proc: add kpagecgroup file

/proc/kpagecgroup contains a 64-bit inode number of the memory cgroup each
page is charged to, indexed by PFN.  Having this information is useful for
estimating a cgroup working set size.

The file is present if CONFIG_PROC_PAGE_MONITOR && CONFIG_MEMCG.

Signed-off-by: Vladimir Davydov <vdavydov@parallels.com>
Reviewed-by: Andres Lagar-Cavilla <andreslc@google.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Greg Thelen <gthelen@google.com>
Cc: Michel Lespinasse <walken@google.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Pavel Emelyanov <xemul@parallels.com>
Cc: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 53 insertions, 0 deletions

diff --git a/fs/proc/page.c b/fs/proc/page.c
index 7eee2d8b97d9..70d23245dd43 100644
--- a/fs/proc/page.c
+++ b/fs/proc/page.c
@@ -9,6 +9,7 @@
 #include <linux/proc_fs.h>
 #include <linux/seq_file.h>
 #include <linux/hugetlb.h>
+#include <linux/memcontrol.h>
 #include <linux/kernel-page-flags.h>
 #include <asm/uaccess.h>
 #include "internal.h"
@@ -225,10 +226,62 @@ static const struct file_operations proc_kpageflags_operations = {
         .read = kpageflags_read,
 };
 
+#ifdef CONFIG_MEMCG
+static ssize_t kpagecgroup_read(struct file *file, char __user *buf,
+                                size_t count, loff_t *ppos)
+{
+        u64 __user *out = (u64 __user *)buf;
+        struct page *ppage;
+        unsigned long src = *ppos;
+        unsigned long pfn;
+        ssize_t ret = 0;
+        u64 ino;
+
+        pfn = src / KPMSIZE;
+        count = min_t(unsigned long, count, (max_pfn * KPMSIZE) - src);
+        if (src & KPMMASK || count & KPMMASK)
+                return -EINVAL;
+
+        while (count > 0) {
+                if (pfn_valid(pfn))
+                        ppage = pfn_to_page(pfn);
+                else
+                        ppage = NULL;
+
+                if (ppage)
+                        ino = page_cgroup_ino(ppage);
+                else
+                        ino = 0;
+
+                if (put_user(ino, out)) {
+                        ret = -EFAULT;
+                        break;
+                }
+
+                pfn++;
+                out++;
+                count -= KPMSIZE;
+        }
+
+        *ppos += (char __user *)out - buf;
+        if (!ret)
+                ret = (char __user *)out - buf;
+        return ret;
+}
+
+static const struct file_operations proc_kpagecgroup_operations = {
+        .llseek = mem_lseek,
+        .read = kpagecgroup_read,
+};
+#endif /* CONFIG_MEMCG */
+
 static int __init proc_page_init(void)
 {
         proc_create("kpagecount", S_IRUSR, NULL, &proc_kpagecount_operations);
         proc_create("kpageflags", S_IRUSR, NULL, &proc_kpageflags_operations);
+#ifdef CONFIG_MEMCG
+        proc_create("kpagecgroup", S_IRUSR, NULL, &proc_kpagecgroup_operations);
+#endif
         return 0;
 }
 fs_initcall(proc_page_init);