mm: make vm_brk killable

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.

Signed-off-by: Michal Hocko <mhocko@suse.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 4 insertions, 7 deletions

diff --git a/include/linux/mm.h b/include/linux/mm.h
index d5eb8dddd7c0..2835d598d258 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -2011,7 +2011,7 @@ 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 ca292a7c2b68..d3d9a94ca031 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);