From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from 003.mia.mailroute.net (003.mia.mailroute.net [199.89.3.6]) (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 3587F2EBBA8 for ; Thu, 30 Oct 2025 19:37:43 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=199.89.3.6 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761853065; cv=none; b=R0JlG0BAr3H82xj0fospd0Xg0bv9NmybzrwsLLU+zVEHDevvRKtVpuMOrGAPcEifpOsIAHyBuIUr3NiLFk5cnnMzhsHb3PNTK54S+OA9u1rf8I7u5Rq1RQ1MTS9x7/SZvfyTMTrXX9IBnF2FkJ5RFOhu9V75Epx7HwNzLzNcvyo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761853065; c=relaxed/simple; bh=XW9yJoCWbcWa/h0L1URy7TuJj9bKlbmA3WTm8OvanDg=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=roh2p/PzsRPorIGPBDzNGX6GAzrje+zaKX0hL0465aY7YOtRbjIwCGa4wPWcrUisd69OKKQjN4U9p2/H06JUByYAWO224ubthPBiYoxle43/FDCRQky9yvr//uv/G6A95yFLJN1s4n6Tq8cbFgviVIxuKGaHePbYRsBsF3w3YGo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=acm.org; spf=pass smtp.mailfrom=acm.org; dkim=pass (2048-bit key) header.d=acm.org header.i=@acm.org header.b=DbdHtkuv; arc=none smtp.client-ip=199.89.3.6 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=acm.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=acm.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=acm.org header.i=@acm.org header.b="DbdHtkuv" Received: from localhost (localhost [127.0.0.1]) by 003.mia.mailroute.net (Postfix) with ESMTP id 4cyDsf2YfszlsxDK; Thu, 30 Oct 2025 19:37:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=acm.org; h= content-transfer-encoding:mime-version:references:in-reply-to :x-mailer:message-id:date:date:subject:subject:from:from :received:received; s=mr01; t=1761853060; x=1764445061; bh=V3STg pz8dXXKgsE/3OTbi1egPdkZS6LtQRl/zBuJfcI=; b=DbdHtkuvjGjS4sW+cHqp4 Vcj7xjnnaai9B79j7Mdl9JvBv+cJ9ZzeJkKdoEPGJWqVD0Og70OvaIXjC7megc+W RHbH5wlCQ8Uo53EwH0xCGKHUWfcpvGVLKH/Tf0x1KEYUWr5Rj/joIQcMQ9Bny8Kk NwXNVigeoHHooJx3cktzoYNRqDqiiozwUG3ftzeQEd43QhR3vOCx1eBDbXXYngY7 RUKVKLIgeJYYAf1ArCC0D+geKpWkNt3CgC/vFI5G93scXudI32xfmSKo7JEVD8h8 wcRi10vku792gehXqOe9FMw9NSqlcn4VvT1v7mlaGdQI5uwMsQSA4kO5w/X/9qWQ g== X-Virus-Scanned: by MailRoute Received: from 003.mia.mailroute.net ([127.0.0.1]) by localhost (003.mia [127.0.0.1]) (mroute_mailscanner, port 10029) with LMTP id H-21z3F28Hri; Thu, 30 Oct 2025 19:37:40 +0000 (UTC) Received: from bvanassche.mtv.corp.google.com (unknown [104.135.180.219]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) (Authenticated sender: bvanassche@acm.org) by 003.mia.mailroute.net (Postfix) with ESMTPSA id 4cyDsY01B3zlscjR; Thu, 30 Oct 2025 19:37:36 +0000 (UTC) From: Bart Van Assche To: "Martin K . Petersen" Cc: linux-scsi@vger.kernel.org, Bart Van Assche , Hannes Reinecke , John Garry , "James E.J. Bottomley" Subject: [PATCH v7 01/28] scsi: core: Support allocating reserved commands Date: Thu, 30 Oct 2025 12:36:00 -0700 Message-ID: <20251030193720.871635-2-bvanassche@acm.org> X-Mailer: git-send-email 2.51.1.930.gacf6e81ea2-goog In-Reply-To: <20251030193720.871635-1-bvanassche@acm.org> References: <20251030193720.871635-1-bvanassche@acm.org> Precedence: bulk X-Mailing-List: linux-scsi@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable From: Hannes Reinecke Quite some drivers are using management commands internally. These commands typically use the same tag pool as regular SCSI commands. Tags for these management commands are set aside before allocating the block-mq tag bitmap for regular SCSI commands. The block layer already supports this via the reserved tag mechanism. Add a new field 'nr_reserved_cmds' to the SCSI host template to instruct the block layer to set aside a tag space for these management commands by using reserved tags. Exclude reserved commands from .can_queue because .can_queue is visible in sysfs. Signed-off-by: Hannes Reinecke [ bvanassche: modified patch title and patch description. Left out the following statements: "if (sht->nr_reserved_cmds)" and also "if (sdev->host->nr_reserved_cmds) flags |=3D BLK_MQ_REQ_RESERVED;". Mo= ved nr_reserved_cmds declarations and statements close to the corresponding can_queue declarations and statements. See also https://lore.kernel.org/linux-scsi/20210503150333.130310-11-hare@suse.d= e/ ] Reviewed-by: John Garry Signed-off-by: Bart Van Assche --- drivers/scsi/hosts.c | 1 + drivers/scsi/scsi_lib.c | 3 ++- include/scsi/scsi_host.h | 21 ++++++++++++++++++++- 3 files changed, 23 insertions(+), 2 deletions(-) diff --git a/drivers/scsi/hosts.c b/drivers/scsi/hosts.c index eb224a338fa2..8b7f5fafa9e0 100644 --- a/drivers/scsi/hosts.c +++ b/drivers/scsi/hosts.c @@ -436,6 +436,7 @@ struct Scsi_Host *scsi_host_alloc(const struct scsi_h= ost_template *sht, int priv shost->hostt =3D sht; shost->this_id =3D sht->this_id; shost->can_queue =3D sht->can_queue; + shost->nr_reserved_cmds =3D sht->nr_reserved_cmds; shost->sg_tablesize =3D sht->sg_tablesize; shost->sg_prot_tablesize =3D sht->sg_prot_tablesize; shost->cmd_per_lun =3D sht->cmd_per_lun; diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c index d7e42293b864..d52bbbe5a357 100644 --- a/drivers/scsi/scsi_lib.c +++ b/drivers/scsi/scsi_lib.c @@ -2083,7 +2083,8 @@ int scsi_mq_setup_tags(struct Scsi_Host *shost) tag_set->ops =3D &scsi_mq_ops_no_commit; tag_set->nr_hw_queues =3D shost->nr_hw_queues ? : 1; tag_set->nr_maps =3D shost->nr_maps ? : 1; - tag_set->queue_depth =3D shost->can_queue; + tag_set->queue_depth =3D shost->can_queue + shost->nr_reserved_cmds; + tag_set->reserved_tags =3D shost->nr_reserved_cmds; tag_set->cmd_size =3D cmd_size; tag_set->numa_node =3D dev_to_node(shost->dma_dev); if (shost->hostt->tag_alloc_policy_rr) diff --git a/include/scsi/scsi_host.h b/include/scsi/scsi_host.h index f5a243261236..7b8f144ccf7d 100644 --- a/include/scsi/scsi_host.h +++ b/include/scsi/scsi_host.h @@ -375,10 +375,19 @@ struct scsi_host_template { /* * This determines if we will use a non-interrupt driven * or an interrupt driven scheme. It is set to the maximum number - * of simultaneous commands a single hw queue in HBA will accept. + * of simultaneous commands a single hw queue in HBA will accept + * excluding internal commands. */ int can_queue; =20 + /* + * This determines how many commands the HBA will set aside + * for internal commands. This number will be added to + * @can_queue to calculate the maximum number of simultaneous + * commands sent to the host. + */ + int nr_reserved_cmds; + /* * In many instances, especially where disconnect / reconnect are * supported, our host also has an ID on the SCSI bus. If this is @@ -611,7 +620,17 @@ struct Scsi_Host { unsigned short max_cmd_len; =20 int this_id; + + /* + * Number of commands this host can handle at the same time. + * This excludes reserved commands as specified by nr_reserved_cmds. + */ int can_queue; + /* + * Number of reserved commands to allocate, if any. + */ + unsigned int nr_reserved_cmds; + short cmd_per_lun; short unsigned int sg_tablesize; short unsigned int sg_prot_tablesize;