From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-3.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id A0ACEC433E0 for ; Tue, 9 Jun 2020 04:33:40 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 612F3207F9 for ; Tue, 9 Jun 2020 04:33:40 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="IhLaHs6w" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 612F3207F9 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linux-foundation.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 067178D000B; Tue, 9 Jun 2020 00:33:40 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 018DF6B00BE; Tue, 9 Jun 2020 00:33:39 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id E71238D000B; Tue, 9 Jun 2020 00:33:39 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0129.hostedemail.com [216.40.44.129]) by kanga.kvack.org (Postfix) with ESMTP id D08586B00BD for ; Tue, 9 Jun 2020 00:33:39 -0400 (EDT) Received: from smtpin28.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id 95017181ABEA4 for ; Tue, 9 Jun 2020 04:33:39 +0000 (UTC) X-FDA: 76908404958.28.knife13_610d74d26dbf Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin28.hostedemail.com (Postfix) with ESMTP id 662D76C16 for ; Tue, 9 Jun 2020 04:33:39 +0000 (UTC) X-HE-Tag: knife13_610d74d26dbf X-Filterd-Recvd-Size: 5175 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf43.hostedemail.com (Postfix) with ESMTP for ; Tue, 9 Jun 2020 04:33:38 +0000 (UTC) Received: from localhost.localdomain (c-73-231-172-41.hsd1.ca.comcast.net [73.231.172.41]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id ADC9420810; Tue, 9 Jun 2020 04:33:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1591677218; bh=fbpy+qOtJ39RRkB8z45QKvt9K/6HweCwR257vJpXvcc=; h=Date:From:To:Subject:In-Reply-To:From; b=IhLaHs6wmeskFKmqyAMPqX9bNkxHh2MnyVgvkU2LEnd6ry1kiboOgvr+X6W+aSgAa d7GAnSkI4DmvRwzw8wOI2ClwPRlbo6l+HOA2nX1DTNovjRZXuNOMh23PFRKuk/UG1l L/qRWIlKHFLLxlJh6Q+uDf1ffa0ch5gj+09n3Bng= Date: Mon, 08 Jun 2020 21:33:37 -0700 From: Andrew Morton To: akpm@linux-foundation.org, daniel.m.jordan@oracle.com, dbueso@suse.de, hughd@google.com, jgg@ziepe.ca, jglisse@redhat.com, jhubbard@nvidia.com, ldufour@linux.ibm.com, Liam.Howlett@oracle.com, linux-mm@kvack.org, mm-commits@vger.kernel.org, peterz@infradead.org, rientjes@google.com, torvalds@linux-foundation.org, vbabka@suse.cz, walken@google.com, willy@infradead.org, yinghan@google.com Subject: [patch 66/93] mmap locking API: add mmap_read_trylock_non_owner() Message-ID: <20200609043337.0WUqyTkKL%akpm@linux-foundation.org> In-Reply-To: <20200608212922.5b7fa74ca3f4e2444441b7f9@linux-foundation.org> User-Agent: s-nail v14.8.16 X-Rspamd-Queue-Id: 662D76C16 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam01 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: From: Michel Lespinasse Subject: mmap locking API: add mmap_read_trylock_non_owner() Add a couple APIs used by kernel/bpf/stackmap.c only: - mmap_read_trylock_non_owner() - mmap_read_unlock_non_owner() (may be called from a work queue). It's still not ideal that bpf/stackmap subverts the lock ownership in this way. Thanks to Peter Zijlstra for suggesting this API as the least-ugly way of addressing this in the short term. Link: http://lkml.kernel.org/r/20200520052908.204642-8-walken@google.com Signed-off-by: Michel Lespinasse Reviewed-by: Daniel Jordan Reviewed-by: Vlastimil Babka Reviewed-by: Davidlohr Bueso Cc: David Rientjes Cc: Hugh Dickins Cc: Jason Gunthorpe Cc: Jerome Glisse Cc: John Hubbard Cc: Laurent Dufour Cc: Liam Howlett Cc: Matthew Wilcox Cc: Peter Zijlstra Cc: Ying Han Signed-off-by: Andrew Morton --- include/linux/mmap_lock.h | 14 ++++++++++++++ kernel/bpf/stackmap.c | 17 +++++------------ 2 files changed, 19 insertions(+), 12 deletions(-) --- a/include/linux/mmap_lock.h~mmap-locking-api-add-mmap_read_trylock_non_owner +++ a/include/linux/mmap_lock.h @@ -56,4 +56,18 @@ static inline void mmap_read_unlock(stru up_read(&mm->mmap_sem); } +static inline bool mmap_read_trylock_non_owner(struct mm_struct *mm) +{ + if (down_read_trylock(&mm->mmap_sem)) { + rwsem_release(&mm->mmap_sem.dep_map, _RET_IP_); + return true; + } + return false; +} + +static inline void mmap_read_unlock_non_owner(struct mm_struct *mm) +{ + up_read_non_owner(&mm->mmap_sem); +} + #endif /* _LINUX_MMAP_LOCK_H */ --- a/kernel/bpf/stackmap.c~mmap-locking-api-add-mmap_read_trylock_non_owner +++ a/kernel/bpf/stackmap.c @@ -33,7 +33,7 @@ struct bpf_stack_map { /* irq_work to run up_read() for build_id lookup in nmi context */ struct stack_map_irq_work { struct irq_work irq_work; - struct rw_semaphore *sem; + struct mm_struct *mm; }; static void do_up_read(struct irq_work *entry) @@ -44,8 +44,7 @@ static void do_up_read(struct irq_work * return; work = container_of(entry, struct stack_map_irq_work, irq_work); - up_read_non_owner(work->sem); - work->sem = NULL; + mmap_read_unlock_non_owner(work->mm); } static DEFINE_PER_CPU(struct stack_map_irq_work, up_read_work); @@ -317,7 +316,7 @@ static void stack_map_get_build_id_offse * with build_id. */ if (!user || !current || !current->mm || irq_work_busy || - mmap_read_trylock(current->mm) == 0) { + !mmap_read_trylock_non_owner(current->mm)) { /* cannot access current->mm, fall back to ips */ for (i = 0; i < trace_nr; i++) { id_offs[i].status = BPF_STACK_BUILD_ID_IP; @@ -342,16 +341,10 @@ static void stack_map_get_build_id_offse } if (!work) { - mmap_read_unlock(current->mm); + mmap_read_unlock_non_owner(current->mm); } else { - work->sem = ¤t->mm->mmap_sem; + work->mm = current->mm; irq_work_queue(&work->irq_work); - /* - * The irq_work will release the mmap_sem with - * up_read_non_owner(). The rwsem_release() is called - * here to release the lock from lockdep's perspective. - */ - rwsem_release(¤t->mm->mmap_sem.dep_map, _RET_IP_); } } _