Re: [PATCH] mm: Split BLK_FEAT_SYNCHRONOUS and SWP_SYNCHRONOUS_IO into separate read and write flags

[Christoph Hellwig]

On Fri, Oct 11, 2024 at 05:11:33PM +0800, Qun-Wei Lin wrote:
> This patch splits the BLK_FEAT_SYNCHRONOUS feature flag into two
> separate flags: BLK_FEAT_READ_SYNCHRONOUS and
> BLK_FEAT_WRITE_SYNCHRONOUS. Similarly, the SWP_SYNCHRONOUS_IO flag is
> split into SWP_READ_SYNCHRONOUS_IO and SWP_WRITE_SYNCHRONOUS_IO.
> 
> These changes are motivated by the need to better accommodate certain
> swap devices that support synchronous read operations but asynchronous write
> operations.
> 
> The existing BLK_FEAT_SYNCHRONOUS and SWP_SYNCHRONOUS_IO flags are not
> sufficient for these devices, as they enforce synchronous behavior for
> both read and write operations.

You're still failing to provide a user.  Without that it is dead in
the water from the very beginning.