From patchwork Wed May 20 05:29:03 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Michel Lespinasse X-Patchwork-Id: 11559327 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 4DDE160D for ; Wed, 20 May 2020 05:29:34 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 1B561207C4 for ; Wed, 20 May 2020 05:29:34 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="QbHMgP/N" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 1B561207C4 Authentication-Results: mail.kernel.org; dmarc=fail (p=reject dis=none) header.from=google.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 1F2288005B; Wed, 20 May 2020 01:29:29 -0400 (EDT) Delivered-To: linux-mm-outgoing@kvack.org Received: by kanga.kvack.org (Postfix, from userid 40) id 179368002C; Wed, 20 May 2020 01:29:29 -0400 (EDT) X-Original-To: int-list-linux-mm@kvack.org X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id F35758005B; Wed, 20 May 2020 01:29:28 -0400 (EDT) X-Original-To: linux-mm@kvack.org X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0014.hostedemail.com [216.40.44.14]) by kanga.kvack.org (Postfix) with ESMTP id CFCA68002C for ; Wed, 20 May 2020 01:29:28 -0400 (EDT) Received: from smtpin05.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id 8D6FF180AD815 for ; Wed, 20 May 2020 05:29:28 +0000 (UTC) X-FDA: 76835969616.05.dust20_52b36f920c114 X-Spam-Summary: 2,0,0,cbfc31dcfb6e4b68,d41d8cd98f00b204,3n8dexgykcmy8mxwqzs00sxq.o0yxuz69-yyw7mow.03s@flex--walken.bounces.google.com,,RULES_HIT:41:69:152:355:379:541:800:960:973:988:989:1260:1277:1313:1314:1345:1359:1437:1516:1518:1535:1543:1593:1594:1711:1730:1747:1777:1792:2198:2199:2393:2553:2559:2562:2693:2901:3138:3139:3140:3141:3142:3152:3354:3865:3866:3867:3870:3871:3872:3874:4117:4250:4321:5007:6261:6653:6742:7875:7903:9969:10004:10400:11026:11473:11658:11914:12043:12114:12296:12297:12438:12555:12895:12986:14181:14394:14659:14721:21080:21324:21433:21444:21450:21451:21627:21740:21795:21987:21990:30046:30051:30054:30064:30090,0,RBL:209.85.222.202:@flex--walken.bounces.google.com:.lbl8.mailshell.net-66.100.201.100 62.18.0.100,CacheIP:none,Bayesian:0.5,0.5,0.5,Netcheck:none,DomainCache:0,MSF:not bulk,SPF:fp,MSBL:0,DNSBL:neutral,Custom_rules:0:0:0,LFtime:24,LUA_SUMMARY:none X-HE-Tag: dust20_52b36f920c114 X-Filterd-Recvd-Size: 6241 Received: from mail-qk1-f202.google.com (mail-qk1-f202.google.com [209.85.222.202]) by imf30.hostedemail.com (Postfix) with ESMTP for ; Wed, 20 May 2020 05:29:28 +0000 (UTC) Received: by mail-qk1-f202.google.com with SMTP id 25so2670823qkc.3 for ; Tue, 19 May 2020 22:29:28 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:in-reply-to:message-id:mime-version:references:subject:from:to :cc; bh=m0T6T+70wSFyJpcmVviJFbhlAnWz1/NcVo+29dwBHOg=; b=QbHMgP/Nig7fT3isiChQjfZKm91tA6CwwAN/Ni4maGfQgte+us6j3UCl2hydLIRd2e uCPWpBZi8mxGT5MRc/Z5W6dFC/DSSKJdiaWAyI48ZVRk7imlbTJc7OI/NbMLdgY2Q5Wy 0Ep6vckOzmrsdSHoDjWtyTasqal/xXzRFtfiA1bn/GZw/aHgcB4ogUOpcnDawY/Lh9hU XdAsYW1xG9j4/Ozmw2bs5h8sJWpABV6n7b8ga52ZHY1uGeL0U8Du12SkGrgZvZTQWEmS /19vryTT69cYt45ryU2SIsSRLRDAq7SyaXmiJgqSM0IZwMQR+H44cmKKObQOEmEcqeIS Nh0g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:in-reply-to:message-id:mime-version :references:subject:from:to:cc; bh=m0T6T+70wSFyJpcmVviJFbhlAnWz1/NcVo+29dwBHOg=; b=gTrCIhp8PAAMtk4fG9QpNFslhe0/yjHkDSSOtbZ8CxlbcIR1TjstEtaIG17Ws4f+lk QKqP1HuG2/BR7CKKY47ywjJ7hoPv26LUnRSA5Zw/C0WA7cdTAof6WS52qiKz8Cdf7bxR Jf4zwVMAHpH9rf0q07eCGsI1BikPsCBBZl1sF89DshJQnfd5kp7UdcAYtLibDn/xF+x2 VT0kCxFq85CadvXL0HV2A01pd97Juo15z4k92ShOte1S+QZzyNSaLiwDiZ2JkThRNCk4 4pwqBOrLtny1UrvYSW/zl5ZV2lmeeswVdiU3lSqC4leAnXTD9PE8YlZkJhkgpiqfP/73 0KeA== X-Gm-Message-State: AOAM5318q3R+lvO3lsE5ixbTabZ3v+zBlTgjn7g+op03j5D+QImiNDWc ggMIF7u2RpkBeL/T22siMf4HUiY1nuE= X-Google-Smtp-Source: ABdhPJxoVK6kzfbip/jyp4MIxHt+TXYAM3wE7U0C5wiZEdI/3dI5eGJJjv/gAGIl6SeusJsJcxC/cs8FXlc= X-Received: by 2002:a0c:f3ca:: with SMTP id f10mr3336511qvm.66.1589952567603; Tue, 19 May 2020 22:29:27 -0700 (PDT) Date: Tue, 19 May 2020 22:29:03 -0700 In-Reply-To: <20200520052908.204642-1-walken@google.com> Message-Id: <20200520052908.204642-8-walken@google.com> Mime-Version: 1.0 References: <20200520052908.204642-1-walken@google.com> X-Mailer: git-send-email 2.26.2.761.g0e0b3e54be-goog Subject: [PATCH v6 07/12] mmap locking API: add mmap_read_trylock_non_owner() From: Michel Lespinasse To: Andrew Morton , linux-mm Cc: LKML , Peter Zijlstra , Laurent Dufour , Vlastimil Babka , Matthew Wilcox , Liam Howlett , Jerome Glisse , Davidlohr Bueso , David Rientjes , Hugh Dickins , Ying Han , Jason Gunthorpe , Daniel Jordan , John Hubbard , Michel Lespinasse 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: 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. Signed-off-by: Michel Lespinasse Reviewed-by: Daniel Jordan Reviewed-by: Vlastimil Babka Reviewed-by: Davidlohr Bueso --- include/linux/mmap_lock.h | 14 ++++++++++++++ kernel/bpf/stackmap.c | 17 +++++------------ 2 files changed, 19 insertions(+), 12 deletions(-) diff --git a/include/linux/mmap_lock.h b/include/linux/mmap_lock.h index a757cb30ae77..d1826ce42f00 100644 --- a/include/linux/mmap_lock.h +++ b/include/linux/mmap_lock.h @@ -56,4 +56,18 @@ static inline void mmap_read_unlock(struct mm_struct *mm) 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 */ diff --git a/kernel/bpf/stackmap.c b/kernel/bpf/stackmap.c index 11d41f0c7005..998968659892 100644 --- a/kernel/bpf/stackmap.c +++ b/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 *entry) 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_offset(struct bpf_stack_build_id *id_offs, * 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_offset(struct bpf_stack_build_id *id_offs, } 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_); } }