mke2fs: adjust the default file system size by the offset

If the user specifies an offset using -E offset without specifying an
explicit size, the system will use the block device (or file) size as
the default file system size.  If we are using the default file system
size, subtract out the offset so the resulting file system will stay
within the block device.  Also print a warning that this might not be
what the user wants.

Addresses-Debian-Bug: #803629

Signed-off-by: Theodore Ts'o <tytso@mit.edu>

diff --git a/misc/mke2fs.c b/misc/mke2fs.c
index b5c7a00..b558214 100644 (file)
--- a/misc/mke2fs.c
+++ b/misc/mke2fs.c
@@ -1456,6 +1456,7 @@ static void PRS(int argc, char *argv[])
        int             b, c, flags;
        int             cluster_size = 0;
        char            *tmp, **cpp;
+       int             explicit_fssize = 0;
        int             blocksize = 0;
        int             inode_ratio = 0;
        int             inode_size = 0;
@@ -1862,7 +1863,7 @@ profile_error:
 
        /* The isatty() test is so we don't break existing scripts */
        flags = CREATE_FILE;
-       if (isatty(0) && isatty(1))
+       if (isatty(0) && isatty(1) && !offset)
                flags |= CHECK_FS_EXIST;
        if (!quiet)
                flags |= VERBOSE_CREATE;
@@ -1875,6 +1876,7 @@ profile_error:
 
        /* Determine the size of the device (if possible) */
        if (noaction && fs_blocks_count) {
+               explicit_fssize = 1;
                dev_size = fs_blocks_count;
                retval = 0;
        } else
@@ -2274,6 +2276,17 @@ profile_error:
        if (extended_opts)
                parse_extended_opts(&fs_param, extended_opts);
 
+       if (explicit_fssize == 0 && offset > 0) {
+               fs_blocks_count -= offset / EXT2_BLOCK_SIZE(&fs_param);
+               ext2fs_blocks_count_set(&fs_param, fs_blocks_count);
+               fprintf(stderr,
+                       _("\nWarning: offset specified without an "
+                         "explicit file system size.\n"
+                         "Creating a file system with %d blocks "
+                         "but this might\n"
+                         "not be what you want.\n\n"), fs_blocks_count);
+       }
+
        /* Don't allow user to set both metadata_csum and uninit_bg bits. */
        if (ext2fs_has_feature_metadata_csum(&fs_param) &&
            ext2fs_has_feature_gdt_csum(&fs_param))