mm/mmap.c: initialize align_offset explicitly for vm_unmapped_area

On passing requirement to vm_unmapped_area, arch_get_unmapped_area and
arch_get_unmapped_area_topdown did not set align_offset.  Internally on
both unmapped_area and unmapped_area_topdown, if info->align_mask is 0,
then info->align_offset was meaningless.

But commit df529ca ("mm: mmap: add trace point of
vm_unmapped_area") always prints info->align_offset even though it is
uninitialized.

Fix this uninitialized value issue by setting it to 0 explicitly.

Before:
  vm_unmapped_area: addr=0x755b155000 err=0 total_vm=0x15aaf0 flags=0x1 len=0x109000 lo=0x8000 hi=0x75eed48000 mask=0x0 ofs=0x4022

After:
  vm_unmapped_area: addr=0x74a4ca1000 err=0 total_vm=0x168ab1 flags=0x1 len=0x9000 lo=0x8000 hi=0x753d94b000 mask=0x0 ofs=0x0

Signed-off-by: Jaewon Kim <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Reviewed-by: Andrew Morton <[email protected]>
Cc: Matthew Wilcox (Oracle) <[email protected]>
Cc: Michel Lespinasse <[email protected]>
Cc: Borislav Petkov <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Linus Torvalds <[email protected]>

Author: Jaewon31Kim

mm/mmap.c

@@ -2123,6 +2123,7 @@ arch_get_unmapped_area(struct file *filp, unsigned long addr,
 	info.low_limit = mm->mmap_base;
 	info.high_limit = mmap_end;
 	info.align_mask = 0;
+	info.align_offset = 0;
 	return vm_unmapped_area(&info);
 }
 #endif
@@ -2164,6 +2165,7 @@ arch_get_unmapped_area_topdown(struct file *filp, unsigned long addr,
 	info.low_limit = max(PAGE_SIZE, mmap_min_addr);
 	info.high_limit = arch_get_mmap_base(addr, mm->mmap_base);
 	info.align_mask = 0;
+	info.align_offset = 0;
 	addr = vm_unmapped_area(&info);
 
 	/*