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From a0e00751052b06508f6cfe4a434ebf2e1a04bf07 Mon Sep 17 00:00:00 2001
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From: Michal Humpula <michal.humpula@hudrydum.cz>
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Date: Wed, 25 Feb 2015 20:25:05 +0100
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Subject: [PATCH 108/116] blkid: make zfs detection more robust
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Try to use all the possible uberblock locations.
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Upstream: https://github.com/karelzak/util-linux/commit/5dd705ba65dc80cf8630b3b1b4f3a1ba153e7eec
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Addresses: https://bugzilla.redhat.com/show_bug.cgi?id=1392661
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Signed-off-by: Karel Zak <kzak@redhat.com>
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---
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 libblkid/src/superblocks/zfs.c | 42 +++++++++++++++++++++++++++---------------
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 1 file changed, 27 insertions(+), 15 deletions(-)
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diff --git a/libblkid/src/superblocks/zfs.c b/libblkid/src/superblocks/zfs.c
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index 86da59d..4a64a03 100644
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--- a/libblkid/src/superblocks/zfs.c
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+++ b/libblkid/src/superblocks/zfs.c
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@@ -19,6 +19,7 @@
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 #define VDEV_LABEL_UBERBLOCK	(128 * 1024ULL)
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 #define VDEV_LABEL_NVPAIR	( 16 * 1024ULL)
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 #define VDEV_LABEL_SIZE		(256 * 1024ULL)
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+#define UBERBLOCK_SIZE		1024ULL
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 /* #include <sys/uberblock_impl.h> */
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 #define UBERBLOCK_MAGIC         0x00bab10c              /* oo-ba-bloc!  */
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@@ -31,7 +32,7 @@ struct zfs_uberblock {
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 	char		ub_rootbp;	/* MOS objset_phys_t		*/
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 } __attribute__((packed));
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-#define ZFS_TRIES	64
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+#define ZFS_TRIES	512
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 #define ZFS_WANT	 4
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 #define DATA_TYPE_UINT64 8
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@@ -162,11 +163,10 @@ static void zfs_extract_guid_name(blkid_probe pr, loff_t offset)
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 #define zdebug(fmt, ...)	do {} while(0)
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 /*#define zdebug(fmt, a...)	fprintf(stderr, fmt, ##a)*/
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-/* ZFS has 128x1kB host-endian root blocks, stored in 2 areas at the start
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- * of the disk, and 2 areas at the end of the disk.  Check only some of them...
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- * #4 (@ 132kB) is the first one written on a new filesystem. */
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-static int probe_zfs(blkid_probe pr,
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-		const struct blkid_idmag *mag __attribute__((__unused__)))
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+/* ZFS has 128x1kB host-endian root blocks, stored in 2 areas (labels)
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+ * at the start of the disk, and 2 areas at the end of the disk.
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+ */
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+static int probe_zfs(blkid_probe pr, const struct blkid_idmag *mag)
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 {
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 	uint64_t swab_magic = swab64(UBERBLOCK_MAGIC);
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 	struct zfs_uberblock *ub;
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@@ -174,15 +174,29 @@ static int probe_zfs(blkid_probe pr,
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 	loff_t offset, ub_offset = 0;
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 	int tried;
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 	int found;
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+	loff_t blk_align = (pr->size % (256 * 1024ULL));
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 	zdebug("probe_zfs\n");
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-	/* Look for at least 4 uberblocks to ensure a positive match */
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+	/* Look for at least 4 uberblocks to ensure a positive match.
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+	   Begin with Label 0 (L0) at the start of the block device. */
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 	for (tried = found = 0, offset = VDEV_LABEL_UBERBLOCK;
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-	     tried < ZFS_TRIES && found < ZFS_WANT;
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-	     tried++, offset += 4096) {
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-		/* also try the second uberblock copy */
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-		if (tried == (ZFS_TRIES / 2))
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+	     found < ZFS_WANT && tried < ZFS_TRIES;
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+	     tried++, offset += UBERBLOCK_SIZE)
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+	{
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+		/* Leave L0 to try other labels */
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+		switch(tried) {
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+		case 128: // jump to L1, just after L0
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 			offset = VDEV_LABEL_SIZE + VDEV_LABEL_UBERBLOCK;
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+			break;
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+		case 256: // jump to L2 near the far end of the block device
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+			offset = pr->size - 2 * VDEV_LABEL_SIZE + VDEV_LABEL_UBERBLOCK - blk_align;
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+			zdebug("probe_zfs: l2 offset %llu\n", offset >> 10);
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+			break;
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+		case 384: // jump to L3 at the furthest end of the block device
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+			offset = pr->size - VDEV_LABEL_SIZE + VDEV_LABEL_UBERBLOCK - blk_align;
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+			zdebug("probe_zfs: l3 offset %llu\n", offset >> 10);
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+			break;
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+		}
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 		ub = (struct zfs_uberblock *)
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 			blkid_probe_get_buffer(pr, offset,
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@@ -193,15 +207,14 @@ static int probe_zfs(blkid_probe pr,
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 		if (ub->ub_magic == UBERBLOCK_MAGIC) {
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 			ub_offset = offset;
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 			found++;
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+			zdebug("probe_zfs: found little-endian uberblock at %llu\n", offset >> 10);
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 		}
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 		if ((swab_endian = (ub->ub_magic == swab_magic))) {
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 			ub_offset = offset;
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 			found++;
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+			zdebug("probe_zfs: found big-endian uberblock at %llu\n", offset >> 10);
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 		}
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-
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-		zdebug("probe_zfs: found %s-endian uberblock at %llu\n",
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-		       swab_endian ? "big" : "little", offset >> 10);
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 	}
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 	if (found < 4)
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@@ -230,4 +243,3 @@ const struct blkid_idinfo zfs_idinfo =
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 	.minsz		= 64 * 1024 * 1024,
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 	.magics		= BLKID_NONE_MAGIC
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 };
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-
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-- 
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2.9.3
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