[PATCH 1/2] btrfs-progs: prepare helper device_is_seed

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

load_device_info() checks if the device is a seed device by reading
superblock::fsid and comparing it with the mount fsid, and it fails
to work if the device is missing (a RAID1 seed fs). Move this part
of the code into a new helper function device_is_seed() in
preparation to make device_is_seed() work with the new sysfs
devinfo/<devid>/fsid interface.

Signed-off-by: Anand Jain <anand.jain@oracle.com>
---
 cmds/filesystem-usage.c | 21 ++++++++++++++++++---
 1 file changed, 18 insertions(+), 3 deletions(-)

diff --git a/cmds/filesystem-usage.c b/cmds/filesystem-usage.c
index 6c0f9aa977d6..0dfc798e8dcc 100644
--- a/cmds/filesystem-usage.c
+++ b/cmds/filesystem-usage.c
@@ -25,6 +25,7 @@
 #include <getopt.h>
 #include <fcntl.h>
 #include <linux/limits.h>
+#include <uuid/uuid.h>
 
 #include "common/utils.h"
 #include "kerncompat.h"
@@ -705,6 +706,21 @@ out:
 	return ret;
 }
 
+static int device_is_seed(const char *dev_path, u8 *mnt_fsid)
+{
+	uuid_t fsid;
+	int ret;
+
+	ret = dev_to_fsid(dev_path, fsid);
+	if (ret)
+		return ret;
+
+	if (memcmp(mnt_fsid, fsid, BTRFS_FSID_SIZE))
+		return 0;
+
+	return -1;
+}
+
 /*
  *  This function loads the device_info structure and put them in an array
  */
@@ -715,7 +731,6 @@ static int load_device_info(int fd, struct device_info **device_info_ptr,
 	struct btrfs_ioctl_fs_info_args fi_args;
 	struct btrfs_ioctl_dev_info_args dev_info;
 	struct device_info *info;
-	u8 fsid[BTRFS_UUID_SIZE];
 
 	*device_info_count = 0;
 	*device_info_ptr = NULL;
@@ -759,8 +774,8 @@ static int load_device_info(int fd, struct device_info **device_info_ptr,
 		 * Ignore any other error including -EACCES, which is seen when
 		 * a non-root process calls dev_to_fsid(path)->open(path).
 		 */
-		ret = dev_to_fsid((const char *)dev_info.path, fsid);
-		if (!ret && memcmp(fi_args.fsid, fsid, BTRFS_FSID_SIZE) != 0)
+		ret = device_is_seed((const char *)dev_info.path, fi_args.fsid);
+		if (!ret)
 			continue;
 
 		info[ndevs].devid = dev_info.devid;
-- 
2.31.1