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Mon, 23 Mar 2026 00:27:19 -0700 (PDT) Received: from localhost ([111.228.63.84]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-82b03aa5aa7sm8476962b3a.1.2026.03.23.00.27.06 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 23 Mar 2026 00:27:18 -0700 (PDT) From: Cen Zhang To: cem@kernel.org Cc: linux-xfs@vger.kernel.org, linux-kernel@vger.kernel.org, baijiaju1990@gmail.com, Cen Zhang , stable@vger.kernel.org Subject: [PATCH v2] xfs: use xfs_trans_ail_copy_lsn for lockless li_lsn read in CIL formatting Date: Mon, 23 Mar 2026 15:09:49 +0800 Message-Id: <20260323070949.3769170-1-zzzccc427@gmail.com> X-Mailer: git-send-email 2.34.1 Precedence: bulk X-Mailing-List: linux-xfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit xfs_inode_item_format_core() reads lip->li_lsn without holding any lock to embed the last on-disk LSN into the log dinode during CIL commit: xfs_inode_to_log_dinode(ip, dic, ip->i_itemp->ili_item.li_lsn); Concurrently, xfs_trans_ail_update_bulk() writes lip->li_lsn under ail_lock when inserting items into the AIL after log IO completion: lip->li_lsn = lsn; The CIL context lock (xc_ctx_lock) and the AIL lock (ail_lock) are independent and provide no mutual exclusion between these paths. On 64-bit architectures this is benign since li_lsn monotonically increases and both old/new values are valid checkpoint LSNs. On 32-bit architectures the 64-bit xfs_lsn_t can be torn into two 32-bit loads, producing a bogus LSN that could cause log recovery to make incorrect replay decisions. Use xfs_trans_ail_copy_lsn() to safely snapshot li_lsn, which takes ail_lock on 32-bit architectures to prevent torn reads. Fixes: 93f958f9c41f ("xfs: cull unnecessary icdinode fields") Cc: stable@vger.kernel.org Signed-off-by: Cen Zhang --- fs/xfs/xfs_inode_item.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/fs/xfs/xfs_inode_item.c b/fs/xfs/xfs_inode_item.c index 8913036b8024..0171f4527f40 100644 --- a/fs/xfs/xfs_inode_item.c +++ b/fs/xfs/xfs_inode_item.c @@ -622,9 +622,12 @@ xfs_inode_item_format_core( struct xlog_format_buf *lfb) { struct xfs_log_dinode *dic; + xfs_lsn_t lsn; + xfs_trans_ail_copy_lsn(ip->i_mount->m_ail, &lsn, + &ip->i_itemp->ili_item.li_lsn); dic = xlog_format_start(lfb, XLOG_REG_TYPE_ICORE); - xfs_inode_to_log_dinode(ip, dic, ip->i_itemp->ili_item.li_lsn); + xfs_inode_to_log_dinode(ip, dic, lsn); xlog_format_commit(lfb, xfs_log_dinode_size(ip->i_mount)); } -- 2.34.1