cgroups: use vmalloc for large cgroups pidlist allocations

Separates all pidlist allocation requests to a separate function that
judges based on the requested size whether or not the array needs to be
vmalloced or can be gotten via kmalloc, and similar for kfree/vfree.

Signed-off-by: Ben Blum <bblum@google.com>
Signed-off-by: Paul Menage <menage@google.com>
Acked-by: Li Zefan <lizf@cn.fujitsu.com>
Cc: Matt Helsley <matthltc@us.ibm.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 97194ba..3e356b0 100644 (file)
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -50,6 +50,7 @@
 #include <linux/smp_lock.h>
 #include <linux/pid_namespace.h>
 #include <linux/idr.h>
+#include <linux/vmalloc.h> /* TODO: replace with more sophisticated array */
 
 #include <asm/atomic.h>
 
@@ -2351,6 +2352,42 @@ int cgroup_scan_tasks(struct cgroup_scanner *scan)
  */
 
 /*
+ * The following two functions "fix" the issue where there are more pids
+ * than kmalloc will give memory for; in such cases, we use vmalloc/vfree.
+ * TODO: replace with a kernel-wide solution to this problem
+ */
+#define PIDLIST_TOO_LARGE(c) ((c) * sizeof(pid_t) > (PAGE_SIZE * 2))
+static void *pidlist_allocate(int count)
+{
+       if (PIDLIST_TOO_LARGE(count))
+               return vmalloc(count * sizeof(pid_t));
+       else
+               return kmalloc(count * sizeof(pid_t), GFP_KERNEL);
+}
+static void pidlist_free(void *p)
+{
+       if (is_vmalloc_addr(p))
+               vfree(p);
+       else
+               kfree(p);
+}
+static void *pidlist_resize(void *p, int newcount)
+{
+       void *newlist;
+       /* note: if new alloc fails, old p will still be valid either way */
+       if (is_vmalloc_addr(p)) {
+               newlist = vmalloc(newcount * sizeof(pid_t));
+               if (!newlist)
+                       return NULL;
+               memcpy(newlist, p, newcount * sizeof(pid_t));
+               vfree(p);
+       } else {
+               newlist = krealloc(p, newcount * sizeof(pid_t), GFP_KERNEL);
+       }
+       return newlist;
+}
+
+/*
  * pidlist_uniq - given a kmalloc()ed list, strip out all duplicate entries
  * If the new stripped list is sufficiently smaller and there's enough memory
  * to allocate a new buffer, will let go of the unneeded memory. Returns the
@@ -2389,7 +2426,7 @@ after:
         * we'll just stay with what we've got.
         */
        if (PIDLIST_REALLOC_DIFFERENCE(length, dest)) {
-               newlist = krealloc(list, dest * sizeof(pid_t), GFP_KERNEL);
+               newlist = pidlist_resize(list, dest);
                if (newlist)
                        *p = newlist;
        }
@@ -2470,7 +2507,7 @@ static int pidlist_array_load(struct cgroup *cgrp, enum cgroup_filetype type,
         * show up until sometime later on.
         */
        length = cgroup_task_count(cgrp);
-       array = kmalloc(length * sizeof(pid_t), GFP_KERNEL);
+       array = pidlist_allocate(length);
        if (!array)
                return -ENOMEM;
        /* now, populate the array */
@@ -2494,11 +2531,11 @@ static int pidlist_array_load(struct cgroup *cgrp, enum cgroup_filetype type,
                length = pidlist_uniq(&array, length);
        l = cgroup_pidlist_find(cgrp, type);
        if (!l) {
-               kfree(array);
+               pidlist_free(array);
                return -ENOMEM;
        }
        /* store array, freeing old if necessary - lock already held */
-       kfree(l->list);
+       pidlist_free(l->list);
        l->list = array;
        l->length = length;
        l->use_count++;
@@ -2659,7 +2696,7 @@ static void cgroup_release_pid_array(struct cgroup_pidlist *l)
                /* we're the last user if refcount is 0; remove and free */
                list_del(&l->links);
                mutex_unlock(&l->owner->pidlist_mutex);
-               kfree(l->list);
+               pidlist_free(l->list);
                put_pid_ns(l->key.ns);
                up_write(&l->mutex);
                kfree(l);