Fixing the ‘btrfs block device size is smaller than total_bytes in device item’ Error

Recently, I ran into a problem with an old SSD formatted with btrfs. The filesystem refused to mount. Checking dmesg I had an error stating that "the device total_bytes should be at most NUMBER1 but found NUBMER2", where NUMBER1 is less than NUMBER2.

The solution is to use the relatively new fix-device-size feature in btrfs rescue. This was added sometime after 2022, likely in Linux 6.3 (the patch to add this feature was submitted in the kernel developer mailing list in mid-2022). At the moment, I can confirm that 6.4.13 has this feature. Syntax wise, the command is:

btrfs rescue fix-device-size <device>

Just replace <device> with the /dev/ path to the device you are having issues mounting due to the size missmatch. This should work for most cases where the total_bytes for the device is only ‘slightly’ larger than the actual device size.

-John Havlik