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-rw-r--r--fs/proc/task_mmu.c22
1 files changed, 20 insertions, 2 deletions
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 85ef60f..5830b2e 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -14,6 +14,7 @@
#include <linux/swapops.h>
#include <linux/mmu_notifier.h>
#include <linux/page_idle.h>
+#include <linux/shmem_fs.h>
#include <asm/elf.h>
#include <asm/uaccess.h>
@@ -717,8 +718,25 @@ static int show_smap(struct seq_file *m, void *v, int is_pid)
#ifdef CONFIG_SHMEM
if (vma->vm_file && shmem_mapping(vma->vm_file->f_mapping)) {
- mss.check_shmem_swap = true;
- smaps_walk.pte_hole = smaps_pte_hole;
+ /*
+ * For shared or readonly shmem mappings we know that all
+ * swapped out pages belong to the shmem object, and we can
+ * obtain the swap value much more efficiently. For private
+ * writable mappings, we might have COW pages that are
+ * not affected by the parent swapped out pages of the shmem
+ * object, so we have to distinguish them during the page walk.
+ * Unless we know that the shmem object (or the part mapped by
+ * our VMA) has no swapped out pages at all.
+ */
+ unsigned long shmem_swapped = shmem_swap_usage(vma);
+
+ if (!shmem_swapped || (vma->vm_flags & VM_SHARED) ||
+ !(vma->vm_flags & VM_WRITE)) {
+ mss.swap = shmem_swapped;
+ } else {
+ mss.check_shmem_swap = true;
+ smaps_walk.pte_hole = smaps_pte_hole;
+ }
}
#endif
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