radix-tree: account nodes to memcg only if explicitly requested

commit 05eb6e7263185a6bb0de9501ccf2addc52429414 upstream.

Radix trees may be used not only for storing page cache pages, so
unconditionally accounting radix tree nodes to the current memory cgroup
is bad: if a radix tree node is used for storing data shared among
different cgroups we risk pinning dead memory cgroups forever.

So let's only account radix tree nodes if it was explicitly requested by
passing __GFP_ACCOUNT to INIT_RADIX_TREE.  Currently, we only want to
account page cache entries, so mark mapping->page_tree so.

Fixes: 58e698af4c63 ("radix-tree: account radix_tree_node to memory cgroup")
Link: http://lkml.kernel.org/r/1470057188-7864-1-git-send-email-vdavydov@virtuozzo.com
Signed-off-by: Vladimir Davydov <vdavydov@virtuozzo.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Michal Hocko <mhocko@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/fs/inode.c b/fs/inode.c
index 68db390504466252449f4bec1aa351c1b1d88a34..9ea421948742860608fef86e3886e2804e52bdc3 100644 (file)
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -345,7 +345,7 @@ EXPORT_SYMBOL(inc_nlink);
 void address_space_init_once(struct address_space *mapping)
 {
        memset(mapping, 0, sizeof(*mapping));
-       INIT_RADIX_TREE(&mapping->page_tree, GFP_ATOMIC);
+       INIT_RADIX_TREE(&mapping->page_tree, GFP_ATOMIC | __GFP_ACCOUNT);
        spin_lock_init(&mapping->tree_lock);
        init_rwsem(&mapping->i_mmap_rwsem);
        INIT_LIST_HEAD(&mapping->private_list);

diff --git a/lib/radix-tree.c b/lib/radix-tree.c
index 8b7d8459bb9dc2ea96269eeb5dd815cf2e169287..bc7852f9544390b00f13e56a7da5dc048b40cd07 100644 (file)
--- a/lib/radix-tree.c
+++ b/lib/radix-tree.c
@@ -274,10 +274,11 @@ radix_tree_node_alloc(struct radix_tree_root *root)
 
                /*
                 * Even if the caller has preloaded, try to allocate from the
-                * cache first for the new node to get accounted.
+                * cache first for the new node to get accounted to the memory
+                * cgroup.
                 */
                ret = kmem_cache_alloc(radix_tree_node_cachep,
-                                      gfp_mask | __GFP_ACCOUNT | __GFP_NOWARN);
+                                      gfp_mask | __GFP_NOWARN);
                if (ret)
                        goto out;
 
@@ -300,8 +301,7 @@ radix_tree_node_alloc(struct radix_tree_root *root)
                kmemleak_update_trace(ret);
                goto out;
        }
-       ret = kmem_cache_alloc(radix_tree_node_cachep,
-                              gfp_mask | __GFP_ACCOUNT);
+       ret = kmem_cache_alloc(radix_tree_node_cachep, gfp_mask);
 out:
        BUG_ON(radix_tree_is_internal_node(ret));
        return ret;
@@ -348,6 +348,12 @@ static int __radix_tree_preload(gfp_t gfp_mask)
        struct radix_tree_node *node;
        int ret = -ENOMEM;
 
+       /*
+        * Nodes preloaded by one cgroup can be be used by another cgroup, so
+        * they should never be accounted to any particular memory cgroup.
+        */
+       gfp_mask &= ~__GFP_ACCOUNT;
+
        preempt_disable();
        rtp = this_cpu_ptr(&radix_tree_preloads);
        while (rtp->nr < RADIX_TREE_PRELOAD_SIZE) {