Re: [PATCH] xfs: fix fallback data device flush for realtime inodes

[Christoph Hellwig]

On Wed, Jul 29, 2026 at 03:39:18PM +0800, Hongling Zeng wrote:
> xfs_file_fsync() has a fallback flush for the case where the log force
> was a no-op, for example fdatasync/O_DSYNC overwrites of already
> allocated file data with no metadata updates.
> 
> The current fallback path is limited to non-realtime inodes and always
> flushes mp->m_ddev_targp. This misses realtime inodes whose data target
> is selected by the inode and may be mp->m_rtdev_targp.

No.  The rt device is flushed before the called to xfs_fsync_flush_log,
as we need to ensure that the data is flushed from the cache before
the log commit.  For the data device, the REQ_PREFLUSH case takes
care that.  After xfs_fsync_flush_log we only need to take care of
the data device if the file is on the data device and the cache
wasn't flushed as part of the log commit.