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Commit d0e91b13 authored by Jan Kara's avatar Jan Kara Committed by Al Viro
Browse files

vfs: Remove unnecessary flushing of block devices 



It is not necessary to write block devices twice. The reason why we first did
flush and then proper sync is that
  for_each_bdev() {
    write_bdev()
    wait_for_completion()
  }
is much slower than
  for_each_bdev()
    write_bdev()
  for_each_bdev()
    wait_for_completion()
when there is bigger amount of data. But as is seen in the above, there's no real
need to scan pages and submit them twice. We just need to separate the submission
and waiting part. This patch does that.

Signed-off-by: default avatarJan Kara <jack@suse.cz>
Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent a8c7176b

fs/sync.c

+8 −8
Original line number Diff line number Diff line
@@ -85,14 +85,14 @@ static void sync_fs_one_sb(struct super_block *sb, void *arg) 
		sb->s_op->sync_fs(sb, *(int *)arg);

}



static void flush_one_bdev(struct block_device *bdev, void *arg)

static void fdatawrite_one_bdev(struct block_device *bdev, void *arg)

{

	__sync_blockdev(bdev, 0);

	filemap_fdatawrite(bdev->bd_inode->i_mapping);

}



static void sync_one_bdev(struct block_device *bdev, void *arg)

static void fdatawait_one_bdev(struct block_device *bdev, void *arg)

{

	sync_blockdev(bdev);

	filemap_fdatawait(bdev->bd_inode->i_mapping);

}



/*
@@ -106,10 +106,10 @@ SYSCALL_DEFINE0(sync) 
	wakeup_flusher_threads(0, WB_REASON_SYNC);

	iterate_supers(writeback_inodes_one_sb, NULL);

	iterate_supers(sync_fs_one_sb, &nowait);

	iterate_bdevs(flush_one_bdev, NULL);

	iterate_supers(sync_inodes_one_sb, NULL);

	iterate_supers(sync_fs_one_sb, &wait);

	iterate_bdevs(sync_one_bdev, NULL);

	iterate_bdevs(fdatawrite_one_bdev, NULL);

	iterate_bdevs(fdatawait_one_bdev, NULL);

	if (unlikely(laptop_mode))

		laptop_sync_completion();

	return 0;
@@ -125,10 +125,10 @@ 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(flush_one_bdev, NULL);

	iterate_bdevs(fdatawrite_one_bdev, NULL);

	iterate_supers(sync_inodes_one_sb, &nowait);

	iterate_supers(sync_fs_one_sb, &nowait);

	iterate_bdevs(flush_one_bdev, NULL);

	iterate_bdevs(fdatawrite_one_bdev, NULL);

	printk("Emergency Sync complete\n");

	kfree(work);

}