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Message-ID: <Z39Lr5jUOTjESyf1@MiWiFi-R3L-srv>
Date: Thu, 9 Jan 2025 12:08:15 +0800
From: Baoquan He <bhe@...hat.com>
To: Kairui Song <kasong@...cent.com>
Cc: linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>,
	Chris Li <chrisl@...nel.org>, Barry Song <v-songbaohua@...o.com>,
	Ryan Roberts <ryan.roberts@....com>,
	Hugh Dickins <hughd@...gle.com>,
	Yosry Ahmed <yosryahmed@...gle.com>,
	"Huang, Ying" <ying.huang@...ux.alibaba.com>,
	Nhat Pham <nphamcs@...il.com>, Johannes Weiner <hannes@...xchg.org>,
	Kalesh Singh <kaleshsingh@...gle.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 05/13] mm, swap: clean up device availability check

On 12/31/24 at 01:46am, Kairui Song wrote:
> From: Kairui Song <kasong@...cent.com>
> 
> Remove highest_bit and lowest_bit. After the HDD allocation path
> has been removed, the only purpose of these two fields is to determine
> whether the device is full or not, which can instead be determined
> by checking the inuse_pages.
> 
> Signed-off-by: Kairui Song <kasong@...cent.com>
> ---
>  fs/btrfs/inode.c     |  1 -
>  fs/f2fs/data.c       |  1 -
>  fs/iomap/swapfile.c  |  1 -
>  include/linux/swap.h |  2 --
>  mm/page_io.c         |  1 -
>  mm/swapfile.c        | 38 ++++++++------------------------------
>  6 files changed, 8 insertions(+), 36 deletions(-)

Reviewed-by: Baoquan He <bhe@...hat.com>

> 
> diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
> index 488edca8333a..a1ba78afab2c 100644
> --- a/fs/btrfs/inode.c
> +++ b/fs/btrfs/inode.c
> @@ -10044,7 +10044,6 @@ static int btrfs_swap_activate(struct swap_info_struct *sis, struct file *file,
>  	*span = bsi.highest_ppage - bsi.lowest_ppage + 1;
>  	sis->max = bsi.nr_pages;
>  	sis->pages = bsi.nr_pages - 1;
> -	sis->highest_bit = bsi.nr_pages - 1;
>  	return bsi.nr_extents;
>  }
>  #else
> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
> index a2478c2afb3a..a9eddd782dbc 100644
> --- a/fs/f2fs/data.c
> +++ b/fs/f2fs/data.c
> @@ -4043,7 +4043,6 @@ static int check_swap_activate(struct swap_info_struct *sis,
>  		cur_lblock = 1;	/* force Empty message */
>  	sis->max = cur_lblock;
>  	sis->pages = cur_lblock - 1;
> -	sis->highest_bit = cur_lblock - 1;
>  out:
>  	if (not_aligned)
>  		f2fs_warn(sbi, "Swapfile (%u) is not align to section: 1) creat(), 2) ioctl(F2FS_IOC_SET_PIN_FILE), 3) fallocate(%lu * N)",
> diff --git a/fs/iomap/swapfile.c b/fs/iomap/swapfile.c
> index 5fc0ac36dee3..b90d0eda9e51 100644
> --- a/fs/iomap/swapfile.c
> +++ b/fs/iomap/swapfile.c
> @@ -189,7 +189,6 @@ int iomap_swapfile_activate(struct swap_info_struct *sis,
>  	*pagespan = 1 + isi.highest_ppage - isi.lowest_ppage;
>  	sis->max = isi.nr_pages;
>  	sis->pages = isi.nr_pages - 1;
> -	sis->highest_bit = isi.nr_pages - 1;
>  	return isi.nr_extents;
>  }
>  EXPORT_SYMBOL_GPL(iomap_swapfile_activate);
> diff --git a/include/linux/swap.h b/include/linux/swap.h
> index 0c681aa5cb98..0c222017b5c6 100644
> --- a/include/linux/swap.h
> +++ b/include/linux/swap.h
> @@ -306,8 +306,6 @@ struct swap_info_struct {
>  	struct list_head frag_clusters[SWAP_NR_ORDERS];
>  					/* list of cluster that are fragmented or contented */
>  	unsigned int frag_cluster_nr[SWAP_NR_ORDERS];
> -	unsigned int lowest_bit;	/* index of first free in swap_map */
> -	unsigned int highest_bit;	/* index of last free in swap_map */
>  	unsigned int pages;		/* total of usable pages of swap */
>  	unsigned int inuse_pages;	/* number of those currently in use */
>  	struct percpu_cluster __percpu *percpu_cluster; /* per cpu's swap location */
> diff --git a/mm/page_io.c b/mm/page_io.c
> index 4b4ea8e49cf6..9b983de351f9 100644
> --- a/mm/page_io.c
> +++ b/mm/page_io.c
> @@ -163,7 +163,6 @@ int generic_swapfile_activate(struct swap_info_struct *sis,
>  		page_no = 1;	/* force Empty message */
>  	sis->max = page_no;
>  	sis->pages = page_no - 1;
> -	sis->highest_bit = page_no - 1;
>  out:
>  	return ret;
>  bad_bmap:
> diff --git a/mm/swapfile.c b/mm/swapfile.c
> index d0e5b9fa0c48..7963a0c646a4 100644
> --- a/mm/swapfile.c
> +++ b/mm/swapfile.c
> @@ -55,7 +55,7 @@ static bool swap_count_continued(struct swap_info_struct *, pgoff_t,
>  static void free_swap_count_continuations(struct swap_info_struct *);
>  static void swap_entry_range_free(struct swap_info_struct *si, swp_entry_t entry,
>  				  unsigned int nr_pages);
> -static void swap_range_alloc(struct swap_info_struct *si, unsigned long offset,
> +static void swap_range_alloc(struct swap_info_struct *si,
>  			     unsigned int nr_entries);
>  static bool folio_swapcache_freeable(struct folio *folio);
>  static struct swap_cluster_info *lock_cluster(struct swap_info_struct *si,
> @@ -650,7 +650,7 @@ static bool cluster_alloc_range(struct swap_info_struct *si, struct swap_cluster
>  	}
>  
>  	memset(si->swap_map + start, usage, nr_pages);
> -	swap_range_alloc(si, start, nr_pages);
> +	swap_range_alloc(si, nr_pages);
>  	ci->count += nr_pages;
>  
>  	if (ci->count == SWAPFILE_CLUSTER) {
> @@ -888,19 +888,11 @@ static void del_from_avail_list(struct swap_info_struct *si)
>  	spin_unlock(&swap_avail_lock);
>  }
>  
> -static void swap_range_alloc(struct swap_info_struct *si, unsigned long offset,
> +static void swap_range_alloc(struct swap_info_struct *si,
>  			     unsigned int nr_entries)
>  {
> -	unsigned int end = offset + nr_entries - 1;
> -
> -	if (offset == si->lowest_bit)
> -		si->lowest_bit += nr_entries;
> -	if (end == si->highest_bit)
> -		WRITE_ONCE(si->highest_bit, si->highest_bit - nr_entries);
>  	WRITE_ONCE(si->inuse_pages, si->inuse_pages + nr_entries);
>  	if (si->inuse_pages == si->pages) {
> -		si->lowest_bit = si->max;
> -		si->highest_bit = 0;
>  		del_from_avail_list(si);
>  
>  		if (si->cluster_info && vm_swap_full())
> @@ -933,15 +925,8 @@ static void swap_range_free(struct swap_info_struct *si, unsigned long offset,
>  	for (i = 0; i < nr_entries; i++)
>  		clear_bit(offset + i, si->zeromap);
>  
> -	if (offset < si->lowest_bit)
> -		si->lowest_bit = offset;
> -	if (end > si->highest_bit) {
> -		bool was_full = !si->highest_bit;
> -
> -		WRITE_ONCE(si->highest_bit, end);
> -		if (was_full && (si->flags & SWP_WRITEOK))
> -			add_to_avail_list(si);
> -	}
> +	if (si->inuse_pages == si->pages)
> +		add_to_avail_list(si);
>  	if (si->flags & SWP_BLKDEV)
>  		swap_slot_free_notify =
>  			si->bdev->bd_disk->fops->swap_slot_free_notify;
> @@ -1051,15 +1036,12 @@ int get_swap_pages(int n_goal, swp_entry_t swp_entries[], int entry_order)
>  		plist_requeue(&si->avail_lists[node], &swap_avail_heads[node]);
>  		spin_unlock(&swap_avail_lock);
>  		spin_lock(&si->lock);
> -		if (!si->highest_bit || !(si->flags & SWP_WRITEOK)) {
> +		if ((si->inuse_pages == si->pages) || !(si->flags & SWP_WRITEOK)) {
>  			spin_lock(&swap_avail_lock);
>  			if (plist_node_empty(&si->avail_lists[node])) {
>  				spin_unlock(&si->lock);
>  				goto nextsi;
>  			}
> -			WARN(!si->highest_bit,
> -			     "swap_info %d in list but !highest_bit\n",
> -			     si->type);
>  			WARN(!(si->flags & SWP_WRITEOK),
>  			     "swap_info %d in list but !SWP_WRITEOK\n",
>  			     si->type);
> @@ -2441,8 +2423,8 @@ static void _enable_swap_info(struct swap_info_struct *si)
>  	 */
>  	plist_add(&si->list, &swap_active_head);
>  
> -	/* add to available list iff swap device is not full */
> -	if (si->highest_bit)
> +	/* add to available list if swap device is not full */
> +	if (si->inuse_pages < si->pages)
>  		add_to_avail_list(si);
>  }
>  
> @@ -2606,7 +2588,6 @@ SYSCALL_DEFINE1(swapoff, const char __user *, specialfile)
>  	drain_mmlist();
>  
>  	/* wait for anyone still in scan_swap_map_slots */
> -	p->highest_bit = 0;		/* cuts scans short */
>  	while (p->flags >= SWP_SCANNING) {
>  		spin_unlock(&p->lock);
>  		spin_unlock(&swap_lock);
> @@ -2941,8 +2922,6 @@ static unsigned long read_swap_header(struct swap_info_struct *si,
>  		return 0;
>  	}
>  
> -	si->lowest_bit  = 1;
> -
>  	maxpages = swapfile_maximum_size;
>  	last_page = swap_header->info.last_page;
>  	if (!last_page) {
> @@ -2959,7 +2938,6 @@ static unsigned long read_swap_header(struct swap_info_struct *si,
>  		if ((unsigned int)maxpages == 0)
>  			maxpages = UINT_MAX;
>  	}
> -	si->highest_bit = maxpages - 1;
>  
>  	if (!maxpages)
>  		return 0;
> -- 
> 2.47.1
> 
> 


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