From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=95.215.58.238 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793861995; b=fu8Jr59OOXe5mYWIwLSMNr40IS6aPZmo45EifNzneuR4oBa8WkCPfPp2FTmbI65+uKCZ PH8toXRoXmd3fkyg5kWWyFdegWHjpiV6NUplVCviMbCqmvcJBdq6xuAkdUTPlIhIy09Nb XuH3wRlbODM2bFYNU3C28i3fr0BqpCwDdhIc24qo58dP5mLmgJuHFptpVi71Od18kwbxN URvk2qWn5eIC4y58uOp4VRJNh/PDy7IQiI4CsEPgFvoZ1Tnx6Zba6LnBoPvjB9ARP1QmS /lGqZRnxeTU384q/+H7npTfuu0iHFTYWXPjuAMw3JCGnwazaCuELr1CZWd10KIsXjzA== 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=Rbr+MW4nWr7uff50v62czrftxpdZLuozMr1uB/c1h768cQKGGlRUcMgguupwQO5HVhzb t7yEQ9krQwR7VDUyWHjOpkYs8t9dt/L8quVJ/X8z6IR/zO5xX4sjpX+DPf4PCGT+YZRlh AF3UI8da0F3XQZq0MQ3P1msEevyzHIBB8g0Pir9EgNZAd6/GI0TGVGW0yVPTiJXrUp+SO 9Tmc/Wn70taNwIXojKjUBVoKZ6oTHp18MGpdSlXPIGQla5Lou66dytz9T6/2zGGgaGt6S 5UY++Kh78lpqNgedpRZFDuFXRnYmaPXndJ1fNE5qXfmkJ93BP3Qw/cHQox+y9CUEqzA== 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=95.215.58.238 Received: from mta1.migadu.com (out-238.mta1.migadu.com [95.215.58.238]) (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 EF47F606A329 for ; Thu, 5 Nov 2026 06:59:54 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.2 smtp.subspace.kernel.org EF47F606A329 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-kernel@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-kernel@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-kernel@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