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Petersen (Oracle)" , Sasha Levin Subject: [PATCH 6.12 043/247] scsi: st: Save the visited block for the partition the drive is in Date: Wed, 28 Oct 2026 17:57:26 +0100 Message-ID: <20261028165948.390482513@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261028165947.349197979@linuxfoundation.org> References: <20261028165947.349197979@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore X-Mailing-List: patches@lists.linux.dev List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: Laurence Oberman [ Upstream commit c9e9f024dd4f61f0f6636c9f2ed0830f87060e11 ] set_location() saves the current tape location before switching partitions, so that switch_partition() can return to it later. It reads the location with READ POSITION but stores it in the st_partstat of STp->partition, ignoring the partition the drive reports. The two differ after a device reset. When the reset is recovered with MTREW, MTSEEK or MTEOM, st_ioctl() sets STp->partition = 0 and calls switch_partition() to return to STp->new_partition. A drive that was in partition 1 is still there, so set_location() files the partition 1 position under partition 0. The next switch to partition 0 locates to that block: if partition 0 holds less data, MTSETPART fails with EIO (BLANK CHECK), otherwise the tape is silently positioned at the wrong block. IBM ULTRIUM-TD5 (LTO-5), LU reset in partition 1 at block 1025: st 12:0:0:0: [st0] Visited block 1025 for partition 0 saved. ... st 12:0:0:0: [st0] Setting block to 1025 and partition to 0. st 12:0:0:0: [st0] Error: 402, cmd: 2b 2 0 0 0 4 st 12:0:0:0: [st0] Sense Key : Blank Check [current] st 12:0:0:0: [st0] Add. Sense: End-of-data detected Store the location in the st_partstat of the partition reported by READ POSITION. With the fix: st 12:0:0:0: [st0] Visited block 1025 for partition 1 saved. This is a pre-existing issue. It was not caught when testing the recent st reset series because the partition test was only run on scsi_debug: on the LTO drive it was skipped, since can-partitions is off in the test harness's stinit.conf, as is normal for LTO. scsi_debug hides the problem because its emulated tape returns to the beginning of partition 0 on an LU reset. It was found while validating a backport of that series to RHEL 9.8, when the partition tests were run on real hardware with can-partitions enabled. The same failure then reproduced on unmodified RHEL 9.8 and on upstream, and the fix makes the test pass on v7.3-rc3 and RHEL 9.8 with an LTO-5. The harness (https://gitlab.com/loberman/tapetest, test X03) now refuses to silently skip the partition tests on hardware. Fixes: 7081dc75df79 ("scsi: st: Restore some drive settings after reset") Assisted-by: Claude Signed-off-by: Laurence Oberman Link: https://patch.msgid.link/20261006164250.773840-1-loberman@redhat.com Signed-off-by: Martin K. Petersen (Oracle) Signed-off-by: Sasha Levin --- drivers/scsi/st.c | 14 ++++++++++---- 1 file changed, 10 insertions(+), 4 deletions(-) diff --git a/drivers/scsi/st.c b/drivers/scsi/st.c index 3e982c166baf9..95da0d15e0490 100644 --- a/drivers/scsi/st.c +++ b/drivers/scsi/st.c @@ -3194,14 +3194,20 @@ static int set_location(struct scsi_tape *STp, unsigned int block, int partition partition >= ST_NBR_PARTITIONS) return (-EINVAL); if (partition != STp->partition) { - if (get_location(STp, &blk, &p, 1)) + /* + * Save the location for the partition the drive reports, + * not for STp->partition: after a reset STp->partition may + * not match the partition the drive is in. + */ + if (get_location(STp, &blk, &p, 1) || + p < 0 || p >= ST_NBR_PARTITIONS) STps->last_block_valid = 0; else { - STps->last_block_valid = 1; - STps->last_block_visited = blk; + STp->ps[p].last_block_valid = 1; + STp->ps[p].last_block_visited = blk; DEBC_printk(STp, "Visited block %d for " "partition %d saved.\n", - blk, STp->partition); + blk, p); } } -- 2.53.0