Re: [PATCH 3/3] fs: fsnotify: account fsnotify metadata to kmemcg

From: Shakeel Butt
Date: Tue Feb 20 2018 - 14:48:06 EST

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On Tue, Feb 20, 2018 at 11:41 AM, Shakeel Butt <shakeelb@xxxxxxxxxx> wrote:
> 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 objects from fsnotify_mark_connector_cachep are not accounted as
> they are small compared to the notification mark or events and it is
> unclear whom to account connector to since it is shared by all events
> attached to the inode.
>
> The allocations from the event caches 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 <shakeelb@xxxxxxxxxx>

Andrew, please don't send this patch to Linus until Jan Kara's changes
are merged. I will let you know when that happens.

> ---
> Changelog since v1:
> - no more charging fsnotify_mark_connector objects
>
> fs/notify/dnotify/dnotify.c | 5 +++--
> fs/notify/fanotify/fanotify.c | 12 +++++++-----
> fs/notify/fanotify/fanotify.h | 3 ++-
> fs/notify/fanotify/fanotify_user.c | 7 +++++--
> fs/notify/group.c | 4 ++++
> fs/notify/inotify/inotify_fsnotify.c | 2 +-
> fs/notify/inotify/inotify_user.c | 5 ++++-
> fs/notify/mark.c | 6 ++++--
> include/linux/fsnotify_backend.h | 12 ++++++++----
> include/linux/memcontrol.h | 7 +++++++
> mm/memcontrol.c | 2 +-
> 11 files changed, 46 insertions(+), 19 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..0d9493ebc7cd 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);
> 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..29c9b3e57a29 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 +757,9 @@ SYSCALL_DEFINE2(fanotify_init, unsigned int, flags, unsigned int, event_f_flags)
>
> group->fanotify_data.user = user;
> atomic_inc(&user->fanotify_listeners);
> + group->memcg = 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);
> if (unlikely(!oevent)) {
> fd = -ENOMEM;
> goto out_destroy_group;
> @@ -951,7 +953,8 @@ 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..3e56459f4773 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)
> + mem_cgroup_put(group->memcg);
> +
> kfree(group);
> }
>
> diff --git a/fs/notify/inotify/inotify_fsnotify.c b/fs/notify/inotify/inotify_fsnotify.c
> index 8b73332735ba..ed8e7b5f3981 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);
> if (unlikely(!event))
> return -ENOMEM;
>
> diff --git a/fs/notify/inotify/inotify_user.c b/fs/notify/inotify/inotify_user.c
> index 5c29bf16814f..e80f4656799f 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 = 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..c0014d0c3783 100644
> --- a/fs/notify/mark.c
> +++ b/fs/notify/mark.c
> @@ -432,7 +432,8 @@ 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;
>
> @@ -517,7 +518,8 @@ 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..e4428e383215 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; /* 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..ee4b6b9d6813 100644
> --- a/include/linux/memcontrol.h
> +++ b/include/linux/memcontrol.h
> @@ -352,6 +352,8 @@ 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 +811,11 @@ 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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