On Sat, Aug 27, 2022 at 12:12 PM Liu Shixin <liushixin2@xxxxxxxxxx> wrote:
>
> Since we are supported to delay zswap initializaton, we need to invoke
> ops->init for the swap device which is already online when register
> backend.
>
> This patch is a revert of f328c1d16e4c ("frontswap: simplify frontswap_register_ops")
> and 633423a09cb5 ("mm: mark swap_lock and swap_active_head static")
>
> Signed-off-by: Liu Shixin <liushixin2@xxxxxxxxxx>
Sorry, is this the revert of 2 patches at the same time? I would
rather not do it like that.
Thanks,
Vitaly
> ---
> include/linux/swapfile.h | 2 ++
> mm/frontswap.c | 47 ++++++++++++++++++++++++++++++++++++++++
> mm/swapfile.c | 4 ++--
> 3 files changed, 51 insertions(+), 2 deletions(-)
>
> diff --git a/include/linux/swapfile.h b/include/linux/swapfile.h
> index 2fbcc9afd814..75fc069594a5 100644
> --- a/include/linux/swapfile.h
> +++ b/include/linux/swapfile.h
> @@ -6,6 +6,8 @@
> * these were static in swapfile.c but frontswap.c needs them and we don't
> * want to expose them to the dozens of source files that include swap.h
> */
> +extern spinlock_t swap_lock;
> +extern struct plist_head swap_active_head;
> extern struct swap_info_struct *swap_info[];
> extern unsigned long generic_max_swapfile_size(void);
> /* Maximum swapfile size supported for the arch (not inclusive). */
> diff --git a/mm/frontswap.c b/mm/frontswap.c
> index 620f95af81dd..449e6f499b88 100644
> --- a/mm/frontswap.c
> +++ b/mm/frontswap.c
> @@ -96,11 +96,58 @@ static inline void inc_frontswap_invalidates(void) { }
> */
> int frontswap_register_ops(const struct frontswap_ops *ops)
> {
> + DECLARE_BITMAP(a, MAX_SWAPFILES);
> + DECLARE_BITMAP(b, MAX_SWAPFILES);
> + struct swap_info_struct *si;
> + unsigned int i;
> +
> if (frontswap_ops)
> return -EINVAL;
>
> + bitmap_zero(a, MAX_SWAPFILES);
> + bitmap_zero(b, MAX_SWAPFILES);
> +
> + spin_lock(&swap_lock);
> + plist_for_each_entry(si, &swap_active_head, list) {
> + if (!WARN_ON(!si->frontswap_map))
> + __set_bit(si->type, a);
> + }
> + spin_unlock(&swap_lock);
> +
> + /* the new ops needs to know the currently active swap devices */
> + for_each_set_bit(i, a, MAX_SWAPFILES) {
> + pr_err("init frontswap_ops\n");
> + ops->init(i);
> + }
> +
> frontswap_ops = ops;
> static_branch_inc(&frontswap_enabled_key);
> +
> + spin_lock(&swap_lock);
> + plist_for_each_entry(si, &swap_active_head, list) {
> + if (si->frontswap_map)
> + __set_bit(si->type, b);
> + }
> + spin_unlock(&swap_lock);
> +
> + /*
> + * On the very unlikely chance that a swap device was added or
> + * removed between setting the "a" list bits and the ops init
> + * calls, we re-check and do init or invalidate for any changed
> + * bits.
> + */
> + if (unlikely(!bitmap_equal(a, b, MAX_SWAPFILES))) {
> + for (i = 0; i < MAX_SWAPFILES; i++) {
> + if (!test_bit(i, a) && test_bit(i, b)) {
> + pr_err("init frontswap_ops re\n");
> + ops->init(i);
> + } else if (test_bit(i, a) && !test_bit(i, b)) {
> + pr_err("inval frontswap_ops re\n");
> + ops->invalidate_area(i);
> + }
> + }
> + }
> +
> return 0;
> }
>
> diff --git a/mm/swapfile.c b/mm/swapfile.c
> index 469d9af86be2..d383b282f269 100644
> --- a/mm/swapfile.c
> +++ b/mm/swapfile.c
> @@ -51,7 +51,7 @@ static bool swap_count_continued(struct swap_info_struct *, pgoff_t,
> unsigned char);
> static void free_swap_count_continuations(struct swap_info_struct *);
>
> -static DEFINE_SPINLOCK(swap_lock);
> +DEFINE_SPINLOCK(swap_lock);
> static unsigned int nr_swapfiles;
> atomic_long_t nr_swap_pages;
> /*
> @@ -77,7 +77,7 @@ static const char Unused_offset[] = "Unused swap offset entry ";
> * all active swap_info_structs
> * protected with swap_lock, and ordered by priority.
> */
> -static PLIST_HEAD(swap_active_head);
> +PLIST_HEAD(swap_active_head);
>
> /*
> * all available (active, not full) swap_info_structs
> --
> 2.25.1
>
