linux-kernel - Re: [PATCH v4 09/12] mm/swap: get the swap device offset directly

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Date: Wed, 08 May 2024 14:28:38 +0800
From: "Huang, Ying" <ying.huang@...el.com>
To: Kairui Song <ryncsn@...il.com>
Cc: linux-mm@...ck.org,  Kairui Song <kasong@...cent.com>,  Andrew Morton
 <akpm@...ux-foundation.org>,  Matthew Wilcox <willy@...radead.org>,  Chris
 Li <chrisl@...nel.org>,  Barry Song <v-songbaohua@...o.com>,  Ryan Roberts
 <ryan.roberts@....com>,  Neil Brown <neilb@...e.de>,  Minchan Kim
 <minchan@...nel.org>,  Hugh Dickins <hughd@...gle.com>,  David Hildenbrand
 <david@...hat.com>,  Yosry Ahmed <yosryahmed@...gle.com>,
  linux-fsdevel@...r.kernel.org,  linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 09/12] mm/swap: get the swap device offset directly

Kairui Song <ryncsn@...il.com> writes:

> From: Kairui Song <kasong@...cent.com>
>
> folio_file_pos and page_file_offset are for mixed usage of swap cache
> and page cache, it can't be page cache here, so introduce a new helper
> to get the swap offset in swap device directly.
>
> Need to include swapops.h in mm/swap.h to ensure swp_offset is always
> defined before use.
>
> Signed-off-by: Kairui Song <kasong@...cent.com>

LGTM!  Thanks!

Reviewed-by: "Huang, Ying" <ying.huang@...el.com>

> ---
>  mm/page_io.c | 6 +++---
>  mm/swap.h    | 9 +++++++++
>  2 files changed, 12 insertions(+), 3 deletions(-)
>
> diff --git a/mm/page_io.c b/mm/page_io.c
> index 46c603dddf04..a360857cf75d 100644
> --- a/mm/page_io.c
> +++ b/mm/page_io.c
> @@ -280,7 +280,7 @@ static void sio_write_complete(struct kiocb *iocb, long ret)
>  		 * be temporary.
>  		 */
>  		pr_err_ratelimited("Write error %ld on dio swapfile (%llu)\n",
> -				   ret, page_file_offset(page));
> +				   ret, swap_dev_pos(page_swap_entry(page)));
>  		for (p = 0; p < sio->pages; p++) {
>  			page = sio->bvec[p].bv_page;
>  			set_page_dirty(page);
> @@ -299,7 +299,7 @@ static void swap_writepage_fs(struct folio *folio, struct writeback_control *wbc
>  	struct swap_iocb *sio = NULL;
>  	struct swap_info_struct *sis = swp_swap_info(folio->swap);
>  	struct file *swap_file = sis->swap_file;
> -	loff_t pos = folio_file_pos(folio);
> +	loff_t pos = swap_dev_pos(folio->swap);
>  
>  	count_swpout_vm_event(folio);
>  	folio_start_writeback(folio);
> @@ -430,7 +430,7 @@ static void swap_read_folio_fs(struct folio *folio, struct swap_iocb **plug)
>  {
>  	struct swap_info_struct *sis = swp_swap_info(folio->swap);
>  	struct swap_iocb *sio = NULL;
> -	loff_t pos = folio_file_pos(folio);
> +	loff_t pos = swap_dev_pos(folio->swap);
>  
>  	if (plug)
>  		sio = *plug;
> diff --git a/mm/swap.h b/mm/swap.h
> index fc2f6ade7f80..82023ab93205 100644
> --- a/mm/swap.h
> +++ b/mm/swap.h
> @@ -5,6 +5,7 @@
>  struct mempolicy;
>  
>  #ifdef CONFIG_SWAP
> +#include <linux/swapops.h> /* for swp_offset */
>  #include <linux/blk_types.h> /* for bio_end_io_t */
>  
>  /* linux/mm/page_io.c */
> @@ -31,6 +32,14 @@ extern struct address_space *swapper_spaces[];
>  	(&swapper_spaces[swp_type(entry)][swp_offset(entry) \
>  		>> SWAP_ADDRESS_SPACE_SHIFT])
>  
> +/*
> + * Return the swap device position of the swap entry.
> + */
> +static inline loff_t swap_dev_pos(swp_entry_t entry)
> +{
> +	return ((loff_t)swp_offset(entry)) << PAGE_SHIFT;
> +}
> +
>  void show_swap_cache_info(void);
>  bool add_to_swap(struct folio *folio);
>  void *get_shadow_from_swap_cache(swp_entry_t entry);