From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 AF81B4EA398; Tue, 13 Oct 2026 12:00:14 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791892815; cv=none; b=LPUT7NRjAp3n5YsyKlDd/gu/ymhHEEqAI+jJxqx323ss/yaZR4mQgjLs1xB2l+rXMTfe53YSwdqQKL4U3nSkPmLI43b3xxXHmGlOUdgJ4jIbqRPWgjcAK7+hH2LAd1prA8mXWCRKS15NTdq9yBMAhEcO6ibfVPmmkkBwMr/kz7k= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791892815; c=relaxed/simple; bh=+8/TCluGKjz3mY8+eHlLPYhywylYLAvRsplvQFyNQyM=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Aeyc37BScUmSwjvMzzlnvlUnURWvNLbB+j5trSSXXUGBJsm0xMhPOwfo6Ww4WkxFir3XGBJs6fFGoyXrpuPPs6U7cT3ZgOZ/GDu73UITqYJZY6bdgIFME4NLW/74SqkUo+7IUa2LjD3jErDV1DBNIHXR6bXjJFY6px+EAK/iK8c= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=vwIFYF5Q; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="vwIFYF5Q" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 088DC1F000FF; Tue, 13 Oct 2026 12:00:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1791892814; bh=kCx/JngA6bx7QVEmlnAXu0tCQKGTKgWhyGWTLp8ywlc=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=vwIFYF5Q3qlxB3c5DybDP45c1Vd/U64B9BurT68Wywz54269c3nrkPdFYUV1yfFjm pZeyR/7G8RrsVYy5kSNmW6hJVCZFnMUjUKd4uzkLCl3sOQzcrxnpNkvcWSoe0lLBfu p0xFDyF7fE4h3GZF7VWlSs92dB47LnbQqGvx9LK8= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, David Howells , Namjae Jeon , Paulo Alcantara , Christian Brauner , Matthew Wilcox , Ronnie Sahlberg , Shyam Prasad N , Tom Talpey , Bharath SM , Sasha Levin Subject: [PATCH 6.18 007/621] netfs: zero the tail of a short DIO/unbuffered read Date: Tue, 13 Oct 2026 13:30:02 +0200 Message-ID: <20261013112921.037576897@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261013112920.855194808@linuxfoundation.org> References: <20261013112920.855194808@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Paulo Alcantara [ Upstream commit dd05add7b2b6004c5fa3a1f276f56d8668f86b65 ] The buffered read collector zero-fills the tail of a short read that stops below the inode's i_size (netfs_clear_unread()), so a read that races an extending write still returns the expected number of bytes. The non-buffered collector path does no such thing: it just records how much was transferred. Add the same zero-fill for the non-buffered case, gated on NETFS_SREQ_CLEAR_TAIL: a subreq's source sets that flag when a short result from it is known to be safe to treat as a hole, as opposed to NETFS_SREQ_HIT_EOF, which means the read genuinely ran off the end of the file and should be reported short as-is. Only CLEAR_TAIL should zero-fill here; a real EOF must stay a real short read. No source currently sets CLEAR_TAIL on an unbuffered/DIO subrequest, so this is inert on its own -- a following change teaches cifs to set it in the one case that needs it. Fixes: e2d46f2ec332 ("netfs: Change the read result collector to only use one work item") Reviewed-by: David Howells Reviewed-by: Namjae Jeon Signed-off-by: Paulo Alcantara Cc: Christian Brauner Cc: Matthew Wilcox Cc: Ronnie Sahlberg Cc: Shyam Prasad N Cc: Tom Talpey Cc: Bharath SM Cc: stable@vger.kernel.org [ sashal: Replaced uoff_t with unsigned long long. ] Signed-off-by: Sasha Levin --- fs/netfs/read_collect.c | 24 ++++++++++++++++++++++++ 1 file changed, 24 insertions(+) diff --git a/fs/netfs/read_collect.c b/fs/netfs/read_collect.c index 4c7312a4c8597..8ad06678e6883 100644 --- a/fs/netfs/read_collect.c +++ b/fs/netfs/read_collect.c @@ -34,6 +34,22 @@ static void netfs_clear_unread(struct netfs_io_subrequest *subreq) __set_bit(NETFS_SREQ_HIT_EOF, &subreq->flags); } +static void netfs_clear_unread_dio(struct netfs_io_subrequest *subreq) +{ + unsigned long long pos = subreq->start + subreq->transferred; + struct netfs_io_request *rreq = subreq->rreq; + size_t fill; + + if (pos >= rreq->i_size) + return; + + fill = min_t(unsigned long long, rreq->i_size - pos, + subreq->len - subreq->transferred); + + netfs_reset_iter(subreq); + subreq->transferred += iov_iter_zero(fill, &subreq->io_iter); +} + /* * Flush, mark and unlock a folio that's now completely read. If we want to * cache the folio, we set the group to NETFS_FOLIO_COPY_TO_CACHE, mark it @@ -259,6 +275,14 @@ static void netfs_collect_read_results(struct netfs_io_request *rreq) test_bit(NETFS_SREQ_HIT_EOF, &front->flags)) netfs_read_unlock_folios(rreq, ¬es); } else { + if (!(notes & HIT_PENDING) && + front->error == 0 && + transferred < front->len && + test_bit(NETFS_SREQ_CLEAR_TAIL, &front->flags)) { + netfs_clear_unread_dio(front); + transferred = front->transferred; + trace_netfs_sreq(front, netfs_sreq_trace_clear); + } stream->collected_to = front->start + transferred; rreq->collected_to = stream->collected_to; } -- 2.53.0