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Date: Fri, 07 Jun 2024 09:47:03 +0800
From: "Huang, Ying" <ying.huang@...el.com>
To: Yosry Ahmed <yosryahmed@...gle.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm: swap: remove 'synchronous' argument to
swap_read_folio()
Yosry Ahmed <yosryahmed@...gle.com> writes:
> swap_read_folio() reads the folio synchronously if synchronous is passed
> as true or if SWP_SYNCHRONOUS_IO is set in swap_info_struct. The only
> caller that passes synchronous=true is in do_swap_page() in the
> SWP_SYNCHRONOUS_IO case.
>
> Hence, the argument is redundant, it is only set to true when the swap
> read would have been synchronous anyway. Remove it.
>
> Signed-off-by: Yosry Ahmed <yosryahmed@...gle.com>
LGTM, Thanks!
Reviewed-by: "Huang, Ying" <ying.huang@...el.com>
And, there's some history information in commit b243dcbf2f13 ("swap:
remove remnants of polling from read_swap_cache_async").
"
Commit [1] introduced IO polling support duding swapin to reduce swap read
latency for block devices that can be polled. However later commit [2]
removed polling support. Therefore it seems safe to remove do_poll
parameter in read_swap_cache_async and always call swap_readpage with
synchronous=false waiting for IO completion in folio_lock_or_retry.
[1] commit 23955622ff8d ("swap: add block io poll in swapin path")
[2] commit 9650b453a3d4 ("block: ignore RWF_HIPRI hint for sync dio")
"
IMO, it will help people to understand the code change to add some
history information as above, or refer to the commit.
--
Best Regards,
Huang, Ying
> ---
> mm/memory.c | 2 +-
> mm/page_io.c | 6 +++---
> mm/swap.h | 6 ++----
> mm/swap_state.c | 10 +++++-----
> 4 files changed, 11 insertions(+), 13 deletions(-)
>
> diff --git a/mm/memory.c b/mm/memory.c
> index db91304882312..2b3ef08e8bb7d 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -4113,7 +4113,7 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
>
> /* To provide entry to swap_read_folio() */
> folio->swap = entry;
> - swap_read_folio(folio, true, NULL);
> + swap_read_folio(folio, NULL);
> folio->private = NULL;
> }
> } else {
> diff --git a/mm/page_io.c b/mm/page_io.c
> index 41e8d738c6d28..f1a9cfab6e748 100644
> --- a/mm/page_io.c
> +++ b/mm/page_io.c
> @@ -493,10 +493,10 @@ static void swap_read_folio_bdev_async(struct folio *folio,
> submit_bio(bio);
> }
>
> -void swap_read_folio(struct folio *folio, bool synchronous,
> - struct swap_iocb **plug)
> +void swap_read_folio(struct folio *folio, struct swap_iocb **plug)
> {
> struct swap_info_struct *sis = swp_swap_info(folio->swap);
> + bool synchronous = sis->flags & SWP_SYNCHRONOUS_IO;
> bool workingset = folio_test_workingset(folio);
> unsigned long pflags;
> bool in_thrashing;
> @@ -521,7 +521,7 @@ void swap_read_folio(struct folio *folio, bool synchronous,
> folio_unlock(folio);
> } else if (data_race(sis->flags & SWP_FS_OPS)) {
> swap_read_folio_fs(folio, plug);
> - } else if (synchronous || (sis->flags & SWP_SYNCHRONOUS_IO)) {
> + } else if (synchronous) {
> swap_read_folio_bdev_sync(folio, sis);
> } else {
> swap_read_folio_bdev_async(folio, sis);
> diff --git a/mm/swap.h b/mm/swap.h
> index 2c0e96272d498..baa1fa946b347 100644
> --- a/mm/swap.h
> +++ b/mm/swap.h
> @@ -11,8 +11,7 @@ struct mempolicy;
> /* linux/mm/page_io.c */
> int sio_pool_init(void);
> struct swap_iocb;
> -void swap_read_folio(struct folio *folio, bool do_poll,
> - struct swap_iocb **plug);
> +void swap_read_folio(struct folio *folio, struct swap_iocb **plug);
> void __swap_read_unplug(struct swap_iocb *plug);
> static inline void swap_read_unplug(struct swap_iocb *plug)
> {
> @@ -83,8 +82,7 @@ static inline unsigned int folio_swap_flags(struct folio *folio)
> }
> #else /* CONFIG_SWAP */
> struct swap_iocb;
> -static inline void swap_read_folio(struct folio *folio, bool do_poll,
> - struct swap_iocb **plug)
> +static inline void swap_read_folio(struct folio *folio, struct swap_iocb **plug)
> {
> }
> static inline void swap_write_unplug(struct swap_iocb *sio)
> diff --git a/mm/swap_state.c b/mm/swap_state.c
> index 0803eedeabe3d..994723cef8217 100644
> --- a/mm/swap_state.c
> +++ b/mm/swap_state.c
> @@ -567,7 +567,7 @@ struct folio *read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask,
> mpol_cond_put(mpol);
>
> if (page_allocated)
> - swap_read_folio(folio, false, plug);
> + swap_read_folio(folio, plug);
> return folio;
> }
>
> @@ -684,7 +684,7 @@ struct folio *swap_cluster_readahead(swp_entry_t entry, gfp_t gfp_mask,
> if (!folio)
> continue;
> if (page_allocated) {
> - swap_read_folio(folio, false, &splug);
> + swap_read_folio(folio, &splug);
> if (offset != entry_offset) {
> folio_set_readahead(folio);
> count_vm_event(SWAP_RA);
> @@ -701,7 +701,7 @@ struct folio *swap_cluster_readahead(swp_entry_t entry, gfp_t gfp_mask,
> &page_allocated, false);
> if (unlikely(page_allocated)) {
> zswap_folio_swapin(folio);
> - swap_read_folio(folio, false, NULL);
> + swap_read_folio(folio, NULL);
> }
> return folio;
> }
> @@ -834,7 +834,7 @@ static struct folio *swap_vma_readahead(swp_entry_t targ_entry, gfp_t gfp_mask,
> if (!folio)
> continue;
> if (page_allocated) {
> - swap_read_folio(folio, false, &splug);
> + swap_read_folio(folio, &splug);
> if (addr != vmf->address) {
> folio_set_readahead(folio);
> count_vm_event(SWAP_RA);
> @@ -853,7 +853,7 @@ static struct folio *swap_vma_readahead(swp_entry_t targ_entry, gfp_t gfp_mask,
> &page_allocated, false);
> if (unlikely(page_allocated)) {
> zswap_folio_swapin(folio);
> - swap_read_folio(folio, false, NULL);
> + swap_read_folio(folio, NULL);
> }
> return folio;
> }
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