From patchwork Tue Jun 2 11:33:11 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Hannes Reinecke X-Patchwork-Id: 11583631 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 5BFBF159A for ; Tue, 2 Jun 2020 11:34:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 42B422074B for ; Tue, 2 Jun 2020 11:34:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726429AbgFBLeV (ORCPT ); Tue, 2 Jun 2020 07:34:21 -0400 Received: from mx2.suse.de ([195.135.220.15]:37940 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726320AbgFBLeV (ORCPT ); Tue, 2 Jun 2020 07:34:21 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id B1D3EAE17; Tue, 2 Jun 2020 11:34:20 +0000 (UTC) From: Hannes Reinecke To: "Martin K. Petersen" Cc: Christoph Hellwig , Doug Gilbert , Daniel Wagner , James Bottomley , linux-scsi@vger.kernel.org, Hannes Reinecke Subject: [PATCH 6/6] scsi: avoid pointless memory allocation in scsi_alloc_target() Date: Tue, 2 Jun 2020 13:33:11 +0200 Message-Id: <20200602113311.121513-7-hare@suse.de> X-Mailer: git-send-email 2.16.4 In-Reply-To: <20200602113311.121513-1-hare@suse.de> References: <20200602113311.121513-1-hare@suse.de> Sender: linux-scsi-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-scsi@vger.kernel.org As we already know the index of the requested target in scsi_alloc_target() we can try to fetch it first before trying to allocate a new one. This will save us a pointless memory allocation in case the target is already present and uncontended. Signed-off-by: Hannes Reinecke --- drivers/scsi/scsi_scan.c | 21 ++++++++++++++++++--- 1 file changed, 18 insertions(+), 3 deletions(-) diff --git a/drivers/scsi/scsi_scan.c b/drivers/scsi/scsi_scan.c index 8afb71c036d5..41818111808e 100644 --- a/drivers/scsi/scsi_scan.c +++ b/drivers/scsi/scsi_scan.c @@ -387,7 +387,7 @@ static void scsi_target_reap_ref_put(struct scsi_target *starget) * is responsible for both reaping and doing a last put */ static struct scsi_target *scsi_alloc_target(struct device *parent, - int channel, uint id) + u16 channel, u16 id) { struct Scsi_Host *shost = dev_to_shost(parent); struct device *dev = NULL; @@ -397,7 +397,23 @@ static struct scsi_target *scsi_alloc_target(struct device *parent, struct scsi_target *starget; struct scsi_target *found_target; int error, ref_got; - unsigned long tid; + unsigned long tid = (channel << 16) | id; + + /* + * Try if the target is already present, and save us + * a pointless memory allocation if so. + */ + spin_lock_irqsave(shost->host_lock, flags); + found_target = xa_load(&shost->__targets, tid); + if (found_target) { + get_device(&found_target->dev); + if (kref_get_unless_zero(&found_target->reap_ref)) { + spin_unlock_irqrestore(shost->host_lock, flags); + return found_target; + } + put_device(&found_target->dev); + } + spin_unlock_irqrestore(shost->host_lock, flags); starget = kzalloc(size, GFP_KERNEL); if (!starget) { @@ -418,7 +434,6 @@ static struct scsi_target *scsi_alloc_target(struct device *parent, starget->state = STARGET_CREATED; starget->scsi_level = SCSI_2; starget->max_target_blocked = SCSI_DEFAULT_TARGET_BLOCKED; - tid = scsi_target_index(starget); retry: spin_lock_irqsave(shost->host_lock, flags); found_target = xa_load(&shost->__targets, tid);