[PATCH RFC 28/28] selftests/filesystems: test xfs remounts after a shutdown

[Christoph Hellwig]

On Mon, Oct 12, 2026 at 12:21:13PM +0200, Christian Brauner wrote:
> Add tests for remounting xfs after FS_IOC_SHUTDOWN with the default, the
> logflush and the nologflush flags and after a shutdown that the remount
> to read-only causes itself:
> 
> - option-only remount keeps it read-write
> - remount to read-only works
> - remount to read-write fails with EIO
> 
> For the last variant the image lives on a tmpfs of its own. The test
> punches out the log and shrinks the tmpfs so the log write during the
> remount fails with ENOSPC.

Please make this a xfstests test case, which has the infrastructure
for all this.  And make it generic, as the same shutdown ioctl is
supported by half a dozen file systems, nothing really xfs-specific
here.