From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alistair Popple Subject: Re: [RFC PATCH 05/19] RMDA/siw: Convert to use vm_account Date: Mon, 30 Jan 2023 22:34:50 +1100 Message-ID: <87lelkz23e.fsf@nvidia.com> References: <4f8b1d54ab5d6909c46ba5470065f8326f9fcc62.1674538665.git-series.apopple@nvidia.com> Mime-Version: 1.0 Return-path: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=Nvidia.com; s=selector2; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=tIiPdkfZ/fZE2PAtlhpufWZGeI6OlvxeJR6i/u8E6ZE=; b=IKmcfYZIzTzE+FOa9C3ZcvcOQ5+xrQCUSqHncijXIwvBmirsKytj0A7M/kwsE7d/H/D19ZWtknuMw8Zcn6PeNfD4aQOeqkZVRtX/5fxpsayNRTWOq3QcRb4abf3aI7FogIC0ECl984cN6FLW06FSxKS1A53E6zVpuPRFfOV2f5TblTaswez8dsHlGu2Z8JeSVOc+pyQynxbv2BVY0xQnqq8qN9xrx2lz+SqrBor/sYenCC3RLXJXWElmoXlGiYyijpHLNKUEo33AUSsVhgLbrxtj/J6ubVFc1SdJ9lmNjlQe80TlXgDRtMZ5H6r5XFDoB4kiNV/vAI7X8/BxsOl/2w== In-reply-to: List-ID: Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Bernard Metzler Cc: Jason Gunthorpe , "linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org" , "cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "jhubbard-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org" , "tjmercier-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org" , "hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org" , "surenb-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org" , "mkoutny-IBi9RG/b67k@public.gmane.org" , "daniel-/w4YWyX8dFk@public.gmane.org" , Leon Romanovsky , "linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" Bernard Metzler writes: >> -----Original Message----- >> From: Jason Gunthorpe >> Sent: Tuesday, 24 January 2023 15:37 >> To: Alistair Popple >> Cc: linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org; cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org; linux- >> kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org; jhubbard-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org; tjmercier-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org; >> hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org; surenb-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org; mkoutny-IBi9RG/b67k@public.gmane.org; daniel-/w4YWyX8dFk@public.gmane.org; >> Bernard Metzler ; Leon Romanovsky ; >> linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org >> Subject: [EXTERNAL] Re: [RFC PATCH 05/19] RMDA/siw: Convert to use >> vm_account >> >> On Tue, Jan 24, 2023 at 04:42:34PM +1100, Alistair Popple wrote: >> >> > @@ -385,20 +382,16 @@ struct siw_umem *siw_umem_get(u64 start, u64 len, >> bool writable) >> > if (!umem) >> > return ERR_PTR(-ENOMEM); >> > >> > - mm_s = current->mm; >> > - umem->owning_mm = mm_s; >> > umem->writable = writable; >> > >> > - mmgrab(mm_s); >> > + vm_account_init_current(&umem->vm_account); >> > >> > if (writable) >> > foll_flags |= FOLL_WRITE; >> > >> > - mmap_read_lock(mm_s); >> > + mmap_read_lock(current->mm); >> > >> > - mlock_limit = rlimit(RLIMIT_MEMLOCK) >> PAGE_SHIFT; >> > - >> > - if (num_pages + atomic64_read(&mm_s->pinned_vm) > mlock_limit) { >> > + if (vm_account_pinned(&umem->vm_account, num_pages)) { >> > rv = -ENOMEM; >> > goto out_sem_up; >> > } >> > @@ -429,7 +422,6 @@ struct siw_umem *siw_umem_get(u64 start, u64 len, >> bool writable) >> > goto out_sem_up; >> > >> > umem->num_pages += rv; >> > - atomic64_add(rv, &mm_s->pinned_vm); >> >> Also fixes the race bug > > But introduces another one. In that loop, umem->num_pages keeps the > number of pages currently pinned, not the target number. The current > patch uses that umem->num_pages to call vm_unaccount_pinned() in > siw_umem_release(). Bailing out before all pages are pinned would > mess up that accounting during release. Maybe introduce another > parameter to siw_umem_release(), or better have another umem member > 'umem->num_pages_accounted' for correct accounting during release. Yes, I see the problem thanks for pointing it out. Will fix for the next version. > Bernard. >> >> Jason