Re: [PATCH 2/3] btrfs-progs: latest_devid is not always the probed devid

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On 26/02/2014 01:27, David Sterba wrote:
On Mon, Feb 24, 2014 at 07:43:38PM +0800, Anand Jain wrote:
@@ -1646,6 +1646,11 @@ int get_fs_info(char *path, struct btrfs_ioctl_fs_info_args *fi_args,
  	memset(fi_args, 0, sizeof(*fi_args));

  	if (is_block_device(path)) {
+
+		struct btrfs_super_block *disk_super;
+		char *buf;
+		u64 devid;
+
  		/* Ensure it's mounted, then set path to the mountpoint */
  		fd = open(path, O_RDONLY);
  		if (fd < 0) {
@@ -1665,8 +1670,23 @@ int get_fs_info(char *path, struct btrfs_ioctl_fs_info_args *fi_args,
  		path = mp;
  		/* Only fill in this one device */
  		fi_args->num_devices = 1;
-		fi_args->max_id = fs_devices_mnt->latest_devid;
-		i = fs_devices_mnt->latest_devid;
+
+		buf = malloc(4096);
+		if (!buf) {
+			ret = -ENOMEM;
+			goto out;
+		}
+		disk_super = (struct btrfs_super_block *)buf;
+		ret = btrfs_read_dev_super(fd, disk_super, BTRFS_SUPER_INFO_OFFSET);
+		if (ret < 0) {
+			ret = -EIO;
+			goto out;
+		}
+		devid = btrfs_stack_device_id(&disk_super->dev_item);
+
+		fi_args->max_id = devid;
+		i = devid;
+
  		memcpy(fi_args->fsid, fs_devices_mnt->fsid, BTRFS_FSID_SIZE);
  		close(fd);

This is leaking memory, but as this is userspace code we can use the
staack for the superblock. I've committed this with the following fixup:

 oh no my bad. thanks for the catch.



--- a/utils.c
+++ b/utils.c
@@ -1680,7 +1680,7 @@ int get_fs_info(char *path, struct btrfs_ioctl_fs_info_args *fi_args,
         if (is_block_device(path)) {

                 struct btrfs_super_block *disk_super;
-               char *buf;
+               char buf[BTRFS_SUPER_INFO_SIZE];
                 u64 devid;

                 /* Ensure it's mounted, then set path to the mountpoint */
@@ -1703,11 +1703,6 @@ int get_fs_info(char *path, struct btrfs_ioctl_fs_info_args *fi_args,
                 /* Only fill in this one device */
                 fi_args->num_devices = 1;

-               buf = malloc(4096);
-               if (!buf) {
-                       ret = -ENOMEM;
-                       goto out;
-               }
                 disk_super = (struct btrfs_super_block *)buf;
                 ret = btrfs_read_dev_super(fd, disk_super, BTRFS_SUPER_INFO_OFFSET);
                 if (ret < 0) {

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