> -----Original Message-----
> From: Nhat Pham <nphamcs@xxxxxxxxx>
> Sent: Tuesday, September 24, 2024 10:25 AM
> To: Sridhar, Kanchana P <kanchana.p.sridhar@xxxxxxxxx>
> Cc: linux-kernel@xxxxxxxxxxxxxxx; linux-mm@xxxxxxxxx;
> hannes@xxxxxxxxxxx; yosryahmed@xxxxxxxxxx;
> chengming.zhou@xxxxxxxxx; usamaarif642@xxxxxxxxx;
> shakeel.butt@xxxxxxxxx; ryan.roberts@xxxxxxx; Huang, Ying
> <ying.huang@xxxxxxxxx>; 21cnbao@xxxxxxxxx; akpm@xxxxxxxxxxxxxxxxxxxx;
> Zou, Nanhai <nanhai.zou@xxxxxxxxx>; Feghali, Wajdi K
> <wajdi.k.feghali@xxxxxxxxx>; Gopal, Vinodh <vinodh.gopal@xxxxxxxxx>
> Subject: Re: [PATCH v7 4/8] mm: zswap: Refactor code to delete stored
> offsets in case of errors.
>
> On Mon, Sep 23, 2024 at 6:17 PM Kanchana P Sridhar
> <kanchana.p.sridhar@xxxxxxxxx> wrote:
> >
> > Added a new procedure zswap_delete_stored_offsets() that can be
> > called to delete stored offsets in a folio in case zswap_store()
> > fails or zswap is disabled.
> >
> > Refactored the code in zswap_store() that handles these cases,
> > to call zswap_delete_stored_offsets().
> >
> > Signed-off-by: Kanchana P Sridhar <kanchana.p.sridhar@xxxxxxxxx>
> > ---
> > mm/zswap.c | 33 ++++++++++++++++++++++++++++++---
> > 1 file changed, 30 insertions(+), 3 deletions(-)
> >
> > diff --git a/mm/zswap.c b/mm/zswap.c
> > index fd35a81b6e36..9bea948d653e 100644
> > --- a/mm/zswap.c
> > +++ b/mm/zswap.c
> > @@ -1435,8 +1435,37 @@ static bool zswap_store_entry(struct xarray
> *tree,
> > return true;
> > }
> >
> > +/*
> > + * If the zswap store fails or zswap is disabled, we must invalidate the
> > + * possibly stale entries which were previously stored at the offsets
> > + * corresponding to each page of the folio. Otherwise, writeback could
> > + * overwrite the new data in the swapfile.
> > + *
> > + * This is called after the store of an offset in a large folio has failed.
>
> "store of a subpage" rather than "stored of an offset"?
Sure, I will make this change in v8.
>
>
> > + * All zswap entries in the folio must be deleted. This helps make sure
> > + * that a swapped-out mTHP is either entirely stored in zswap, or entirely
> > + * not stored in zswap.
> > + *
> > + * This is also called if zswap_store() is invoked, but zswap is not enabled.
> > + * All offsets for the folio are deleted from zswap in this case.
> > + */
> > +static void zswap_delete_stored_offsets(struct xarray *tree,
> > + pgoff_t offset,
> > + long nr_pages)
> > +{
> > + struct zswap_entry *entry;
> > + long i;
> > +
> > + for (i = 0; i < nr_pages; ++i) {
> > + entry = xa_erase(tree, offset + i);
> > + if (entry)
> > + zswap_entry_free(entry);
> > + }
> > +}
> > +
