On 2017年12月05日 16:39, Nikolay Borisov wrote: > Signed-off-by: Nikolay Borisov <nbori...@suse.com> > --- > disk-io.c | 17 +++++++++++++++++ > 1 file changed, 17 insertions(+) > > diff --git a/disk-io.c b/disk-io.c > index 3d8785d5bb37..40077d4919c6 100644 > --- a/disk-io.c > +++ b/disk-io.c > @@ -1419,6 +1419,23 @@ static int check_super(struct btrfs_super_block *sb, > unsigned sbflags) > return -EIO; > } > > +/* > + * btrfs_read_dev_super - read a valid superblock from a block device > + * @fd: file descrioptor of the device > + * @sb: buffer where the superblock is going to be read in > + * @sb_bytenr: offset of the particular superblock copie 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.
Although the logic is not as straightforward, it's still acceptable and
the comment does makes it clearer.
Reviewed-by: Qu Wenruo <w...@suse.com>
Thanks,
Qu
> + */
> int btrfs_read_dev_super(int fd, struct btrfs_super_block *sb, u64 sb_bytenr,
> unsigned sbflags)
> {
>
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