How to check the version of a XFS filesystem on a system, whether it is V5 or later?
Since version 3.15, the kernel tells you the version of XFS used in each filesystem as it mounts it;
dmesg | grep XFS should give you something like
[1578018.463269] XFS (loop0): Mounting V5 Filesystem
loop0 on your system you'll get the underlying device, and
V5 will be replaced by whatever version your filesystem uses.
Older kernels officially supported XFS version 4 filesystems, but could mount version 5 filesystems (since mid 2013); for the latter, the kernel would print
Version 5 superblock detected. This kernel has EXPERIMENTAL support enabled!
when the filesystem was mounted.
You can check the on disk format version of a XFS file system with
Example output of an old (V4) XFS file system on my system:
xfs_db -r /dev/... xfs_db> version versionnum [0xb5b4+0x8a] = V4,NLINK,DIRV2,ATTR,ALIGN,DALIGN,LOGV2,EXTFLG,MOREBITS,ATTR2,LAZYSBCOUNT,PROJID32BIT
Output of a new (V5) XFS file system (created with xfsprogs version 4.9.0):
xfs_db -r /dev/... xfs_db> version versionnum [0xb4a5+0x18a] = V5,NLINK,DIRV2,ALIGN,LOGV2,EXTFLG,MOREBITS,ATTR2,LAZYSBCOUNT,PROJID32BIT,CRC,FTYPE,FINOBT