From nobody Sun May 24 18:42:57 2026 Received: from mailgw.kylinos.cn (mailgw.kylinos.cn [124.126.103.232]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id CF3181AB6F1; Fri, 22 May 2026 08:38:29 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=124.126.103.232 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779439115; cv=none; b=scksdL6QWRqbge0YvGVqkBJBBSpdXv365iIEsSohFiFNWtsn91sxCtQ0FcoxWwGVMt0H9c2+YzNEecX+hjW20SPLwp9CBuzBt41GA/RAUc95he2hVvTxwzJLRFHaRbMyBbdR4CNoRC74AcF+pAHEgDILwZxdxxVIByAm5TkNHQ8= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779439115; c=relaxed/simple; bh=aFeiWHHjwplmtqR86PbVfh26F2Yjo6+t+uRET83jyOs=; h=From:To:Cc:Subject:Date:Message-Id:MIME-Version; b=pGzZswJz7Gs8xqWbleu07GvBnqPXD03uWctwQAGDMfICeDgrFURz2KglXjfz8J6DFiLSrjpC9GZuuCc9RCnGOSvuVUXALIxR2YTq8bRSITZaLknOLIA+BkpfKtyh6xla4bRakeJB9wZFjMRwQn3VpC8G7K9Xba6lGoFmRtlb69c= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=kylinos.cn; spf=pass smtp.mailfrom=kylinos.cn; arc=none smtp.client-ip=124.126.103.232 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=kylinos.cn Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=kylinos.cn X-UUID: 9696fd8255b911f1aa26b74ffac11d73-20260522 X-CTIC-Tags: HR_CC_COUNT, HR_CC_DOMAIN_COUNT, HR_CC_NAME, HR_CC_NO_NAME, HR_CTE_8B HR_CTT_MISS, HR_DATE_H, HR_DATE_WKD, HR_DATE_ZONE, HR_FROM_NAME HR_SJ_LANG, HR_SJ_LEN, HR_SJ_LETTER, HR_SJ_NOR_SYM, HR_SJ_PHRASE HR_SJ_PHRASE_LEN, HR_SJ_WS, HR_TO_COUNT, HR_TO_DOMAIN_COUNT, HR_TO_NAME IP_TRUSTED, SRC_TRUSTED, DN_TRUSTED, SA_TRUSTED, SA_EXISTED SN_TRUSTED, SN_EXISTED, SPF_NOPASS, DKIM_NOPASS, DMARC_NOPASS CIE_BAD, CIE_GOOD, CIE_GOOD_SPF, GTI_FG_BS, GTI_RG_INFO GTI_C_BU, AMN_GOOD, ABX_MISS_RDNS X-CID-P-RULE: Release_Ham X-CID-O-INFO: VERSION:1.3.12,REQID:b2a463b7-03f3-4b19-85dd-2b9ef2b180ea,IP:10, URL:0,TC:0,Content:0,EDM:25,RT:0,SF:0,FILE:0,BULK:0,RULE:Release_Ham,ACTIO N:release,TS:35 X-CID-INFO: VERSION:1.3.12,REQID:b2a463b7-03f3-4b19-85dd-2b9ef2b180ea,IP:10,UR L:0,TC:0,Content:0,EDM:25,RT:0,SF:0,FILE:0,BULK:0,RULE:Release_Ham,ACTION: release,TS:35 X-CID-META: VersionHash:e7bac3a,CLOUDID:4a09e9b9540fcc9e8441bc7c26fc0e3f,BulkI D:26052216382141C37NUY,BulkQuantity:0,Recheck:0,SF:17|19|66|78|102|127|865 |898,TC:nil,Content:0|15|50,EDM:5,IP:-2,URL:0,File:nil,RT:nil,Bulk:nil,QS: nil,BEC:nil,COL:0,OSI:0,OSA:0,AV:0,LES:1,SPR:NO,DKR:0,DKP:0,BRR:0,BRE:0,AR C:0 X-CID-BVR: 2,SSN|SDN X-CID-BAS: 2,SSN|SDN,0,_ X-CID-FACTOR: TF_CID_SPAM_FSD,TF_CID_SPAM_SNR,TF_CID_SPAM_FAS X-CID-RHF: D41D8CD98F00B204E9800998ECF8427E X-UUID: 9696fd8255b911f1aa26b74ffac11d73-20260522 X-User: liwang@kylinos.cn Received: from computer.. [(116.128.244.169)] by mailgw.kylinos.cn (envelope-from ) (Generic MTA with TLSv1.3 TLS_AES_256_GCM_SHA384 256/256) with ESMTP id 164961715; Fri, 22 May 2026 16:38:20 +0800 From: Li Wang To: Miklos Szeredi Cc: Joanne Koong , Bernd Schubert , Amir Goldstein , fuse-devel@lists.linux.dev, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, Li Wang Subject: [PATCH] fuse: use READ_ONCE in fuse_chan_num_background() Date: Fri, 22 May 2026 16:38:05 +0800 Message-Id: <20260522083805.569007-1-liwang@kylinos.cn> X-Mailer: git-send-email 2.34.1 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" fuse_chan_num_background() is called without holding fch->bg_lock (for example from fuse_writepages() to compare against fc->congestion_threshold), while fch->num_background is updated under bg_lock in dev.c and dev_uring.c. This is the same locked-write/lockless-read pattern already used for max_background in fuse_chan_max_background(). Use READ_ONCE() on the read side so that: - The compiler does not cache or coalesce loads of a value that may change concurrently on another CPU. - Prevent KCSAN from reporting an unexpected race. Signed-off-by: Li Wang --- fs/fuse/dev.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c index 6254307c07e6..69fcfdfed409 100644 --- a/fs/fuse/dev.c +++ b/fs/fuse/dev.c @@ -401,7 +401,7 @@ EXPORT_SYMBOL_GPL(fuse_dev_chan_new); =20 unsigned int fuse_chan_num_background(struct fuse_chan *fch) { - return fch->num_background; + return READ_ONCE(fch->num_background); } =20 unsigned int fuse_chan_max_background(struct fuse_chan *fch) --=20 2.34.1