This is RFC patch and the discussion on the API is still happening at
the following link but I am sending the early draft for feedback.
[link] https://marc.info/?l=linux-api&m=151850343717274

A lot of memory can be consumed by the events generated for the huge or
unlimited queues if there is either no or slow listener. This can cause
system level memory pressure or OOMs. So, it's better to account the
fsnotify kmem caches to the memcg of the listener.

There are seven fsnotify kmem caches and among them allocations from
dnotify_struct_cache, dnotify_mark_cache, fanotify_mark_cache and
inotify_inode_mark_cachep happens in the context of syscall from the
listener. So, SLAB_ACCOUNT is enough for these caches. The allocations
from the remaining caches can happen in the context of the event
producer. For such caches we will need to remote charge the allocations
to the listener's memcg. Thus we save the memcg reference in the
fsnotify_group structure of the listener.

This patch has also moved the members of fsnotify_group to keep the
size same, at least for 64 bit build, even with additional member by
filling the holes.

Signed-off-by: Shakeel Butt <shake...@google.com>
---
 fs/notify/dnotify/dnotify.c          |  5 +++--
 fs/notify/fanotify/fanotify.c        | 12 +++++++-----
 fs/notify/fanotify/fanotify.h        |  3 ++-
 fs/notify/fanotify/fanotify_user.c   |  8 ++++++--
 fs/notify/group.c                    |  4 ++++
 fs/notify/inotify/inotify_fsnotify.c |  2 +-
 fs/notify/inotify/inotify_user.c     |  5 ++++-
 fs/notify/mark.c                     |  9 ++++++---
 include/linux/fsnotify_backend.h     | 12 ++++++++----
 include/linux/memcontrol.h           |  6 ++++++
 mm/memcontrol.c                      |  2 +-
 11 files changed, 48 insertions(+), 20 deletions(-)

diff --git a/fs/notify/dnotify/dnotify.c b/fs/notify/dnotify/dnotify.c
index 63a1ca4b9dee..eb5c41284649 100644
--- a/fs/notify/dnotify/dnotify.c
+++ b/fs/notify/dnotify/dnotify.c
@@ -384,8 +384,9 @@ int fcntl_dirnotify(int fd, struct file *filp, unsigned 
long arg)
 
 static int __init dnotify_init(void)
 {
-       dnotify_struct_cache = KMEM_CACHE(dnotify_struct, SLAB_PANIC);
-       dnotify_mark_cache = KMEM_CACHE(dnotify_mark, SLAB_PANIC);
+       dnotify_struct_cache = KMEM_CACHE(dnotify_struct,
+                                         SLAB_PANIC|SLAB_ACCOUNT);
+       dnotify_mark_cache = KMEM_CACHE(dnotify_mark, SLAB_PANIC|SLAB_ACCOUNT);
 
        dnotify_group = fsnotify_alloc_group(&dnotify_fsnotify_ops);
        if (IS_ERR(dnotify_group))
diff --git a/fs/notify/fanotify/fanotify.c b/fs/notify/fanotify/fanotify.c
index 6702a6a0bbb5..4ffd195ca605 100644
--- a/fs/notify/fanotify/fanotify.c
+++ b/fs/notify/fanotify/fanotify.c
@@ -140,22 +140,24 @@ static bool fanotify_should_send_event(struct 
fsnotify_mark *inode_mark,
 }
 
 struct fanotify_event_info *fanotify_alloc_event(struct inode *inode, u32 mask,
-                                                const struct path *path)
+                                                const struct path *path,
+                                                struct mem_cgroup *memcg)
 {
        struct fanotify_event_info *event;
 
        if (fanotify_is_perm_event(mask)) {
                struct fanotify_perm_event_info *pevent;
 
-               pevent = kmem_cache_alloc(fanotify_perm_event_cachep,
-                                         GFP_KERNEL);
+               pevent = kmem_cache_alloc_memcg(fanotify_perm_event_cachep,
+                                               GFP_KERNEL, memcg);
                if (!pevent)
                        return NULL;
                event = &pevent->fae;
                pevent->response = 0;
                goto init;
        }
-       event = kmem_cache_alloc(fanotify_event_cachep, GFP_KERNEL);
+       event = kmem_cache_alloc_memcg(fanotify_event_cachep, GFP_KERNEL,
+                                      memcg);
        if (!event)
                return NULL;
 init: __maybe_unused
@@ -210,7 +212,7 @@ static int fanotify_handle_event(struct fsnotify_group 
*group,
                        return 0;
        }
 
-       event = fanotify_alloc_event(inode, mask, data);
+       event = fanotify_alloc_event(inode, mask, data, group->memcg_to_charge);
        ret = -ENOMEM;
        if (unlikely(!event))
                goto finish;
diff --git a/fs/notify/fanotify/fanotify.h b/fs/notify/fanotify/fanotify.h
index 256d9d1ddea9..51b797896c87 100644
--- a/fs/notify/fanotify/fanotify.h
+++ b/fs/notify/fanotify/fanotify.h
@@ -53,4 +53,5 @@ static inline struct fanotify_event_info *FANOTIFY_E(struct 
fsnotify_event *fse)
 }
 
 struct fanotify_event_info *fanotify_alloc_event(struct inode *inode, u32 mask,
-                                                const struct path *path);
+                                                const struct path *path,
+                                                struct mem_cgroup *memcg);
diff --git a/fs/notify/fanotify/fanotify_user.c 
b/fs/notify/fanotify/fanotify_user.c
index ef08d64c84b8..456c8146843a 100644
--- a/fs/notify/fanotify/fanotify_user.c
+++ b/fs/notify/fanotify/fanotify_user.c
@@ -16,6 +16,7 @@
 #include <linux/uaccess.h>
 #include <linux/compat.h>
 #include <linux/sched/signal.h>
+#include <linux/memcontrol.h>
 
 #include <asm/ioctls.h>
 
@@ -756,8 +757,10 @@ SYSCALL_DEFINE2(fanotify_init, unsigned int, flags, 
unsigned int, event_f_flags)
 
        group->fanotify_data.user = user;
        atomic_inc(&user->fanotify_listeners);
+       group->memcg_to_charge = get_mem_cgroup_from_mm(current->mm);
 
-       oevent = fanotify_alloc_event(NULL, FS_Q_OVERFLOW, NULL);
+       oevent = fanotify_alloc_event(NULL, FS_Q_OVERFLOW, NULL,
+                                     group->memcg_to_charge);
        if (unlikely(!oevent)) {
                fd = -ENOMEM;
                goto out_destroy_group;
@@ -951,7 +954,8 @@ COMPAT_SYSCALL_DEFINE6(fanotify_mark,
  */
 static int __init fanotify_user_setup(void)
 {
-       fanotify_mark_cache = KMEM_CACHE(fsnotify_mark, SLAB_PANIC);
+       fanotify_mark_cache = KMEM_CACHE(fsnotify_mark,
+                                        SLAB_PANIC|SLAB_ACCOUNT);
        fanotify_event_cachep = KMEM_CACHE(fanotify_event_info, SLAB_PANIC);
        if (IS_ENABLED(CONFIG_FANOTIFY_ACCESS_PERMISSIONS)) {
                fanotify_perm_event_cachep =
diff --git a/fs/notify/group.c b/fs/notify/group.c
index b7a4b6a69efa..555a5ec4e882 100644
--- a/fs/notify/group.c
+++ b/fs/notify/group.c
@@ -22,6 +22,7 @@
 #include <linux/srcu.h>
 #include <linux/rculist.h>
 #include <linux/wait.h>
+#include <linux/memcontrol.h>
 
 #include <linux/fsnotify_backend.h>
 #include "fsnotify.h"
@@ -36,6 +37,9 @@ static void fsnotify_final_destroy_group(struct 
fsnotify_group *group)
        if (group->ops->free_group_priv)
                group->ops->free_group_priv(group);
 
+       if (group->memcg_to_charge)
+               mem_cgroup_put(group->memcg_to_charge);
+
        kfree(group);
 }
 
diff --git a/fs/notify/inotify/inotify_fsnotify.c 
b/fs/notify/inotify/inotify_fsnotify.c
index 8b73332735ba..6c4a7485d524 100644
--- a/fs/notify/inotify/inotify_fsnotify.c
+++ b/fs/notify/inotify/inotify_fsnotify.c
@@ -98,7 +98,7 @@ int inotify_handle_event(struct fsnotify_group *group,
        i_mark = container_of(inode_mark, struct inotify_inode_mark,
                              fsn_mark);
 
-       event = kmalloc(alloc_len, GFP_KERNEL);
+       event = kmalloc_memcg(alloc_len, GFP_KERNEL, group->memcg_to_charge);
        if (unlikely(!event))
                return -ENOMEM;
 
diff --git a/fs/notify/inotify/inotify_user.c b/fs/notify/inotify/inotify_user.c
index 5c29bf16814f..b1d29b360519 100644
--- a/fs/notify/inotify/inotify_user.c
+++ b/fs/notify/inotify/inotify_user.c
@@ -38,6 +38,7 @@
 #include <linux/uaccess.h>
 #include <linux/poll.h>
 #include <linux/wait.h>
+#include <linux/memcontrol.h>
 
 #include "inotify.h"
 #include "../fdinfo.h"
@@ -618,6 +619,7 @@ static struct fsnotify_group *inotify_new_group(unsigned 
int max_events)
        oevent->name_len = 0;
 
        group->max_events = max_events;
+       group->memcg_to_charge = get_mem_cgroup_from_mm(current->mm);
 
        spin_lock_init(&group->inotify_data.idr_lock);
        idr_init(&group->inotify_data.idr);
@@ -785,7 +787,8 @@ static int __init inotify_user_setup(void)
 
        BUG_ON(hweight32(ALL_INOTIFY_BITS) != 21);
 
-       inotify_inode_mark_cachep = KMEM_CACHE(inotify_inode_mark, SLAB_PANIC);
+       inotify_inode_mark_cachep = KMEM_CACHE(inotify_inode_mark,
+                                              SLAB_PANIC|SLAB_ACCOUNT);
 
        inotify_max_queued_events = 16384;
        init_user_ns.ucount_max[UCOUNT_INOTIFY_INSTANCES] = 128;
diff --git a/fs/notify/mark.c b/fs/notify/mark.c
index e9191b416434..9f0f54dd8a9f 100644
--- a/fs/notify/mark.c
+++ b/fs/notify/mark.c
@@ -432,11 +432,13 @@ int fsnotify_compare_groups(struct fsnotify_group *a, 
struct fsnotify_group *b)
 static int fsnotify_attach_connector_to_object(
                                struct fsnotify_mark_connector __rcu **connp,
                                struct inode *inode,
-                               struct vfsmount *mnt)
+                               struct vfsmount *mnt,
+                               struct fsnotify_group *group)
 {
        struct fsnotify_mark_connector *conn;
 
-       conn = kmem_cache_alloc(fsnotify_mark_connector_cachep, GFP_KERNEL);
+       conn = kmem_cache_alloc_memcg(fsnotify_mark_connector_cachep,
+                                     GFP_KERNEL, group->memcg_to_charge);
        if (!conn)
                return -ENOMEM;
        spin_lock_init(&conn->lock);
@@ -517,7 +519,8 @@ static int fsnotify_add_mark_list(struct fsnotify_mark 
*mark,
        conn = fsnotify_grab_connector(connp);
        if (!conn) {
                spin_unlock(&mark->lock);
-               err = fsnotify_attach_connector_to_object(connp, inode, mnt);
+               err = fsnotify_attach_connector_to_object(connp, inode, mnt,
+                                                         mark->group);
                if (err)
                        return err;
                goto restart;
diff --git a/include/linux/fsnotify_backend.h b/include/linux/fsnotify_backend.h
index 067d52e95f02..e1ed0f32ff92 100644
--- a/include/linux/fsnotify_backend.h
+++ b/include/linux/fsnotify_backend.h
@@ -84,6 +84,8 @@ struct fsnotify_event_private_data;
 struct fsnotify_fname;
 struct fsnotify_iter_info;
 
+struct mem_cgroup;
+
 /*
  * Each group much define these ops.  The fsnotify infrastructure will call
  * these operations for each relevant group.
@@ -129,6 +131,8 @@ struct fsnotify_event {
  * everything will be cleaned up.
  */
 struct fsnotify_group {
+       const struct fsnotify_ops *ops; /* how this group handles things */
+
        /*
         * How the refcnt is used is up to each group.  When the refcnt hits 0
         * fsnotify will clean up all of the resources associated with this 
group.
@@ -139,8 +143,6 @@ struct fsnotify_group {
         */
        refcount_t refcnt;              /* things with interest in this group */
 
-       const struct fsnotify_ops *ops; /* how this group handles things */
-
        /* needed to send notification to userspace */
        spinlock_t notification_lock;           /* protect the 
notification_list */
        struct list_head notification_list;     /* list of event_holder this 
group needs to send to userspace */
@@ -162,6 +164,8 @@ struct fsnotify_group {
        atomic_t num_marks;             /* 1 for each mark and 1 for not being
                                         * past the point of no return when 
freeing
                                         * a group */
+       atomic_t user_waits;            /* Number of tasks waiting for user
+                                        * response */
        struct list_head marks_list;    /* all inode marks for this group */
 
        struct fasync_struct *fsn_fa;    /* async notification */
@@ -169,8 +173,8 @@ struct fsnotify_group {
        struct fsnotify_event *overflow_event;  /* Event we queue when the
                                                 * notification list is too
                                                 * full */
-       atomic_t user_waits;            /* Number of tasks waiting for user
-                                        * response */
+
+       struct mem_cgroup *memcg_to_charge; /* memcg to charge allocations */
 
        /* groups can define private fields here or use the void *private */
        union {
diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 9dec8a5c0ca2..0c877ddae4ef 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -352,6 +352,7 @@ struct mem_cgroup *mem_cgroup_from_css(struct 
cgroup_subsys_state *css){
        return css ? container_of(css, struct mem_cgroup, css) : NULL;
 }
 
+struct mem_cgroup *get_mem_cgroup_from_mm(struct mm_struct *mm);
 static inline void mem_cgroup_put(struct mem_cgroup *memcg)
 {
        css_put(&memcg->css);
@@ -809,6 +810,11 @@ static inline bool task_in_mem_cgroup(struct task_struct 
*task,
        return true;
 }
 
+static inline struct mem_cgroup *get_mem_cgroup_from_mm(struct mm_struct *mm)
+{
+       return NULL;
+}
+
 static inline void mem_cgroup_put(struct mem_cgroup *memcg)
 {
 }
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 0dcd6ab6cc94..3a72394510a7 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -678,7 +678,7 @@ struct mem_cgroup *mem_cgroup_from_task(struct task_struct 
*p)
 }
 EXPORT_SYMBOL(mem_cgroup_from_task);
 
-static struct mem_cgroup *get_mem_cgroup_from_mm(struct mm_struct *mm)
+struct mem_cgroup *get_mem_cgroup_from_mm(struct mm_struct *mm)
 {
        struct mem_cgroup *memcg = NULL;
 
-- 
2.16.1.291.g4437f3f132-goog

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