[RFC PATCH v2 1/4] mm/madvise: split out mmap locking operations for madvise()

[SeongJae Park <sj@kernel.org>]

Split out the madvise behavior-dependent mmap_lock operations from
do_madvise(), for easier reuse of the logic in an upcoming change.

Signed-off-by: SeongJae Park <sj@kernel.org>
---
 mm/madvise.c | 45 ++++++++++++++++++++++++++++++++-------------
 1 file changed, 32 insertions(+), 13 deletions(-)

diff --git a/mm/madvise.c b/mm/madvise.c
index 49f3a75046f6..ae0964bc4d88 100644
--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -1565,6 +1565,33 @@ int madvise_set_anon_name(struct mm_struct *mm, unsigned long start,
 				 madvise_vma_anon_name);
 }
 #endif /* CONFIG_ANON_VMA_NAME */
+
+static int madvise_lock(struct mm_struct *mm, int behavior)
+{
+
+#ifdef CONFIG_MEMORY_FAILURE
+	if (behavior == MADV_HWPOISON || behavior == MADV_SOFT_OFFLINE)
+		return 0;
+#endif
+
+	if (madvise_need_mmap_write(behavior)) {
+		if (mmap_write_lock_killable(mm))
+			return -EINTR;
+	} else {
+		mmap_read_lock(mm);
+	}
+	return 0;
+
+}
+
+static void madvise_unlock(struct mm_struct *mm, int behavior)
+{
+	if (madvise_need_mmap_write(behavior))
+		mmap_write_unlock(mm);
+	else
+		mmap_read_unlock(mm);
+}
+
 /*
  * The madvise(2) system call.
  *
@@ -1641,7 +1668,6 @@ int do_madvise(struct mm_struct *mm, unsigned long start, size_t len_in, int beh
 {
 	unsigned long end;
 	int error;
-	int write;
 	size_t len;
 	struct blk_plug plug;
 
@@ -1663,19 +1689,15 @@ int do_madvise(struct mm_struct *mm, unsigned long start, size_t len_in, int beh
 	if (end == start)
 		return 0;
 
+	error = madvise_lock(mm, behavior);
+	if (error)
+		return error;
+
 #ifdef CONFIG_MEMORY_FAILURE
 	if (behavior == MADV_HWPOISON || behavior == MADV_SOFT_OFFLINE)
 		return madvise_inject_error(behavior, start, start + len_in);
 #endif
 
-	write = madvise_need_mmap_write(behavior);
-	if (write) {
-		if (mmap_write_lock_killable(mm))
-			return -EINTR;
-	} else {
-		mmap_read_lock(mm);
-	}
-
 	start = untagged_addr_remote(mm, start);
 	end = start + len;
 
@@ -1692,10 +1714,7 @@ int do_madvise(struct mm_struct *mm, unsigned long start, size_t len_in, int beh
 	}
 	blk_finish_plug(&plug);
 
-	if (write)
-		mmap_write_unlock(mm);
-	else
-		mmap_read_unlock(mm);
+	madvise_unlock(mm, behavior);
 
 	return error;
 }
-- 
2.39.5