Ignore wipe operation on non-block devices.

The implementation of make_ext4fs() calls make_ext4fs_internal() by
forcing the |wipe| parameter to true, which is problematic when the
library is used within the emulator (the wipe operation will always
fail on non-Linux platforms).

This patch does the following:

- Add a 'is_block_device_fd()' function to check that a file descriptor
  points to a real block device.

- Modify the implementation of wipe_block_device() uses it to return
  silently when trying to wipe a non-block-device file.

- Add a WIPE_IS_SUPPORTED flag in wipe.h that indicates whether
  block device wiping is supported on the current platform
  (for now, this is only the case on Linux).

BUG=NONE

Change-Id: I62b62b7c3e99b465c3b876154231e7c2fe541b23

1 files changed, 1 insertions, 0 deletions

diff --git a/ext4_utils/ext4_utils.h b/ext4_utils/ext4_utils.h
index 447d4161..c6f52b5b 100644
--- a/ext4_utils/ext4_utils.h
+++ b/ext4_utils/ext4_utils.h
@@ -140,6 +140,7 @@ void ext4_create_journal_inode(void);
 void ext4_update_free(void);
 void ext4_queue_sb(void);
 u64 get_block_device_size(int fd);
+int is_block_device_fd(int fd);
 u64 get_file_size(int fd);
 u64 parse_num(const char *arg);
 void ext4_parse_sb_info(struct ext4_super_block *sb);