, addr, pte, mk_pte(page, prot));
 
@@ -2097,7 +2086,8 @@ static int wp_page_copy(struct mm_struct *mm, struct vm_area_struct *vma,
         if (likely(pte_same(*page_table, orig_pte))) {
                 if (old_page) {
                         if (!PageAnon(old_page)) {
-                                dec_mm_counter_fast(mm, MM_FILEPAGES);
+                                dec_mm_counter_fast(mm,
+                                                mm_counter_file(old_page));
                                 inc_mm_counter_fast(mm, MM_ANONPAGES);
                         }
                 } else {
@@ -2820,7 +2810,7 @@ void do_set_pte(struct vm_area_struct *vma, unsigned long address,
                 inc_mm_counter_fast(vma->vm_mm, MM_ANONPAGES);
                 page_add_new_anon_rmap(page, vma, address);
         } else {
-                inc_mm_counter_fast(vma->vm_mm, MM_FILEPAGES);
+                inc_mm_counter_fast(vma->vm_mm, mm_counter_file(page));
                 page_add_file_rmap(page);
         }
         set_pte_at(vma->vm_mm, address, pte, entry);