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