Re: [PATCH] mmc: core: Use GFP_NOIO in ACMD22

[Adrian Hunter <adrian.hunter@intel.com>]

On 14/10/24 14:44, Avri Altman wrote:
> While reviewing the SDUC series, Adrian made a comment concerning the
> memory allocation code in mmc_sd_num_wr_blocks() - see [1].
> Prevent memory allocations from triggering I/O operations while ACMD22
> is in progress.
> 
> [1] https://www.spinics.net/lists/linux-mmc/msg82199.html
> 
> Suggested-by: Adrian Hunter <adrian.hunter@intel.com>
> Signed-off-by: Avri Altman <avri.altman@wdc.com>
> Cc: stable@vger.kernel.org
> ---
>  drivers/mmc/core/block.c | 10 +++++++++-
>  1 file changed, 9 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/mmc/core/block.c b/drivers/mmc/core/block.c
> index 04f3165cf9ae..042b0147d47e 100644
> --- a/drivers/mmc/core/block.c
> +++ b/drivers/mmc/core/block.c
> @@ -995,6 +995,8 @@ static int mmc_sd_num_wr_blocks(struct mmc_card *card, u32 *written_blocks)
>  	u32 result;
>  	__be32 *blocks;
>  	u8 resp_sz = mmc_card_ult_capacity(card) ? 8 : 4;
> +	unsigned int noio_flag;
> +
>  	struct mmc_request mrq = {};
>  	struct mmc_command cmd = {};
>  	struct mmc_data data = {};
> @@ -1018,9 +1020,13 @@ static int mmc_sd_num_wr_blocks(struct mmc_card *card, u32 *written_blocks)
>  	mrq.cmd = &cmd;
>  	mrq.data = &data;
>  
> +	noio_flag = memalloc_noio_save();
> +
>  	blocks = kmalloc(resp_sz, GFP_KERNEL);

Could have memalloc_noio_restore() here:

	memalloc_noio_restore(noio_flag);

but I feel maybe adding something like:

	u64 __aligned(8)	tiny_io_buf;

to either struct mmc_card or struct mmc_host is better?
Ulf, any thoughts?

> -	if (!blocks)
> +	if (!blocks) {
> +		memalloc_noio_restore(noio_flag);
>  		return -ENOMEM;
> +	}
>  
>  	sg_init_one(&sg, blocks, resp_sz);
>  
> @@ -1041,6 +1047,8 @@ static int mmc_sd_num_wr_blocks(struct mmc_card *card, u32 *written_blocks)
>  	}
>  	kfree(blocks);
>  
> +	memalloc_noio_restore(noio_flag);
> +
>  	if (cmd.error || data.error)
>  		return -EIO;
>