---- 在 星期二, 2020-04-14 21:44:39 Amir Goldstein <amir73il@xxxxxxxxx> 撰写 ----
> On Tue, Apr 14, 2020 at 12:53 PM Chengguang Xu <cgxu519@xxxxxxxxxxxx> wrote:
> >
> > Sharing inode with different whiteout files for saving
> > inode and speeding up deleting operation.
> >
> > Signed-off-by: Chengguang Xu <cgxu519@xxxxxxxxxxxx>
> > ---
> > v1->v2:
> > - Address Amir's comments in v1
> >
> > v2->v3:
> > - Address Amir's comments in v2
> > - Rebase on Amir's "Overlayfs use index dir as work dir" patch set
> > - Keep at most one whiteout tmpfile in work dir
> >
> > fs/overlayfs/dir.c | 35 ++++++++++++++++++++++++++++-------
> > fs/overlayfs/overlayfs.h | 9 +++++++--
> > fs/overlayfs/ovl_entry.h | 4 ++++
> > fs/overlayfs/readdir.c | 3 ++-
> > fs/overlayfs/super.c | 9 +++++++++
> > fs/overlayfs/util.c | 3 ++-
> > 6 files changed, 52 insertions(+), 11 deletions(-)
> >
> > diff --git a/fs/overlayfs/dir.c b/fs/overlayfs/dir.c
> > index 279009dee366..dbe5e54dcb16 100644
> > --- a/fs/overlayfs/dir.c
> > +++ b/fs/overlayfs/dir.c
> > @@ -62,35 +62,55 @@ struct dentry *ovl_lookup_temp(struct dentry *workdir)
> > }
> >
> > /* caller holds i_mutex on workdir */
> > -static struct dentry *ovl_whiteout(struct dentry *workdir)
> > +static struct dentry *ovl_whiteout(struct ovl_fs *ofs, struct dentry *workdir)
> > {
> > int err;
> > + bool retried = false;
> > + bool should_link = (ofs->whiteout_link_max > 1);
> > struct dentry *whiteout;
> > struct inode *wdir = workdir->d_inode;
> >
> > +retry:
> > whiteout = ovl_lookup_temp(workdir);
> > if (IS_ERR(whiteout))
> > return whiteout;
> >
> > + if (should_link && ofs->whiteout) {
>
> What happens with ofs->whiteout_link_max == 2 is that half of the
> times, whiteout gets linked and then unlinked.
> That is not needed.
> I think code would look better like this:
>
> if (ovl_whiteout_linkable(ofs)) {
> err = ovl_do_link(ofs->whiteout, wdir, whiteout);
> ...
> } else if (ofs->whiteout) {
> ovl_cleanup(wdir, ofs->whiteout);
> ....
>
> With:
>
> static inline bool ovl_whiteout_linkable(struct ovl_fs *ofs)
> {
> return ofs->whiteout &&
> ofs->whiteout->d_inode->i_nlink < ofs->whiteout_link_max;
> }
>
tmpfile has occupied one link, so the maximum link count of whiteout inode
in your code will be ofs->whiteout_link_max - 1, right?
Thanks,
cgxu
