A future change will remove device private pages from the physical address space. This will mean that device private pages no longer have pfns and must be handled separately.
When migrating a device private page a migration entry is created for that page. This includes the pfn for that page. Once device private pages begin using device memory offsets instead of pfns we will need to be able to determine which kind of value is in the entry so we can associate it with the correct page. Introduce new swap types that correspond to the existing migration entries: - SWP_MIGRATION_DEVICE_READ -> SWP_MIGRATION_READ - SWP_MIGRATION_DEVICE_WRITE -> SWP_MIGRATION_WRITE - SWP_MIGRATION_DEVICE_READ_EXCLUSIVE -> SWP_MIGRATION_READ_EXCLUSIVE The SWP_MIGRATION_DEVICE swap types are meant as specializations of the SWP_MIGRATION types - they are equivalent except the new entries contain device private offsets. Forgo creating new predicates for these new types in favour of new softleaf predicates that will be introduced in a subsequent patch. Currently the softleaf infrastructure does not have the means for creating new entries so provide swap entry helpers to that end. Actually using these creation helpers is deferred until a later patch when the softleaf predicates have been updated, otherwise the existing checks for migration entries would be broken. Note that SWP_DEVICE_NUM is increasing from 3 to 6. This reduces the maximum number of swap files in the worst case (i.e. CONFIG_DEVICE_PRIVATE, CONFIG_MIGRATION, CONFIG_MEMORY_FAILURE) from 24 to 21. Signed-off-by: Jordan Niethe <[email protected]> Signed-off-by: Alistair Popple <[email protected]> --- v1: - Update for softleaf infrastructure - Handle make_readable_migration_entry_from_page() and friends - s/make_device_migration_readable_exclusive_migration_entry/make_readable_exclusive_migration_device_private_entry - s/is_device_migration_readable_exclusive_entry/is_readable_exclusive_device_private_migration_entry/ v2: - Add softleaf_is_migration_device_private_read() v3: - Move softleaf changes to new patch - Update commit message to explain the change reduces the number of swap files. - Move creating the device private migration changes to a separate patch - Remove predicates - we'll rely on softleaf predicates entirely --- include/linux/swap.h | 8 +++++++- include/linux/swapops.h | 30 ++++++++++++++++++++++++++++++ 2 files changed, 37 insertions(+), 1 deletion(-) diff --git a/include/linux/swap.h b/include/linux/swap.h index 38ca3df68716..c15e3b3067cd 100644 --- a/include/linux/swap.h +++ b/include/linux/swap.h @@ -74,12 +74,18 @@ static inline int current_is_kswapd(void) * * When a page is mapped by the device for exclusive access we set the CPU page * table entries to a special SWP_DEVICE_EXCLUSIVE entry. + * + * Because device private pages do not use regular PFNs, special migration + * entries are also needed. */ #ifdef CONFIG_DEVICE_PRIVATE -#define SWP_DEVICE_NUM 3 +#define SWP_DEVICE_NUM 6 #define SWP_DEVICE_WRITE (MAX_SWAPFILES+SWP_HWPOISON_NUM+SWP_MIGRATION_NUM) #define SWP_DEVICE_READ (MAX_SWAPFILES+SWP_HWPOISON_NUM+SWP_MIGRATION_NUM+1) #define SWP_DEVICE_EXCLUSIVE (MAX_SWAPFILES+SWP_HWPOISON_NUM+SWP_MIGRATION_NUM+2) +#define SWP_MIGRATION_DEVICE_READ (MAX_SWAPFILES+SWP_HWPOISON_NUM+SWP_MIGRATION_NUM+3) +#define SWP_MIGRATION_DEVICE_READ_EXCLUSIVE (MAX_SWAPFILES+SWP_HWPOISON_NUM+SWP_MIGRATION_NUM+4) +#define SWP_MIGRATION_DEVICE_WRITE (MAX_SWAPFILES+SWP_HWPOISON_NUM+SWP_MIGRATION_NUM+5) #else #define SWP_DEVICE_NUM 0 #endif diff --git a/include/linux/swapops.h b/include/linux/swapops.h index a9ad997bd5ec..a70a6809e9c6 100644 --- a/include/linux/swapops.h +++ b/include/linux/swapops.h @@ -148,6 +148,21 @@ static inline swp_entry_t make_device_exclusive_entry(pgoff_t offset) return swp_entry(SWP_DEVICE_EXCLUSIVE, offset); } +static inline swp_entry_t make_readable_migration_device_private_entry(pgoff_t offset) +{ + return swp_entry(SWP_MIGRATION_DEVICE_READ, offset); +} + +static inline swp_entry_t make_writable_migration_device_private_entry(pgoff_t offset) +{ + return swp_entry(SWP_MIGRATION_DEVICE_WRITE, offset); +} + +static inline swp_entry_t make_readable_exclusive_migration_device_private_entry(pgoff_t offset) +{ + return swp_entry(SWP_MIGRATION_DEVICE_READ_EXCLUSIVE, offset); +} + #else /* CONFIG_DEVICE_PRIVATE */ static inline swp_entry_t make_readable_device_private_entry(pgoff_t offset) { @@ -164,6 +179,21 @@ static inline swp_entry_t make_device_exclusive_entry(pgoff_t offset) return swp_entry(0, 0); } +static inline swp_entry_t make_readable_migration_device_private_entry(pgoff_t offset) +{ + return swp_entry(0, 0); +} + +static inline swp_entry_t make_writable_migration_device_private_entry(pgoff_t offset) +{ + return swp_entry(0, 0); +} + +static inline swp_entry_t make_readable_exclusive_migration_device_private_entry(pgoff_t offset) +{ + return swp_entry(0, 0); +} + #endif /* CONFIG_DEVICE_PRIVATE */ #ifdef CONFIG_MIGRATION -- 2.34.1
