[PATCH 06/18] mm: make vm_brk killable

[Michal Hocko]

From: Michal Hocko <mhocko@xxxxxxxx>

Now that all the callers handle vm_brk failure we can change it
wait for mmap_sem killable to help oom_reaper to not get blocked
just because vm_brk gets blocked behind mmap_sem readers.

Cc: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Acked-by: Vlastimil Babka <vbabka@xxxxxxx>
Signed-off-by: Michal Hocko <mhocko@xxxxxxxx>
---
 include/linux/mm.h | 2 +-
 mm/mmap.c          | 9 +++------
 2 files changed, 4 insertions(+), 7 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 1085e025852a..7b52750caf9e 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -2003,7 +2003,7 @@ static inline void mm_populate(unsigned long addr, unsigned long len) {}
 #endif
 
 /* These take the mm semaphore themselves */
-extern unsigned long vm_brk(unsigned long, unsigned long);
+extern unsigned long __must_check vm_brk(unsigned long, unsigned long);
 extern int vm_munmap(unsigned long, size_t);
 extern unsigned long __must_check vm_mmap(struct file *, unsigned long,
         unsigned long, unsigned long,
diff --git a/mm/mmap.c b/mm/mmap.c
index 032605bda665..62cb02310494 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -2712,12 +2712,9 @@ unsigned long vm_brk(unsigned long addr, unsigned long len)
 	unsigned long ret;
 	bool populate;
 
-	/*
-	 * XXX not all users are chcecking the return value, convert
-	 * to down_write_killable after they are able to cope with
-	 * error
-	 */
-	down_write(&mm->mmap_sem);
+	if (down_write_killable(&mm->mmap_sem))
+		return -EINTR;
+
 	ret = do_brk(addr, len);
 	populate = ((mm->def_flags & VM_LOCKED) != 0);
 	up_write(&mm->mmap_sem);
-- 
2.8.0.rc3