On Wed, Jan 17, 2024 at 1:23 AM Chengming Zhou
<zhouchengming@xxxxxxxxxxxxx> wrote:
>
> Not all zswap interfaces can handle the absence of the zswap rb-tree,
> actually only zswap_store() has handled it for now.
>
> To make things simple, we make sure each swapfile always have the
> zswap rb-tree prepared before being enabled and used. The preparation
> is unlikely to fail in practice, this patch just make it explicit.
>
> Signed-off-by: Chengming Zhou <zhouchengming@xxxxxxxxxxxxx>
This seems fine to me. IIUC, zswap_swapon() only fails when the rbtree
allocation fails, and the tree's memory footprint is small so that's
unlikely anyway.
Acked-by: Nhat Pham <nphamcs@xxxxxxxxx>
> ---
> include/linux/zswap.h | 7 +++++--
> mm/swapfile.c | 10 +++++++---
> mm/zswap.c | 7 ++++---
> 3 files changed, 16 insertions(+), 8 deletions(-)
>
> diff --git a/include/linux/zswap.h b/include/linux/zswap.h
> index 0b709f5bc65f..eca388229d9a 100644
> --- a/include/linux/zswap.h
> +++ b/include/linux/zswap.h
> @@ -30,7 +30,7 @@ struct zswap_lruvec_state {
> bool zswap_store(struct folio *folio);
> bool zswap_load(struct folio *folio);
> void zswap_invalidate(int type, pgoff_t offset);
> -void zswap_swapon(int type);
> +int zswap_swapon(int type);
> void zswap_swapoff(int type);
> void zswap_memcg_offline_cleanup(struct mem_cgroup *memcg);
> void zswap_lruvec_state_init(struct lruvec *lruvec);
> @@ -51,7 +51,10 @@ static inline bool zswap_load(struct folio *folio)
> }
>
> static inline void zswap_invalidate(int type, pgoff_t offset) {}
> -static inline void zswap_swapon(int type) {}
> +static inline int zswap_swapon(int type)
> +{
> + return 0;
> +}
> static inline void zswap_swapoff(int type) {}
> static inline void zswap_memcg_offline_cleanup(struct mem_cgroup *memcg) {}
> static inline void zswap_lruvec_state_init(struct lruvec *lruvec) {}
> diff --git a/mm/swapfile.c b/mm/swapfile.c
> index 3eec686484ef..6c53ea06626b 100644
> --- a/mm/swapfile.c
> +++ b/mm/swapfile.c
> @@ -2347,8 +2347,6 @@ static void enable_swap_info(struct swap_info_struct *p, int prio,
> unsigned char *swap_map,
> struct swap_cluster_info *cluster_info)
> {
> - zswap_swapon(p->type);
> -
> spin_lock(&swap_lock);
> spin_lock(&p->lock);
> setup_swap_info(p, prio, swap_map, cluster_info);
> @@ -3166,6 +3164,10 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
> if (error)
> goto bad_swap_unlock_inode;
>
> + error = zswap_swapon(p->type);
> + if (error)
> + goto free_swap_address_space;
> +
> /*
> * Flush any pending IO and dirty mappings before we start using this
> * swap device.
> @@ -3174,7 +3176,7 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
> error = inode_drain_writes(inode);
> if (error) {
> inode->i_flags &= ~S_SWAPFILE;
> - goto free_swap_address_space;
> + goto free_swap_zswap;
> }
>
> mutex_lock(&swapon_mutex);
> @@ -3198,6 +3200,8 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
>
> error = 0;
> goto out;
> +free_swap_zswap:
> + zswap_swapoff(p->type);
> free_swap_address_space:
> exit_swap_address_space(p->type);
> bad_swap_unlock_inode:
> diff --git a/mm/zswap.c b/mm/zswap.c
> index ca25b676048e..d88faea85978 100644
> --- a/mm/zswap.c
> +++ b/mm/zswap.c
> @@ -1519,7 +1519,7 @@ bool zswap_store(struct folio *folio)
> if (folio_test_large(folio))
> return false;
>
> - if (!zswap_enabled || !tree)
> + if (!zswap_enabled)
> return false;
>
> /*
> @@ -1772,19 +1772,20 @@ void zswap_invalidate(int type, pgoff_t offset)
> spin_unlock(&tree->lock);
> }
>
> -void zswap_swapon(int type)
> +int zswap_swapon(int type)
> {
> struct zswap_tree *tree;
>
> tree = kzalloc(sizeof(*tree), GFP_KERNEL);
> if (!tree) {
> pr_err("alloc failed, zswap disabled for swap type %d\n", type);
> - return;
> + return -ENOMEM;
> }
>
> tree->rbroot = RB_ROOT;
> spin_lock_init(&tree->lock);
> zswap_trees[type] = tree;
> + return 0;
> }
>
> void zswap_swapoff(int type)
>
> --
> b4 0.10.1
