From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx2.suse.de ([195.135.220.15]:33325 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752662AbdLEIjz (ORCPT ); Tue, 5 Dec 2017 03:39:55 -0500 Received: from relay2.suse.de (charybdis-ext.suse.de [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id 5F54CADE9 for ; Tue, 5 Dec 2017 08:39:54 +0000 (UTC) From: Nikolay Borisov To: linux-btrfs@vger.kernel.org Cc: Nikolay Borisov Subject: [PATCH 5/7] btrfs-progs: Document logic of btrfs_read_dev_super Date: Tue, 5 Dec 2017 10:39:47 +0200 Message-Id: <1512463189-24724-6-git-send-email-nborisov@suse.com> In-Reply-To: <1512463189-24724-1-git-send-email-nborisov@suse.com> References: <1512463189-24724-1-git-send-email-nborisov@suse.com> Sender: linux-btrfs-owner@vger.kernel.org List-ID: Signed-off-by: Nikolay Borisov --- 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. + */ int btrfs_read_dev_super(int fd, struct btrfs_super_block *sb, u64 sb_bytenr, unsigned sbflags) { -- 2.7.4