fs/ntfs3: Fix alternative boot searching

Signed-off-by: Konstantin Komarov <almaz.alexandrovich@paragon-software.com>

Author: aalexandrovich

fs/ntfs3/super.c

@@ -846,7 +846,7 @@ static int ntfs_init_from_boot(struct super_block *sb, u32 sector_size,
 	struct ntfs_sb_info *sbi = sb->s_fs_info;
 	int err;
 	u32 mb, gb, boot_sector_size, sct_per_clst, record_size;
-	u64 sectors, clusters, mlcn, mlcn2;
+	u64 sectors, clusters, mlcn, mlcn2, dev_size0;
 	struct NTFS_BOOT *boot;
 	struct buffer_head *bh;
 	struct MFT_REC *rec;
@@ -855,6 +855,9 @@ static int ntfs_init_from_boot(struct super_block *sb, u32 sector_size,
 	u32 boot_off = 0;
 	const char *hint = "Primary boot";
 
+	/* Save original dev_size. Used with alternative boot. */
+	dev_size0 = dev_size;
+
 	sbi->volume.blocks = dev_size >> PAGE_SHIFT;
 
 	bh = ntfs_bread(sb, 0);
@@ -1087,9 +1090,9 @@ static int ntfs_init_from_boot(struct super_block *sb, u32 sector_size,
 	}
 
 out:
-	if (err == -EINVAL && !bh->b_blocknr && dev_size > PAGE_SHIFT) {
+	if (err == -EINVAL && !bh->b_blocknr && dev_size0 > PAGE_SHIFT) {
 		u32 block_size = min_t(u32, sector_size, PAGE_SIZE);
-		u64 lbo = dev_size - sizeof(*boot);
+		u64 lbo = dev_size0 - sizeof(*boot);
 
 		/*
 	 	 * Try alternative boot (last sector)
@@ -1103,6 +1106,7 @@ static int ntfs_init_from_boot(struct super_block *sb, u32 sector_size,
 
 		boot_off = lbo & (block_size - 1);
 		hint = "Alternative boot";
+		dev_size = dev_size0; /* restore original size. */
 		goto check_boot;
 	}
 	brelse(bh);