Re: [PATCH] ovl: skip overlayfs superblocks at global sync

[Dave Chinner]

On Thu, Apr 09, 2020 at 11:29:47AM +0300, Konstantin Khlebnikov wrote:
> Stacked filesystems like overlayfs has no own writeback, but they have to
> forward syncfs() requests to backend for keeping data integrity.
> 
> During global sync() each overlayfs instance calls method ->sync_fs()
> for backend although it itself is in global list of superblocks too.
> As a result one syscall sync() could write one superblock several times
> and send multiple disk barriers.
> 
> This patch adds flag SB_I_SKIP_SYNC into sb->sb_iflags to avoid that.

Why wouldn't you just remove the ->sync_fs method from overlay?

I mean, if you don't need the filesystem to do anything special for
one specific data integrity sync_fs call, you don't need it for any
of them, yes?

-Dave.
-- 
Dave Chinner
david@xxxxxxxxxxxxx