On Mon, Apr 12, 2021 at 2:24 PM Chengguang Xu <cgxu519@xxxxxxxxxxxx> wrote:
>
> ---- 在 星期五, 2021-04-09 21:51:26 Miklos Szeredi <miklos@xxxxxxxxxx> 撰写 ----
> > On Fri, Nov 13, 2020 at 7:57 AM Chengguang Xu <cgxu519@xxxxxxxxxxxx> wrote:
> > >
> > > Now overlayfs can only sync dirty inode during syncfs,
> > > so remove unnecessary sync_filesystem() on upper file
> > > system.
> > >
> > > Signed-off-by: Chengguang Xu <cgxu519@xxxxxxxxxxxx>
> > > ---
> > > fs/overlayfs/super.c | 11 ++++++++---
> > > 1 file changed, 8 insertions(+), 3 deletions(-)
> > >
> > > diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
> > > index 982b3954b47c..58507f1cd583 100644
> > > --- a/fs/overlayfs/super.c
> > > +++ b/fs/overlayfs/super.c
> > > @@ -15,6 +15,8 @@
> > > #include <linux/seq_file.h>
> > > #include <linux/posix_acl_xattr.h>
> > > #include <linux/exportfs.h>
> > > +#include <linux/blkdev.h>
> > > +#include <linux/writeback.h>
> > > #include "overlayfs.h"
> > >
> > > MODULE_AUTHOR("Miklos Szeredi <miklos@xxxxxxxxxx>");
> > > @@ -270,8 +272,7 @@ static int ovl_sync_fs(struct super_block *sb, int wait)
> > > * Not called for sync(2) call or an emergency sync (SB_I_SKIP_SYNC).
> > > * All the super blocks will be iterated, including upper_sb.
> > > *
> > > - * If this is a syncfs(2) call, then we do need to call
> > > - * sync_filesystem() on upper_sb, but enough if we do it when being
> > > + * if this is a syncfs(2) call, it will be enough we do it when being
> > > * called with wait == 1.
> > > */
> > > if (!wait)
> > > @@ -280,7 +281,11 @@ static int ovl_sync_fs(struct super_block *sb, int wait)
> > > upper_sb = ovl_upper_mnt(ofs)->mnt_sb;
> > >
> > > down_read(&upper_sb->s_umount);
> > > - ret = sync_filesystem(upper_sb);
> > > + wait_sb_inodes(upper_sb);
> > > + if (upper_sb->s_op->sync_fs)
> > > + ret = upper_sb->s_op->sync_fs(upper_sb, wait);
> > > + if (!ret)
> > > + ret = sync_blockdev(upper_sb->s_bdev);
> >
> > Should this instead be __sync_blockdev(..., wait)?
>
> I don't remember why we skipped the case of (wait == 0) here, just guess it's not worth
> to export internal function __sync_blockdev() to modules, do you prefer to call __sync_blockdev()
> and handle both nowait and wait cases?
Possibly it would make most sense to export the "->sync_fs() +
__sync_blockdev()" part of __sync_filesystem() as a separate helper.
Thanks,
Miklos
