On Wed, 2024-07-17 at 13:31 +0200, Jan Kara wrote:

On Mon 15-07-24 08:48:56, Jeff Layton wrote:

quoted

Add a high-level document that describes how multigrain timestamps work,
rationale for them, and some info about implementation and tradeoffs.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Jeff Layton <jlayton@kernel.org>

One comment below. With that fixed feel free to add:

Reviewed-by: Jan Kara <jack@suse.cz>

quoted

+Implementation Notes
+====================
+Multigrain timestamps are intended for use by local filesystems that get
+ctime values from the local clock. This is in contrast to network filesystems
+and the like that just mirror timestamp values from a server.
+
+For most filesystems, it's sufficient to just set the FS_MGTIME flag in the
+fstype->fs_flags in order to opt-in, providing the ctime is only ever set via
+inode_set_ctime_current(). If the filesystem has a ->getattr routine that
+doesn't call generic_fillattr, then you should have it call fill_mg_cmtime to
+fill those values.

I think you should explicitely mention that ->setattr() implementation
needs to use setattr_copy() or otherwise mimic its behavior...

								Honza

I've added a sentence like you suggest to the patch in my tree. Thanks
for all the reviews!
-- 
Jeff Layton [off-list ref]