diff options
author | Nikolay Borisov <nborisov@suse.com> | 2017-12-05 10:39:47 +0200 |
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committer | David Sterba <dsterba@suse.com> | 2018-01-31 15:14:01 +0100 |
commit | 90a16b10b328d63ea90b3f4a04fd52a0bc0b689f (patch) | |
tree | f9bf12150ee9d7a536abb6a1248c079eeedc0535 /disk-io.c | |
parent | 8075fd4da1a5c759261413461a4bd7f9af81722c (diff) |
btrfs-progs: Document logic of btrfs_read_dev_super
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Diffstat (limited to 'disk-io.c')
-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) { |