From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id BF173480DF5 for ; Tue, 28 Apr 2026 13:19:55 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777382397; cv=none; b=rqY3BaHUwBVkabc+SM84/VZorJgKWMHalZ/TK98WfBuKaCze9qk3lI1V8g4Za+/tPYh+BPy6RXVJg2xhzyQfyHDNECnYX7NG53aMN7JExJjAyZx1KdSoby/W9Q9+E/Uv5qmIqeII8CCILDPUDv6zO4CxE+tPW4eknaDYWo/dyWc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777382397; c=relaxed/simple; bh=lShWzYTWI8ZUl/3TWOlKibNVqtrcytr9UqfpImgWSR8=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=cDeLGJYkdh3egPdaQYutUwNSPVnZfmlV8vxgWM2ClvnUzsvdVr4QzIfD015u0ZUe0hfMKTP2/YJcDQVkXKFTeQmeyoJm7bx3tNI/Ye5Iuyqp19rGz6P7OPwK57iXTS1+EwM5Itmu+TtrTwNyQxG0hh27vZH7LX+aE+uYaxYC+x0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=EQlj3h+w; arc=none smtp.client-ip=170.10.129.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="EQlj3h+w" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1777382394; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=TrTX3198kpCCtDQYOVWR0o7cIHQgx0i2zjy1/WuKGSY=; b=EQlj3h+w86vE6usiOzkAQTF3pwT2tYEcf9UpDQ0zxANJtY+u7kUxzMEoYUhsahpXOmjf1G GzqD6rGDOrikcswH7+A06a5kwrYv/4ZM6YMmUTEfM2DwRODFARE1EQGQAxDK0OCD7rNBZ5 LixmFgh/gjrvdR70Q8bwSNKqv3xba6g= Received: from mx-prod-mc-06.mail-002.prod.us-west-2.aws.redhat.com (ec2-35-165-154-97.us-west-2.compute.amazonaws.com [35.165.154.97]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-359-6l-1WpSePNiY0FvjE4FSxA-1; Tue, 28 Apr 2026 09:19:46 -0400 X-MC-Unique: 6l-1WpSePNiY0FvjE4FSxA-1 X-Mimecast-MFC-AGG-ID: 6l-1WpSePNiY0FvjE4FSxA_1777382383 Received: from mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.17]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 246C4185A926; Tue, 28 Apr 2026 13:19:20 +0000 (UTC) Received: from warthog.procyon.org.com (unknown [10.44.32.126]) by mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 357AA195608E; Tue, 28 Apr 2026 13:19:16 +0000 (UTC) From: David Howells To: Christian Brauner Cc: David Howells , Paulo Alcantara , netfs@lists.linux.dev, linux-afs@lists.infradead.org, linux-cifs@vger.kernel.org, ceph-devel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, Matthew Wilcox Subject: [PATCH v5 16/24] netfs: Fix write streaming disablement if fd open O_RDWR Date: Tue, 28 Apr 2026 14:17:46 +0100 Message-ID: <20260428131756.922303-17-dhowells@redhat.com> In-Reply-To: <20260428131756.922303-1-dhowells@redhat.com> References: <20260428131756.922303-1-dhowells@redhat.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.0 on 10.30.177.17 In netfs_perform_write(), "write streaming" (the caching of dirty data in dirty but !uptodate folios) is performed to avoid the need to read data that is just going to get immediately overwritten. However, this is/will be disabled in three circumstances: if the fd is open O_RDWR, if fscache is in use (as we need to round out the blocks for DIO) or if content encryption is enabled (again for rounding out purposes). The idea behind disabling it if the fd is open O_RDWR is that we'd need to flush the write-streaming page before we could read the data, particularly through mmap. But netfs now fills in the gaps if ->read_folio() is called on the page, so that is unnecessary. Further, this doesn't actually work if a separate fd is open for reading. Fix this by removing the check for O_RDWR, thereby allowing streaming writes even when we might read. This caused a number of problems with the generic/522 xfstest, but those are now fixed. Fixes: c38f4e96e605 ("netfs: Provide func to copy data to pagecache for buffered write") Signed-off-by: David Howells cc: Paulo Alcantara cc: Matthew Wilcox cc: netfs@lists.linux.dev cc: linux-fsdevel@vger.kernel.org --- fs/netfs/buffered_write.c | 17 +++++++---------- 1 file changed, 7 insertions(+), 10 deletions(-) diff --git a/fs/netfs/buffered_write.c b/fs/netfs/buffered_write.c index 25571a570ac9..11a8f64b1177 100644 --- a/fs/netfs/buffered_write.c +++ b/fs/netfs/buffered_write.c @@ -203,11 +203,11 @@ ssize_t netfs_perform_write(struct kiocb *iocb, struct iov_iter *iter, } /* Decide how we should modify a folio. We might be attempting - * to do write-streaming, in which case we don't want to a - * local RMW cycle if we can avoid it. If we're doing local - * caching or content crypto, we award that priority over - * avoiding RMW. If the file is open readably, then we also - * assume that we may want to read what we wrote. + * to do write-streaming, as we don't want to a local RMW cycle + * if we can avoid it. If we're doing local caching or content + * crypto, we award that priority over avoiding RMW. If the + * file is open readably, then we let ->read_folio() fill in + * the gaps. */ finfo = netfs_folio_info(folio); group = netfs_folio_group(folio); @@ -283,12 +283,9 @@ ssize_t netfs_perform_write(struct kiocb *iocb, struct iov_iter *iter, /* We don't want to do a streaming write on a file that loses * caching service temporarily because the backing store got - * culled and we don't really want to get a streaming write on - * a file that's open for reading as ->read_folio() then has to - * be able to flush it. + * culled. */ - if ((file->f_mode & FMODE_READ) || - netfs_is_cache_enabled(ctx)) { + if (netfs_is_cache_enabled(ctx)) { if (finfo) { netfs_stat(&netfs_n_wh_wstream_conflict); goto flush_content;