VisionFive2 Linux kernel

StarFive Tech Linux Kernel for VisionFive (JH7110) boards (mirror)

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author: Jan Kara <jack@suse.cz> 2012-07-03 16:45:34 +0200 committer: Al Viro <viro@zeniv.linux.org.uk> 2012-07-22 23:59:01 +0400 commit: 4ea425b63a3dfeb7707fc7cc7161c11a51e871ed parent: d0e91b13eb34d449922124c34f8a05e498daa089
Commit Summary:
vfs: Avoid unnecessary WB_SYNC_NONE writeback during sys_sync and reorder sync passes
Diffstat:
1 file changed, 9 insertions, 10 deletions
diff --git a/fs/sync.c b/fs/sync.c
index 131ddae87a1d..eb8722dc556f 100644
--- a/fs/sync.c
+++ b/fs/sync.c
@@ -73,12 +73,6 @@ static void sync_inodes_one_sb(struct super_block *sb, void *arg)
 		sync_inodes_sb(sb);
 }
 
-static void writeback_inodes_one_sb(struct super_block *sb, void *arg)
-{
-	if (!(sb->s_flags & MS_RDONLY))
-		writeback_inodes_sb(sb, WB_REASON_SYNC);
-}
-
 static void sync_fs_one_sb(struct super_block *sb, void *arg)
 {
 	if (!(sb->s_flags & MS_RDONLY) && sb->s_op->sync_fs)
@@ -96,17 +90,22 @@ static void fdatawait_one_bdev(struct block_device *bdev, void *arg)
 }
 
 /*
- * sync everything.  Start out by waking pdflush, because that writes back
- * all queues in parallel.
+ * 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
+ * which effectively also waits for all flusher threads to finish doing
+ * writeback. At this point all data is on disk so metadata should be stable
+ * and we tell filesystems to sync their metadata via ->sync_fs() calls.
+ * Finally, we writeout all block devices because some filesystems (e.g. ext2)
+ * just write metadata (such as inodes or bitmaps) to block device page cache
+ * and do not sync it on their own in ->sync_fs().
  */
 SYSCALL_DEFINE0(sync)
 {
 	int nowait = 0, wait = 1;
 
 	wakeup_flusher_threads(0, WB_REASON_SYNC);
-	iterate_supers(writeback_inodes_one_sb, NULL);
-	iterate_supers(sync_fs_one_sb, &nowait);
 	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);
 	iterate_bdevs(fdatawait_one_bdev, NULL);