Commit dcba277d119a for kernel

commit dcba277d119af323c267d1f27f61b868dac62753
Author: Stefan Haberland <sth@linux.ibm.com>
Date:   Mon Jul 27 16:28:38 2026 +0200

    s390/dasd: Fix path verification interrupted by concurrent dasd_sleep_on_immediatly

    When all channel paths to a DASD device are lost and subsequently
    recovered, the path event handler starts one IO per path via
    dasd_sleep_on_immediatly() to execute read configuration data (RCD) with
    high priority.

    dasd_sleep_on_immediatly() works by terminating the currently running
    request before inserting the new request.
    If a concurrent caller, such as the attention handler
    dasd_eckd_check_attention_work() or the summary unit
    check handler summary_unit_check_handling_work(), also calls
    dasd_sleep_on_immediatly() while a path verification RCD is in progress,
    the RCD gets terminated.

    The problem is that a terminated request transitions from CLEARED to
    TERMINATED without going through the normal retry path in
    __dasd_device_process_ccw_queue.

    The RCD therefore returns -EIO, and the affected paths remain
    non-operational after recovery. RCD CQRs used for path verification
    already carry the DASD_CQR_VERIFY_PATH flag.

    Extend _dasd_term_running_cqr() to check this flag: instead of terminating
    such a request, return -EAGAIN. In dasd_sleep_on_immediatly(), loop on
    -EAGAIN with a short sleep, waiting for the path verification request to
    complete before inserting the new request.

    This is consistent with the already indefinite wait_event() that
    dasd_sleep_on_immediatly() uses for its own request, and all other callers
    (attention handler, summary unit check handler, reserve/release/steal-lock)
    benefit automatically without requiring changes.

    Reviewed-by: Jan Höppner <hoeppner@linux.ibm.com>
    Signed-off-by: Stefan Haberland <sth@linux.ibm.com>
    Link: https://patch.msgid.link/20260727142840.567286-2-sth@linux.ibm.com
    Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/drivers/s390/block/dasd.c b/drivers/s390/block/dasd.c
index 3181c06d91ce..d8d912a3b3fe 100644
--- a/drivers/s390/block/dasd.c
+++ b/drivers/s390/block/dasd.c
@@ -21,6 +21,7 @@
 #include <linux/debugfs.h>
 #include <linux/seq_file.h>
 #include <linux/vmalloc.h>
+#include <linux/delay.h>

 #include <asm/machine.h>
 #include <asm/ccwdev.h>
@@ -2511,6 +2512,13 @@ static inline int _dasd_term_running_cqr(struct dasd_device *device)
 	if (list_empty(&device->ccw_queue))
 		return 0;
 	cqr = list_entry(device->ccw_queue.next, struct dasd_ccw_req, devlist);
+	/*
+	 * Path verification requests must not be terminated. They are critical
+	 * for bringing paths back online. Terminating them would cause rc=-EIO
+	 * because CLEARED requests skip the retry path.
+	 */
+	if (test_bit(DASD_CQR_VERIFY_PATH, &cqr->flags))
+		return -EAGAIN;
 	rc = device->discipline->term_IO(cqr);
 	if (!rc)
 		/*
@@ -2535,7 +2543,11 @@ int dasd_sleep_on_immediatly(struct dasd_ccw_req *cqr)
 		return -EIO;
 	}
 	spin_lock_irq(get_ccwdev_lock(device->cdev));
-	rc = _dasd_term_running_cqr(device);
+	while ((rc = _dasd_term_running_cqr(device)) == -EAGAIN) {
+		spin_unlock_irq(get_ccwdev_lock(device->cdev));
+		msleep(1);
+		spin_lock_irq(get_ccwdev_lock(device->cdev));
+	}
 	if (rc) {
 		spin_unlock_irq(get_ccwdev_lock(device->cdev));
 		return rc;