From: Jerome Marchand <jmarc...@redhat.com>

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.
This patch adds MM_SHMEMPAGES counter to mm_rss_stat to account for
shmem pages instead of MM_FILEPAGES.

[vba...@suse.cz: port to 4.0, add #ifdefs, mm_counter_file() variant]
Signed-off-by: Jerome Marchand <jmarc...@redhat.com>
Signed-off-by: Vlastimil Babka <vba...@suse.cz>
---
 arch/s390/mm/pgtable.c   |  5 +----
 fs/proc/task_mmu.c       |  4 +++-
 include/linux/mm.h       | 28 ++++++++++++++++++++++++++++
 include/linux/mm_types.h |  9 ++++++---
 kernel/events/uprobes.c  |  2 +-
 mm/memory.c              | 30 ++++++++++--------------------
 mm/oom_kill.c            |  5 +++--
 mm/rmap.c                | 15 ++++-----------
 8 files changed, 56 insertions(+), 42 deletions(-)

diff --git a/arch/s390/mm/pgtable.c b/arch/s390/mm/pgtable.c
index b2c1542..5bffd5d 100644
--- a/arch/s390/mm/pgtable.c
+++ b/arch/s390/mm/pgtable.c
@@ -617,10 +617,7 @@ static void gmap_zap_swap_entry(swp_entry_t entry, struct 
mm_struct *mm)
        else if (is_migration_entry(entry)) {
                struct page *page = migration_entry_to_page(entry);
 
-               if (PageAnon(page))
-                       dec_mm_counter(mm, MM_ANONPAGES);
-               else
-                       dec_mm_counter(mm, MM_FILEPAGES);
+               dec_mm_counter(mm, mm_counter(page));
        }
        free_swap_and_cache(entry);
 }
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 0410309..d70334c 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -81,7 +81,8 @@ unsigned long task_statm(struct mm_struct *mm,
                         unsigned long *shared, unsigned long *text,
                         unsigned long *data, unsigned long *resident)
 {
-       *shared = get_mm_counter(mm, MM_FILEPAGES);
+       *shared = get_mm_counter(mm, MM_FILEPAGES) +
+               get_mm_counter(mm, MM_SHMEMPAGES);
        *text = (PAGE_ALIGN(mm->end_code) - (mm->start_code & PAGE_MASK))
                                                                >> PAGE_SHIFT;
        *data = mm->total_vm - mm->shared_vm;
@@ -501,6 +502,7 @@ static void smaps_pte_entry(pte_t *pte, unsigned long addr,
                                        pte_none(*pte) && vma->vm_file) {
                struct address_space *mapping =
                        file_inode(vma->vm_file)->i_mapping;
+               pgoff_t pgoff = linear_page_index(vma, addr);
 
                /*
                 * shmem does not use swap pte's so we have to consult
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 47a9392..adfbb5b 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1364,6 +1364,16 @@ static inline unsigned long get_mm_counter(struct 
mm_struct *mm, int member)
        return (unsigned long)val;
 }
 
+/* A wrapper for the CONFIG_SHMEM dependent counter */
+static inline unsigned long get_mm_counter_shmem(struct mm_struct *mm)
+{
+#ifdef CONFIG_SHMEM
+       return get_mm_counter(mm, MM_SHMEMPAGES);
+#else
+       return 0;
+#endif
+}
+
 static inline void add_mm_counter(struct mm_struct *mm, int member, long value)
 {
        atomic_long_add(value, &mm->rss_stat.count[member]);
@@ -1379,9 +1389,27 @@ static inline void dec_mm_counter(struct mm_struct *mm, 
int member)
        atomic_long_dec(&mm->rss_stat.count[member]);
 }
 
+/* Optimized variant when page is already known not to be PageAnon */
+static inline int mm_counter_file(struct page *page)
+{
+#ifdef CONFIG_SHMEM
+       if (PageSwapBacked(page))
+               return MM_SHMEMPAGES;
+#endif
+       return MM_FILEPAGES;
+}
+
+static inline int mm_counter(struct page *page)
+{
+       if (PageAnon(page))
+               return MM_ANONPAGES;
+       return mm_counter_file(page);
+}
+
 static inline unsigned long get_mm_rss(struct mm_struct *mm)
 {
        return get_mm_counter(mm, MM_FILEPAGES) +
+               get_mm_counter_shmem(mm) +
                get_mm_counter(mm, MM_ANONPAGES);
 }
 
diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index 199a03a..d3c2372 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -327,9 +327,12 @@ struct core_state {
 };
 
 enum {
-       MM_FILEPAGES,
-       MM_ANONPAGES,
-       MM_SWAPENTS,
+       MM_FILEPAGES,   /* Resident file mapping pages */
+       MM_ANONPAGES,   /* Resident anonymous pages */
+       MM_SWAPENTS,    /* Anonymous swap entries */
+#ifdef CONFIG_SHMEM
+       MM_SHMEMPAGES,  /* Resident shared memory pages */
+#endif
        NR_MM_COUNTERS
 };
 
diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index cb346f2..0a08fdd 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -188,7 +188,7 @@ static int __replace_page(struct vm_area_struct *vma, 
unsigned long addr,
        lru_cache_add_active_or_unevictable(kpage, vma);
 
        if (!PageAnon(page)) {
-               dec_mm_counter(mm, MM_FILEPAGES);
+               dec_mm_counter(mm, mm_counter_file(page));
                inc_mm_counter(mm, MM_ANONPAGES);
        }
 
diff --git a/mm/memory.c b/mm/memory.c
index 8068893..f145d9e 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));
 
@@ -2174,7 +2163,8 @@ gotten:
        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
@@ -2703,7 +2693,7 @@ 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);
diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index 642f38c..a5ee3a2 100644
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -573,10 +573,11 @@ void oom_kill_process(struct task_struct *p, gfp_t 
gfp_mask, int order,
        /* mm cannot safely be dereferenced after task_unlock(victim) */
        mm = victim->mm;
        mark_tsk_oom_victim(victim);
-       pr_err("Killed process %d (%s) total-vm:%lukB, anon-rss:%lukB, 
file-rss:%lukB\n",
+       pr_err("Killed process %d (%s) total-vm:%lukB, anon-rss:%lukB, 
file-rss:%lukB, shmem-rss:%lukB\n",
                task_pid_nr(victim), victim->comm, K(victim->mm->total_vm),
                K(get_mm_counter(victim->mm, MM_ANONPAGES)),
-               K(get_mm_counter(victim->mm, MM_FILEPAGES)));
+               K(get_mm_counter(victim->mm, MM_FILEPAGES)),
+               K(get_mm_counter_shmem(victim->mm)));
        task_unlock(victim);
 
        /*
diff --git a/mm/rmap.c b/mm/rmap.c
index 5e3e090..e3c4392 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1216,12 +1216,8 @@ static int try_to_unmap_one(struct page *page, struct 
vm_area_struct *vma,
        update_hiwater_rss(mm);
 
        if (PageHWPoison(page) && !(flags & TTU_IGNORE_HWPOISON)) {
-               if (!PageHuge(page)) {
-                       if (PageAnon(page))
-                               dec_mm_counter(mm, MM_ANONPAGES);
-                       else
-                               dec_mm_counter(mm, MM_FILEPAGES);
-               }
+               if (!PageHuge(page))
+                       dec_mm_counter(mm, mm_counter(page));
                set_pte_at(mm, address, pte,
                           swp_entry_to_pte(make_hwpoison_entry(page)));
        } else if (pte_unused(pteval)) {
@@ -1230,10 +1226,7 @@ static int try_to_unmap_one(struct page *page, struct 
vm_area_struct *vma,
                 * interest anymore. Simply discard the pte, vmscan
                 * will take care of the rest.
                 */
-               if (PageAnon(page))
-                       dec_mm_counter(mm, MM_ANONPAGES);
-               else
-                       dec_mm_counter(mm, MM_FILEPAGES);
+               dec_mm_counter(mm, mm_counter(page));
        } else if (PageAnon(page)) {
                swp_entry_t entry = { .val = page_private(page) };
                pte_t swp_pte;
@@ -1276,7 +1269,7 @@ static int try_to_unmap_one(struct page *page, struct 
vm_area_struct *vma,
                entry = make_migration_entry(page, pte_write(pteval));
                set_pte_at(mm, address, pte, swp_entry_to_pte(entry));
        } else
-               dec_mm_counter(mm, MM_FILEPAGES);
+               dec_mm_counter(mm, mm_counter_file(page));
 
        page_remove_rmap(page);
        page_cache_release(page);
-- 
2.1.4

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