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 0EA5545978; Tue, 16 Jan 2024 00:26:33 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="bhANO5dZ" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0FE90C433F1; Tue, 16 Jan 2024 00:26:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1705364792; bh=vcfSvqwRZ9L/gCXdaQi9Dk9JTiUb7mqTRVd8HYmtt5E=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=bhANO5dZ9benbWk+slZkeGwkOwDSq5GAnvWOeziQV6RnhzdCDsZGgsMf+x9I0aBja AGOenSIxH5+fk6vhmv9yiBlx6xQYtD2Tc70KH5ArmtBCZldebCxjm47CGveTya6T8p /bl4XAJa1oPiAEwd96DL47J4yDyYZcTSr0KPQZ5l5WEIa8WeOsGg0cR7gr5G7ThiNx nsXPqeR1yGvX0hJFiiIrKubgAyzwONj7HKNiSrcihC1rMUIJlxnuBET1W3gQpU3KjP wxv1yfSmqrnhRF4n1LKeqza/DJo9ppFi6ozcK9JSJewH/awIZpj5mGtjdTSVraiRi3 yJDxyNxx1ee1Q== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Oleg Nesterov , David Howells , Marc Dionne , linux-afs@lists.infradead.org, Sasha Levin Subject: [PATCH AUTOSEL 5.15 11/13] afs: fix the usage of read_seqbegin_or_lock() in afs_find_server*() Date: Mon, 15 Jan 2024 19:25:47 -0500 Message-ID: <20240116002603.215942-11-sashal@kernel.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20240116002603.215942-1-sashal@kernel.org> References: <20240116002603.215942-1-sashal@kernel.org> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore X-stable-base: Linux 5.15.147 Content-Transfer-Encoding: 8bit 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 ffed828622b6..34b47218129e 100644 --- a/fs/afs/server.c +++ b/fs/afs/server.c @@ -27,7 +27,7 @@ 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(); @@ -35,6 +35,7 @@ struct afs_server *afs_find_server(struct afs_net *net, if (server) afs_unuse_server_notime(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) { @@ -90,7 +91,7 @@ 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); @@ -102,7 +103,7 @@ struct afs_server *afs_find_server_by_uuid(struct afs_net *net, const uuid_t *uu if (server) afs_unuse_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