diff options
| -rw-r--r-- | disk-io.c | 17 |
1 files changed, 17 insertions, 0 deletions
@@ -1419,6 +1419,23 @@ error_out: return -EIO; } +/* + * btrfs_read_dev_super - read a valid superblock from a block device + * @fd: file descriptor of the device + * @sb: buffer where the superblock is going to be read in + * @sb_bytenr: offset of the particular superblock copy we want + * @sbflags: flags controlling how the superblock is read + * + * This function is used by various btrfs comands to obtain a valid superblock. + * + * It's mode of operation is controlled by the @sb_bytenr and @sbdflags + * parameters. If SBREAD_RECOVER flag is set and @sb_bytenr is + * BTRFS_SUPER_INFO_OFFSET then the function reads all 3 superblock copies and + * returns the newest one. If SBREAD_RECOVER is not set then only a single + * copy is read, which one is decided by @sb_bytenr. If @sb_bytenr != + * BTRFS_SUPER_INFO_OFFSET then the @sbflags is effectively ignored and only a + * single copy is read. + */ int btrfs_read_dev_super(int fd, struct btrfs_super_block *sb, u64 sb_bytenr, unsigned sbflags) { |