From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 F139969D38; Wed, 21 Feb 2024 14:19:24 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1708525165; cv=none; b=FDQGcvRkvNWd/9yk+KlzPsnNG4By2x20ZbREWy6qGK2ZVMC4M/XsNMnZqaPdV34mSBUGe6pF6jY013voyw1Fhm3eAn1TloLA+Rtp6uKm/PHHmSzo7A1Kw44TfnxrM9F7ts/1Bp1rPlk8LH4i7z+PS8ddtmpB0J2UbRIKC1YAZXQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1708525165; c=relaxed/simple; bh=nK5aBoDjaRimcmPkFAFEl3Jm0sCzA7YOTMSEQEjU478=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=G+RPyCKhNL5vgf4NnN8423uTq6GB5VFXkhDASXAo4ZyEs+O/pDwngDOKMCBTVgk8F2vG+HAU4mRX/5isqfLnubuSEAdhN+hX1caxChjiT1az/PEd3wXUgXVX7MOKexUE5IXIB37YRiPim+tmfd41P+OMR2LDQqhjgKEqtm+Jdac= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=JA/uGFjr; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="JA/uGFjr" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 60E05C433F1; Wed, 21 Feb 2024 14:19:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1708525164; bh=nK5aBoDjaRimcmPkFAFEl3Jm0sCzA7YOTMSEQEjU478=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=JA/uGFjrU1tAe8n4swSoaP2jDDLScjwh49/k2wm05wdoE71xYTcG3gkms/pNW1S66 ofwPTNd0zURO0hGYneoSh7KflCj9tM/jQigDpDKmTN3CcIllXdVHti3tmvXzFGBt+x Wa5NXStkjh8ReDSg+OEWF/D1bXBWJknUCRs9p1Bw= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Oleg Nesterov , David Howells , Marc Dionne , linux-afs@lists.infradead.org, Sasha Levin Subject: [PATCH 5.4 080/267] afs: fix the usage of read_seqbegin_or_lock() in afs_find_server*() Date: Wed, 21 Feb 2024 14:07:01 +0100 Message-ID: <20240221125942.486259475@linuxfoundation.org> X-Mailer: git-send-email 2.43.2 In-Reply-To: <20240221125940.058369148@linuxfoundation.org> References: <20240221125940.058369148@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 5.4-stable review patch. If anyone has any objections, please let me know. ------------------ From: Oleg Nesterov [ Upstream commit 1702e0654ca9a7bcd7c7619c8a5004db58945b71 ] David Howells says: (5) afs_find_server(). There could be a lot of servers in the list and each server can have multiple addresses, so I think this would be better with an exclusive second pass. The server list isn't likely to change all that often, but when it does change, there's a good chance several servers are going to be added/removed one after the other. Further, this is only going to be used for incoming cache management/callback requests from the server, which hopefully aren't going to happen too often - but it is remotely drivable. (6) afs_find_server_by_uuid(). Similarly to (5), there could be a lot of servers to search through, but they are in a tree not a flat list, so it should be faster to process. Again, it's not likely to change that often and, again, when it does change it's likely to involve multiple changes. This can be driven remotely by an incoming cache management request but is mostly going to be driven by setting up or reconfiguring a volume's server list - something that also isn't likely to happen often. Make the "seq" counter odd on the 2nd pass, otherwise read_seqbegin_or_lock() never takes the lock. Signed-off-by: Oleg Nesterov Signed-off-by: David Howells cc: Marc Dionne cc: linux-afs@lists.infradead.org Link: https://lore.kernel.org/r/20231130115614.GA21581@redhat.com/ Signed-off-by: Sasha Levin --- fs/afs/server.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/fs/afs/server.c b/fs/afs/server.c index d3a9288f7556..44985ca6602e 100644 --- a/fs/afs/server.c +++ b/fs/afs/server.c @@ -35,7 +35,7 @@ struct afs_server *afs_find_server(struct afs_net *net, const struct afs_addr_list *alist; struct afs_server *server = NULL; unsigned int i; - int seq = 0, diff; + int seq = 1, diff; rcu_read_lock(); @@ -43,6 +43,7 @@ struct afs_server *afs_find_server(struct afs_net *net, if (server) afs_put_server(net, server, afs_server_trace_put_find_rsq); server = NULL; + seq++; /* 2 on the 1st/lockless path, otherwise odd */ read_seqbegin_or_lock(&net->fs_addr_lock, &seq); if (srx->transport.family == AF_INET6) { @@ -98,7 +99,7 @@ struct afs_server *afs_find_server_by_uuid(struct afs_net *net, const uuid_t *uu { struct afs_server *server = NULL; struct rb_node *p; - int diff, seq = 0; + int diff, seq = 1; _enter("%pU", uuid); @@ -110,7 +111,7 @@ struct afs_server *afs_find_server_by_uuid(struct afs_net *net, const uuid_t *uu if (server) afs_put_server(net, server, afs_server_trace_put_uuid_rsq); server = NULL; - + seq++; /* 2 on the 1st/lockless path, otherwise odd */ read_seqbegin_or_lock(&net->fs_lock, &seq); p = net->fs_servers.rb_node; -- 2.43.0