xfs_mdrestore: Don't rewind source file stream

Today, xfs_mdrestore from stdin will fail if the -i flag is
specified, because it attempts to rewind the stream after
the initial read of the metablock.  This fails, and
results in an abort with "specified file is not a metadata
dump."

Read the metablock exactly once in main(), validate the magic,
print informational flags if requested, and then pass it to
perform_restore() which will then continue the restore process.

Reported-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Marco A Benatto <marco.antonio.780@gmail.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Eric Sandeen <sandeen@sandeen.net>

diff --git a/mdrestore/xfs_mdrestore.c b/mdrestore/xfs_mdrestore.c
index 0bb4ac8df96a46c7711107a6c91d1e369d5b87a8..c9d4b0c1497c619a103f3f21b96cb94f43d570d6 100644 (file)
--- a/mdrestore/xfs_mdrestore.c
+++ b/mdrestore/xfs_mdrestore.c
@@ -51,57 +51,55 @@ print_progress(const char *fmt, ...)
        progress_since_warning = 1;
 }
 
+/*
+ * perform_restore() -- do the actual work to restore the metadump
+ *
+ * @src_f: A FILE pointer to the source metadump
+ * @dst_fd: the file descriptor for the target file
+ * @is_target_file: designates whether the target is a regular file
+ * @mbp: pointer to metadump's first xfs_metablock, read and verified by the caller
+ *
+ * src_f should be positioned just past a read the previously validated metablock
+ */
 static void
 perform_restore(
        FILE                    *src_f,
        int                     dst_fd,
-       int                     is_target_file)
+       int                     is_target_file,
+       const struct xfs_metablock      *mbp)
 {
-       xfs_metablock_t         *metablock;     /* header + index + blocks */
+       struct xfs_metablock    *metablock;     /* header + index + blocks */
        __be64                  *block_index;
        char                    *block_buffer;
        int                     block_size;
        int                     max_indices;
        int                     cur_index;
        int                     mb_count;
-       xfs_metablock_t         tmb;
        xfs_sb_t                sb;
        int64_t                 bytes_read;
 
-       /*
-        * read in first blocks (superblock 0), set "inprogress" flag for it,
-        * read in the rest of the file, and if complete, clear SB 0's
-        * "inprogress flag"
-        */
-
-       if (fread(&tmb, sizeof(tmb), 1, src_f) != 1)
-               fatal("error reading from file: %s\n", strerror(errno));
-
-       if (be32_to_cpu(tmb.mb_magic) != XFS_MD_MAGIC)
-               fatal("specified file is not a metadata dump\n");
-
-       block_size = 1 << tmb.mb_blocklog;
+       block_size = 1 << mbp->mb_blocklog;
        max_indices = (block_size - sizeof(xfs_metablock_t)) / sizeof(__be64);
 
        metablock = (xfs_metablock_t *)calloc(max_indices + 1, block_size);
        if (metablock == NULL)
                fatal("memory allocation failure\n");
 
-       mb_count = be16_to_cpu(tmb.mb_count);
+       mb_count = be16_to_cpu(mbp->mb_count);
        if (mb_count == 0 || mb_count > max_indices)
                fatal("bad block count: %u\n", mb_count);
 
        block_index = (__be64 *)((char *)metablock + sizeof(xfs_metablock_t));
        block_buffer = (char *)metablock + block_size;
 
-       if (fread(block_index, block_size - sizeof(tmb), 1, src_f) != 1)
+       if (fread(block_index, block_size - sizeof(struct xfs_metablock), 1, src_f) != 1)
                fatal("error reading from file: %s\n", strerror(errno));
 
        if (block_index[0] != 0)
                fatal("first block is not the primary superblock\n");
 
 
-       if (fread(block_buffer, mb_count << tmb.mb_blocklog,
+       if (fread(block_buffer, mb_count << mbp->mb_blocklog,
                        1, src_f) != 1)
                fatal("error reading from file: %s\n", strerror(errno));
 
@@ -148,7 +146,7 @@ perform_restore(
 
                for (cur_index = 0; cur_index < mb_count; cur_index++) {
                        if (pwrite(dst_fd, &block_buffer[cur_index <<
-                                       tmb.mb_blocklog], block_size,
+                                       mbp->mb_blocklog], block_size,
                                        be64_to_cpu(block_index[cur_index]) <<
                                                BBSHIFT) < 0)
                                fatal("error writing block %llu: %s\n",
@@ -167,11 +165,11 @@ perform_restore(
                if (mb_count > max_indices)
                        fatal("bad block count: %u\n", mb_count);
 
-               if (fread(block_buffer, mb_count << tmb.mb_blocklog,
+               if (fread(block_buffer, mb_count << mbp->mb_blocklog,
                                                                1, src_f) != 1)
                        fatal("error reading from file: %s\n", strerror(errno));
 
-               bytes_read += block_size + (mb_count << tmb.mb_blocklog);
+               bytes_read += block_size + (mb_count << mbp->mb_blocklog);
        }
 
        if (progress_since_warning)
@@ -211,6 +209,7 @@ main(
        int             open_flags;
        struct stat     statbuf;
        int             is_target_file;
+       struct xfs_metablock    mb;
 
        progname = basename(argv[0]);
 
@@ -237,7 +236,12 @@ main(
        if (!show_info && argc - optind != 2)
                usage();
 
-       /* open source */
+       /*
+        * open source and test if this really is a dump. The first metadump block
+        * will be passed to perform_restore() which will continue to read the
+        * file from this point. This avoids rewind the stream, which causes
+        * restore to fail when source was being read from stdin.
+        */
        if (strcmp(argv[optind], "-") == 0) {
                src_f = stdin;
                if (isatty(fileno(stdin)))
@@ -248,15 +252,12 @@ main(
                        fatal("cannot open source dump file\n");
        }
 
-       if (show_info) {
-               xfs_metablock_t         mb;
-
-               if (fread(&mb, sizeof(mb), 1, src_f) != 1)
-                       fatal("error reading from file: %s\n", strerror(errno));
-
-               if (be32_to_cpu(mb.mb_magic) != XFS_MD_MAGIC)
-                       fatal("specified file is not a metadata dump\n");
+       if (fread(&mb, sizeof(mb), 1, src_f) != 1)
+               fatal("error reading from file: %s\n", strerror(errno));
+       if (mb.mb_magic != cpu_to_be32(XFS_MD_MAGIC))
+               fatal("specified file is not a metadata dump\n");
 
+       if (show_info) {
                if (mb.mb_info & XFS_METADUMP_INFO_FLAGS) {
                        printf("%s: %sobfuscated, %s log, %s metadata blocks\n",
                        argv[optind],
@@ -270,9 +271,6 @@ main(
 
                if (argc - optind == 1)
                        exit(0);
-
-               /* Go back to the beginning for the restore function */
-               fseek(src_f, 0L, SEEK_SET);
        }
 
        optind++;
@@ -301,7 +299,7 @@ main(
        if (dst_fd < 0)
                fatal("couldn't open target \"%s\"\n", argv[optind]);
 
-       perform_restore(src_f, dst_fd, is_target_file);
+       perform_restore(src_f, dst_fd, is_target_file, &mb);
 
        close(dst_fd);
        if (src_f != stdin)