![Cyrill Gorcunov](/assets/img/avatar_default.png)
Andy Lutomirski reported that if a page with _PAGE_SOFT_DIRTY bit set get swapped out, the bit is getting lost and no longer available when pte read back. To resolve this we introduce _PTE_SWP_SOFT_DIRTY bit which is saved in pte entry for the page being swapped out. When such page is to be read back from a swap cache we check for bit presence and if it's there we clear it and restore the former _PAGE_SOFT_DIRTY bit back. One of the problem was to find a place in pte entry where we can save the _PTE_SWP_SOFT_DIRTY bit while page is in swap. The _PAGE_PSE was chosen for that, it doesn't intersect with swap entry format stored in pte. Reported-by: Andy Lutomirski <luto@amacapital.net> Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org> Acked-by: Pavel Emelyanov <xemul@parallels.com> Cc: Matt Mackall <mpm@selenic.com> Cc: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com> Cc: Marcelo Tosatti <mtosatti@redhat.com> Cc: KOSAKI Motohiro <kosaki.motohiro@gmail.com> Cc: Stephen Rothwell <sfr@canb.auug.org.au> Cc: Peter Zijlstra <peterz@infradead.org> Cc: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com> Reviewed-by: Minchan Kim <minchan@kernel.org> Reviewed-by: Wanpeng Li <liwanp@linux.vnet.ibm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
203 lines
5.1 KiB
C
203 lines
5.1 KiB
C
#ifndef _LINUX_SWAPOPS_H
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#define _LINUX_SWAPOPS_H
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#include <linux/radix-tree.h>
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#include <linux/bug.h>
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/*
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* swapcache pages are stored in the swapper_space radix tree. We want to
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* get good packing density in that tree, so the index should be dense in
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* the low-order bits.
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*
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* We arrange the `type' and `offset' fields so that `type' is at the seven
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* high-order bits of the swp_entry_t and `offset' is right-aligned in the
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* remaining bits. Although `type' itself needs only five bits, we allow for
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* shmem/tmpfs to shift it all up a further two bits: see swp_to_radix_entry().
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*
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* swp_entry_t's are *never* stored anywhere in their arch-dependent format.
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*/
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#define SWP_TYPE_SHIFT(e) ((sizeof(e.val) * 8) - \
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(MAX_SWAPFILES_SHIFT + RADIX_TREE_EXCEPTIONAL_SHIFT))
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#define SWP_OFFSET_MASK(e) ((1UL << SWP_TYPE_SHIFT(e)) - 1)
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/*
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* Store a type+offset into a swp_entry_t in an arch-independent format
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*/
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static inline swp_entry_t swp_entry(unsigned long type, pgoff_t offset)
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{
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swp_entry_t ret;
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ret.val = (type << SWP_TYPE_SHIFT(ret)) |
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(offset & SWP_OFFSET_MASK(ret));
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return ret;
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}
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/*
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* Extract the `type' field from a swp_entry_t. The swp_entry_t is in
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* arch-independent format
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*/
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static inline unsigned swp_type(swp_entry_t entry)
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{
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return (entry.val >> SWP_TYPE_SHIFT(entry));
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}
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/*
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* Extract the `offset' field from a swp_entry_t. The swp_entry_t is in
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* arch-independent format
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*/
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static inline pgoff_t swp_offset(swp_entry_t entry)
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{
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return entry.val & SWP_OFFSET_MASK(entry);
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}
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#ifdef CONFIG_MMU
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/* check whether a pte points to a swap entry */
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static inline int is_swap_pte(pte_t pte)
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{
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return !pte_none(pte) && !pte_present(pte) && !pte_file(pte);
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}
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#endif
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/*
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* Convert the arch-dependent pte representation of a swp_entry_t into an
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* arch-independent swp_entry_t.
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*/
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static inline swp_entry_t pte_to_swp_entry(pte_t pte)
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{
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swp_entry_t arch_entry;
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BUG_ON(pte_file(pte));
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if (pte_swp_soft_dirty(pte))
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pte = pte_swp_clear_soft_dirty(pte);
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arch_entry = __pte_to_swp_entry(pte);
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return swp_entry(__swp_type(arch_entry), __swp_offset(arch_entry));
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}
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/*
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* Convert the arch-independent representation of a swp_entry_t into the
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* arch-dependent pte representation.
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*/
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static inline pte_t swp_entry_to_pte(swp_entry_t entry)
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{
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swp_entry_t arch_entry;
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arch_entry = __swp_entry(swp_type(entry), swp_offset(entry));
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BUG_ON(pte_file(__swp_entry_to_pte(arch_entry)));
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return __swp_entry_to_pte(arch_entry);
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}
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static inline swp_entry_t radix_to_swp_entry(void *arg)
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{
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swp_entry_t entry;
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entry.val = (unsigned long)arg >> RADIX_TREE_EXCEPTIONAL_SHIFT;
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return entry;
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}
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static inline void *swp_to_radix_entry(swp_entry_t entry)
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{
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unsigned long value;
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value = entry.val << RADIX_TREE_EXCEPTIONAL_SHIFT;
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return (void *)(value | RADIX_TREE_EXCEPTIONAL_ENTRY);
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}
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#ifdef CONFIG_MIGRATION
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static inline swp_entry_t make_migration_entry(struct page *page, int write)
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{
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BUG_ON(!PageLocked(page));
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return swp_entry(write ? SWP_MIGRATION_WRITE : SWP_MIGRATION_READ,
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page_to_pfn(page));
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}
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static inline int is_migration_entry(swp_entry_t entry)
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{
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return unlikely(swp_type(entry) == SWP_MIGRATION_READ ||
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swp_type(entry) == SWP_MIGRATION_WRITE);
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}
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static inline int is_write_migration_entry(swp_entry_t entry)
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{
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return unlikely(swp_type(entry) == SWP_MIGRATION_WRITE);
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}
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static inline struct page *migration_entry_to_page(swp_entry_t entry)
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{
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struct page *p = pfn_to_page(swp_offset(entry));
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/*
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* Any use of migration entries may only occur while the
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* corresponding page is locked
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*/
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BUG_ON(!PageLocked(p));
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return p;
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}
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static inline void make_migration_entry_read(swp_entry_t *entry)
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{
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*entry = swp_entry(SWP_MIGRATION_READ, swp_offset(*entry));
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}
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extern void migration_entry_wait(struct mm_struct *mm, pmd_t *pmd,
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unsigned long address);
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extern void migration_entry_wait_huge(struct mm_struct *mm, pte_t *pte);
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#else
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#define make_migration_entry(page, write) swp_entry(0, 0)
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static inline int is_migration_entry(swp_entry_t swp)
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{
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return 0;
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}
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#define migration_entry_to_page(swp) NULL
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static inline void make_migration_entry_read(swp_entry_t *entryp) { }
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static inline void migration_entry_wait(struct mm_struct *mm, pmd_t *pmd,
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unsigned long address) { }
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static inline void migration_entry_wait_huge(struct mm_struct *mm,
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pte_t *pte) { }
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static inline int is_write_migration_entry(swp_entry_t entry)
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{
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return 0;
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}
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#endif
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#ifdef CONFIG_MEMORY_FAILURE
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/*
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* Support for hardware poisoned pages
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*/
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static inline swp_entry_t make_hwpoison_entry(struct page *page)
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{
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BUG_ON(!PageLocked(page));
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return swp_entry(SWP_HWPOISON, page_to_pfn(page));
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}
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static inline int is_hwpoison_entry(swp_entry_t entry)
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{
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return swp_type(entry) == SWP_HWPOISON;
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}
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#else
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static inline swp_entry_t make_hwpoison_entry(struct page *page)
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{
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return swp_entry(0, 0);
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}
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static inline int is_hwpoison_entry(swp_entry_t swp)
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{
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return 0;
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}
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#endif
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#if defined(CONFIG_MEMORY_FAILURE) || defined(CONFIG_MIGRATION)
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static inline int non_swap_entry(swp_entry_t entry)
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{
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return swp_type(entry) >= MAX_SWAPFILES;
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}
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#else
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static inline int non_swap_entry(swp_entry_t entry)
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{
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return 0;
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}
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#endif
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#endif /* _LINUX_SWAPOPS_H */
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