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 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 59051C6FD1F for ; Sat, 30 Mar 2024 12:55:38 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 953D16B007B; Sat, 30 Mar 2024 08:55:37 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 903DC6B0082; Sat, 30 Mar 2024 08:55:37 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 7F2566B0083; Sat, 30 Mar 2024 08:55:37 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0012.hostedemail.com [216.40.44.12]) by kanga.kvack.org (Postfix) with ESMTP id 634F16B007B for ; Sat, 30 Mar 2024 08:55:37 -0400 (EDT) Received: from smtpin10.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay03.hostedemail.com (Postfix) with ESMTP id 1DFF2A0217 for ; Sat, 30 Mar 2024 12:55:37 +0000 (UTC) X-FDA: 81953701914.10.E86759C Received: from mail-lj1-f178.google.com (mail-lj1-f178.google.com [209.85.208.178]) by imf11.hostedemail.com (Postfix) with ESMTP id 1AEC14000C for ; Sat, 30 Mar 2024 12:55:33 +0000 (UTC) Authentication-Results: imf11.hostedemail.com; dkim=pass header.d=gmail.com header.s=20230601 header.b=D+M0wOGF; dmarc=pass (policy=none) header.from=gmail.com; spf=pass (imf11.hostedemail.com: domain of urezki@gmail.com designates 209.85.208.178 as permitted sender) smtp.mailfrom=urezki@gmail.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1711803334; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=1m9ovnxUmO4jM14h7Q0jSZVXsOuJTF/qtN6BxjeYGvU=; b=hAon2tA5JDGG9U9OuSR3KZsYQ1Dlu5rfXEYKuqUpmlcJkF8ZlZtSFQa0CS4AP+wHELN83e uSdXfs76oDjmjLDSUpMJxTbKrKUot72MQnzJc0GfkJtBuL88N2O3siERjyw9Ww16UnFR9B 9gDvmFyLUkUb4J8gub3dP/hxkA4xr1k= ARC-Authentication-Results: i=1; imf11.hostedemail.com; dkim=pass header.d=gmail.com header.s=20230601 header.b=D+M0wOGF; dmarc=pass (policy=none) header.from=gmail.com; spf=pass (imf11.hostedemail.com: domain of urezki@gmail.com designates 209.85.208.178 as permitted sender) smtp.mailfrom=urezki@gmail.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1711803334; a=rsa-sha256; cv=none; b=f2DRackte72pCj03P2KnHU+SrFIxFB1d48lhL1U159RkSKbg+jPP4cq/VWgWw8ZjbmHcLw dQWf1tRWoNv3M6Kh/2FVxRZ1cuzIu/y98boAjGFSbnmJ3oBoaEeQW4nm7COWqfSvK8QV6K Ee23fjj+QLJ1tf8MDFu1f70z2tyA4AM= Received: by mail-lj1-f178.google.com with SMTP id 38308e7fff4ca-2d109e82bd0so34501191fa.3 for ; Sat, 30 Mar 2024 05:55:33 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1711803332; x=1712408132; darn=kvack.org; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:date:from:from:to:cc:subject:date:message-id:reply-to; bh=1m9ovnxUmO4jM14h7Q0jSZVXsOuJTF/qtN6BxjeYGvU=; b=D+M0wOGFO8fK7Zf3t6X7kzOHWQfvR/xdhknkhk2WUwWDZTxmkn+Aaf5lWR21j6QidS rie4NyVo7Te1Jxr9aOlZM92CMelzVT+SRI3OSNNwbLFcWE2qepyNKwrsMnTHVpIjbDE+ ologIrEGnjxoBsFxhcBUoC/8oBSjCbE/mlbHjZNKMn2SWQIg0Fl3NFZ8zFcAm0yT8kkC FeNcluMbZ+MC5PAty1JuGBFCXdiD4fPQIx1/W3qMakdivogdGlbKirEOQ+JlxMZtXD4U mah39qlYuWHDR6iB+n5vhhwsu8mbu73dQivCbZkdr/qo/0lbnfduBZ1vhtJpTdBYzQp0 EySA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1711803332; x=1712408132; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:date:from:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=1m9ovnxUmO4jM14h7Q0jSZVXsOuJTF/qtN6BxjeYGvU=; b=wEjCs+KTe4sA0cZ26L3SHnq/3tTYlHXsUoNRia6rY+EAJMz57Z49FpyVl7wG5dfXnj agC6EdLObGqI1pldRuc6247uTUWrjU3/UA0oxOW+3hiQi0TH90GVXFgVsDWMjJmQ+ZSX knvLJuTwKKVwVSi89UQJ4ug3zMAn6FNhaXPm/KaUyJSUDBsOD2hSYAomN6/BdP5B4+E1 3UO0aa7EswhOPF2eYgkAJsCFKlwvw0thcg0i58k6EH1S0PHmbPH5ZeRhRtvqGUQSGdWD K2XO7eq5pmK4lDJxiwo9RoGEPKGFYmGJ2STful8iKxllVWQhG+h52Mra/tEttvllo3kQ jqYA== X-Forwarded-Encrypted: i=1; AJvYcCVexGy8iXO52uvDhbvJKcEZg/txAKat8OGF1eQjfzvHGx5fzjXaiaY9wP/e3hRudXzNGJbWAI9SrR84ouf8rm/m8zU= X-Gm-Message-State: AOJu0YzxxpfU91UeBVxHwERS6cfhQxQ6T9qTJZUSRZ1AGjFZwm6arukc j5iAGXRH5vqjf8DZ0nc91zKjLTp6HwESXfVp+HSD0xj9jXtEn3vh X-Google-Smtp-Source: AGHT+IElPPMcrF0eTA1Tziki8z1EtpiGvO6Hr2cCipUkj2rBlXzYWXvrEVMBrleMs8fkd3kc/SfWnA== X-Received: by 2002:a2e:a176:0:b0:2d4:78ba:fa45 with SMTP id u22-20020a2ea176000000b002d478bafa45mr3423019ljl.2.1711803331820; Sat, 30 Mar 2024 05:55:31 -0700 (PDT) Received: from pc636 (host-185-121-47-193.sydskane.nu. [185.121.47.193]) by smtp.gmail.com with ESMTPSA id x20-20020a2ea994000000b002d435cdf2adsm879682ljq.111.2024.03.30.05.55.31 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 30 Mar 2024 05:55:31 -0700 (PDT) From: Uladzislau Rezki X-Google-Original-From: Uladzislau Rezki Date: Sat, 30 Mar 2024 13:55:29 +0100 To: Baoquan He Cc: "Uladzislau Rezki (Sony)" , linux-mm@kvack.org, Andrew Morton , LKML , Lorenzo Stoakes , Christoph Hellwig , Matthew Wilcox , Dave Chinner , Oleksiy Avramchenko , Jens Axboe , Omar Sandoval Subject: Re: [PATCH 1/1] mm: vmalloc: Fix lockdep warning Message-ID: References: <20240328140330.4747-1-urezki@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 1AEC14000C X-Stat-Signature: 7gffjzzrask57sz3b36crtfoq4fen96d X-Rspam-User: X-HE-Tag: 1711803333-688160 X-HE-Meta: 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 bezAhZw9 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 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: List-Subscribe: List-Unsubscribe: On Fri, Mar 29, 2024 at 03:44:40PM +0800, Baoquan He wrote: > On 03/28/24 at 03:03pm, Uladzislau Rezki (Sony) wrote: > > A lockdep reports a possible deadlock in the find_vmap_area_exceed_addr_lock() > > function: > > > > ============================================ > > WARNING: possible recursive locking detected > > 6.9.0-rc1-00060-ged3ccc57b108-dirty #6140 Not tainted > > -------------------------------------------- > > drgn/455 is trying to acquire lock: > > ffff0000c00131d0 (&vn->busy.lock/1){+.+.}-{2:2}, at: find_vmap_area_exceed_addr_lock+0x64/0x124 > > > > but task is already holding lock: > > ffff0000c0011878 (&vn->busy.lock/1){+.+.}-{2:2}, at: find_vmap_area_exceed_addr_lock+0x64/0x124 > > > > other info that might help us debug this: > > Possible unsafe locking scenario: > > > > CPU0 > > ---- > > lock(&vn->busy.lock/1); > > lock(&vn->busy.lock/1); > > > > *** DEADLOCK *** > > > > indeed it can happen if the find_vmap_area_exceed_addr_lock() > > gets called concurrently because it tries to acquire two nodes > > locks. It was done to prevent removing a lowest VA found on a > > previous step. > > > > To address this a lowest VA is found first without holding a > > node lock where it resides. As a last step we check if a VA > > still there because it can go away, if removed, proceed with > > next lowest. > > > > Fixes: 53becf32aec1 ("mm: vmalloc: support multiple nodes in vread_iter") > > Tested-by: Jens Axboe > > Tested-by: Omar Sandoval > > Reported-by: Jens Axboe > > Signed-off-by: Uladzislau Rezki (Sony) > > --- > > mm/vmalloc.c | 74 +++++++++++++++++++++++++++++++--------------------- > > 1 file changed, 44 insertions(+), 30 deletions(-) > > > > diff --git a/mm/vmalloc.c b/mm/vmalloc.c > > index e94ce4562805..a5a5dfc3843e 100644 > > --- a/mm/vmalloc.c > > +++ b/mm/vmalloc.c > > @@ -989,6 +989,27 @@ unsigned long vmalloc_nr_pages(void) > > return atomic_long_read(&nr_vmalloc_pages); > > } > > > > +static struct vmap_area *__find_vmap_area(unsigned long addr, struct rb_root *root) > > +{ > > + struct rb_node *n = root->rb_node; > > + > > + addr = (unsigned long)kasan_reset_tag((void *)addr); > > + > > + while (n) { > > + struct vmap_area *va; > > + > > + va = rb_entry(n, struct vmap_area, rb_node); > > + if (addr < va->va_start) > > + n = n->rb_left; > > + else if (addr >= va->va_end) > > + n = n->rb_right; > > + else > > + return va; > > + } > > + > > + return NULL; > > +} > > + > > /* Look up the first VA which satisfies addr < va_end, NULL if none. */ > > static struct vmap_area * > > __find_vmap_area_exceed_addr(unsigned long addr, struct rb_root *root) > > @@ -1025,47 +1046,40 @@ __find_vmap_area_exceed_addr(unsigned long addr, struct rb_root *root) > > static struct vmap_node * > > find_vmap_area_exceed_addr_lock(unsigned long addr, struct vmap_area **va) > > { > > - struct vmap_node *vn, *va_node = NULL; > > - struct vmap_area *va_lowest; > > + unsigned long va_start_lowest; > > + struct vmap_node *vn; > > int i; > > > > - for (i = 0; i < nr_vmap_nodes; i++) { > > +repeat: > > + for (i = 0, va_start_lowest = 0; i < nr_vmap_nodes; i++) { > > vn = &vmap_nodes[i]; > > > > spin_lock(&vn->busy.lock); > > - va_lowest = __find_vmap_area_exceed_addr(addr, &vn->busy.root); > > - if (va_lowest) { > > - if (!va_node || va_lowest->va_start < (*va)->va_start) { > > - if (va_node) > > - spin_unlock(&va_node->busy.lock); > > - > > - *va = va_lowest; > > - va_node = vn; > > - continue; > > - } > > - } > > + *va = __find_vmap_area_exceed_addr(addr, &vn->busy.root); > > + > > + if (*va) > > + if (!va_start_lowest || (*va)->va_start < va_start_lowest) > > + va_start_lowest = (*va)->va_start; > > How about below change about va_start_lowest? Personal preference, not > strong opinion. > > diff --git a/mm/vmalloc.c b/mm/vmalloc.c > index 9b1a41e12d70..bd6a66c54ad2 100644 > --- a/mm/vmalloc.c > +++ b/mm/vmalloc.c > @@ -1046,19 +1046,19 @@ __find_vmap_area_exceed_addr(unsigned long addr, struct rb_root *root) > static struct vmap_node * > find_vmap_area_exceed_addr_lock(unsigned long addr, struct vmap_area **va) > { > - unsigned long va_start_lowest; > + unsigned long va_start_lowest = ULONG_MAX; > struct vmap_node *vn; > int i; > > repeat: > - for (i = 0, va_start_lowest = 0; i < nr_vmap_nodes; i++) { > + for (i = 0; i < nr_vmap_nodes; i++) { > vn = &vmap_nodes[i]; > > spin_lock(&vn->busy.lock); > *va = __find_vmap_area_exceed_addr(addr, &vn->busy.root); > > if (*va) > - if (!va_start_lowest || (*va)->va_start < va_start_lowest) > + if ((*va)->va_start < va_start_lowest) > va_start_lowest = (*va)->va_start; > spin_unlock(&vn->busy.lock); > } > @@ -1069,7 +1069,7 @@ find_vmap_area_exceed_addr_lock(unsigned long addr, struct vmap_area **va) > * been removed concurrently thus we need to proceed > * with next one what is a rare case. > */ > - if (va_start_lowest) { > + if (va_start_lowest != ULONG_MAX) { > vn = addr_to_node(va_start_lowest); > > spin_lock(&vn->busy.lock); > > To me it looks as incomplete. The "va_start_lowest" should be initialized when repeat. Otherwise we can end up with an infinite repeating because va_start_lowest != ULONG_MAX. > > } > > > > - return va_node; > > -} > > - > > -static struct vmap_area *__find_vmap_area(unsigned long addr, struct rb_root *root) > > -{ > > - struct rb_node *n = root->rb_node; > > + /* > > + * Check if found VA exists, it might it is gone away. > ~~~~ grammer mistake? > > + * In this case we repeat the search because a VA has > > + * been removed concurrently thus we need to proceed > > + * with next one what is a rare case. > ~~~~ typo, which? > > + */ > > + if (va_start_lowest) { > > + vn = addr_to_node(va_start_lowest); > > > > - addr = (unsigned long)kasan_reset_tag((void *)addr); > > + spin_lock(&vn->busy.lock); > > + *va = __find_vmap_area(va_start_lowest, &vn->busy.root); > > > > - while (n) { > > - struct vmap_area *va; > > + if (*va) > > + return vn; > > > > - va = rb_entry(n, struct vmap_area, rb_node); > > - if (addr < va->va_start) > > - n = n->rb_left; > > - else if (addr >= va->va_end) > > - n = n->rb_right; > > - else > > - return va; > > + spin_unlock(&vn->busy.lock); > > + goto repeat; > > } > > Other than above nickpick concerns, this looks good to me. > > Reviewed-by: Baoquan He > Thank you! -- Uladzislau Rezki