On 2021/5/24 20:06, Christoph Hellwig wrote:
> Please just fold it into the only caller and update the comments
> referring to it. Something like:
Sounds reasonable. Many thanks for your suggestion! Will do it in next version.
>
> diff --git a/mm/swapfile.c b/mm/swapfile.c
> index 149e77454e3c..0e575b45bb87 100644
> --- a/mm/swapfile.c
> +++ b/mm/swapfile.c
> @@ -452,10 +452,10 @@ static void swap_cluster_schedule_discard(struct swap_info_struct *si,
> unsigned int idx)
> {
> /*
> - * If scan_swap_map() can't find a free cluster, it will check
> + * If scan_swap_map_slots() can't find a free cluster, it will check
> * si->swap_map directly. To make sure the discarding cluster isn't
> - * taken by scan_swap_map(), mark the swap entries bad (occupied). It
> - * will be cleared after discard
> + * taken by scan_swap_map_slots(), mark the swap entries bad (occupied).
> + * It will be cleared after discard
> */
> memset(si->swap_map + idx * SWAPFILE_CLUSTER,
> SWAP_MAP_BAD, SWAPFILE_CLUSTER);
> @@ -580,7 +580,7 @@ static void dec_cluster_info_page(struct swap_info_struct *p,
> }
>
> /*
> - * It's possible scan_swap_map() uses a free cluster in the middle of free
> + * It's possible scan_swap_map_slots() uses a free cluster in the middle of free
> * cluster list. Avoiding such abuse to avoid list corruption.
> */
> static bool
> @@ -1028,21 +1028,6 @@ static void swap_free_cluster(struct swap_info_struct *si, unsigned long idx)
> swap_range_free(si, offset, SWAPFILE_CLUSTER);
> }
>
> -static unsigned long scan_swap_map(struct swap_info_struct *si,
> - unsigned char usage)
> -{
> - swp_entry_t entry;
> - int n_ret;
> -
> - n_ret = scan_swap_map_slots(si, usage, 1, &entry);
> -
> - if (n_ret)
> - return swp_offset(entry);
> - else
> - return 0;
> -
> -}
> -
> int get_swap_pages(int n_goal, swp_entry_t swp_entries[], int entry_size)
> {
> unsigned long size = swap_entry_size(entry_size);
> @@ -1105,14 +1090,14 @@ int get_swap_pages(int n_goal, swp_entry_t swp_entries[], int entry_size)
> nextsi:
> /*
> * if we got here, it's likely that si was almost full before,
> - * and since scan_swap_map() can drop the si->lock, multiple
> - * callers probably all tried to get a page from the same si
> - * and it filled up before we could get one; or, the si filled
> - * up between us dropping swap_avail_lock and taking si->lock.
> - * Since we dropped the swap_avail_lock, the swap_avail_head
> - * list may have been modified; so if next is still in the
> - * swap_avail_head list then try it, otherwise start over
> - * if we have not gotten any slots.
> + * and since scan_swap_map_slots() can drop the si->lock,
> + * multiple callers probably all tried to get a page from the
> + * same si and it filled up before we could get one; or, the si
> + * filled up between us dropping swap_avail_lock and taking
> + * si->lock. Since we dropped the swap_avail_lock, the
> + * swap_avail_head list may have been modified; so if next is
> + * still in the swap_avail_head list then try it, otherwise
> + * start over if we have not gotten any slots.
> */
> if (plist_node_empty(&next->avail_lists[node]))
> goto start_over;
> @@ -1132,24 +1117,18 @@ int get_swap_pages(int n_goal, swp_entry_t swp_entries[], int entry_size)
> swp_entry_t get_swap_page_of_type(int type)
> {
> struct swap_info_struct *si = swap_type_to_swap_info(type);
> - pgoff_t offset;
> + swp_entry_t entry = { };
>
> if (!si)
> goto fail;
>
> + /* This is called for allocating swap entry, not cache */
> spin_lock(&si->lock);
> - if (si->flags & SWP_WRITEOK) {
> - /* This is called for allocating swap entry, not cache */
> - offset = scan_swap_map(si, 1);
> - if (offset) {
> - atomic_long_dec(&nr_swap_pages);
> - spin_unlock(&si->lock);
> - return swp_entry(type, offset);
> - }
> - }
> + if ((si->flags & SWP_WRITEOK) && scan_swap_map_slots(si, 1, 1, &entry))
> + atomic_long_dec(&nr_swap_pages);
> spin_unlock(&si->lock);
> fail:
> - return (swp_entry_t) {0};
> + return entry;
> }
>
> static struct swap_info_struct *__swap_info_get(swp_entry_t entry)
> .
>
