Merge patch series "re-enable IOCB_NOWAIT writes to files v6"

Christoph Hellwig <hch@lst.de> says:

Hi all,

commit 66fa3cedf16a ("fs: Add async write file modification handling.")
effectively disabled IOCB_NOWAIT writes as timestamp updates currently
always require blocking, and the modern timestamp resolution means we
always update timestamps.  This leads to a lot of context switches from
applications using io_uring to submit file writes, making it often worse
than using the legacy aio code that is not using IOCB_NOWAIT.

This series allows non-blocking updates for lazytime if the file system
supports it, and adds that support for XFS.

* patches from https://patch.msgid.link/20260108141934.2052404-1-hch@lst.de:
  xfs: enable non-blocking timestamp updates
  xfs: implement ->sync_lazytime
  fs: refactor file_update_time_flags
  fs: add support for non-blocking timestamp updates
  fs: add a ->sync_lazytime method
  fs: factor out a sync_lazytime helper
  fs: refactor ->update_time handling
  fat: cleanup the flags for fat_truncate_time
  nfs: split nfs_update_timestamps
  fs: allow error returns from generic_update_time
  fs: remove inode_update_time

Link: https://patch.msgid.link/20260108141934.2052404-1-hch@lst.de
Signed-off-by: Christian Brauner <brauner@kernel.org>