md: don't call bitmap_create() while array is quiesced.

bitmap_create() allocates memory with GFP_KERNEL and
so can wait for IO.
If called while the array is quiesced, it could wait indefinitely
for write out to the array - deadlock.
So call bitmap_create() before quiescing the array.
Signed-off-by: NeilBrown <neilb@suse.com>
Signed-off-by: Shaohua Li <shli@fb.com>

drivers/md/md.c

@@ -6621,22 +6621,26 @@ static int set_bitmap_file(struct mddev *mddev, int fd)
 		return -ENOENT; /* cannot remove what isn't there */
 	err = 0;
 	if (mddev->pers) {
-		mddev->pers->quiesce(mddev, 1);
 		if (fd >= 0) {
 			struct bitmap *bitmap;
 
 			bitmap = bitmap_create(mddev, -1);
+			mddev->pers->quiesce(mddev, 1);
 			if (!IS_ERR(bitmap)) {
 				mddev->bitmap = bitmap;
 				err = bitmap_load(mddev);
 			} else
 				err = PTR_ERR(bitmap);
-		}
-		if (fd < 0 || err) {
+			if (err) {
 				bitmap_destroy(mddev);
-			fd = -1; /* make sure to put the file */
+				fd = -1;
 			}
 			mddev->pers->quiesce(mddev, 0);
+		} else if (fd < 0) {
+			mddev->pers->quiesce(mddev, 1);
+			bitmap_destroy(mddev);
+			mddev->pers->quiesce(mddev, 0);
+		}
 	}
 	if (fd < 0) {
 		struct file *f = mddev->bitmap_info.file;
@@ -6920,8 +6924,8 @@ static int update_array_info(struct mddev *mddev, mdu_array_info_t *info)
 				mddev->bitmap_info.default_offset;
 			mddev->bitmap_info.space =
 				mddev->bitmap_info.default_space;
-			mddev->pers->quiesce(mddev, 1);
 			bitmap = bitmap_create(mddev, -1);
+			mddev->pers->quiesce(mddev, 1);
 			if (!IS_ERR(bitmap)) {
 				mddev->bitmap = bitmap;
 				rv = bitmap_load(mddev);