From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=91.218.175.175 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793861995; b=QlnmCm3zfmD9JLyPLHm9k5vtIQas7jj6k0Gbb4lKZZeOgZ31vD6A22AXkjKzuFxGchND 1Nr5HO8cPGOrRqKBOOFvMrfzK0ofE/CZ2aqb8Vvu8Fd3rcY/nFnXkzK0Obl4oJbFIRXMa 0lP0K+Cv6G+87FwHMRzrY7i1V/SY1QGD2tDsmYxlFK0vnrxHoNTNoYXYCfEDaqD5ymTmG xuIPCSTELjQJIO4Z/oEhT1KvJZMhptgm2/uqb3xeXE55oPyFXSKtQKHYthqxFflK+TYcv 7TGX4AckGKhrUkKmkNb1J7RKUKEDVM4vpEJn84KUCjgSiLqEQqhbaI1ZcpMeI9Vp3sA== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793861995; h=DMARC-Filter:X-Envelope-To:DKIM-Signature:X-Envelope-To:Received: X-Mizu-Trace-ID:X-Migadu-Flow:From:To:Cc:Subject:Date:Message-ID: X-Mailer:In-Reply-To:References:MIME-Version: Content-Transfer-Encoding; bh=giKD9GBB7SqWcODKYmNlG0gh8SE1gt/R19vK2YjohsA=; b=J+KZBPVWlrACALpf03b1fIFpYnDt8QY8JkPi5J1wcHkOnRDTO9d3zsnCi2xYsqW6MNwF hgWXH17M6jC/ZCFSyfBgzVufDksNGy2WaXcXZ0k8TQ6Vu3DS9E13NlALi7g5leaFR3Jm4 +M4Z3IR5rcVZJPARh8UZ7RSYNkalnm1IhfYCKfMjozFfbfkRXo55q3w565F2GetQNxi+1 Cdo2pOMkpTpLNGO7Drf5C9FmmG4PjJnM9L3gNvyeeuSuv1T/ilaHNSp8kJZknPO7zQjE5 vfAaj2SiSOkH7MOhTnfOUHB3+iFKPf2WzFgbCWE9k2y7nH9e1vKZPbl9uyhOPkyJLVA== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass header.d=linux.dev header.i=@linux.dev header.a=rsa-sha256 header.s=key1 header.b=UJkINKzK; arc=none smtp.remote-ip=91.218.175.175 Received: from mta0.migadu.com (out-175.mta0.migadu.com [91.218.175.175]) (using TLSv1.3 with cipher TLS_AES_128_GCM_SHA256 (128/128 bits) key-exchange X25519 server-signature ECDSA (prime256v1) server-digest SHA256) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 034C6606A32C for ; Thu, 5 Nov 2026 06:59:54 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.2 smtp.subspace.kernel.org 034C6606A32C Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key, unprotected) header.d=linux.dev header.i=@linux.dev header.a=rsa-sha256 header.s=key1 header.b=UJkINKzK X-Envelope-To: linux-ext4@vger.kernel.org DKIM-Signature: a=rsa-sha256; bh=Ht9W8rG1bvFhZOOVFyVUZBS1JBc1APtNoV+i3qOiW1c=; c=simple/simple; d=linux.dev; h=from:to:subject:date:message-id:mime-version:content-type; s=key1; t=1793861993; v=1; x=1794466793; b=UJkINKzKdtLYR8KtpZuaFU8oFOUGl8oRWRJRBWewSilr+ADj9oA9XTq+T9+x9L2sd0LBRZ6i Z/2TgFvG+kvx8D/3Hx3IU7wQqdyh+09q4ppm9LSPVLNI+LaQrJFS/qWfkiLqiLjqQ0vCkhMYn3y KBzd3Uw2/VTZ5LBroZQj6YH4= X-Envelope-To: linux-ext4@vger.kernel.org Received: by smtp.migadu.com with ESMTPS id 770e8c686bfb0362; Thu, 05 Nov 2026 06:59:52 +0000 X-Mizu-Trace-ID: 770e8c686bfb0362 X-Migadu-Flow: FLOW_OUT From: Mengmeng Zhao To: Jens Axboe , Dan Williams , Matthew Wilcox , Jan Kara , Alexander Viro , Christian Brauner , tytso@mit.edu, Andreas Dilger , Baokun Li , Ojaswin Mujoo , "Ritesh Harjani (IBM)" , Zhang Yi , "Darrick J. Wong" , Andrew Morton , asml.silence@gmail.com, hch@lst.de, Anuj Gupta Cc: linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, nvdimm@lists.linux.dev, linux-ext4@vger.kernel.org, linux-xfs@vger.kernel.org, linux-mm@kvack.org, Li Wang Subject: [RFC 3/6] dax: refuse dmabuf iterators in dax_iomap_rw() Date: Thu, 5 Nov 2026 14:58:44 +0800 Message-ID: <20261105065847.196540-4-mengmeng.zhao@linux.dev> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20261105065847.196540-1-mengmeng.zhao@linux.dev> References: <20261105065847.196540-1-mengmeng.zhao@linux.dev> X-Mailing-List: linux-ext4@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Mengmeng Zhao A dax access copies through the CPU linear address, which a device mapping cannot provide. A dmabuf iterator reaching dax_iomap_rw() splats a WARN_ON_ONCE from iterate_and_advance2() and fails the I/O with EFAULT. Refuse it up front with -EOPNOTSUPP, as the generic buffered copy paths already do. Signed-off-by: Mengmeng Zhao Signed-off-by: Li Wang --- fs/dax.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/fs/dax.c b/fs/dax.c index 6ba50142eeb2..6ec08316aa6c 100644 --- a/fs/dax.c +++ b/fs/dax.c @@ -1759,6 +1759,10 @@ dax_iomap_rw(struct kiocb *iocb, struct iov_iter *iter, if (!iomi.len) return 0; + /* dax copies through the CPU, which a device mapping bypasses */ + if (iov_iter_is_dmabuf_map(iter)) + return -EOPNOTSUPP; + if (iov_iter_rw(iter) == WRITE) { lockdep_assert_held_write(&iomi.inode->i_rwsem); iomi.flags |= IOMAP_WRITE; -- 2.43.0