/* SPDX-License-Identifier: GPL-2.0 */ #ifndef _MM_SWAP_TABLE_H #define _MM_SWAP_TABLE_H #include #include #include "swap.h" /* A typical flat array in each cluster as swap table */ struct swap_table { atomic_long_t entries[SWAPFILE_CLUSTER]; }; #define SWP_TABLE_USE_PAGE (sizeof(struct swap_table) == PAGE_SIZE) /* * A swap table entry represents the status of a swap slot on a swap * (physical or virtual) device. The swap table in each cluster is a * 1:1 map of the swap slots in this cluster. * * Each swap table entry could be a pointer (folio), a XA_VALUE * (shadow), or NULL. */ /* * Helpers for casting one type of info into a swap table entry. */ static inline unsigned long null_to_swp_tb(void) { BUILD_BUG_ON(sizeof(unsigned long) != sizeof(atomic_long_t)); return 0; } static inline unsigned long folio_to_swp_tb(struct folio *folio) { BUILD_BUG_ON(sizeof(unsigned long) != sizeof(void *)); return (unsigned long)folio; } static inline unsigned long shadow_swp_to_tb(void *shadow) { BUILD_BUG_ON((BITS_PER_XA_VALUE + 1) != BITS_PER_BYTE * sizeof(unsigned long)); VM_WARN_ON_ONCE(shadow && !xa_is_value(shadow)); return (unsigned long)shadow; } /* * Helpers for swap table entry type checking. */ static inline bool swp_tb_is_null(unsigned long swp_tb) { return !swp_tb; } static inline bool swp_tb_is_folio(unsigned long swp_tb) { return !xa_is_value((void *)swp_tb) && !swp_tb_is_null(swp_tb); } static inline bool swp_tb_is_shadow(unsigned long swp_tb) { return xa_is_value((void *)swp_tb); } /* * Helpers for retrieving info from swap table. */ static inline struct folio *swp_tb_to_folio(unsigned long swp_tb) { VM_WARN_ON(!swp_tb_is_folio(swp_tb)); return (void *)swp_tb; } static inline void *swp_tb_to_shadow(unsigned long swp_tb) { VM_WARN_ON(!swp_tb_is_shadow(swp_tb)); return (void *)swp_tb; } /* * Helpers for accessing or modifying the swap table of a cluster, * the swap cluster must be locked. */ static inline void __swap_table_set(struct swap_cluster_info *ci, unsigned int off, unsigned long swp_tb) { atomic_long_t *table = rcu_dereference_protected(ci->table, true); lockdep_assert_held(&ci->lock); VM_WARN_ON_ONCE(off >= SWAPFILE_CLUSTER); atomic_long_set(&table[off], swp_tb); } static inline unsigned long __swap_table_xchg(struct swap_cluster_info *ci, unsigned int off, unsigned long swp_tb) { atomic_long_t *table = rcu_dereference_protected(ci->table, true); lockdep_assert_held(&ci->lock); VM_WARN_ON_ONCE(off >= SWAPFILE_CLUSTER); /* Ordering is guaranteed by cluster lock, relax */ return atomic_long_xchg_relaxed(&table[off], swp_tb); } static inline unsigned long __swap_table_get(struct swap_cluster_info *ci, unsigned int off) { atomic_long_t *table; VM_WARN_ON_ONCE(off >= SWAPFILE_CLUSTER); table = rcu_dereference_check(ci->table, lockdep_is_held(&ci->lock)); return atomic_long_read(&table[off]); } static inline unsigned long swap_table_get(struct swap_cluster_info *ci, unsigned int off) { atomic_long_t *table; unsigned long swp_tb; rcu_read_lock(); table = rcu_dereference(ci->table); swp_tb = table ? atomic_long_read(&table[off]) : null_to_swp_tb(); rcu_read_unlock(); return swp_tb; } #endif