block: simplify the block device syncing code

Get rid of the indirections and just provide a sync_bdevs
helper for the generic sync code.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20211019062530.2174626-8-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>

block/bdev.c

@@ -1021,7 +1021,7 @@ int __invalidate_device(struct block_device *bdev, bool kill_dirty)
 }
 EXPORT_SYMBOL(__invalidate_device);
 
-void iterate_bdevs(void (*func)(struct block_device *, void *), void *arg)
+void sync_bdevs(bool wait)
 {
 	struct inode *inode, *old_inode = NULL;
 
@@ -1052,8 +1052,19 @@ void iterate_bdevs(void (*func)(struct block_device *, void *), void *arg)
 		bdev = I_BDEV(inode);
 
 		mutex_lock(&bdev->bd_disk->open_mutex);
-		if (bdev->bd_openers)
+		if (!bdev->bd_openers) {
-			func(bdev, arg);
+			; /* skip */
+		} else if (wait) {
+			/*
+			 * We keep the error status of individual mapping so
+			 * that applications can catch the writeback error using
+			 * fsync(2). See filemap_fdatawait_keep_errors() for
+			 * details.
+			 */
+			filemap_fdatawait_keep_errors(inode->i_mapping);
+		} else {
+			filemap_fdatawrite(inode->i_mapping);
+		}
 		mutex_unlock(&bdev->bd_disk->open_mutex);
 
 		spin_lock(&blockdev_superblock->s_inode_list_lock);

fs/internal.h

@@ -23,17 +23,11 @@ struct pipe_inode_info;
 #ifdef CONFIG_BLOCK
 extern void __init bdev_cache_init(void);
 
-void iterate_bdevs(void (*)(struct block_device *, void *), void *);
 void emergency_thaw_bdev(struct super_block *sb);
 #else
 static inline void bdev_cache_init(void)
 {
 }
-
-static inline void iterate_bdevs(void (*f)(struct block_device *, void *),
-		void *arg)
-{
-}
 static inline int emergency_thaw_bdev(struct super_block *sb)
 {
 	return 0;

fs/sync.c

@@ -78,21 +78,6 @@ static void sync_fs_one_sb(struct super_block *sb, void *arg)
 		sb->s_op->sync_fs(sb, *(int *)arg);
 }
 
-static void fdatawrite_one_bdev(struct block_device *bdev, void *arg)
-{
-	filemap_fdatawrite(bdev->bd_inode->i_mapping);
-}
-
-static void fdatawait_one_bdev(struct block_device *bdev, void *arg)
-{
-	/*
-	 * We keep the error status of individual mapping so that
-	 * applications can catch the writeback error using fsync(2).
-	 * See filemap_fdatawait_keep_errors() for details.
-	 */
-	filemap_fdatawait_keep_errors(bdev->bd_inode->i_mapping);
-}
-
 /*
  * Sync everything. We start by waking flusher threads so that most of
  * writeback runs on all devices in parallel. Then we sync all inodes reliably
@@ -111,8 +96,8 @@ void ksys_sync(void)
 	iterate_supers(sync_inodes_one_sb, NULL);
 	iterate_supers(sync_fs_one_sb, &nowait);
 	iterate_supers(sync_fs_one_sb, &wait);
-	iterate_bdevs(fdatawrite_one_bdev, NULL);
+	sync_bdevs(false);
-	iterate_bdevs(fdatawait_one_bdev, NULL);
+	sync_bdevs(true);
 	if (unlikely(laptop_mode))
 		laptop_sync_completion();
 }
@@ -133,10 +118,10 @@ static void do_sync_work(struct work_struct *work)
 	 */
 	iterate_supers(sync_inodes_one_sb, &nowait);
 	iterate_supers(sync_fs_one_sb, &nowait);
-	iterate_bdevs(fdatawrite_one_bdev, NULL);
+	sync_bdevs(false);
 	iterate_supers(sync_inodes_one_sb, &nowait);
 	iterate_supers(sync_fs_one_sb, &nowait);
-	iterate_bdevs(fdatawrite_one_bdev, NULL);
+	sync_bdevs(false);
 	printk("Emergency Sync complete\n");
 	kfree(work);
 }

include/linux/blkdev.h

@@ -1267,6 +1267,7 @@ int truncate_bdev_range(struct block_device *bdev, fmode_t mode, loff_t lstart,
 void invalidate_bdev(struct block_device *bdev);
 int sync_blockdev(struct block_device *bdev);
 int sync_blockdev_nowait(struct block_device *bdev);
+void sync_bdevs(bool wait);
 #else
 static inline void invalidate_bdev(struct block_device *bdev)
 {
@@ -1279,6 +1280,9 @@ static inline int sync_blockdev_nowait(struct block_device *bdev)
 {
 	return 0;
 }
+static inline void sync_bdevs(bool wait)
+{
+}
 #endif
 int fsync_bdev(struct block_device *bdev);