Re-scan for partitions on vdev expansion

When expansion is requested rescan the partition tables to ensure
that the kernel is not operating with a stale version.  A little
care needs to be taken because as long as the disk has a open
partition the partition table cannot be updated.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>

config/kernel-blkdev-get.m4

@@ -0,0 +1,20 @@
+dnl #
+dnl # 2.6.38 API, holder argument added to blkdev_get().
+dnl #
+AC_DEFUN([ZFS_AC_KERNEL_BLKDEV_GET], [
+	AC_MSG_CHECKING([whether blkdev_get() takes holder])
+	ZFS_LINUX_TRY_COMPILE([
+		#include <linux/fs.h>
+	], [
+		struct block_device *bdev = NULL;
+		int error;
+
+		error = blkdev_get(bdev, FMODE_READ, NULL);
+	], [
+		AC_MSG_RESULT(yes)
+		AC_DEFINE(HAVE_3ARG_BLKDEV_GET, 1,
+		    [blkdev_gett() takes holder])
+	], [
+		AC_MSG_RESULT(no)
+	])
+])

config/kernel-blkdev-reread-part.m4

@@ -0,0 +1,21 @@
+dnl #
+dnl # 4.1 API, exported blkdev_reread_part() symbol, backported to the
+dnl # 3.10.0 CentOS 7.x enterprise kernels.
+dnl #
+AC_DEFUN([ZFS_AC_KERNEL_BLKDEV_REREAD_PART], [
+	AC_MSG_CHECKING([whether blkdev_reread_part() is available])
+	ZFS_LINUX_TRY_COMPILE([
+		#include <linux/fs.h>
+	], [
+		struct block_device *bdev = NULL;
+		int error;
+
+		error = blkdev_reread_part(bdev);
+	], [
+		AC_MSG_RESULT(yes)
+		AC_DEFINE(HAVE_BLKDEV_REREAD_PART, 1,
+		    [blkdev_reread_part() is available])
+	], [
+		AC_MSG_RESULT(no)
+	])
+])

config/kernel.m4

@@ -44,7 +44,9 @@ AC_DEFUN([ZFS_AC_CONFIG_KERNEL], [
 	ZFS_AC_KERNEL_BLOCK_DEVICE_OPERATIONS_CHECK_EVENTS
 	ZFS_AC_KERNEL_BLOCK_DEVICE_OPERATIONS_RELEASE_VOID
 	ZFS_AC_KERNEL_TYPE_FMODE_T
+	ZFS_AC_KERNEL_BLKDEV_GET
 	ZFS_AC_KERNEL_BLKDEV_GET_BY_PATH
+	ZFS_AC_KERNEL_BLKDEV_REREAD_PART
 	ZFS_AC_KERNEL_OPEN_BDEV_EXCLUSIVE
 	ZFS_AC_KERNEL_LOOKUP_BDEV
 	ZFS_AC_KERNEL_INVALIDATE_BDEV_ARGS

include/linux/blkdev_compat.h

@@ -364,6 +364,32 @@ bio_set_bi_error(struct bio *bio, int error)
 #define	vdev_bdev_close(bdev, md)	close_bdev_excl(bdev)
 #endif /* HAVE_BLKDEV_GET_BY_PATH | HAVE_OPEN_BDEV_EXCLUSIVE */
 
+/*
+ * 2.6.38 API change.
+ * The holder argument was added to blkdev_get()
+ */
+#ifdef HAVE_3ARG_BLKDEV_GET
+#define	vdev_bdev_get(bdev)		blkdev_get(bdev, FMODE_READ, NULL)
+#define	vdev_bdev_put(bdev)		blkdev_put(bdev, FMODE_READ)
+#else
+#define	vdev_bdev_get(bdev)		blkdev_get(bdev, FMODE_READ)
+#define	vdev_bdev_put(bdev)		blkdev_put(bdev, FMODE_READ)
+#endif
+
+/*
+ * 4.1 - x.y.z API,
+ * 3.10.0 CentOS 7.x API,
+ *   blkdev_reread_part()
+ *
+ * For older kernels trigger a re-reading of the partition table by calling
+ * check_disk_change() which calls flush_disk() to invalidate the device.
+ */
+#ifdef HAVE_BLKDEV_REREAD_PART
+#define	vdev_bdev_reread_part(bdev)	blkdev_reread_part(bdev)
+#else
+#define	vdev_bdev_reread_part(bdev)	check_disk_change(bdev)
+#endif /* HAVE_BLKDEV_REREAD_PART */
+
 /*
  * 2.6.22 API change
  * The function invalidate_bdev() lost it's second argument because

module/zfs/vdev_disk.c

@@ -91,10 +91,7 @@ vdev_bdev_mode(int smode)
 static uint64_t
 bdev_capacity(struct block_device *bdev)
 {
-	if (bdev->bd_part != NULL)
-		return (bdev->bd_part->nr_sects << SECTOR_BITS);
-	else
-		return (i_size_read(bdev->bd_inode));
+	return (i_size_read(bdev->bd_inode));
 }
 
 /*
@@ -208,7 +205,7 @@ static int
 vdev_disk_open(vdev_t *v, uint64_t *psize, uint64_t *max_psize,
     uint64_t *ashift)
 {
-	struct block_device *bdev = ERR_PTR(-ENXIO);
+	struct block_device *disk_bdev, *bdev = ERR_PTR(-ENXIO);
 	vdev_disk_t *vd;
 	int count = 0, mode, block_size;
 
@@ -223,17 +220,34 @@ vdev_disk_open(vdev_t *v, uint64_t *psize, uint64_t *max_psize,
 	mode = spa_mode(v->vdev_spa);
 
 	/*
-	 * Reopen the device if it is not currently open. Otherwise, when
-	 * expanding a device close and open it to trigger a re-scanning
-	 * of the partition table in order to get an accurate size.
+	 * Reopen the device if it is not currently open. When expanding a
+	 * device get a reference on the disk then close the partition.
+	 * Trigger a re-scanning of the disk partition table to get an
+	 * accurate size, close the disk, and then reopen the partition.
 	 */
 	if (v->vdev_tsd != NULL) {
 		ASSERT(v->vdev_reopening);
 		vd = v->vdev_tsd;
 
 		if (vd->vd_bdev && v->vdev_wholedisk && v->vdev_expanding) {
+			int error = -EINVAL;
+
+			disk_bdev = vd->vd_bdev->bd_contains;
+			if (vd->vd_bdev != disk_bdev)
+				error = vdev_bdev_get(disk_bdev);
+
 			vdev_bdev_close(vd->vd_bdev, vdev_bdev_mode(mode));
 			vd->vd_bdev = NULL;
+
+			if (error == 0) {
+				error = vdev_bdev_reread_part(disk_bdev);
+				if (error) {
+					vdev_dbgmsg(v, "Error re-reading "
+					    "partition table: %d", error);
+				}
+
+				vdev_bdev_put(disk_bdev);
+			}
 		} else {
 			goto skip_open;
 		}