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Blame btrfs-progs-correct-uninitialized-fsid-variable.patch

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From 6eba9002956ac40db87d42fb653a0524dc568810 Mon Sep 17 00:00:00 2001
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From: Goffredo Baroncelli <kreijack@inwind.it>
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Date: Tue, 4 Sep 2012 19:59:26 +0200
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Subject: [PATCH 1/1] Correct un-initialized fsid variable
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---
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 disk-io.c |   20 ++++++++++++++++----
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 1 files changed, 16 insertions(+), 4 deletions(-)
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diff --git a/disk-io.c b/disk-io.c
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index b21a87f..0395205 100644
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--- a/disk-io.c
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+++ b/disk-io.c
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@@ -910,6 +910,7 @@ struct btrfs_root *open_ctree_fd(int fp, const char *path, u64 sb_bytenr,
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 int btrfs_read_dev_super(int fd, struct btrfs_super_block *sb, u64 sb_bytenr)
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 {
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 	u8 fsid[BTRFS_FSID_SIZE];
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+	int fsid_is_initialized = 0;
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 	struct btrfs_super_block buf;
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 	int i;
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 	int ret;
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@@ -936,15 +937,26 @@ int btrfs_read_dev_super(int fd, struct btrfs_super_block *sb, u64 sb_bytenr)
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 		if (ret < sizeof(buf))
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 			break;
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-		if (btrfs_super_bytenr(&buf) != bytenr ||
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-		    strncmp((char *)(&buf.magic), BTRFS_MAGIC,
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+		if (btrfs_super_bytenr(&buf) != bytenr )
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+			continue;
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+		/* if magic is NULL, the device was removed */
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+		if (buf.magic == 0 && i == 0) 
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+			return -1;
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+		if (strncmp((char *)(&buf.magic), BTRFS_MAGIC,
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 			    sizeof(buf.magic)))
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 			continue;
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-		if (i == 0)
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+		if (!fsid_is_initialized) {
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 			memcpy(fsid, buf.fsid, sizeof(fsid));
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-		else if (memcmp(fsid, buf.fsid, sizeof(fsid)))
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+			fsid_is_initialized = 1;
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+		} else if (memcmp(fsid, buf.fsid, sizeof(fsid))) {
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+			/*
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+			 * the superblocks (the original one and
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+			 * its backups) contain data of different
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+			 * filesystems -> the super cannot be trusted
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+			 */
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 			continue;
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+		}
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 		if (btrfs_super_generation(&buf) > transid) {
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 			memcpy(sb, &buf, sizeof(*sb));
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-- 
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1.7.7.6
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