linux-kernel - [PATCH v1 1/4] ata: libata: Remove redundant sense

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Date: Fri, 14 Jun 2024 19:18:32 +0000
From: Igor Pylypiv <ipylypiv@...gle.com>
To: Damien Le Moal <dlemoal@...nel.org>, Niklas Cassel <cassel@...nel.org>
Cc: Tejun Heo <tj@...nel.org>, Hannes Reinecke <hare@...e.de>, linux-ide@...r.kernel.org, 
	linux-kernel@...r.kernel.org, Igor Pylypiv <ipylypiv@...gle.com>
Subject: [PATCH v1 1/4] ata: libata: Remove redundant sense_buffer memsets

scsi_queue_rq() memsets sense_buffer before a command is dispatched.

Libata is not memsetting sense_buffer before setting sense data that
was obtained from a disk so there should be no reason to do a memset
for ATA PASS-THROUGH / ATAPI.

Memsetting the sense_buffer in ata_gen_passthru_sense() is erasing valid
sense data that was previously obtained from a disk. A follow-up patch
will modify ata_gen_passthru_sense() to stop generating sense data based
on ATA status register bits if a valid sense data is already present.

Signed-off-by: Igor Pylypiv <ipylypiv@...gle.com>
---
 drivers/ata/libata-eh.c   | 2 --
 drivers/ata/libata-scsi.c | 4 ----
 2 files changed, 6 deletions(-)

diff --git a/drivers/ata/libata-eh.c b/drivers/ata/libata-eh.c
index 214b935c2ced..b5e05efe73f6 100644
--- a/drivers/ata/libata-eh.c
+++ b/drivers/ata/libata-eh.c
@@ -1479,8 +1479,6 @@ unsigned int atapi_eh_request_sense(struct ata_device *dev,
 	struct ata_port *ap = dev->link->ap;
 	struct ata_taskfile tf;
 
-	memset(sense_buf, 0, SCSI_SENSE_BUFFERSIZE);
-
 	/* initialize sense_buf with the error register,
 	 * for the case where they are -not- overwritten
 	 */
diff --git a/drivers/ata/libata-scsi.c b/drivers/ata/libata-scsi.c
index cdf29b178ddc..032cf11d0bcc 100644
--- a/drivers/ata/libata-scsi.c
+++ b/drivers/ata/libata-scsi.c
@@ -858,8 +858,6 @@ static void ata_gen_passthru_sense(struct ata_queued_cmd *qc)
 	unsigned char *desc = sb + 8;
 	u8 sense_key, asc, ascq;
 
-	memset(sb, 0, SCSI_SENSE_BUFFERSIZE);
-
 	/*
 	 * Use ata_to_sense_error() to map status register bits
 	 * onto sense key, asc & ascq.
@@ -953,8 +951,6 @@ static void ata_gen_ata_sense(struct ata_queued_cmd *qc)
 	u64 block;
 	u8 sense_key, asc, ascq;
 
-	memset(sb, 0, SCSI_SENSE_BUFFERSIZE);
-
 	if (ata_dev_disabled(dev)) {
 		/* Device disabled after error recovery */
 		/* LOGICAL UNIT NOT READY, HARD RESET REQUIRED */
-- 
2.45.2.627.g7a2c4fd464-goog