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Message-ID: <SJ0PR11MB56782B4EFAD5D9E0B3343705C9682@SJ0PR11MB5678.namprd11.prod.outlook.com>
Date: Tue, 24 Sep 2024 22:22:27 +0000
From: "Sridhar, Kanchana P" <kanchana.p.sridhar@...el.com>
To: Yosry Ahmed <yosryahmed@...gle.com>
CC: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"linux-mm@...ck.org" <linux-mm@...ck.org>, "hannes@...xchg.org"
<hannes@...xchg.org>, "nphamcs@...il.com" <nphamcs@...il.com>,
"chengming.zhou@...ux.dev" <chengming.zhou@...ux.dev>,
"usamaarif642@...il.com" <usamaarif642@...il.com>, "shakeel.butt@...ux.dev"
<shakeel.butt@...ux.dev>, "ryan.roberts@....com" <ryan.roberts@....com>,
"Huang, Ying" <ying.huang@...el.com>, "21cnbao@...il.com"
<21cnbao@...il.com>, "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
"Zou, Nanhai" <nanhai.zou@...el.com>, "Feghali, Wajdi K"
<wajdi.k.feghali@...el.com>, "Gopal, Vinodh" <vinodh.gopal@...el.com>,
"Sridhar, Kanchana P" <kanchana.p.sridhar@...el.com>
Subject: RE: [PATCH v7 3/8] mm: zswap: Refactor code to store an entry in
zswap xarray.
> -----Original Message-----
> From: Yosry Ahmed <yosryahmed@...gle.com>
> Sent: Tuesday, September 24, 2024 12:15 PM
> To: Sridhar, Kanchana P <kanchana.p.sridhar@...el.com>
> Cc: linux-kernel@...r.kernel.org; linux-mm@...ck.org;
> hannes@...xchg.org; nphamcs@...il.com; chengming.zhou@...ux.dev;
> usamaarif642@...il.com; shakeel.butt@...ux.dev; ryan.roberts@....com;
> Huang, Ying <ying.huang@...el.com>; 21cnbao@...il.com; akpm@...ux-
> foundation.org; Zou, Nanhai <nanhai.zou@...el.com>; Feghali, Wajdi K
> <wajdi.k.feghali@...el.com>; Gopal, Vinodh <vinodh.gopal@...el.com>
> Subject: Re: [PATCH v7 3/8] mm: zswap: Refactor code to store an entry in
> zswap xarray.
>
> On Mon, Sep 23, 2024 at 6:17 PM Kanchana P Sridhar
> <kanchana.p.sridhar@...el.com> wrote:
> >
> > Added a new procedure zswap_store_entry() that refactors the code
> > currently in zswap_store() to store an entry in the zswap xarray.
> > This will allow us to call this procedure for each storing the swap
> > offset of each page in an mTHP in the xarray, as part of zswap_store()
> > supporting mTHP.
> >
> > Also, made a minor edit in the comments for 'struct zswap_entry' to delete
> > the description of the 'value' member that was deleted in commit
> > 20a5532ffa53d6ecf41ded920a7b0ff9c65a7dcf ("mm: remove code to
> handle
> > same filled pages").
> >
> > Signed-off-by: Kanchana P Sridhar <kanchana.p.sridhar@...el.com>
> > ---
> > mm/zswap.c | 51 ++++++++++++++++++++++++++++++++++-----------------
> > 1 file changed, 34 insertions(+), 17 deletions(-)
> >
> > diff --git a/mm/zswap.c b/mm/zswap.c
> > index 59b7733a62d3..fd35a81b6e36 100644
> > --- a/mm/zswap.c
> > +++ b/mm/zswap.c
> > @@ -190,7 +190,6 @@ static struct shrinker *zswap_shrinker;
> > * section for context.
> > * pool - the zswap_pool the entry's data is in
> > * handle - zpool allocation handle that stores the compressed page data
> > - * value - value of the same-value filled pages which have same content
> > * objcg - the obj_cgroup that the compressed memory is charged to
> > * lru - handle to the pool's lru used to evict pages.
> > */
> > @@ -1404,12 +1403,44 @@ static void shrink_worker(struct work_struct
> *w)
> > /*********************************
> > * main API
> > **********************************/
> > +
> > +/*
> > + * Returns true if the entry was successfully
> > + * stored in the xarray, and false otherwise.
> > + */
> > +static bool zswap_store_entry(struct xarray *tree,
> > + struct zswap_entry *entry)
>
>
> I think zswap_tree_store() is a more descriptive name.
Thanks Yosry for the code review comments!
Sure, will change this to zswap_tree_store() in v8.
>
> >
> > +{
> > + struct zswap_entry *old;
> > + pgoff_t offset = swp_offset(entry->swpentry);
>
>
> Reverse xmas tree where possible please (longest to shortest declarations).
>
> >
> > +
> > + old = xa_store(tree, offset, entry, GFP_KERNEL);
> > +
>
> No need for the blank line here.
Ok, will fix in v8.
Thanks,
Kanchana
>
> > + if (xa_is_err(old)) {
> > + int err = xa_err(old);
> > +
> > + WARN_ONCE(err != -ENOMEM, "unexpected xarray error: %d\n",
> err);
> > + zswap_reject_alloc_fail++;
> > + return false;
> > + }
> > +
> > + /*
> > + * We may have had an existing entry that became stale when
> > + * the folio was redirtied and now the new version is being
> > + * swapped out. Get rid of the old.
> > + */
> > + if (old)
> > + zswap_entry_free(old);
> > +
> > + return true;
> > +}
> > +
> > bool zswap_store(struct folio *folio)
> > {
> > swp_entry_t swp = folio->swap;
> > pgoff_t offset = swp_offset(swp);
> > struct xarray *tree = swap_zswap_tree(swp);
> > - struct zswap_entry *entry, *old;
> > + struct zswap_entry *entry;
> > struct obj_cgroup *objcg = NULL;
> > struct mem_cgroup *memcg = NULL;
> >
> > @@ -1465,22 +1496,8 @@ bool zswap_store(struct folio *folio)
> > entry->objcg = objcg;
> > entry->referenced = true;
> >
> > - old = xa_store(tree, offset, entry, GFP_KERNEL);
> > - if (xa_is_err(old)) {
> > - int err = xa_err(old);
> > -
> > - WARN_ONCE(err != -ENOMEM, "unexpected xarray error: %d\n",
> err);
> > - zswap_reject_alloc_fail++;
> > + if (!zswap_store_entry(tree, entry))
> > goto store_failed;
> > - }
> > -
> > - /*
> > - * We may have had an existing entry that became stale when
> > - * the folio was redirtied and now the new version is being
> > - * swapped out. Get rid of the old.
> > - */
> > - if (old)
> > - zswap_entry_free(old);
> >
> > if (objcg) {
> > obj_cgroup_charge_zswap(objcg, entry->length);
> > --
> > 2.27.0
> >
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