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Wed, 09 Jul 2025 20:37:41 -0700 (PDT) Received: from KASONG-MC4 ([43.132.141.20]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-31c300689aasm3716320a91.13.2025.07.09.20.37.37 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Wed, 09 Jul 2025 20:37:40 -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 , Dev Jain Subject: [PATCH v5 2/8] mm/shmem, swap: avoid redundant Xarray lookup during swapin Date: Thu, 10 Jul 2025 11:37:00 +0800 Message-ID: <20250710033706.71042-3-ryncsn@gmail.com> X-Mailer: git-send-email 2.50.0 In-Reply-To: <20250710033706.71042-1-ryncsn@gmail.com> References: <20250710033706.71042-1-ryncsn@gmail.com> Reply-To: Kairui Song MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 5DA4240003 X-Stat-Signature: en6wi5978hwkqc5pno7jzifye48rcr7i X-HE-Tag: 1752118663-746 X-HE-Meta: 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 cZst6lVs 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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: 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 Reviewed-by: Kemeng Shi Reviewed-by: Dev Jain Reviewed-by: Baolin Wang --- mm/shmem.c | 32 ++++++++++++++++++++++++-------- 1 file changed, 24 insertions(+), 8 deletions(-) diff --git a/mm/shmem.c b/mm/shmem.c index e3c9a1365ff4..85ecc6709b5f 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_confirm_swap(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_confirm_swap(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_confirm_swap(mapping, index, swap) < 0) error = -EEXIST; if (error == -EIO) shmem_set_folio_swapin_error(inode, index, folio, swap, -- 2.50.0