diff options
Diffstat (limited to 'include/linux/migrate.h')
| -rw-r--r-- | include/linux/migrate.h | 104 |
1 files changed, 104 insertions, 0 deletions
diff --git a/include/linux/migrate.h b/include/linux/migrate.h index 7db4c812a2a6..8f73cebfc3f5 100644 --- a/include/linux/migrate.h +++ b/include/linux/migrate.h @@ -156,4 +156,108 @@ static inline int migrate_misplaced_transhuge_page(struct mm_struct *mm, } #endif /* CONFIG_NUMA_BALANCING && CONFIG_TRANSPARENT_HUGEPAGE*/ + +#ifdef CONFIG_MIGRATION + +#define MIGRATE_PFN_VALID (1UL << 0) +#define MIGRATE_PFN_MIGRATE (1UL << 1) +#define MIGRATE_PFN_LOCKED (1UL << 2) +#define MIGRATE_PFN_WRITE (1UL << 3) +#define MIGRATE_PFN_ERROR (1UL << 4) +#define MIGRATE_PFN_SHIFT 5 + +static inline struct page *migrate_pfn_to_page(unsigned long mpfn) +{ + if (!(mpfn & MIGRATE_PFN_VALID)) + return NULL; + return pfn_to_page(mpfn >> MIGRATE_PFN_SHIFT); +} + +static inline unsigned long migrate_pfn(unsigned long pfn) +{ + return (pfn << MIGRATE_PFN_SHIFT) | MIGRATE_PFN_VALID; +} + +/* + * struct migrate_vma_ops - migrate operation callback + * + * @alloc_and_copy: alloc destination memory and copy source memory to it + * @finalize_and_map: allow caller to map the successfully migrated pages + * + * + * The alloc_and_copy() callback happens once all source pages have been locked, + * unmapped and checked (checked whether pinned or not). All pages that can be + * migrated will have an entry in the src array set with the pfn value of the + * page and with the MIGRATE_PFN_VALID and MIGRATE_PFN_MIGRATE flag set (other + * flags might be set but should be ignored by the callback). + * + * The alloc_and_copy() callback can then allocate destination memory and copy + * source memory to it for all those entries (ie with MIGRATE_PFN_VALID and + * MIGRATE_PFN_MIGRATE flag set). Once these are allocated and copied, the + * callback must update each corresponding entry in the dst array with the pfn + * value of the destination page and with the MIGRATE_PFN_VALID and + * MIGRATE_PFN_LOCKED flags set (destination pages must have their struct pages + * locked, via lock_page()). + * + * At this point the alloc_and_copy() callback is done and returns. + * + * Note that the callback does not have to migrate all the pages that are + * marked with MIGRATE_PFN_MIGRATE flag in src array unless this is a migration + * from device memory to system memory (ie the MIGRATE_PFN_DEVICE flag is also + * set in the src array entry). If the device driver cannot migrate a device + * page back to system memory, then it must set the corresponding dst array + * entry to MIGRATE_PFN_ERROR. This will trigger a SIGBUS if CPU tries to + * access any of the virtual addresses originally backed by this page. Because + * a SIGBUS is such a severe result for the userspace process, the device + * driver should avoid setting MIGRATE_PFN_ERROR unless it is really in an + * unrecoverable state. + * + * THE alloc_and_copy() CALLBACK MUST NOT CHANGE ANY OF THE SRC ARRAY ENTRIES + * OR BAD THINGS WILL HAPPEN ! + * + * + * The finalize_and_map() callback happens after struct page migration from + * source to destination (destination struct pages are the struct pages for the + * memory allocated by the alloc_and_copy() callback). Migration can fail, and + * thus the finalize_and_map() allows the driver to inspect which pages were + * successfully migrated, and which were not. Successfully migrated pages will + * have the MIGRATE_PFN_MIGRATE flag set for their src array entry. + * + * It is safe to update device page table from within the finalize_and_map() + * callback because both destination and source page are still locked, and the + * mmap_sem is held in read mode (hence no one can unmap the range being + * migrated). + * + * Once callback is done cleaning up things and updating its page table (if it + * chose to do so, this is not an obligation) then it returns. At this point, + * the HMM core will finish up the final steps, and the migration is complete. + * + * THE finalize_and_map() CALLBACK MUST NOT CHANGE ANY OF THE SRC OR DST ARRAY + * ENTRIES OR BAD THINGS WILL HAPPEN ! + */ +struct migrate_vma_ops { + void (*alloc_and_copy)(struct vm_area_struct *vma, + const unsigned long *src, + unsigned long *dst, + unsigned long start, + unsigned long end, + void *private); + void (*finalize_and_map)(struct vm_area_struct *vma, + const unsigned long *src, + const unsigned long *dst, + unsigned long start, + unsigned long end, + void *private); +}; + +int migrate_vma(const struct migrate_vma_ops *ops, + struct vm_area_struct *vma, + unsigned long start, + unsigned long end, + unsigned long *src, + unsigned long *dst, + void *private); + +#endif /* CONFIG_MIGRATION */ + #endif /* _LINUX_MIGRATE_H */ |