[PATCH v2 26/30] cxlflash: Fix to prevent EEH recovery failure

[PATCH v2 26/30] cxlflash: Fix to prevent EEH recovery failure

[Matthew R. Ochs]

The process_sense() routine can perform a read capacity which
can take some time to complete. If an EEH occurs while waiting
on the read capacity, the EEH handler is unable to obtain the
context's mutex in order to put the context in an error state.
The EEH handler will sit and wait until the context is free,
but this wait can last longer than the EEH handler tolerates,
leading to a failed recovery.

To address this issue, make the context unavailable to new,
non-system owned threads and release the context while calling
into process_sense(). After returning from process_sense() the
context mutex is reacquired and the context is made available
again. The context can be safely moved to the error state if
needed during the unavailable window as no other threads will
hold its reference.

Signed-off-by: Matthew R. Ochs <mrochs@linux.vnet.ibm.com>
Signed-off-by: Manoj N. Kumar <manoj@linux.vnet.ibm.com>
---
 drivers/scsi/cxlflash/superpipe.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/scsi/cxlflash/superpipe.c b/drivers/scsi/cxlflash/superpipe.c
index fb79b79fe..1c5e9ac 100644
--- a/drivers/scsi/cxlflash/superpipe.c
+++ b/drivers/scsi/cxlflash/superpipe.c
@@ -1790,12 +1790,21 @@ static int cxlflash_disk_verify(struct scsi_device *sdev,
 	 * inquiry (i.e. the Unit attention is due to the WWN changing).
 	 */
 	if (verify->hint & DK_CXLFLASH_VERIFY_HINT_SENSE) {
+		/* Can't hold mutex across process_sense/read_cap16,
+		 * since we could have an intervening EEH event.
+		 */
+		ctxi->unavail = true;
+		mutex_unlock(&ctxi->mutex);
 		rc = process_sense(sdev, verify);
 		if (unlikely(rc)) {
 			dev_err(dev, "%s: Failed to validate sense data (%d)\n",
 				__func__, rc);
+			mutex_lock(&ctxi->mutex);
+			ctxi->unavail = false;
 			goto out;
 		}
+		mutex_lock(&ctxi->mutex);
+		ctxi->unavail = false;
 	}
 
 	switch (gli->mode) {
-- 
2.1.0

[PATCH v2 00/30] cxlflash: Miscellaneous bug fixes and corrections

[Matthew R. Ochs]

This patch set contains various fixes and corrections for issues that
were found during test and code review. The series is based upon the
code upstreamed in 4.3 and is intended for the rc phase. The entire
set is bisectable. Please reference the changelog below for details
on what has been altered from previous versions of this patch set.

v2 Changes:
- Incorporate comments from Ian Munsie
- Rework commit messages to be more descriptive
- Add state change serialization patch

Manoj Kumar (3):
  cxlflash: Fix to avoid invalid port_sel value
  cxlflash: Replace magic numbers with literals
  cxlflash: Fix read capacity timeout

Matthew R. Ochs (27):
  cxlflash: Fix potential oops following LUN removal
  cxlflash: Fix data corruption when vLUN used over multiple cards
  cxlflash: Fix to avoid sizeof(bool)
  cxlflash: Fix context encode mask width
  cxlflash: Fix to avoid CXL services during EEH
  cxlflash: Check for removal when processing interrupt
  cxlflash: Correct naming of limbo state and waitq
  cxlflash: Make functions static
  cxlflash: Refine host/device attributes
  cxlflash: Fix to avoid spamming the kernel log
  cxlflash: Fix to avoid stall while waiting on TMF
  cxlflash: Fix location of setting resid
  cxlflash: Fix host link up event handling
  cxlflash: Fix async interrupt bypass logic
  cxlflash: Remove dual port online dependency
  cxlflash: Fix AFU version access/storage and add check
  cxlflash: Correct usage of scsi_host_put()
  cxlflash: Fix to prevent workq from accessing freed memory
  cxlflash: Correct behavior in device reset handler following EEH
  cxlflash: Remove unnecessary scsi_block_requests
  cxlflash: Fix function prolog parameters and return codes
  cxlflash: Fix MMIO and endianness errors
  cxlflash: Fix to prevent EEH recovery failure
  cxlflash: Correct spelling, grammar, and alignment mistakes
  cxlflash: Fix to prevent stale AFU RRQ
  cxlflash: Fix to avoid state change collision
  MAINTAINERS: Add cxlflash driver

 MAINTAINERS                       |    9 +
 drivers/scsi/cxlflash/common.h    |   29 +-
 drivers/scsi/cxlflash/lunmgt.c    |    9 +-
 drivers/scsi/cxlflash/main.c      | 1575 ++++++++++++++++++++-----------------
 drivers/scsi/cxlflash/main.h      |    1 +
 drivers/scsi/cxlflash/sislite.h   |    8 +-
 drivers/scsi/cxlflash/superpipe.c |  177 +++--
 drivers/scsi/cxlflash/superpipe.h |   11 +-
 drivers/scsi/cxlflash/vlun.c      |   39 +-
 9 files changed, 1036 insertions(+), 822 deletions(-)

-- 
2.1.0

[PATCH v2 26/30] cxlflash: Fix to prevent EEH recovery failure

[Matthew R. Ochs]

The process_sense() routine can perform a read capacity which
can take some time to complete. If an EEH occurs while waiting
on the read capacity, the EEH handler is unable to obtain the
context's mutex in order to put the context in an error state.
The EEH handler will sit and wait until the context is free,
but this wait can last longer than the EEH handler tolerates,
leading to a failed recovery.

To address this issue, make the context unavailable to new,
non-system owned threads and release the context while calling
into process_sense(). After returning from process_sense() the
context mutex is reacquired and the context is made available
again. The context can be safely moved to the error state if
needed during the unavailable window as no other threads will
hold its reference.

Signed-off-by: Matthew R. Ochs <mrochs@linux.vnet.ibm.com>
Signed-off-by: Manoj N. Kumar <manoj@linux.vnet.ibm.com>
---
 drivers/scsi/cxlflash/superpipe.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/scsi/cxlflash/superpipe.c b/drivers/scsi/cxlflash/superpipe.c
index fb79b79fe..1c5e9ac 100644
--- a/drivers/scsi/cxlflash/superpipe.c
+++ b/drivers/scsi/cxlflash/superpipe.c
@@ -1790,12 +1790,21 @@ static int cxlflash_disk_verify(struct scsi_device *sdev,
 	 * inquiry (i.e. the Unit attention is due to the WWN changing).
 	 */
 	if (verify->hint & DK_CXLFLASH_VERIFY_HINT_SENSE) {
+		/* Can't hold mutex across process_sense/read_cap16,
+		 * since we could have an intervening EEH event.
+		 */
+		ctxi->unavail = true;
+		mutex_unlock(&ctxi->mutex);
 		rc = process_sense(sdev, verify);
 		if (unlikely(rc)) {
 			dev_err(dev, "%s: Failed to validate sense data (%d)\n",
 				__func__, rc);
+			mutex_lock(&ctxi->mutex);
+			ctxi->unavail = false;
 			goto out;
 		}
+		mutex_lock(&ctxi->mutex);
+		ctxi->unavail = false;
 	}
 
 	switch (gli->mode) {
-- 
2.1.0

Re: [PATCH v2 26/30] cxlflash: Fix to prevent EEH recovery failure

[Brian King]

Reviewed-by: Brian King <brking@linux.vnet.ibm.com>

-- 
Brian King
Power Linux I/O
IBM Linux Technology Center