From nobody Mon Jun 22 18:09:28 2026 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id D6EA8C433F5 for ; Sat, 19 Mar 2022 00:16:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240524AbiCSASI (ORCPT ); Fri, 18 Mar 2022 20:18:08 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43010 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233178AbiCSASG (ORCPT ); Fri, 18 Mar 2022 20:18:06 -0400 Received: from mail-pg1-x54a.google.com (mail-pg1-x54a.google.com [IPv6:2607:f8b0:4864:20::54a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4310C30A8BE for ; Fri, 18 Mar 2022 17:16:47 -0700 (PDT) Received: by mail-pg1-x54a.google.com with SMTP id x5-20020a637c05000000b003817f40e072so4035024pgc.17 for ; Fri, 18 Mar 2022 17:16:47 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=date:message-id:mime-version:subject:from:to:cc; bh=8kLMxs/CvqJZP0KCbxy42TuXckQwVilQVIyMYVLn0uY=; b=F+XzdVUPzB6Qc26IhOBE69o28h3KUC1mIIntciiBSN16f5Zu30B1nhsVBzQkgkxqER 8YTzAhbFmtEiUqWJR+GHpfHSYoy5Z3NXa9rivOCVgtMCqFQISyLlEeV/QrA/t0RXlDYt 3crVEvZt3bK2BWJG0sOdtdRTMDavbqjPTM7oTdOg6WWASczWA9nTBWiJq94R/SC+fzr/ OKEf3RYLbZouPvrztTodm28GeVBvQGXtxhQ2CfqC/zCPvtsorHobvRBr0PzXANx5EBQo 0sZcPuE4oVDCxmhikJvWaoeY+pilbeU3mgH+8llOnqJE8ThEt3hxnJGLCI/opc/Rxkqv 8h1A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:message-id:mime-version:subject:from:to:cc; bh=8kLMxs/CvqJZP0KCbxy42TuXckQwVilQVIyMYVLn0uY=; b=DO9IQ0E4HIZUNw1rJPReaG2zRJNo30/qgbR3xtpHIY25PKgSlRipGvZZLWIHofIb15 m7TZUR0DNmWCwj1n/RvuhoydsVVIbH2a5MwzwtOwDsg67HMumOGdEfXktAvsgpEi/yzp hMWbwD03dLOSl7/yadDpVa1zOkOrFXQd7mmOWVXV7k/aePko95TF+0B02N2H+RQefXtJ kQ6a121OGlAiekyZFrKp7IRpRNiA3I1/Mgr0a/yPXsCUQdysAKNI8a3d8rhnVPhe9qjm l83tdIdDY0pTUvBzXymmYz8CMtUyOw2git9XRbKwFToctg8/z91A0Z5W/qE0DwPLwCOn Pkjw== X-Gm-Message-State: AOAM533OOxISPcUzKjQ5UutN76hzJxGF/plrIOuwNyzwhdLPiuWNraja D05Zu8JfEjB8zuQqTPvwH2ZBV/M/4VM= X-Google-Smtp-Source: ABdhPJyw+5UCojVLuo2jkstLVsgWPSMq9PTXXa78BrdrS5rmZl+MtF4r1dvc4lwaR7/kd++jxGcD2lVXvho= X-Received: from khazhy-linux.svl.corp.google.com ([2620:15c:2cd:202:62b3:bbf6:1668:e469]) (user=khazhy job=sendgmr) by 2002:a62:8c11:0:b0:4f6:e890:5be5 with SMTP id m17-20020a628c11000000b004f6e8905be5mr12629327pfd.19.1647649006753; Fri, 18 Mar 2022 17:16:46 -0700 (PDT) Date: Fri, 18 Mar 2022 17:16:35 -0700 Message-Id: <20220319001635.4097742-1-khazhy@google.com> Mime-Version: 1.0 X-Mailer: git-send-email 2.35.1.894.gb6a874cedc-goog Subject: [PATCH RFC] nfsd: avoid recursive locking through fsnotify From: Khazhismel Kumykov To: "J. Bruce Fields" , Chuck Lever Cc: linux-nfs@vger.kernel.org, linux-kernel@vger.kernel.org, Khazhismel Kumykov Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" fsnotify_add_inode_mark may allocate with GFP_KERNEL, which may result in recursing back into nfsd, resulting in deadlock. See below stack. nfsd D 0 1591536 2 0x80004080 Call Trace: __schedule+0x497/0x630 schedule+0x67/0x90 schedule_preempt_disabled+0xe/0x10 __mutex_lock+0x347/0x4b0 fsnotify_destroy_mark+0x22/0xa0 nfsd_file_free+0x79/0xd0 [nfsd] nfsd_file_put_noref+0x7c/0x90 [nfsd] nfsd_file_lru_dispose+0x6d/0xa0 [nfsd] nfsd_file_lru_scan+0x57/0x80 [nfsd] do_shrink_slab+0x1f2/0x330 shrink_slab+0x244/0x2f0 shrink_node+0xd7/0x490 do_try_to_free_pages+0x12f/0x3b0 try_to_free_pages+0x43f/0x540 __alloc_pages_slowpath+0x6ab/0x11c0 __alloc_pages_nodemask+0x274/0x2c0 alloc_slab_page+0x32/0x2e0 new_slab+0xa6/0x8b0 ___slab_alloc+0x34b/0x520 kmem_cache_alloc+0x1c4/0x250 fsnotify_add_mark_locked+0x18d/0x4c0 fsnotify_add_mark+0x48/0x70 nfsd_file_acquire+0x570/0x6f0 [nfsd] nfsd_read+0xa7/0x1c0 [nfsd] nfsd3_proc_read+0xc1/0x110 [nfsd] nfsd_dispatch+0xf7/0x240 [nfsd] svc_process_common+0x2f4/0x610 [sunrpc] svc_process+0xf9/0x110 [sunrpc] nfsd+0x10e/0x180 [nfsd] kthread+0x130/0x140 ret_from_fork+0x35/0x40 Signed-off-by: Khazhismel Kumykov --- fs/nfsd/filecache.c | 4 ++++ 1 file changed, 4 insertions(+) Marking this RFC since I haven't actually had a chance to test this, we we're seeing this deadlock for some customers. diff --git a/fs/nfsd/filecache.c b/fs/nfsd/filecache.c index fdf89fcf1a0c..a14760f9b486 100644 --- a/fs/nfsd/filecache.c +++ b/fs/nfsd/filecache.c @@ -121,6 +121,7 @@ nfsd_file_mark_find_or_create(struct nfsd_file *nf) struct fsnotify_mark *mark; struct nfsd_file_mark *nfm =3D NULL, *new; struct inode *inode =3D nf->nf_inode; + unsigned int pflags; =20 do { mutex_lock(&nfsd_file_fsnotify_group->mark_mutex); @@ -149,7 +150,10 @@ nfsd_file_mark_find_or_create(struct nfsd_file *nf) new->nfm_mark.mask =3D FS_ATTRIB|FS_DELETE_SELF; refcount_set(&new->nfm_ref, 1); =20 + /* fsnotify allocates, avoid recursion back into nfsd */ + pflags =3D memalloc_nofs_save(); err =3D fsnotify_add_inode_mark(&new->nfm_mark, inode, 0); + memalloc_nofs_restore(pflags); =20 /* * If the add was successful, then return the object. --=20 2.35.1.894.gb6a874cedc-goog