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From: Long Li <longli@microsoft.com>
To: "Aurélien Aptel" <aaptel@suse.com>,
	"longli@linuxonhyperv.com" <longli@linuxonhyperv.com>,
	"Steve French" <sfrench@samba.org>,
	"linux-cifs@vger.kernel.org" <linux-cifs@vger.kernel.org>,
	"samba-technical@lists.samba.org"
	<samba-technical@lists.samba.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: RE: [PATCH] cifs: Remove locking in smb2_verify_signature() when calculating SMB2/SMB3 signature on receiving packets
Date: Fri, 27 Mar 2020 05:41:21 +0000
Message-ID: <BN8PR21MB1155DCB17C62EDCE529922ABCECC0@BN8PR21MB1155.namprd21.prod.outlook.com> (raw)
In-Reply-To: <87d08zzbg6.fsf@suse.com>

>Subject: Re: [PATCH] cifs: Remove locking in smb2_verify_signature() when
>calculating SMB2/SMB3 signature on receiving packets
>
>longli@linuxonhyperv.com writes:
>> On the sending and receiving paths, CIFS uses the same cypto data
>> structures to calculate SMB2/SMB3 packet signatures. A lock on the
>> receiving path is necessary to control shared access to crypto data
>> structures. This lock degrades performance because it races with the
>sending path.
>>
>> Define separate crypto data structures for sending and receiving paths
>> and remove this lock.
>
>Something I've often wondered: why do we keep crypto state in the server
>structure instead of creating it as needed in the caller stack (thus avoiding the
>need for locks). AFAIK there's no state that need to be kept between
>signing/encrypting calls beside the access to keys. Is it that expensive to
>create/release?

My guess is that crypto_alloc_shash() is a heavy call?

>
>Cheers,
>--
>Aurélien Aptel / SUSE Labs Samba Team
>GPG: 1839 CB5F 9F5B FB9B AA97  8C99 03C8 A49B 521B D5D3 SUSE Software
>Solutions Germany GmbH, Maxfeldstr. 5, 90409 Nürnberg, DE
>GF: Felix Imendörffer, Mary Higgins, Sri Rasiah HRB 247165 (AG München)

  reply index

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-25 18:13 longli
2020-03-25 21:39 ` Pavel Shilovsky
2020-03-25 23:29   ` Long Li
2020-03-26  1:37     ` Steve French
2020-03-26  1:57       ` Long Li
2020-03-26  9:56 ` Aurélien Aptel
2020-03-27  5:41   ` Long Li [this message]
2020-03-27 11:05     ` Aurélien Aptel

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