Re: [PATCH v4 11/19] mm, swap: split locked entry duplicating into a standalone helper

Baoquan He
2025-12-17T11:23:01Z

On 12/05/25 at 03:29am, Kairui Song wrote:
> From: Kairui Song <kasong@tencent.com>
>
> No feature change, split the common logic into a stand alone helper to
~~~~~~~~~~~
standalone, typo?
> be reused later.

In phase 2, I saw the newly added swap_dup_entries() is only called by
__swap_duplicate(). The 'reused later' means?

>
> Signed-off-by: Kairui Song <kasong@tencent.com>
> ---
> mm/swapfile.c | 62 +++++++++++++++++++++++++++++------------------------------
> 1 file changed, 31 insertions(+), 31 deletions(-)
>
> diff --git a/mm/swapfile.c b/mm/swapfile.c
> index 2703dfafc632..d9d943fc7b8d 100644
> --- a/mm/swapfile.c
> +++ b/mm/swapfile.c
> @@ -3666,26 +3666,14 @@ void si_swapinfo(struct sysinfo *val)
> * - swap-cache reference is requested but the entry is not used. -> ENOENT
> * - swap-mapped reference requested but needs continued swap count. -> ENOMEM
> */
> -static int __swap_duplicate(swp_entry_t entry, unsigned char usage, int nr)
> +static int swap_dup_entries(struct swap_info_struct *si,
> + struct swap_cluster_info *ci,
> + unsigned long offset,
> + unsigned char usage, int nr)
> {
> - struct swap_info_struct *si;
> - struct swap_cluster_info *ci;
> - unsigned long offset;
> - unsigned char count;
> - unsigned char has_cache;
> - int err, i;
> -
> - si = swap_entry_to_info(entry);
> - if (WARN_ON_ONCE(!si)) {
> - pr_err("%s%08lx\n", Bad_file, entry.val);
> - return -EINVAL;
> - }
> -
> - offset = swp_offset(entry);
> - VM_WARN_ON(nr > SWAPFILE_CLUSTER - offset % SWAPFILE_CLUSTER);
> - ci = swap_cluster_lock(si, offset);
> + int i;
> + unsigned char count, has_cache;
>
> - err = 0;
> for (i = 0; i < nr; i++) {
> count = si->swap_map[offset + i];
>
> @@ -3693,25 +3681,20 @@ static int __swap_duplicate(swp_entry_t entry, unsigned char usage, int nr)
> * Allocator never allocates bad slots, and readahead is guarded
> * by swap_entry_swapped.
> */
> - if (WARN_ON(swap_count(count) == SWAP_MAP_BAD)) {
> - err = -ENOENT;
> - goto unlock_out;
> - }
> + if (WARN_ON(swap_count(count) == SWAP_MAP_BAD))
> + return -ENOENT;
>
> has_cache = count & SWAP_HAS_CACHE;
> count &= ~SWAP_HAS_CACHE;
>
> if (!count && !has_cache) {
> - err = -ENOENT;
> + return -ENOENT;
> } else if (usage == SWAP_HAS_CACHE) {
> if (has_cache)
> - err = -EEXIST;
> + return -EEXIST;
> } else if ((count & ~COUNT_CONTINUED) > SWAP_MAP_MAX) {
> - err = -EINVAL;
> + return -EINVAL;
> }
> -
> - if (err)
> - goto unlock_out;
> }
>
> for (i = 0; i < nr; i++) {
> @@ -3730,14 +3713,31 @@ static int __swap_duplicate(swp_entry_t entry, unsigned char usage, int nr)
> * Don't need to rollback changes, because if
> * usage == 1, there must be nr == 1.
> */
> - err = -ENOMEM;
> - goto unlock_out;
> + return -ENOMEM;
> }
>
> WRITE_ONCE(si->swap_map[offset + i], count | has_cache);
> }
>
> -unlock_out:
> + return 0;
> +}
> +
> +static int __swap_duplicate(swp_entry_t entry, unsigned char usage, int nr)
> +{
> + int err;
> + struct swap_info_struct *si;
> + struct swap_cluster_info *ci;
> + unsigned long offset = swp_offset(entry);
> +
> + si = swap_entry_to_info(entry);
> + if (WARN_ON_ONCE(!si)) {
> + pr_err("%s%08lx\n", Bad_file, entry.val);
> + return -EINVAL;
> + }
> +
> + VM_WARN_ON(nr > SWAPFILE_CLUSTER - offset % SWAPFILE_CLUSTER);
> + ci = swap_cluster_lock(si, offset);
> + err = swap_dup_entries(si, ci, offset, usage, nr);
> swap_cluster_unlock(ci);
> return err;
> }
>
> --
> 2.52.0
>