Version 6.2.0.197

Note: This is a pre-release version, future versions of VDO may not support
VDO devices created with this version.
- Enabled the setting of max_discard_sectors for VDO devices via sysfs.
  This allows users stacking dm-thin devices on top of VDO to set a value
  which is large enough that dm-thin will send discards to VDO.

kvdo.spec

@@ -1,6 +1,6 @@
 %define spec_release 1
 %define kmod_name		kvdo
-%define kmod_driver_version	6.2.0.187
+%define kmod_driver_version	6.2.0.197
 %define kmod_rpm_release	%{spec_release}
 %define kmod_kernel_version	3.10.0-693.el7
 
@@ -85,5 +85,5 @@ rm -rf $RPM_BUILD_ROOT
 %{_usr}/src/%{kmod_name}-%{version}-%{kmod_driver_version}/*
 
 %changelog
-* Fri Jul 27 2018 - J. corwin Coburn <[email protected]> - 6.2.0.187-1
-HASH(0x229f768)
+* Mon Aug 06 2018 - J. corwin Coburn <[email protected]> - 6.2.0.197-1
+HASH(0x26d07a0)

vdo/Makefile

@@ -1,4 +1,4 @@
-VDO_VERSION = 6.2.0.187
+VDO_VERSION = 6.2.0.197
 
 VDO_VERSION_MAJOR = $(word 1,$(subst ., ,$(VDO_VERSION)))
 VDO_VERSION_MINOR = $(word 2,$(subst ., ,$(VDO_VERSION)))

vdo/kernel/dmvdo.c

@@ -16,7 +16,7 @@
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
  * 02110-1301, USA. 
  *
- * $Id: //eng/vdo-releases/aluminum/src/c++/vdo/kernel/dmvdo.c#6 $
+ * $Id: //eng/vdo-releases/aluminum/src/c++/vdo/kernel/dmvdo.c#7 $
  */
 
 #include "dmvdo.h"
@@ -57,20 +57,10 @@ struct kvdoDevice kvdoDevice;   // global driver state (poorly named)
  * /var/log/kern.log.  In order to avoid these warnings, we choose to use the
  * smallest reasonable value.  See VDO-3062 and VDO-3087.
  *
- * Pre kernel version 4.3, we use the functionality in blkdev_issue_discard
- * and the value in max_discard_sectors to split large discards into smaller
- * ones. 4.3 and beyond kernels have removed the code in blkdev_issue_discard
- * and so after that point, we use the code in device mapper itself to
- * split the discards. Unfortunately, it uses the same value to split large
- * discards as it does to split large data bios. As such, we should never
- * change the value of max_discard_sectors in kernel versions beyond that.
- * We continue to set the value for max_discard_sectors as it is used in other
- * code, like sysfs display of queue limits and since we are actually splitting
- * discards it makes sense to show the correct value there.
- *
- * DO NOT CHANGE VALUE for kernel versions 4.3 and beyond to anything other
- * than what is set to the max_io_len field below. We mimic to_sector here
- * as a non const, otherwise compile would fail.
+ * We allow setting of the value for max_discard_sectors even in situations 
+ * where we only split on 4k (see comments for HAS_NO_BLKDEV_SPLIT) as the
+ * value is still used in other code, like sysfs display of queue limits and 
+ * most especially in dm-thin to determine whether to pass down discards.
  */
 unsigned int maxDiscardSectors = VDO_SECTORS_PER_BLOCK;
 
@@ -94,6 +84,23 @@ unsigned int maxDiscardSectors = VDO_SECTORS_PER_BLOCK;
 #endif
 #endif
 
+/*
+ * Pre kernel version 4.3, we use the functionality in blkdev_issue_discard
+ * and the value in max_discard_sectors to split large discards into smaller
+ * ones. 4.3 to 4.18 kernels have removed the code in blkdev_issue_discard
+ * and so in place of that, we use the code in device mapper itself to
+ * split the discards. Unfortunately, it uses the same value to split large
+ * discards as it does to split large data bios. 
+ *
+ * In kernel version 4.18, support for splitting discards was added
+ * back into blkdev_issue_discard. Since this mode of splitting 
+ * (based on max_discard_sectors) is preferable to splitting always
+ * on 4k, we are turning off the device mapper splitting from 4.18
+ * on.
+ */
+#define HAS_NO_BLKDEV_SPLIT LINUX_VERSION_CODE >= KERNEL_VERSION(4,3,0) \
+                            && LINUX_VERSION_CODE < KERNEL_VERSION(4,18,0)
+
 /*
  * We want to support flush requests in async mode, but early device mapper
  * versions got in the way if the underlying device did not also support
@@ -534,15 +541,9 @@ static void configureTargetCapabilities(struct dm_target *ti,
 #endif
 
 /*
- * As of linux kernel version 4.3, support for splitting discards
- * was removed from blkdev_issue_discard. Luckily, device mapper
- * added its own support for splitting discards in kernel version
- * 3.6 and beyond. We will begin using this support from 4.3 on.
- * Please keep in mind the device mapper support uses the same value
- * for splitting discards as it does for splitting regular data i/os.
- * See the max_io_len setting above.
+ * Please see comments above where the macro is defined.
  */
-#if (LINUX_VERSION_CODE >= KERNEL_VERSION(4,3,0))
+#if HAS_NO_BLKDEV_SPLIT
   ti->split_discard_bios = 1;
 #endif
 }

vdo/kernel/sysfs.c

@@ -16,7 +16,7 @@
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
  * 02110-1301, USA. 
  *
- * $Id: //eng/vdo-releases/aluminum/src/c++/vdo/kernel/sysfs.c#2 $
+ * $Id: //eng/vdo-releases/aluminum/src/c++/vdo/kernel/sysfs.c#3 $
  */
 
 #include "sysfs.h"
@@ -28,12 +28,7 @@
 #include "dmvdo.h"
 #include "logger.h"
 
-#define HAS_MAX_DISCARD_SECTORS (LINUX_VERSION_CODE < KERNEL_VERSION(4,3,0))
-
-#if HAS_MAX_DISCARD_SECTORS
 extern unsigned int maxDiscardSectors;
-#endif /* HAS_MAX_DISCARD_SECTORS */
-
 extern int defaultMaxRequestsActive;
 
 typedef struct vdoAttribute {
@@ -194,15 +189,13 @@ static ssize_t vdoMaxReqActiveStore(struct kvdoDevice *device,
   return scanInt(buf, n, &defaultMaxRequestsActive, 1, MAXIMUM_USER_VIOS);
 }
 
-#if HAS_MAX_DISCARD_SECTORS
 /**********************************************************************/
 static ssize_t vdoMaxDiscardSectors(struct kvdoDevice *device,
                                     const char        *buf,
                                     size_t             n)
 {
   return scanUInt(buf, n, &maxDiscardSectors, 8, UINT_MAX);
 }
-#endif /* HAS_MAX_DISCARD_SECTORS */
 
 /**********************************************************************/
 static ssize_t vdoAlbireoTimeoutIntervalStore(struct kvdoDevice *device,
@@ -285,14 +278,12 @@ static VDOAttribute vdoMaxReqActiveAttr = {
   .valuePtr = &defaultMaxRequestsActive,
 };
 
-#if HAS_MAX_DISCARD_SECTORS
 static VDOAttribute vdoMaxDiscardSectorsAttr = {
   .attr     = {.name = "max_discard_sectors", .mode = 0644, },
   .show     = showUInt,
   .store    = vdoMaxDiscardSectors,
   .valuePtr = &maxDiscardSectors,
 };
-#endif /* HAS_MAX_DISCARD_SECTORS */
 
 static VDOAttribute vdoAlbireoTimeoutInterval = {
   .attr     = {.name = "deduplication_timeout_interval", .mode = 0644, },
@@ -324,9 +315,7 @@ static struct attribute *defaultAttrs[] = {
   &vdoStatusAttr.attr,
   &vdoLogLevelAttr.attr,
   &vdoMaxReqActiveAttr.attr,
-#if HAS_MAX_DISCARD_SECTORS
   &vdoMaxDiscardSectorsAttr.attr,
-#endif /* HAS_MAX_DISCARD_SECTORS */
   &vdoAlbireoTimeoutInterval.attr,
   &vdoMinAlbireoTimerInterval.attr,
   &vdoTraceRecording.attr,