From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=91.218.175.165 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793861981; b=xRG2A6Im0t9DySnoRbl5r9I/e+/oEFgyxNy9vGIXjCduGZMkXbUL/Tr+8ab0XSN7rgft NB/uSemsq7Ri8nS2pjhXOHs7WjMlwoTsmOxWeaxyNtjWfGNVNw7PmPa6fjriqp8sHg1dy lF41pCRmGot+xsHFf7As7AhwYZJTaJjF5jOya+TKTHWgYc4dlfT47euPRmssCp0i875+n JNZ7GAGsmfFjeyWlHfoGeeqZRh/EBVApaHklvvRfQ6EZcZ2yLJJe5hWh5nlR614B5cvMs xyU5HiGtd9aPdpdhe2AH2BBNrvye7oNlXAIQMdJ0FYTxC+ezu1BWz9FIaNMkIrULiZA== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793861981; 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=V6jXYvV9dka+3jN4FlL/QeRxDjLIKwLo+qsWJ9KiY6Q=; b=iidVRd62IKaauhBK4VKvz/BiKSQiLTggMoqwEa473JR5SjnNatGlaBmJmI4PMoDAFSHs 2+IX6p+//Nz/eZaHXHpjCjwNZrJujrqTn37xGhqid0PbjKx39JuiKa6qi1o2MhfSzW55K rg/Mr2cOtfhKkhTHf3sSxEJuxTsUZ7w29WwAEfLr92DJ7eCeC7BHeBjphXz1Rd5xIwUnJ 9A2u0Qh/A1LbfpI2wASjGC8n4CEEz6jQoZzIdNUS2YnVUGX8Kd502TX3jbbUvmJWPyS2d zILKxt56Eq8ZhKvac38wc477CGycs5r9dNksOMczEDJ12JjWi7FcF2GkDVqB3pRSAIw== 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=QaWf9wb7; arc=none smtp.remote-ip=91.218.175.165 Received: from mta0.migadu.com (out-165.mta0.migadu.com [91.218.175.165]) (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 4C967606D803 for ; Thu, 5 Nov 2026 06:59:39 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.2 smtp.subspace.kernel.org 4C967606D803 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=QaWf9wb7 X-Envelope-To: linux-ext4@vger.kernel.org DKIM-Signature: a=rsa-sha256; bh=BRMlNTa2IFz117u+LpOsOZxcnQTogf6s+dFMFzcP0xM=; c=simple/simple; d=linux.dev; h=from:to:subject:date:message-id:mime-version:content-type; s=key1; t=1793861978; v=1; x=1794466778; b=QaWf9wb7wFivbY4mUbRehlCWWKN3tB0cW4ajPirSzhAocmjyx9TuV37CtcFab/80djMAdLFe jRYRmmPTKw1NfQidftHLvJl0yYWgWkAWXm2oWhCr421bGdGGf0wTAUxeGgQ/rZbnokP26pzIvY7 ddWpsDXwlLWg655twgRVJAOQ= X-Envelope-To: linux-ext4@vger.kernel.org Received: by smtp.migadu.com with ESMTPS id 724bcf4c5e474fe1; Thu, 05 Nov 2026 06:59:38 +0000 X-Mizu-Trace-ID: 724bcf4c5e474fe1 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 2/6] mm/filemap: refuse dmabuf iterators in the generic read/write copy paths Date: Thu, 5 Nov 2026 14:58:43 +0800 Message-ID: <20261105065847.196540-3-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 The generic copy helpers cannot touch device memory. Refuse a dmabuf iterator in generic_perform_write() and the filemap_read() fallback while keeping any direct-I/O progress, and report a busy folio from generic_file_direct_write() as -EAGAIN instead of asking for the buffered fallback such an iterator cannot take. Signed-off-by: Mengmeng Zhao Signed-off-by: Li Wang --- mm/filemap.c | 22 +++++++++++++++++++++- 1 file changed, 21 insertions(+), 1 deletion(-) diff --git a/mm/filemap.c b/mm/filemap.c index 6afec636881f..ab8a5391a699 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -3013,6 +3013,14 @@ generic_file_read_iter(struct kiocb *iocb, struct iov_iter *iter) return retval; } + /* + * Buffered I/O read is not supported for dmabuf; a short direct + * read before this point stands on its own, as in + * direct_write_fallback(). + */ + if (iov_iter_is_dmabuf_map(iter)) + return retval > 0 ? retval : -EOPNOTSUPP; + return filemap_read(iocb, iter, retval); } EXPORT_SYMBOL(generic_file_read_iter); @@ -4300,8 +4308,14 @@ generic_file_direct_write(struct kiocb *iocb, struct iov_iter *from) */ written = kiocb_invalidate_pages(iocb, write_len); if (written) { - if (written == -EBUSY) + if (written == -EBUSY) { + /* + * Avoid fallback to buffered write for dmabuf. + */ + if (iov_iter_is_dmabuf_map(from)) + return -EAGAIN; return 0; + } return written; } @@ -4353,6 +4367,12 @@ ssize_t generic_perform_write(struct kiocb *iocb, struct iov_iter *i) long status = 0; ssize_t written = 0; + /* + * Buffered write is not supported for dmabuf. + */ + if (iov_iter_is_dmabuf_map(i)) + return -EOPNOTSUPP; + do { struct folio *folio; size_t offset; /* Offset into folio */ -- 2.43.0