[systemd-devel] [EXT] Re: [PATCH] libblkid: fix spurious ext superblock checksum mismatches

[Windl, Ulrich]

> -----Original Message-----
> From: systemd-devel <systemd-devel-bounces at lists.freedesktop.org> On
> Behalf Of Krister Johansen
> Sent: Tuesday, November 19, 2024 12:14 AM
> To: Lennart Poettering <lennart at poettering.net>
> Cc: util-linux at vger.kernel.org; Karel Zak <kzak at redhat.com>; systemd-
> devel at lists.freedesktop.org; David Reaver <me at davidreaver.com>;
> Theodore Ts'o <tytso at mit.edu>
> Subject: [EXT] Re: [systemd-devel] [PATCH] libblkid: fix spurious ext
> superblock checksum mismatches
> 
... 
> I may have done a poor job of explaining this.  This is ext writing its
> own superblock from the kernel, but reads seeing an potentially
> inconsistent view of that write.  O_DIRECT causes us to seralize with
> the locks ext4 holds when it writes the superblock, which prevents the
> read from observing a partial update.
> 
> It's not necessarily the partitioning tools causing this, but any
> filesystem level udpdate that modifies the contents of the superblock.

As I wrote before: I don't think the needless O_DIRECT fixes things some other code broke.