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AJvYcCXvACYcc9L+rCZsmUwgMNPDVoRFBUvKI56IGJc7AYMLY2BprocVE8bSUuckmkn6OoM1VQIpcthodGMnROPZbx9m/r8= X-Gm-Message-State: AOJu0YytBhfxsVQvL1VYWX1GugG4RSSVmclPw7nZJg2R99gaFWMZs3gM KmMz3t60gbLUYftnRzWY5J9PHReREeDXvlqsBJsZcysM5WD5eR4Law9qsg3bczBS4YKnTYNDsDC NFKM+VJKdoN/WzpOe3s1PzdraB60= X-Google-Smtp-Source: AGHT+IF1hr1CJo+evRVIfzH2sj7nOEmf2zzNTCkvZD7vuBhTgtU6J/x32S+gYuXY6SfIXfRbzCHeZEw6zbHjqo+ebls= X-Received: by 2002:a1f:4883:0:b0:4da:ddb4:feca with SMTP id v125-20020a1f4883000000b004daddb4fecamr7980943vka.8.1714777666946; Fri, 03 May 2024 16:07:46 -0700 (PDT) MIME-Version: 1.0 References: <20240503005023.174597-1-21cnbao@gmail.com> <20240503005023.174597-4-21cnbao@gmail.com> In-Reply-To: From: Barry Song <21cnbao@gmail.com> Date: Sat, 4 May 2024 07:07:35 +0800 Message-ID: Subject: Re: [PATCH v3 3/6] mm: introduce pte_move_swp_offset() helper which can move offset bidirectionally To: Chris Li Cc: akpm@linux-foundation.org, linux-mm@kvack.org, baolin.wang@linux.alibaba.com, david@redhat.com, hanchuanhua@oppo.com, hannes@cmpxchg.org, hughd@google.com, kasong@tencent.com, linux-kernel@vger.kernel.org, ryan.roberts@arm.com, surenb@google.com, v-songbaohua@oppo.com, willy@infradead.org, xiang@kernel.org, ying.huang@intel.com, yosryahmed@google.com, yuzhao@google.com, ziy@nvidia.com Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: E7DE14000A X-Stat-Signature: 4zw3or9ecum94ya4pfip4qwcrdjidq7y X-Rspam-User: X-HE-Tag: 1714777667-574962 X-HE-Meta: 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 8AnnDsaS 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Sat, May 4, 2024 at 4:51=E2=80=AFAM Chris Li wrote: > > On Thu, May 2, 2024 at 5:51=E2=80=AFPM Barry Song <21cnbao@gmail.com> wro= te: > > > > From: Barry Song > > > > There could arise a necessity to obtain the first pte_t from a swap > > pte_t located in the middle. For instance, this may occur within the > > context of do_swap_page(), where a page fault can potentially occur in > > any PTE of a large folio. To address this, the following patch introduc= es > > pte_move_swp_offset(), a function capable of bidirectional movement by > > a specified delta argument. Consequently, pte_increment_swp_offset() > > will directly invoke it with delta =3D 1. > > BTW, this patch has conflict with the latest mm-unstable. You might > need to refresh it. > > I do not see the delta =3D -1 usage case here. Maybe merge the patch > with the follow up patch that uses the delta =3D -1? > Does delta only make sense as 1 and -1? nop. delta can be any value from -1 to -(nr_pages - 1). This is used to get the first pte from vmf->pte in patdh6. it might be better to be a separate patch as it is introducing a new helper? do_swap_page() might not be the only user in the future? > > This patch doesn't seem straightly necessary to me. > > Chris > > > Chris > > > > > Suggested-by: "Huang, Ying" > > Signed-off-by: Barry Song > > --- > > mm/internal.h | 25 +++++++++++++++++++++---- > > 1 file changed, 21 insertions(+), 4 deletions(-) > > > > diff --git a/mm/internal.h b/mm/internal.h > > index c5552d35d995..cfe4aed66a5c 100644 > > --- a/mm/internal.h > > +++ b/mm/internal.h > > @@ -211,18 +211,21 @@ static inline int folio_pte_batch(struct folio *f= olio, unsigned long addr, > > } > > > > /** > > - * pte_next_swp_offset - Increment the swap entry offset field of a sw= ap pte. > > + * pte_move_swp_offset - Move the swap entry offset field of a swap pt= e > > + * forward or backward by delta > > * @pte: The initial pte state; is_swap_pte(pte) must be true and > > * non_swap_entry() must be false. > > + * @delta: The direction and the offset we are moving; forward if delt= a > > + * is positive; backward if delta is negative > > * > > - * Increments the swap offset, while maintaining all other fields, inc= luding > > + * Moves the swap offset, while maintaining all other fields, includin= g > > * swap type, and any swp pte bits. The resulting pte is returned. > > */ > > -static inline pte_t pte_next_swp_offset(pte_t pte) > > +static inline pte_t pte_move_swp_offset(pte_t pte, long delta) > > { > > swp_entry_t entry =3D pte_to_swp_entry(pte); > > pte_t new =3D __swp_entry_to_pte(__swp_entry(swp_type(entry), > > - (swp_offset(entry) += 1))); > > + (swp_offset(entry) += delta))); > > > > if (pte_swp_soft_dirty(pte)) > > new =3D pte_swp_mksoft_dirty(new); > > @@ -234,6 +237,20 @@ static inline pte_t pte_next_swp_offset(pte_t pte) > > return new; > > } > > > > + > > +/** > > + * pte_next_swp_offset - Increment the swap entry offset field of a sw= ap pte. > > + * @pte: The initial pte state; is_swap_pte(pte) must be true and > > + * non_swap_entry() must be false. > > + * > > + * Increments the swap offset, while maintaining all other fields, inc= luding > > + * swap type, and any swp pte bits. The resulting pte is returned. > > + */ > > +static inline pte_t pte_next_swp_offset(pte_t pte) > > +{ > > + return pte_move_swp_offset(pte, 1); > > +} > > + > > /** > > * swap_pte_batch - detect a PTE batch for a set of contiguous swap en= tries > > * @start_ptep: Page table pointer for the first entry. > > -- > > 2.34.1 Thanks Barry