Introduce a new vma flag to indicate the property of device-dax VMAs that, while file-backed, do not require notification to a filesystem agent to sync metadata after a fault. In particular this enables persistent memory applications to know if they can commit transactions to media via cpu instructions alone, or need to call back into the kernel to synchronize metadata. Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx> --- drivers/dax/Kconfig | 1 + drivers/dax/dax.c | 2 +- fs/proc/task_mmu.c | 3 +++ include/linux/mm.h | 21 +++++++++++++++++---- 4 files changed, 22 insertions(+), 5 deletions(-) diff --git a/drivers/dax/Kconfig b/drivers/dax/Kconfig index cedab7572de3..a4d99e637623 100644 --- a/drivers/dax/Kconfig +++ b/drivers/dax/Kconfig @@ -2,6 +2,7 @@ menuconfig DEV_DAX tristate "DAX: direct access to differentiated memory" default m if NVDIMM_DAX depends on TRANSPARENT_HUGEPAGE + select ARCH_USES_HIGH_VMA_FLAGS if 64BIT help Support raw access to differentiated (persistence, bandwidth, latency...) memory via an mmap(2) capable character diff --git a/drivers/dax/dax.c b/drivers/dax/dax.c index 29f600f2c447..88fad2519907 100644 --- a/drivers/dax/dax.c +++ b/drivers/dax/dax.c @@ -528,7 +528,7 @@ static int dax_dev_mmap(struct file *filp, struct vm_area_struct *vma) kref_get(&dax_dev->kref); vma->vm_ops = &dax_dev_vm_ops; - vma->vm_flags |= VM_MIXEDMAP | VM_HUGEPAGE; + vma->vm_flags |= VM_MIXEDMAP | VM_HUGEPAGE | VM_SYNC; return 0; } diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c index f6fa99eca515..03a65ac7f222 100644 --- a/fs/proc/task_mmu.c +++ b/fs/proc/task_mmu.c @@ -675,6 +675,9 @@ static void show_smap_vma_flags(struct seq_file *m, struct vm_area_struct *vma) [ilog2(VM_PKEY_BIT2)] = "", [ilog2(VM_PKEY_BIT3)] = "", #endif +#ifdef CONFIG_ARCH_USES_HIGH_VMA_FLAGS + [ilog2(VM_SYNC)] = "sn", +#endif }; size_t i; diff --git a/include/linux/mm.h b/include/linux/mm.h index ef815b9cd426..f3f6df6bb498 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -198,14 +198,17 @@ extern unsigned int kobjsize(const void *objp); #define VM_MERGEABLE 0x80000000 /* KSM may merge identical pages */ #ifdef CONFIG_ARCH_USES_HIGH_VMA_FLAGS -#define VM_HIGH_ARCH_BIT_0 32 /* bit only usable on 64-bit architectures */ -#define VM_HIGH_ARCH_BIT_1 33 /* bit only usable on 64-bit architectures */ -#define VM_HIGH_ARCH_BIT_2 34 /* bit only usable on 64-bit architectures */ -#define VM_HIGH_ARCH_BIT_3 35 /* bit only usable on 64-bit architectures */ +/* bits below only usable on 64-bit architectures */ +#define VM_HIGH_ARCH_BIT_0 32 +#define VM_HIGH_ARCH_BIT_1 33 +#define VM_HIGH_ARCH_BIT_2 34 +#define VM_HIGH_ARCH_BIT_3 35 +#define VM_HIGH_ARCH_BIT_4 36 #define VM_HIGH_ARCH_0 BIT(VM_HIGH_ARCH_BIT_0) #define VM_HIGH_ARCH_1 BIT(VM_HIGH_ARCH_BIT_1) #define VM_HIGH_ARCH_2 BIT(VM_HIGH_ARCH_BIT_2) #define VM_HIGH_ARCH_3 BIT(VM_HIGH_ARCH_BIT_3) +#define VM_HIGH_ARCH_4 BIT(VM_HIGH_ARCH_BIT_4) #endif /* CONFIG_ARCH_USES_HIGH_VMA_FLAGS */ #if defined(CONFIG_X86) @@ -234,6 +237,16 @@ extern unsigned int kobjsize(const void *objp); # define VM_MPX VM_ARCH_2 #endif +#ifdef CONFIG_ARCH_USES_HIGH_VMA_FLAGS +/* + * The metadata for file-backed vma does not exist or is otherwise + * synced before fault handler returns to userspace + */ +#define VM_SYNC VM_HIGH_ARCH_4 +#else +#define VM_SYNC 0 +#endif + #ifndef VM_GROWSUP # define VM_GROWSUP VM_NONE #endif -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>