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Tue, 17 Jun 2025 11:35:32 -0700 (PDT) Received: from KASONG-MC4.tencent.com ([106.37.123.168]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2365de781c7sm83753715ad.128.2025.06.17.11.35.27 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Tue, 17 Jun 2025 11:35:32 -0700 (PDT) From: Kairui Song To: linux-mm@kvack.org Cc: Andrew Morton , Hugh Dickins , Baolin Wang , Matthew Wilcox , Kemeng Shi , Chris Li , Nhat Pham , Baoquan He , Barry Song , linux-kernel@vger.kernel.org, Kairui Song Subject: [PATCH 2/4] mm/shmem, swap: avoid redundant Xarray lookup during swapin Date: Wed, 18 Jun 2025 02:35:01 +0800 Message-ID: <20250617183503.10527-3-ryncsn@gmail.com> X-Mailer: git-send-email 2.50.0 In-Reply-To: <20250617183503.10527-1-ryncsn@gmail.com> References: <20250617183503.10527-1-ryncsn@gmail.com> Reply-To: Kairui Song MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Queue-Id: 6FF8A40016 X-Rspamd-Server: rspam10 X-Stat-Signature: rtpyffm9e68csmwjppk4be9qccs7z53p X-HE-Tag: 1750185334-218097 X-HE-Meta: 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 SQNOv4IV GF9bcnfgCtB85y4R2N/IUOzEBvYegZ2slXKHuV9SoWH4WXr6OWK43sFU1cWaOLVBRivW//Ba/lM+wSf5VsngMH54Y0VyYeohkS/wQaMCebrFrjIy4qps9TetRjcd53+6t+XMG7HQfTnkdmr+LwXq8ajC56xErjEZqNcoS7wxiKOvj49d5TUh7RvYomhqgfGacn4HvnC1X0c/OwegM2OOePBhbtg== 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: From: Kairui Song Currently shmem calls xa_get_order to get the swap radix entry order, requiring a full tree walk. This can be easily combined with the swap entry value checking (shmem_confirm_swap) to avoid the duplicated lookup, which should improve the performance. Signed-off-by: Kairui Song --- mm/shmem.c | 33 ++++++++++++++++++++++++--------- 1 file changed, 24 insertions(+), 9 deletions(-) diff --git a/mm/shmem.c b/mm/shmem.c index 4e7ef343a29b..0ad49e57f736 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -505,15 +505,27 @@ static int shmem_replace_entry(struct address_space *mapping, /* * Sometimes, before we decide whether to proceed or to fail, we must check - * that an entry was not already brought back from swap by a racing thread. + * that an entry was not already brought back or split by a racing thread. * * Checking folio is not enough: by the time a swapcache folio is locked, it * might be reused, and again be swapcache, using the same swap as before. + * Returns the swap entry's order if it still presents, else returns -1. */ -static bool shmem_confirm_swap(struct address_space *mapping, - pgoff_t index, swp_entry_t swap) +static int shmem_swap_check_entry(struct address_space *mapping, pgoff_t index, + swp_entry_t swap) { - return xa_load(&mapping->i_pages, index) == swp_to_radix_entry(swap); + XA_STATE(xas, &mapping->i_pages, index); + int ret = -1; + void *entry; + + rcu_read_lock(); + do { + entry = xas_load(&xas); + if (entry == swp_to_radix_entry(swap)) + ret = xas_get_order(&xas); + } while (xas_retry(&xas, entry)); + rcu_read_unlock(); + return ret; } /* @@ -2256,16 +2268,20 @@ static int shmem_swapin_folio(struct inode *inode, pgoff_t index, return -EIO; si = get_swap_device(swap); - if (!si) { - if (!shmem_confirm_swap(mapping, index, swap)) + order = shmem_swap_check_entry(mapping, index, swap); + if (unlikely(!si)) { + if (order < 0) return -EEXIST; else return -EINVAL; } + if (unlikely(order < 0)) { + put_swap_device(si); + return -EEXIST; + } /* Look it up and read it in.. */ folio = swap_cache_get_folio(swap, NULL, 0); - order = xa_get_order(&mapping->i_pages, index); if (!folio) { int nr_pages = 1 << order; bool fallback_order0 = false; @@ -2415,7 +2431,7 @@ static int shmem_swapin_folio(struct inode *inode, pgoff_t index, *foliop = folio; return 0; failed: - if (!shmem_confirm_swap(mapping, index, swap)) + if (shmem_swap_check_entry(mapping, index, swap) < 0) error = -EEXIST; if (error == -EIO) shmem_set_folio_swapin_error(inode, index, folio, swap, @@ -2428,7 +2444,6 @@ static int shmem_swapin_folio(struct inode *inode, pgoff_t index, folio_put(folio); } put_swap_device(si); - return error; } -- 2.50.0