mm: Define MAP_SYNC and VM_SYNC flags

Define new MAP_SYNC flag and corresponding VMA VM_SYNC flag. As the
MAP_SYNC flag is not part of LEGACY_MAP_MASK, currently it will be
refused by all MAP_SHARED_VALIDATE map attempts and silently ignored for
everything else.
Reviewed-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

fs/proc/task_mmu.c

@@ -664,6 +664,7 @@ static void show_smap_vma_flags(struct seq_file *m, struct vm_area_struct *vma)
 		[ilog2(VM_ACCOUNT)]	= "ac",
 		[ilog2(VM_NORESERVE)]	= "nr",
 		[ilog2(VM_HUGETLB)]	= "ht",
+		[ilog2(VM_SYNC)]	= "sf",
 		[ilog2(VM_ARCH_1)]	= "ar",
 		[ilog2(VM_WIPEONFORK)]	= "wf",
 		[ilog2(VM_DONTDUMP)]	= "dd",

include/linux/mm.h

@@ -189,6 +189,7 @@ extern unsigned int kobjsize(const void *objp);
 #define VM_ACCOUNT	0x00100000	/* Is a VM accounted object */
 #define VM_NORESERVE	0x00200000	/* should the VM suppress accounting */
 #define VM_HUGETLB	0x00400000	/* Huge TLB Page VM */
+#define VM_SYNC		0x00800000	/* Synchronous page faults */
 #define VM_ARCH_1	0x01000000	/* Architecture-specific flag */
 #define VM_WIPEONFORK	0x02000000	/* Wipe VMA contents in child. */
 #define VM_DONTDUMP	0x04000000	/* Do not include in the core dump */

include/linux/mman.h

@@ -9,7 +9,7 @@
 
 /*
  * Arrange for legacy / undefined architecture specific flags to be
- * ignored by default in LEGACY_MAP_MASK.
+ * ignored by mmap handling code.
  */
 #ifndef MAP_32BIT
 #define MAP_32BIT 0
@@ -23,6 +23,9 @@
 #ifndef MAP_UNINITIALIZED
 #define MAP_UNINITIALIZED 0
 #endif
+#ifndef MAP_SYNC
+#define MAP_SYNC 0
+#endif
 
 /*
  * The historical set of flags that all mmap implementations implicitly
@@ -126,7 +129,8 @@ calc_vm_flag_bits(unsigned long flags)
 {
 	return _calc_vm_trans(flags, MAP_GROWSDOWN,  VM_GROWSDOWN ) |
 	       _calc_vm_trans(flags, MAP_DENYWRITE,  VM_DENYWRITE ) |
-	       _calc_vm_trans(flags, MAP_LOCKED,     VM_LOCKED    );
+	       _calc_vm_trans(flags, MAP_LOCKED,     VM_LOCKED    ) |
+	       _calc_vm_trans(flags, MAP_SYNC,	     VM_SYNC      );
 }
 
 unsigned long vm_commit_limit(void);

include/uapi/asm-generic/mman.h

@@ -12,6 +12,7 @@
 #define MAP_NONBLOCK	0x10000		/* do not block on IO */
 #define MAP_STACK	0x20000		/* give out an address that is best suited for process/thread stacks */
 #define MAP_HUGETLB	0x40000		/* create a huge page mapping */
+#define MAP_SYNC	0x80000		/* perform synchronous page faults for the mapping */
 
 /* Bits [26:31] are reserved, see mman-common.h for MAP_HUGETLB usage */