| Message ID | 20190429171332.152992-2-shakeelb@google.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [1/2] memcg, oom: no oom-kill for __GFP_RETRY_MAYFAIL | expand |
On Mon 29-04-19 10:13:32, Shakeel Butt wrote: [...] > /* > * For queues with unlimited length lost events are not expected and > * can possibly have security implications. Avoid losing events when > * memory is short. > + * > + * Note: __GFP_NOFAIL takes precedence over __GFP_RETRY_MAYFAIL. > */ No, I there is no rule like that. Combining the two is undefined currently and I do not think we want to legitimize it. What does it even mean?
On Mon, Apr 29, 2019 at 5:41 PM Michal Hocko <mhocko@kernel.org> wrote: > > On Mon 29-04-19 10:13:32, Shakeel Butt wrote: > [...] > > /* > > * For queues with unlimited length lost events are not expected and > > * can possibly have security implications. Avoid losing events when > > * memory is short. > > + * > > + * Note: __GFP_NOFAIL takes precedence over __GFP_RETRY_MAYFAIL. > > */ > > No, I there is no rule like that. Combining the two is undefined > currently and I do not think we want to legitimize it. What does it even > mean? > Actually the code is doing that but I agree this is not documented and weird. I will fix this. Shakeel
diff --git a/fs/notify/fanotify/fanotify.c b/fs/notify/fanotify/fanotify.c index 6b9c27548997..9aa5d325e6d8 100644 --- a/fs/notify/fanotify/fanotify.c +++ b/fs/notify/fanotify/fanotify.c @@ -282,13 +282,15 @@ struct fanotify_event *fanotify_alloc_event(struct fsnotify_group *group, __kernel_fsid_t *fsid) { struct fanotify_event *event = NULL; - gfp_t gfp = GFP_KERNEL_ACCOUNT; + gfp_t gfp = GFP_KERNEL_ACCOUNT | __GFP_RETRY_MAYFAIL; struct inode *id = fanotify_fid_inode(inode, mask, data, data_type); /* * For queues with unlimited length lost events are not expected and * can possibly have security implications. Avoid losing events when * memory is short. + * + * Note: __GFP_NOFAIL takes precedence over __GFP_RETRY_MAYFAIL. */ if (group->max_events == UINT_MAX) gfp |= __GFP_NOFAIL; diff --git a/fs/notify/inotify/inotify_fsnotify.c b/fs/notify/inotify/inotify_fsnotify.c index ff30abd6a49b..17c08daa1ba7 100644 --- a/fs/notify/inotify/inotify_fsnotify.c +++ b/fs/notify/inotify/inotify_fsnotify.c @@ -99,9 +99,12 @@ int inotify_handle_event(struct fsnotify_group *group, i_mark = container_of(inode_mark, struct inotify_inode_mark, fsn_mark); - /* Whoever is interested in the event, pays for the allocation. */ + /* + * Whoever is interested in the event, pays for the allocation. However + * do not trigger the OOM killer in the target memcg. + */ memalloc_use_memcg(group->memcg); - event = kmalloc(alloc_len, GFP_KERNEL_ACCOUNT); + event = kmalloc(alloc_len, GFP_KERNEL_ACCOUNT | __GFP_RETRY_MAYFAIL); memalloc_unuse_memcg(); if (unlikely(!event)) {
The commit d46eb14b735b ("fs: fsnotify: account fsnotify metadata to kmemcg") added remote memcg charging for fanotify and inotify event objects. The aim was to charge the memory to the listener who is interested in the events but without triggering the OOM killer. Otherwise there would be security concerns for the listener. At the time, oom-kill trigger was not in the charging path. A parallel work added the oom-kill back to charging path i.e. commit 29ef680ae7c2 ("memcg, oom: move out_of_memory back to the charge path"). So to not trigger oom-killer in the remote memcg, explicitly add __GFP_RETRY_MAYFAIL to the fanotify and inotify event allocations. Signed-off-by: Shakeel Butt <shakeelb@google.com> --- fs/notify/fanotify/fanotify.c | 4 +++- fs/notify/inotify/inotify_fsnotify.c | 7 +++++-- 2 files changed, 8 insertions(+), 3 deletions(-)