[PATCH] xfs_mdrestore: Don't restore over a dump file

[Marco A Benatto <marco.antonio.780@gmail.com>]

Currently, if the user switch source and target parameters
position, xfs_mdrestore truncates the dumpfile before abort
the execution.

This patch checks the target parameter and if XFS_MD_MAGIC is
found, it aborts execution and leave dump file intact.

Signed-off-by: Marco A Benatto <marco.antonio.780@gmail.com>
---
 mdrestore/xfs_mdrestore.c | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/mdrestore/xfs_mdrestore.c b/mdrestore/xfs_mdrestore.c
index c49c13a..b4bf7b4 100644
--- a/mdrestore/xfs_mdrestore.c
+++ b/mdrestore/xfs_mdrestore.c
@@ -205,7 +205,7 @@ main(
 	int 		argc,
 	char 		**argv)
 {
-	FILE		*src_f;
+	FILE		*src_f, *dst_f;
 	int		dst_fd;
 	int		c;
 	int		open_flags;
@@ -277,6 +277,7 @@ main(
 
 	optind++;
 
+
 	/* check and open target */
 	open_flags = O_RDWR;
 	is_target_file = 0;
@@ -285,6 +286,19 @@ main(
 		open_flags |= O_CREAT;
 		is_target_file = 1;
 	} else if (S_ISREG(statbuf.st_mode))  {
+		xfs_metablock_t mb;
+
+		dst_f = fopen(argv[optind], "rb");
+		if (dst_f == NULL)
+			fatal("cannot open target\n");
+
+		if (fread(&mb, sizeof(mb), 1, dst_f) == 1) {
+			if (be32_to_cpu(mb.mb_magic) == XFS_MD_MAGIC)
+				fatal("target file is a xfs_metadump. switched arguments?\n");
+		}
+
+		fclose(dst_f);
+
 		open_flags |= O_TRUNC;
 		is_target_file = 1;
 	} else  {
-- 
1.8.3.1