[RFC PATCH 2/6] mm: mempolicy: Refactor out mpol_init_from_nodemask

[Ackerley Tng <ackerleytng@google.com>]

Refactor out mpol_init_from_nodemask() to simplify logic in do_mbind().

mpol_init_from_nodemask() will be used to perform similar
functionality in do_memfd_restricted_bind() in a later patch.

Signed-off-by: Ackerley Tng <ackerleytng@google.com>
---
 mm/mempolicy.c | 32 +++++++++++++++++++++-----------
 1 file changed, 21 insertions(+), 11 deletions(-)

diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index a256a241fd1d..a2655b626731 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -1254,6 +1254,25 @@ static struct page *new_page(struct page *page, unsigned long start)
 }
 #endif
 
+static long mpol_init_from_nodemask(struct mempolicy *mpol, const nodemask_t *nmask,
+				    bool always_unlock)
+{
+	long err;
+	NODEMASK_SCRATCH(scratch);
+
+	if (!scratch)
+		return -ENOMEM;
+
+	/* Cannot take lock before allocating in NODEMASK_SCRATCH */
+	mmap_write_lock(current->mm);
+	err = mpol_set_nodemask(mpol, nmask, scratch);
+	if (always_unlock || err)
+		mmap_write_unlock(current->mm);
+
+	NODEMASK_SCRATCH_FREE(scratch);
+	return err;
+}
+
 static long do_mbind(unsigned long start, unsigned long len,
 		     unsigned short mode, unsigned short mode_flags,
 		     nodemask_t *nmask, unsigned long flags)
@@ -1306,17 +1325,8 @@ static long do_mbind(unsigned long start, unsigned long len,
 
 		lru_cache_disable();
 	}
-	{
-		NODEMASK_SCRATCH(scratch);
-		if (scratch) {
-			mmap_write_lock(mm);
-			err = mpol_set_nodemask(new, nmask, scratch);
-			if (err)
-				mmap_write_unlock(mm);
-		} else
-			err = -ENOMEM;
-		NODEMASK_SCRATCH_FREE(scratch);
-	}
+
+	err = mpol_init_from_nodemask(new, nmask, false);
 	if (err)
 		goto mpol_out;
 
-- 
2.40.0.634.g4ca3ef3211-goog