Re: [PATCH 5/5] fs/buffer: reduce stack usage on bh_read_iter()

[Luis Chamberlain <mcgrof@kernel.org>]

On Tue, Dec 17, 2024 at 06:26:26PM -0800, Luis Chamberlain wrote:
> Now that we can read asynchronously buffer heads from a folio in
> chunks,  we can chop up bh_read_iter() with a smaller array size.
> Use an array of 8 to avoid stack growth warnings on systems with
> huge base page sizes.
> 
> Reviewed-by: Hannes Reinecke <hare@suse.de>
> Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
> ---
>  fs/buffer.c | 15 ++++++++++-----
>  1 file changed, 10 insertions(+), 5 deletions(-)
> 
> diff --git a/fs/buffer.c b/fs/buffer.c
> index b8ba72f2f211..bfa9c09b8597 100644
> --- a/fs/buffer.c
> +++ b/fs/buffer.c
> @@ -2415,7 +2415,10 @@ static void bh_read_batch_async(struct folio *folio,
>           (__tmp);					\
>           (__tmp) = bh_next(__tmp, __head))
>  
> +#define MAX_BUF_CHUNK 8
> +
>  struct bh_iter {
> +	int chunk_number;
>  	sector_t iblock;
>  	get_block_t *get_block;
>  	bool any_get_block_error;

Oh... this can be cleaned up even further, chunk_idx and be removed now,
and we can also remove the unused i variable... I'll wait for more
feedback for a v2.

  Luis