[PATCH v2] btrfs-progs: there is devid 0 when replace is running

[Anand Jain <anand.jain@oracle.com>]

During disk replacement a new disk is temporarily
added to the fs devlist with devid 0 and fs num_device is
incremented by 1. However when progs reads the devlist it
fail to obtain details of devid 0 because it doesn't query
devid 0 at all.

reproducer:

 btrfs rep start /dev/sdb /dev/sdf /btrfs
 btrfs fi show
 Label: none  uuid: f8fb9819-16c8-47b7-b62f-0ff90f8c56cd
        Total devices 3 FS bytes used 1.94GiB
        devid    1 size 1.10GiB used 1.10GiB path /dev/sdb
        devid    2 size 1.10GiB used 1.08GiB path /dev/sdc
        devid    0 size 0.00 used 0.00 path

  this patch will make it proper by querying devid 0.

 btrfs repl start /dev/sdb /dev/sdf /btrfs
 btrfs fi show /btrfs
 Label: none  uuid: f8fb9819-16c8-47b7-b62f-0ff90f8c56cd
        Total devices 3 FS bytes used 1.94GiB
        devid    0 size 1.10GiB used 1.10GiB path /dev/sdf
        devid    1 size 1.10GiB used 1.10GiB path /dev/sdb
        devid    2 size 1.10GiB used 1.08GiB path /dev/sdc

 Its fine to query devid 0 when there is no replace
 activity as well, because we just skip the error ENODEV

 btrfs fi show /btrfs
 Label: none  uuid: f8fb9819-16c8-47b7-b62f-0ff90f8c56cd
        Total devices 2 FS bytes used 1.94GiB
        devid    1 size 1.10GiB used 1.10GiB path /dev/sdf
        devid    2 size 1.10GiB used 1.08GiB path /dev/sdc
---

 v2: fix commit message

 utils.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/utils.c b/utils.c
index de513b6..a045ffd 100644
--- a/utils.c
+++ b/utils.c
@@ -1696,7 +1696,7 @@ int get_fs_info(char *path, struct btrfs_ioctl_fs_info_args *fi_args,
 		goto out;
 	}
 
-	for (; i <= fi_args->max_id; ++i) {
+	for (i = 0; i <= fi_args->max_id; ++i) {
 		BUG_ON(ndevs >= fi_args->num_devices);
 		ret = get_device_info(fd, i, &di_args[ndevs]);
 		if (ret == -ENODEV)
-- 
1.7.1