From patchwork Thu Jan 30 17:09:46 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Brian Foster X-Patchwork-Id: 13954737 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 3348D1EF08D for ; Thu, 30 Jan 2025 17:07:45 +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=1738256866; cv=none; b=bpmFvDXDDVJ+YprgOpNFAD97YXv5KN1a69z6JzvE3uLm0xpg32n/j6vFTCkR24O9Pw6Ik16vZ0sG9sqbRcNxTVZKy17D3vdDdz5+ehNScQbe+zr0jPSxRhNQ1ZWmDgUa4o16D1AN7dtadfvH0FGSJmlX7UsdN4mwHQEEeWD9B6w= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1738256866; c=relaxed/simple; bh=ekrO+DIvIeJsTz3MJBLWCVr0aC9MqZ4JDuo8KuVyjhI=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=TBBIWsutAJauZGHQ4MMxl4qJT1BWGJP7iU0z7xFDeTKS7G4ehA/7fhRtHMP/WF291M5vrYioqRNzfouKpnrlIiGmcXJ2C66IDwFIMuPf5ade5jaObfm/M8BVlORv07BglqTQZVDDAD/FP4HMgmrGczF4G0elHdcfPy2SV/+8pgs= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none 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=DJFHvAqK; arc=none smtp.client-ip=170.10.129.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none 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="DJFHvAqK" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1738256864; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=itUrYc7cJ83YbakxDByAcgZzeORx1fTgCGYX7hsyg/g=; b=DJFHvAqKf4t7QNtq5Q84NnctuXMKc09kkuBnQTYX0mncrbPSYskB2S/lntqxSADLlrJRFU KGeGCAuwf3oahM6LkRh0K9X63SUU2NpMxstCv7Aw/7KWzVUqAIVDLH1P//rBp1xr8ycdiF BNBAniEKEXuTx+vQn0L2Swqs5kphw6g= Received: from mx-prod-mc-04.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-677-PrhoPEawPzeTun3hxhkJzQ-1; Thu, 30 Jan 2025 12:07:42 -0500 X-MC-Unique: PrhoPEawPzeTun3hxhkJzQ-1 X-Mimecast-MFC-AGG-ID: PrhoPEawPzeTun3hxhkJzQ Received: from mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.4]) (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-04.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id C7E8E19560A3; Thu, 30 Jan 2025 17:07:41 +0000 (UTC) Received: from bfoster.redhat.com (unknown [10.22.80.113]) by mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 071A230001BE; Thu, 30 Jan 2025 17:07:40 +0000 (UTC) From: Brian Foster To: linux-fsdevel@vger.kernel.org Cc: linux-xfs@vger.kernel.org, Christoph Hellwig Subject: [PATCH v3 5/7] iomap: advance the iter directly on buffered writes Date: Thu, 30 Jan 2025 12:09:46 -0500 Message-ID: <20250130170949.916098-6-bfoster@redhat.com> In-Reply-To: <20250130170949.916098-1-bfoster@redhat.com> References: <20250130170949.916098-1-bfoster@redhat.com> Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.4 Modify the buffered write path to advance the iter directly. Replace the local pos and length calculations with direct advances and loop based on iter state instead. Also remove the -EAGAIN return hack as it is no longer necessary now that separate return channels exist for processing progress and error returns. For example, the existing write handler must return either a count of bytes written or error if the write is interrupted, but presumably wants to return -EAGAIN directly in order to break the higher level iomap_iter() loop. Since the current iteration may have made some progress, it unwinds the iter on the way out to return the error while ensuring that portion of the write can be retried. If -EAGAIN occurs at any point beyond the first iteration, iomap_file_buffered_write() will then observe progress based on iter->pos to return a short write. With incremental advances on the iomap_iter, iomap_write_iter() can simply return the error. iomap_iter() completes whatever progress was made based on iomap_iter position and still breaks out of the iter loop based on the error code in iter.processed. The end result of the write is similar in terms of being a short write if progress was made or error return otherwise. Signed-off-by: Brian Foster Reviewed-by: Christoph Hellwig --- fs/iomap/buffered-io.c | 20 +++++++------------- 1 file changed, 7 insertions(+), 13 deletions(-) diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c index d303e6c8900c..678c189faa58 100644 --- a/fs/iomap/buffered-io.c +++ b/fs/iomap/buffered-io.c @@ -909,8 +909,6 @@ static bool iomap_write_end(struct iomap_iter *iter, loff_t pos, size_t len, static loff_t iomap_write_iter(struct iomap_iter *iter, struct iov_iter *i) { - loff_t length = iomap_length(iter); - loff_t pos = iter->pos; ssize_t total_written = 0; long status = 0; struct address_space *mapping = iter->inode->i_mapping; @@ -923,7 +921,8 @@ static loff_t iomap_write_iter(struct iomap_iter *iter, struct iov_iter *i) size_t offset; /* Offset into folio */ size_t bytes; /* Bytes to write to folio */ size_t copied; /* Bytes copied from user */ - size_t written; /* Bytes have been written */ + u64 written; /* Bytes have been written */ + loff_t pos = iter->pos; bytes = iov_iter_count(i); retry: @@ -934,8 +933,8 @@ static loff_t iomap_write_iter(struct iomap_iter *iter, struct iov_iter *i) if (unlikely(status)) break; - if (bytes > length) - bytes = length; + if (bytes > iomap_length(iter)) + bytes = iomap_length(iter); /* * Bring in the user page that we'll copy from _first_. @@ -1006,17 +1005,12 @@ static loff_t iomap_write_iter(struct iomap_iter *iter, struct iov_iter *i) goto retry; } } else { - pos += written; total_written += written; - length -= written; + iomap_iter_advance(iter, &written); } - } while (iov_iter_count(i) && length); + } while (iov_iter_count(i) && iomap_length(iter)); - if (status == -EAGAIN) { - iov_iter_revert(i, total_written); - return -EAGAIN; - } - return total_written ? total_written : status; + return total_written ? 0 : status; } ssize_t