scsi: zfcp: move maximum age of diagnostic buffers into a per-adapter variable

Replace the static define (ZFCP_DIAG_MAX_AGE) with a per-adapter variable
(${adapter}->diagnostics->max_age). This new variable is exported via
sysfs, along with other, already existing adapter variables, and can both
be read and written. This way users can choose how much time should pass
between refreshes of diagnostic buffers. The default value for the age
remains to be five seconds.

By setting this new variable to 0, the caching of diagnostic buffers for
userspace accesses can also be completely removed.

All diagnostic buffers of a given adapter are subject to this setting in
the same way.

Link: https://lore.kernel.org/r/b1d0977cc884b16dd4ca6418e4320c56a4c31d63.1572018132.git.bblock@linux.ibm.com
Reviewed-by: Steffen Maier <maier@linux.ibm.com>
Signed-off-by: Benjamin Block <bblock@linux.ibm.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

1 files changed, 12 insertions, 11 deletions

diff --git a/drivers/s390/scsi/zfcp_diag.c b/drivers/s390/scsi/zfcp_diag.c
index 5ef7b3288c6f..67a8f4e57db1 100644
--- a/drivers/s390/scsi/zfcp_diag.c
+++ b/drivers/s390/scsi/zfcp_diag.c
@@ -19,9 +19,6 @@
 #include "zfcp_ext.h"
 #include "zfcp_def.h"
 
-/* Max age of data in a diagnostics buffer before it needs a refresh (in ms). */
-#define ZFCP_DIAG_MAX_AGE (5 * 1000)
-
 static DECLARE_WAIT_QUEUE_HEAD(__zfcp_diag_publish_wait);
 
 /**
@@ -38,9 +35,6 @@ static DECLARE_WAIT_QUEUE_HEAD(__zfcp_diag_publish_wait);
  */
 int zfcp_diag_adapter_setup(struct zfcp_adapter *const adapter)
 {
-	/* set the timestamp so that the first test on age will always fail */
-	const unsigned long initial_timestamp =
-		jiffies - msecs_to_jiffies(ZFCP_DIAG_MAX_AGE);
 	struct zfcp_diag_adapter *diag;
 	struct zfcp_diag_header *hdr;
 
@@ -48,13 +42,16 @@ int zfcp_diag_adapter_setup(struct zfcp_adapter *const adapter)
 	if (diag == NULL)
 		return -ENOMEM;
 
+	diag->max_age = (5 * 1000); /* default value: 5 s */
+
 	/* setup header for port_data */
 	hdr = &diag->port_data.header;
 
 	spin_lock_init(&hdr->access_lock);
 	hdr->buffer = &diag->port_data.data;
 	hdr->buffer_size = sizeof(diag->port_data.data);
-	hdr->timestamp = initial_timestamp;
+	/* set the timestamp so that the first test on age will always fail */
+	hdr->timestamp = jiffies - msecs_to_jiffies(diag->max_age);
 
 	/* setup header for config_data */
 	hdr = &diag->config_data.header;
@@ -62,7 +59,8 @@ int zfcp_diag_adapter_setup(struct zfcp_adapter *const adapter)
 	spin_lock_init(&hdr->access_lock);
 	hdr->buffer = &diag->config_data.data;
 	hdr->buffer_size = sizeof(diag->config_data.data);
-	hdr->timestamp = initial_timestamp;
+	/* set the timestamp so that the first test on age will always fail */
+	hdr->timestamp = jiffies - msecs_to_jiffies(diag->max_age);
 
 	adapter->diagnostics = diag;
 	return 0;
@@ -240,7 +238,8 @@ static int __zfcp_diag_update_buffer(struct zfcp_adapter *const adapter,
 }
 
 static bool
-__zfcp_diag_test_buffer_age_isfresh(const struct zfcp_diag_header *const hdr)
+__zfcp_diag_test_buffer_age_isfresh(const struct zfcp_diag_adapter *const diag,
+				    const struct zfcp_diag_header *const hdr)
 	__must_hold(hdr->access_lock)
 {
 	const unsigned long now = jiffies;
@@ -252,7 +251,7 @@ __zfcp_diag_test_buffer_age_isfresh(const struct zfcp_diag_header *const hdr)
 	if (!time_after_eq(now, hdr->timestamp))
 		return false;
 
-	if (jiffies_to_msecs(now - hdr->timestamp) >= ZFCP_DIAG_MAX_AGE)
+	if (jiffies_to_msecs(now - hdr->timestamp) >= diag->max_age)
 		return false;
 
 	return true;
@@ -291,7 +290,9 @@ int zfcp_diag_update_buffer_limited(struct zfcp_adapter *const adapter,
 
 	spin_lock_irqsave(&hdr->access_lock, flags);
 
-	for (rc = 0; !__zfcp_diag_test_buffer_age_isfresh(hdr); rc = 0) {
+	for (rc = 0;
+	     !__zfcp_diag_test_buffer_age_isfresh(adapter->diagnostics, hdr);
+	     rc = 0) {
 		rc = __zfcp_diag_update_buffer(adapter, hdr, buffer_update,
 					       &flags);
 		if (rc != -EAGAIN)