util.h - unmap region of block device

doc/tgtadm.8.xml

@@ -418,9 +418,14 @@ tgtadm --lld iscsi --mode logicalunit --op update --tid 1 --lun 1 \
 	    This parameter only applies to DISK devices.
           </para>
           <para>
-	    Thin-provisioning only works for LUNs stored on filesystems
+	    Thin-provisioning works for LUNs stored on filesystems
 	    that support FALLOC_FL_PUNCH_HOLE.
           </para>
+	  <para>
+	    When using thin-provisioning option with a block device such a
+	    SSD or ZVOL, UNMAP SCSI command discards the region from
+	    the block device.
+	  </para>
         </listitem>
       </varlistentry>
 

usr/util.h

@@ -15,6 +15,10 @@
 #include <string.h>
 #include <limits.h>
 #include <linux/types.h>
+#include <sys/ioctl.h>
+#include <linux/fs.h>
+#include <sys/types.h>
+#include <sys/stat.h>
 
 #include "be_byteshift.h"
 
@@ -208,15 +212,27 @@ void concat_buf_release(struct concat_buf *b);
 
 
 /* If we have recent enough glibc to support PUNCH HOLE we try to unmap
- * the region.
+ * the region of file.
+ * If supported BLKDISCARD, try to unmap the region of block device.
  */
 static inline int unmap_file_region(int fd, off_t offset, off_t length)
 {
+	struct stat64 st;
+	if (fstat64(fd, &st) < 0)
+		return -1;
+	if (S_ISREG(st.st_mode)) {
 #ifdef FALLOC_FL_PUNCH_HOLE
-	if (fallocate(fd, FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE,
-			offset, length) == 0)
-		return 0;
+		if (fallocate(fd, FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE,
+				offset, length) == 0)
+			return 0;
+#endif
+	} else if (S_ISBLK(st.st_mode)) {
+#ifdef BLKDISCARD
+		uint64_t range[] = { offset, length };
+		if (ioctl(fd, BLKDISCARD, &range) == 0)
+			return 0;
 #endif
+	}
 	return -1;
 }