Re: [PATCH v3 05/13] mm, swap: clean up device availability check

Baoquan He
2025-01-09T04:08:51Z

On 12/31/24 at 01:46am, Kairui Song wrote:
> From: Kairui Song <kasong@tencent.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@tencent.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@redhat.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
>
>