[PATCH 12/29] xfs: enforce GFP_NOIO implicitly during nowait time update

[Matthew Wilcox]

On Fri, Aug 25, 2023 at 09:54:14PM +0800, Hao Xu wrote:
> +++ b/fs/xfs/xfs_iops.c
> @@ -1037,6 +1037,8 @@ xfs_vn_update_time(
>  	int			log_flags = XFS_ILOG_TIMESTAMP;
>  	struct xfs_trans	*tp;
>  	int			error;
> +	int			old_pflags;
> +	bool			nowait = flags & S_NOWAIT;
>  
>  	trace_xfs_update_time(ip);
>  
> @@ -1049,13 +1051,18 @@ xfs_vn_update_time(
>  		log_flags |= XFS_ILOG_CORE;
>  	}
>  
> +	if (nowait)
> +		old_pflags = memalloc_noio_save();
> +
>  	error = xfs_trans_alloc(mp, &M_RES(mp)->tr_fsyncts, 0, 0, 0, &tp);

This is an abuse of the memalloc_noio_save() interface.  You shouldn't
be setting it around individual allocations; it's the part of the kernel
which decides "I can't afford to do I/O" that should be setting it.
In this case, it should probably be set by io_uring, way way way up at
the top.

But Jens didn't actually answer my question about that:

https://lore.kernel.org/all/ZMhZh2EYPMH1wIXX@casper.infradead.org/