On Fri, Sep 27, 2024 at 7:16 PM Kanchana P Sridhar
<kanchana.p.sridhar@xxxxxxxxx> wrote:
>
> For zswap_store() to support large folios, we need to be able to do
> a batch update of zswap_stored_pages upon successful store of all pages
> in the folio. For this, we need to add folio_nr_pages(), which returns
> a long, to zswap_stored_pages.
Do we really need this? A lot of places in the kernel assign the
result of folio_nr_pages() to an int (thp_nr_pages(),
split_huge_pages_all(), etc). I don't think we need to worry about
folio_nr_pages() exceeding INT_MAX for a while.
>
> Signed-off-by: Kanchana P Sridhar <kanchana.p.sridhar@xxxxxxxxx>
> ---
> fs/proc/meminfo.c | 2 +-
> include/linux/zswap.h | 2 +-
> mm/zswap.c | 19 +++++++++++++------
> 3 files changed, 15 insertions(+), 8 deletions(-)
>
> diff --git a/fs/proc/meminfo.c b/fs/proc/meminfo.c
> index 245171d9164b..8ba9b1472390 100644
> --- a/fs/proc/meminfo.c
> +++ b/fs/proc/meminfo.c
> @@ -91,7 +91,7 @@ static int meminfo_proc_show(struct seq_file *m, void *v)
> #ifdef CONFIG_ZSWAP
> show_val_kb(m, "Zswap: ", zswap_total_pages());
> seq_printf(m, "Zswapped: %8lu kB\n",
> - (unsigned long)atomic_read(&zswap_stored_pages) <<
> + (unsigned long)atomic_long_read(&zswap_stored_pages) <<
> (PAGE_SHIFT - 10));
> #endif
> show_val_kb(m, "Dirty: ",
> diff --git a/include/linux/zswap.h b/include/linux/zswap.h
> index 9cd1beef0654..d961ead91bf1 100644
> --- a/include/linux/zswap.h
> +++ b/include/linux/zswap.h
> @@ -7,7 +7,7 @@
>
> struct lruvec;
>
> -extern atomic_t zswap_stored_pages;
> +extern atomic_long_t zswap_stored_pages;
>
> #ifdef CONFIG_ZSWAP
>
> diff --git a/mm/zswap.c b/mm/zswap.c
> index 0f281e50a034..43e4e216db41 100644
> --- a/mm/zswap.c
> +++ b/mm/zswap.c
> @@ -43,7 +43,7 @@
> * statistics
> **********************************/
> /* The number of compressed pages currently stored in zswap */
> -atomic_t zswap_stored_pages = ATOMIC_INIT(0);
> +atomic_long_t zswap_stored_pages = ATOMIC_INIT(0);
>
> /*
> * The statistics below are not protected from concurrent access for
> @@ -802,7 +802,7 @@ static void zswap_entry_free(struct zswap_entry *entry)
> obj_cgroup_put(entry->objcg);
> }
> zswap_entry_cache_free(entry);
> - atomic_dec(&zswap_stored_pages);
> + atomic_long_dec(&zswap_stored_pages);
> }
>
> /*********************************
> @@ -1232,7 +1232,7 @@ static unsigned long zswap_shrinker_count(struct shrinker *shrinker,
> nr_stored = memcg_page_state(memcg, MEMCG_ZSWAPPED);
> } else {
> nr_backing = zswap_total_pages();
> - nr_stored = atomic_read(&zswap_stored_pages);
> + nr_stored = atomic_long_read(&zswap_stored_pages);
> }
>
> if (!nr_stored)
> @@ -1501,7 +1501,7 @@ bool zswap_store(struct folio *folio)
> }
>
> /* update stats */
> - atomic_inc(&zswap_stored_pages);
> + atomic_long_inc(&zswap_stored_pages);
> count_vm_event(ZSWPOUT);
>
> return true;
> @@ -1650,6 +1650,13 @@ static int debugfs_get_total_size(void *data, u64 *val)
> }
> DEFINE_DEBUGFS_ATTRIBUTE(total_size_fops, debugfs_get_total_size, NULL, "%llu\n");
>
> +static int debugfs_get_stored_pages(void *data, u64 *val)
> +{
> + *val = atomic_long_read(&zswap_stored_pages);
> + return 0;
> +}
> +DEFINE_DEBUGFS_ATTRIBUTE(stored_pages_fops, debugfs_get_stored_pages, NULL, "%llu\n");
> +
> static int zswap_debugfs_init(void)
> {
> if (!debugfs_initialized())
> @@ -1673,8 +1680,8 @@ static int zswap_debugfs_init(void)
> zswap_debugfs_root, &zswap_written_back_pages);
> debugfs_create_file("pool_total_size", 0444,
> zswap_debugfs_root, NULL, &total_size_fops);
> - debugfs_create_atomic_t("stored_pages", 0444,
> - zswap_debugfs_root, &zswap_stored_pages);
> + debugfs_create_file("stored_pages", 0444,
> + zswap_debugfs_root, NULL, &stored_pages_fops);
>
> return 0;
> }
> --
> 2.27.0
>
