Although the ratio of the slab is one, we also should read the ratio
from the related memory_stats instead of hard-coding. And the local
variable of size is already the value of slab_unreclaimable. So we
do not need to read again.

To do this we need some code like below:

if (unlikely(memory_stats[i].idx == NR_SLAB_UNRECLAIMABLE_B)) {
-       size = memcg_page_state(memcg, NR_SLAB_RECLAIMABLE_B) +
-              memcg_page_state(memcg, NR_SLAB_UNRECLAIMABLE_B);
+       VM_BUG_ON(i < 1);
+       VM_BUG_ON(memory_stats[i - 1].idx != NR_SLAB_RECLAIMABLE_B);
+       size += memcg_page_state(memcg, memory_stats[i - 1].idx) *
+               memory_stats[i - 1].ratio;

It requires a series of VM_BUG_ONs or comments to ensure these two
items are actually adjacent and in the right order. So it would
probably be easier to implement this using a wrapper that has a big
switch() for unit conversion.

More details about this discussion can refer to:

    https://lore.kernel.org/patchwork/patch/1348611/

This would fix the ratio inconsistency and get rid of the order
guarantee.

Signed-off-by: Muchun Song <songmuc...@bytedance.com>
---
 mm/memcontrol.c | 105 +++++++++++++++++++++++++++++++++++---------------------
 1 file changed, 66 insertions(+), 39 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index a40797a27f87..eec44918d373 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1511,49 +1511,71 @@ static bool mem_cgroup_wait_acct_move(struct mem_cgroup 
*memcg)
 
 struct memory_stat {
        const char *name;
-       unsigned int ratio;
        unsigned int idx;
 };
 
 static const struct memory_stat memory_stats[] = {
-       { "anon", PAGE_SIZE, NR_ANON_MAPPED },
-       { "file", PAGE_SIZE, NR_FILE_PAGES },
-       { "kernel_stack", 1024, NR_KERNEL_STACK_KB },
-       { "pagetables", PAGE_SIZE, NR_PAGETABLE },
-       { "percpu", 1, MEMCG_PERCPU_B },
-       { "sock", PAGE_SIZE, MEMCG_SOCK },
-       { "shmem", PAGE_SIZE, NR_SHMEM },
-       { "file_mapped", PAGE_SIZE, NR_FILE_MAPPED },
-       { "file_dirty", PAGE_SIZE, NR_FILE_DIRTY },
-       { "file_writeback", PAGE_SIZE, NR_WRITEBACK },
+       { "anon",                       NR_ANON_MAPPED                  },
+       { "file",                       NR_FILE_PAGES                   },
+       { "kernel_stack",               NR_KERNEL_STACK_KB              },
+       { "pagetables",                 NR_PAGETABLE                    },
+       { "percpu",                     MEMCG_PERCPU_B                  },
+       { "sock",                       MEMCG_SOCK                      },
+       { "shmem",                      NR_SHMEM                        },
+       { "file_mapped",                NR_FILE_MAPPED                  },
+       { "file_dirty",                 NR_FILE_DIRTY                   },
+       { "file_writeback",             NR_WRITEBACK                    },
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
-       { "anon_thp", PAGE_SIZE, NR_ANON_THPS },
-       { "file_thp", PAGE_SIZE, NR_FILE_THPS },
-       { "shmem_thp", PAGE_SIZE, NR_SHMEM_THPS },
+       { "anon_thp",                   NR_ANON_THPS                    },
+       { "file_thp",                   NR_FILE_THPS                    },
+       { "shmem_thp",                  NR_SHMEM_THPS                   },
 #endif
-       { "inactive_anon", PAGE_SIZE, NR_INACTIVE_ANON },
-       { "active_anon", PAGE_SIZE, NR_ACTIVE_ANON },
-       { "inactive_file", PAGE_SIZE, NR_INACTIVE_FILE },
-       { "active_file", PAGE_SIZE, NR_ACTIVE_FILE },
-       { "unevictable", PAGE_SIZE, NR_UNEVICTABLE },
-
-       /*
-        * Note: The slab_reclaimable and slab_unreclaimable must be
-        * together and slab_reclaimable must be in front.
-        */
-       { "slab_reclaimable", 1, NR_SLAB_RECLAIMABLE_B },
-       { "slab_unreclaimable", 1, NR_SLAB_UNRECLAIMABLE_B },
+       { "inactive_anon",              NR_INACTIVE_ANON                },
+       { "active_anon",                NR_ACTIVE_ANON                  },
+       { "inactive_file",              NR_INACTIVE_FILE                },
+       { "active_file",                NR_ACTIVE_FILE                  },
+       { "unevictable",                NR_UNEVICTABLE                  },
+       { "slab_reclaimable",           NR_SLAB_RECLAIMABLE_B           },
+       { "slab_unreclaimable",         NR_SLAB_UNRECLAIMABLE_B         },
 
        /* The memory events */
-       { "workingset_refault_anon", 1, WORKINGSET_REFAULT_ANON },
-       { "workingset_refault_file", 1, WORKINGSET_REFAULT_FILE },
-       { "workingset_activate_anon", 1, WORKINGSET_ACTIVATE_ANON },
-       { "workingset_activate_file", 1, WORKINGSET_ACTIVATE_FILE },
-       { "workingset_restore_anon", 1, WORKINGSET_RESTORE_ANON },
-       { "workingset_restore_file", 1, WORKINGSET_RESTORE_FILE },
-       { "workingset_nodereclaim", 1, WORKINGSET_NODERECLAIM },
+       { "workingset_refault_anon",    WORKINGSET_REFAULT_ANON         },
+       { "workingset_refault_file",    WORKINGSET_REFAULT_FILE         },
+       { "workingset_activate_anon",   WORKINGSET_ACTIVATE_ANON        },
+       { "workingset_activate_file",   WORKINGSET_ACTIVATE_FILE        },
+       { "workingset_restore_anon",    WORKINGSET_RESTORE_ANON         },
+       { "workingset_restore_file",    WORKINGSET_RESTORE_FILE         },
+       { "workingset_nodereclaim",     WORKINGSET_NODERECLAIM          },
 };
 
+/* Translate stat items to the correct unit for memory.stat output */
+static int memcg_page_state_unit(int item)
+{
+       switch (item) {
+       case MEMCG_PERCPU_B:
+       case NR_SLAB_RECLAIMABLE_B:
+       case NR_SLAB_UNRECLAIMABLE_B:
+       case WORKINGSET_REFAULT_ANON:
+       case WORKINGSET_REFAULT_FILE:
+       case WORKINGSET_ACTIVATE_ANON:
+       case WORKINGSET_ACTIVATE_FILE:
+       case WORKINGSET_RESTORE_ANON:
+       case WORKINGSET_RESTORE_FILE:
+       case WORKINGSET_NODERECLAIM:
+               return 1;
+       case NR_KERNEL_STACK_KB:
+               return SZ_1K;
+       default:
+               return PAGE_SIZE;
+       }
+}
+
+static inline unsigned long memcg_page_state_output(struct mem_cgroup *memcg,
+                                                   int item)
+{
+       return memcg_page_state(memcg, item) * memcg_page_state_unit(item);
+}
+
 static char *memory_stat_format(struct mem_cgroup *memcg)
 {
        struct seq_buf s;
@@ -1577,13 +1599,12 @@ static char *memory_stat_format(struct mem_cgroup 
*memcg)
        for (i = 0; i < ARRAY_SIZE(memory_stats); i++) {
                u64 size;
 
-               size = memcg_page_state(memcg, memory_stats[i].idx);
-               size *= memory_stats[i].ratio;
+               size = memcg_page_state_output(memcg, memory_stats[i].idx);
                seq_buf_printf(&s, "%s %llu\n", memory_stats[i].name, size);
 
                if (unlikely(memory_stats[i].idx == NR_SLAB_UNRECLAIMABLE_B)) {
-                       size = memcg_page_state(memcg, NR_SLAB_RECLAIMABLE_B) +
-                              memcg_page_state(memcg, NR_SLAB_UNRECLAIMABLE_B);
+                       size += memcg_page_state_output(memcg,
+                                                       NR_SLAB_RECLAIMABLE_B);
                        seq_buf_printf(&s, "slab %llu\n", size);
                }
        }
@@ -6377,6 +6398,12 @@ static int memory_stat_show(struct seq_file *m, void *v)
 }
 
 #ifdef CONFIG_NUMA
+static inline unsigned long lruvec_page_state_output(struct lruvec *lruvec,
+                                                    int item)
+{
+       return lruvec_page_state(lruvec, item) * memcg_page_state_unit(item);
+}
+
 static int memory_numa_stat_show(struct seq_file *m, void *v)
 {
        int i;
@@ -6394,8 +6421,8 @@ static int memory_numa_stat_show(struct seq_file *m, void 
*v)
                        struct lruvec *lruvec;
 
                        lruvec = mem_cgroup_lruvec(memcg, NODE_DATA(nid));
-                       size = lruvec_page_state(lruvec, memory_stats[i].idx);
-                       size *= memory_stats[i].ratio;
+                       size = lruvec_page_state_output(lruvec,
+                                                       memory_stats[i].idx);
                        seq_printf(m, " N%d=%llu", nid, size);
                }
                seq_putc(m, '\n');
-- 
2.11.0

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