On Fri, Feb 02, 2018 at 05:11:14PM -0200, Marco A Benatto wrote:
> 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@xxxxxxxxxx>
> Signed-off-by: Marco A Benatto <marco.antonio.780@xxxxxxxxx>
> ---
> mdrestore/xfs_mdrestore.c | 52 +++++++++++++++++++++++------------------------
> 1 file changed, 25 insertions(+), 27 deletions(-)
>
> diff --git a/mdrestore/xfs_mdrestore.c b/mdrestore/xfs_mdrestore.c
> index 0bb4ac8..15231a1 100644
> --- a/mdrestore/xfs_mdrestore.c
> +++ b/mdrestore/xfs_mdrestore.c
> @@ -51,11 +51,22 @@ 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
> + * @mb: the metadump's first xfs_metablock_t, 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 xfs_metablock_t tmb)
"const struct xfs_metablock *tmp"
Please don't pass the whole structure on the stack, and since this is
new code, don't use the structure typedef aliases (which we are slowly
trying to eliminate).
> {
> xfs_metablock_t *metablock; /* header + index + blocks */
> __be64 *block_index;
> @@ -64,22 +75,9 @@ perform_restore(
> 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;
> max_indices = (block_size - sizeof(xfs_metablock_t)) / sizeof(__be64);
>
> @@ -211,6 +209,7 @@ main(
> int open_flags;
> struct stat statbuf;
> int is_target_file;
> + xfs_metablock_t mb;
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 metadatablock
"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 (be32_to_cpu(mb.mb_magic) != XFS_MD_MAGIC)
if (mb.mb_magic != cpu_to_be32(XFS_MD_MAGIC))
...so that we can let the horrible macro definitions turn that into a
byteswapped constant instead of a function call. It's not critical
here, but it's a convention we try to maintain everywhere else.
The rest looks fine.
--D
> + 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)
> --
> 1.8.3.1
>
> --
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