cxlflash: Fix to avoid CXL services during EEH

During an EEH freeze event, certain CXL services should not be
called until after the hardware reset has taken place. Doing so
can result in unnecessary failures and possibly cause other ill
effects by triggering hardware accesses. This translates to a
requirement to quiesce all threads that may potentially use CXL
runtime service during this window. In particular, multiple ioctls
make use of the CXL services when acting on contexts on behalf of
the user. Thus, it is essential to 'drain' running ioctls _before_
proceeding with handling the EEH freeze event.

Create the ability to drain ioctls by wrapping the ioctl handler
call in a read semaphore and then implementing a small routine that
obtains the write semaphore, effectively creating a wait point for
all currently executing ioctls.

Signed-off-by: Matthew R. Ochs <mrochs@linux.vnet.ibm.com>
Signed-off-by: Manoj N. Kumar <manoj@linux.vnet.ibm.com>
Reviewed-by: Brian King <brking@linux.vnet.ibm.com>
Reviewed-by: Daniel Axtens <dja@axtens.net>
Reviewed-by: Tomas Henzl <thenzl@redhat.com>
Signed-off-by: James Bottomley <JBottomley@Odin.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/drivers/scsi/cxlflash/common.h b/drivers/scsi/cxlflash/common.h
index 1c56037146e1..1abe4e0e7a49 100644
--- a/drivers/scsi/cxlflash/common.h
+++ b/drivers/scsi/cxlflash/common.h
@@ -16,6 +16,7 @@
 #define _CXLFLASH_COMMON_H
 
 #include <linux/list.h>
+#include <linux/rwsem.h>
 #include <linux/types.h>
 #include <scsi/scsi.h>
 #include <scsi/scsi_device.h>
@@ -110,6 +111,7 @@ struct cxlflash_cfg {
 	atomic_t recovery_threads;
 	struct mutex ctx_recovery_mutex;
 	struct mutex ctx_tbl_list_mutex;
+	struct rw_semaphore ioctl_rwsem;
 	struct ctx_info *ctx_tbl[MAX_CONTEXT];
 	struct list_head ctx_err_recovery; /* contexts w/ recovery pending */
 	struct file_operations cxl_fops;