From 8646f60d1b421b48b43405fa286548a0bf3f5da4 Mon Sep 17 00:00:00 2001

From: Michal Humpula <michal.humpula@hudrydum.cz>

Date: Sat, 28 Feb 2015 21:19:42 +0100

Subject: [PATCH 109/116] zfs: make less syscalls

Upstream: https://github.com/karelzak/util-linux/commit/e44a4c7ac9522c03b76d8b62ce88b443771fdb0b

Addresses: https://bugzilla.redhat.com/show_bug.cgi?id=1392661

Signed-off-by: Karel Zak <kzak@redhat.com>

---

 libblkid/src/superblocks/zfs.c | 95 ++++++++++++++++++++++++++----------------

 1 file changed, 58 insertions(+), 37 deletions(-)

diff --git a/libblkid/src/superblocks/zfs.c b/libblkid/src/superblocks/zfs.c

index 4a64a03..9b5601e 100644

--- a/libblkid/src/superblocks/zfs.c

+++ b/libblkid/src/superblocks/zfs.c

@@ -20,6 +20,7 @@

 #define VDEV_LABEL_NVPAIR	( 16 * 1024ULL)

 #define VDEV_LABEL_SIZE		(256 * 1024ULL)

 #define UBERBLOCK_SIZE		1024ULL

+#define UBERBLOCKS_COUNT   128

 /* #include <sys/uberblock_impl.h> */

 #define UBERBLOCK_MAGIC         0x00bab10c              /* oo-ba-bloc!  */

@@ -32,7 +33,6 @@ struct zfs_uberblock {

 	char		ub_rootbp;	/* MOS objset_phys_t		*/

 } __attribute__((packed));

-#define ZFS_TRIES	512

 #define ZFS_WANT	 4

 #define DATA_TYPE_UINT64 8

@@ -163,61 +163,82 @@ static void zfs_extract_guid_name(blkid_probe pr, loff_t offset)

 #define zdebug(fmt, ...)	do {} while(0)

 /*#define zdebug(fmt, a...)	fprintf(stderr, fmt, ##a)*/

-/* ZFS has 128x1kB host-endian root blocks, stored in 2 areas (labels)

- * at the start of the disk, and 2 areas at the end of the disk.

- */

+static int find_uberblocks(const void *label, loff_t *ub_offset, int *swap_endian)

+{

+	uint64_t swab_magic = swab64(UBERBLOCK_MAGIC);

+	struct zfs_uberblock *ub;

+	int i, found = 0;

+	loff_t offset = VDEV_LABEL_UBERBLOCK;

+

+	for (i = 0; i < UBERBLOCKS_COUNT; i++, offset += UBERBLOCK_SIZE) {

+		ub = (struct zfs_uberblock *)(label + offset);

+

+		if (ub->ub_magic == UBERBLOCK_MAGIC) {

+			*ub_offset = offset;

+			*swap_endian = 0;

+			found++;

+			zdebug("probe_zfs: found little-endian uberblock at %llu\n", offset >> 10);

+		}

+

+		if (ub->ub_magic == swab_magic) {

+			*ub_offset = offset;

+			*swap_endian = 1;

+			found++;

+			zdebug("probe_zfs: found big-endian uberblock at %llu\n", offset >> 10);

+		}

+  }

+

+  return found;

+}

+

+/* ZFS has 128x1kB host-endian root blocks, stored in 2 areas at the start

+ * of the disk, and 2 areas at the end of the disk.  Check only some of them...

+ * #4 (@ 132kB) is the first one written on a new filesystem. */

 static int probe_zfs(blkid_probe pr, const struct blkid_idmag *mag)

 {

 	uint64_t swab_magic = swab64(UBERBLOCK_MAGIC);

+	int swab_endian = 0;

 	struct zfs_uberblock *ub;

-	int swab_endian;

 	loff_t offset, ub_offset = 0;

-	int tried;

-	int found;

+	int label_no, found = 0, found_in_label;

+	void *label;

 	loff_t blk_align = (pr->size % (256 * 1024ULL));

 	zdebug("probe_zfs\n");

-	/* Look for at least 4 uberblocks to ensure a positive match.

-	   Begin with Label 0 (L0) at the start of the block device. */

-	for (tried = found = 0, offset = VDEV_LABEL_UBERBLOCK;

-	     found < ZFS_WANT && tried < ZFS_TRIES;

-	     tried++, offset += UBERBLOCK_SIZE)

-	{

-		/* Leave L0 to try other labels */

-		switch(tried) {

-		case 128: // jump to L1, just after L0

-			offset = VDEV_LABEL_SIZE + VDEV_LABEL_UBERBLOCK;

+	/* Look for at least 4 uberblocks to ensure a positive match */

+	for (label_no = 0; label_no < 4; label_no++) {

+		switch(label_no) {

+		case 0: // jump to L0

+			offset = 0;

 			break;

-		case 256: // jump to L2 near the far end of the block device

-			offset = pr->size - 2 * VDEV_LABEL_SIZE + VDEV_LABEL_UBERBLOCK - blk_align;

-			zdebug("probe_zfs: l2 offset %llu\n", offset >> 10);

+		case 1: // jump to L1

+			offset = VDEV_LABEL_SIZE;

 			break;

-		case 384: // jump to L3 at the furthest end of the block device

-			offset = pr->size - VDEV_LABEL_SIZE + VDEV_LABEL_UBERBLOCK - blk_align;

-			zdebug("probe_zfs: l3 offset %llu\n", offset >> 10);

+		case 2: // jump to L2

+			offset = pr->size - 2 * VDEV_LABEL_SIZE - blk_align;

+			break;

+		case 3: // jump to L3

+			offset = pr->size - VDEV_LABEL_SIZE - blk_align;

 			break;

 		}

-		ub = (struct zfs_uberblock *)

-			blkid_probe_get_buffer(pr, offset,

-					       sizeof(struct zfs_uberblock));

-		if (ub == NULL)

+		label = blkid_probe_get_buffer(pr, offset, VDEV_LABEL_SIZE);

+		if (label == NULL)

 			return errno ? -errno : 1;

-		if (ub->ub_magic == UBERBLOCK_MAGIC) {

-			ub_offset = offset;

-			found++;

-			zdebug("probe_zfs: found little-endian uberblock at %llu\n", offset >> 10);

-		}

+		found_in_label = find_uberblocks(label, &ub_offset, &swab_endian);

-		if ((swab_endian = (ub->ub_magic == swab_magic))) {

-			ub_offset = offset;

-			found++;

-			zdebug("probe_zfs: found big-endian uberblock at %llu\n", offset >> 10);

+		if (found_in_label > 0) {

+			found+= found_in_label;

+			ub = (struct zfs_uberblock *)(label + ub_offset);

+			ub_offset += offset;

+

+			if (found >= ZFS_WANT)

+				break;

 		}

 	}

-	if (found < 4)

+	if (found < ZFS_WANT)

 		return 1;

 	/* If we found the 4th uberblock, then we will have exited from the

-- 

2.9.3