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X-CSE-ConnectionGUID: HpzeCSxcQFmtOc+PPZFJTA== X-CSE-MsgGUID: esiTMmjBR9+HXt+40kLQRg== X-IronPort-AV: E=McAfee;i="6700,10204,11373"; a="43358416" X-IronPort-AV: E=Sophos;i="6.14,246,1736841600"; d="scan'208";a="43358416" Received: from orviesa008.jf.intel.com ([10.64.159.148]) by fmvoesa108.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 14 Mar 2025 14:09:49 -0700 X-CSE-ConnectionGUID: 3wpcDs1oTOeE+KZV1DRGnw== X-CSE-MsgGUID: 8qPtg8DqQaadwOsnzF3rSw== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.14,246,1736841600"; d="scan'208";a="122332839" Received: from dnelso2-mobl.amr.corp.intel.com (HELO [10.125.108.212]) ([10.125.108.212]) by orviesa008-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 14 Mar 2025 14:09:49 -0700 Message-ID: <8624268dd3a211e656b3fb179c46c1742fe80790.camel@linux.intel.com> Subject: Re: [PATCH 4/9] mm: swap: remove unneeded VM_BUG_ON(*map != SWAP_HAS_CACHE) in swap_entry_range_free() From: Tim Chen To: Kemeng Shi , akpm@linux-foundation.org Cc: kasong@tencent.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Date: Fri, 14 Mar 2025 14:09:48 -0700 In-Reply-To: <20250313210515.9920-5-shikemeng@huaweicloud.com> References: <20250313210515.9920-1-shikemeng@huaweicloud.com> <20250313210515.9920-5-shikemeng@huaweicloud.com> Autocrypt: addr=tim.c.chen@linux.intel.com; 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charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.50.4 (3.50.4-1.fc39) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Fri, 2025-03-14 at 05:05 +0800, Kemeng Shi wrote: > As all callers of swap_entry_range_free() have already ensured slots to > be freed are marked as SWAP_HAS_CACHE while holding the cluster lock, > the BUG_ON check can be safely removed. After this, the function > swap_entry_range_free() could drop any kind of last flag, rename it to > swap_entries_free() and update it's comment accordingly. >=20 > This is a preparation to use swap_entries_free() to drop last 1 and Probably clearer to say=20 drop last ref count=20 instead or drop last 1 > SWAP_MAP_SHMEM flag. >=20 > Signed-off-by: Kemeng Shi > --- > mm/swapfile.c | 21 ++++++++++----------- > 1 file changed, 10 insertions(+), 11 deletions(-) >=20 > diff --git a/mm/swapfile.c b/mm/swapfile.c > index ba37b9bff586..14b7b37996ff 100644 > --- a/mm/swapfile.c > +++ b/mm/swapfile.c > @@ -52,9 +52,9 @@ > static bool swap_count_continued(struct swap_info_struct *, pgoff_t, > unsigned char); > static void free_swap_count_continuations(struct swap_info_struct *); > -static void swap_entry_range_free(struct swap_info_struct *si, > - struct swap_cluster_info *ci, > - swp_entry_t entry, unsigned int nr_pages); > +static void swap_entries_free(struct swap_info_struct *si, > + struct swap_cluster_info *ci, > + swp_entry_t entry, unsigned int nr_pages); > static void swap_range_alloc(struct swap_info_struct *si, > unsigned int nr_entries); > static bool folio_swapcache_freeable(struct folio *folio); > @@ -1511,7 +1511,7 @@ static bool swap_entries_put_nr(struct swap_info_st= ruct *si, > for (i =3D 0; i < nr; i++) > WRITE_ONCE(si->swap_map[offset + i], SWAP_HAS_CACHE); > if (!has_cache) > - swap_entry_range_free(si, ci, entry, nr); > + swap_entries_free(si, ci, entry, nr); > unlock_cluster(ci); > =20 > return has_cache; > @@ -1530,12 +1530,12 @@ static bool swap_entries_put_nr(struct swap_info_= struct *si, > } > =20 > /* > - * Drop the last HAS_CACHE flag of swap entries, caller have to > - * ensure all entries belong to the same cgroup. > + * Drop the last flag(1, SWAP_HAS_CACHE or SWAP_MAP_SHMEM) of swap entri= es, > + * caller have to ensure all entries belong to the same cgroup. Will be nice to modify the above comment:=C2=A0 all entries belong to the same cgroup and cluster. Otherwise Reviewed-by: Tim Chen =20 > =20 > -static void swap_entry_range_free(struct swap_info_struct *si, > - struct swap_cluster_info *ci, > - swp_entry_t entry, unsigned int nr_pages) > +static void swap_entries_free(struct swap_info_struct *si, > + struct swap_cluster_info *ci, > + swp_entry_t entry, unsigned int nr_pages) > { > unsigned long offset =3D swp_offset(entry); > unsigned char *map =3D si->swap_map + offset; > @@ -1545,7 +1545,6 @@ static void swap_entry_range_free(struct swap_info_= struct *si, > VM_BUG_ON(ci !=3D offset_to_cluster(si, offset + nr_pages - 1)); > =20 > do { > - VM_BUG_ON(*map !=3D SWAP_HAS_CACHE); > *map =3D 0; > } while (++map < map_end); > =20 > @@ -1605,7 +1604,7 @@ void put_swap_folio(struct folio *folio, swp_entry_= t entry) > =20 > ci =3D lock_cluster(si, offset); > if (swap_only_has_cache(si, offset, size)) > - swap_entry_range_free(si, ci, entry, size); > + swap_entries_free(si, ci, entry, size); > else > for (int i =3D 0; i < size; i++, entry.val++) > swap_entry_put_locked(si, ci, entry, SWAP_HAS_CACHE);