Re: [PATCH RFC 1/4] md/dm-integrity: replace async_tx with synchronous xor for journal

[Mikulas Patocka <mpatocka@redhat.com>]

On Thu, 15 Oct 2026, Frank.Li@oss.nxp.com wrote:

> From: Frank Li <Frank.Li@nxp.com>
> 
> Remove the dependency on the async_tx framework from dm-integrity's
> xor_journal() function.  The async_xor() + async_tx_issue_pending_all()
> pattern is replaced with direct kmap_local_page() + memcpy() +
> crypto_xor() + kunmap_local() per page, which is simpler and removes
> the need for #include <linux/async_tx.h>.
> 
> async_tx adds significant complexity and maintenance overhead while
> providing little practical benefit on modern systems, where RAID parity
> computation is typically performed more efficiently by CPU-based XOR/PQ
> implementations than by DMA engine offload.
> 
> Signed-off-by: Frank Li <Frank.Li@nxp.com>

Reviewed-by: Mikulas Patocka <mpatocka@redhat.com>

> ---
>  drivers/md/dm-integrity.c | 26 ++++++++++++++------------
>  1 file changed, 14 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/md/dm-integrity.c b/drivers/md/dm-integrity.c
> index 802b377613b06..6bd0623b6402a 100644
> --- a/drivers/md/dm-integrity.c
> +++ b/drivers/md/dm-integrity.c
> @@ -23,7 +23,6 @@
>  #include <crypto/hash.h>
>  #include <crypto/skcipher.h>
>  #include <crypto/utils.h>
> -#include <linux/async_tx.h>
>  #include <linux/dm-bufio.h>
>  
>  #include "dm-audit.h"
> @@ -896,7 +895,6 @@ static void complete_journal_op(void *context)
>  static void xor_journal(struct dm_integrity_c *ic, bool encrypt, unsigned int section,
>  			unsigned int n_sections, struct journal_completion *comp)
>  {
> -	struct async_submit_ctl submit;
>  	size_t n_bytes = (size_t)(n_sections * ic->journal_section_sectors) << SECTOR_SHIFT;
>  	unsigned int pl_index, pl_offset, section_index;
>  	struct page_list *source_pl, *target_pl;
> @@ -913,14 +911,11 @@ static void xor_journal(struct dm_integrity_c *ic, bool encrypt, unsigned int se
>  
>  	atomic_add(roundup(pl_offset + n_bytes, PAGE_SIZE) >> PAGE_SHIFT, &comp->in_flight);
>  
> -	init_async_submit(&submit, ASYNC_TX_XOR_ZERO_DST, NULL, complete_journal_op, comp, NULL);
> -
>  	section_index = pl_index;
>  
>  	do {
>  		size_t this_step;
> -		struct page *src_pages[2];
> -		struct page *dst_page;
> +		void *src0, *src1, *dst;
>  
>  		while (unlikely(pl_index == section_index)) {
>  			unsigned int dummy;
> @@ -935,11 +930,20 @@ static void xor_journal(struct dm_integrity_c *ic, bool encrypt, unsigned int se
>  		}
>  
>  		this_step = min(n_bytes, (size_t)PAGE_SIZE - pl_offset);
> -		dst_page = target_pl[pl_index].page;
> -		src_pages[0] = source_pl[pl_index].page;
> -		src_pages[1] = ic->journal_xor[pl_index].page;
>  
> -		async_xor(dst_page, src_pages, pl_offset, 2, this_step, &submit);
> +		src0 = kmap_local_page(source_pl[pl_index].page);
> +		src1 = kmap_local_page(ic->journal_xor[pl_index].page);
> +		dst  = kmap_local_page(target_pl[pl_index].page);
> +
> +		memcpy(dst + pl_offset, src0 + pl_offset, this_step);
> +		crypto_xor(dst + pl_offset, src1 + pl_offset, this_step);
> +
> +		kunmap_local(dst);
> +		kunmap_local(src1);
> +		kunmap_local(src0);
> +
> +		/* mirror async_tx per-page completion accounting */
> +		complete_journal_op(comp);
>  
>  		pl_index++;
>  		pl_offset = 0;
> @@ -947,8 +951,6 @@ static void xor_journal(struct dm_integrity_c *ic, bool encrypt, unsigned int se
>  	} while (n_bytes);
>  
>  	BUG_ON(n_sections);
> -
> -	async_tx_issue_pending_all();
>  }
>  
>  static void complete_journal_encrypt(void *data, int err)
> 
> -- 
> 2.43.0
>