From patchwork Fri Oct 13 16:03:54 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Howells X-Patchwork-Id: 733364 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id EF095CDB47E for ; Fri, 13 Oct 2023 16:27:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231694AbjJMQ13 (ORCPT ); Fri, 13 Oct 2023 12:27:29 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58062 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231359AbjJMQ04 (ORCPT ); Fri, 13 Oct 2023 12:26:56 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A853CD5D for ; Fri, 13 Oct 2023 09:06:00 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1697213157; 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=28kgPZMsHEWnVwc0vT6VK3Ue5Bj5q+rjSv2U7JFM+9k=; b=cn+8DeBEgZv/5FVL0Iu0ZdDxK9y2OMNrR+O94rXZaLhRl9QOszKgHturHSuY5m3CISxzae O4t5ouuJpknH4KaVcjX1lj57IP8mmh4TShMwLtT6asHpKUMK/vMxI5xSdf/Jsfv0wUJBQs 6U/q2PUiz9fufGVlKCe5VpBUABdMCWA= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-93-P-Ft7OcvOIWG1ggPzh_5og-1; Fri, 13 Oct 2023 12:05:56 -0400 X-MC-Unique: P-Ft7OcvOIWG1ggPzh_5og-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.rdu2.redhat.com [10.11.54.1]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 4C57B858293; Fri, 13 Oct 2023 16:05:55 +0000 (UTC) Received: from warthog.procyon.org.uk (unknown [10.42.28.226]) by smtp.corp.redhat.com (Postfix) with ESMTP id 9012925C0; Fri, 13 Oct 2023 16:05:52 +0000 (UTC) From: David Howells To: Jeff Layton , Steve French Cc: David Howells , Matthew Wilcox , Marc Dionne , Paulo Alcantara , Shyam Prasad N , Tom Talpey , Dominique Martinet , Ilya Dryomov , Christian Brauner , linux-afs@lists.infradead.org, linux-cifs@vger.kernel.org, linux-nfs@vger.kernel.org, ceph-devel@vger.kernel.org, v9fs@lists.linux.dev, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, linux-cachefs@redhat.com Subject: [RFC PATCH 25/53] netfs: Make netfs_read_folio() handle streaming-write pages Date: Fri, 13 Oct 2023 17:03:54 +0100 Message-ID: <20231013160423.2218093-26-dhowells@redhat.com> In-Reply-To: <20231013160423.2218093-1-dhowells@redhat.com> References: <20231013160423.2218093-1-dhowells@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.1 Precedence: bulk List-ID: X-Mailing-List: ceph-devel@vger.kernel.org netfs_read_folio() needs to handle partially-valid pages that are marked dirty, but not uptodate in the event that someone tries to read a page was used to cache data by a streaming write. In such a case, make netfs_read_folio() set up a bvec iterator that points to the parts of the folio that need filling and to a sink page for the data that should be discarded and use that instead of i_pages as the iterator to be written to. This requires netfs_rreq_unlock_folios() to convert the page into a normal dirty uptodate page, getting rid of the partial write record and bumping the group pointer over to folio->private. Signed-off-by: David Howells cc: Jeff Layton cc: linux-cachefs@redhat.com cc: linux-fsdevel@vger.kernel.org cc: linux-mm@kvack.org --- fs/netfs/buffered_read.c | 61 ++++++++++++++++++++++++++++++++++-- include/trace/events/netfs.h | 2 ++ 2 files changed, 60 insertions(+), 3 deletions(-) diff --git a/fs/netfs/buffered_read.c b/fs/netfs/buffered_read.c index 2f06344bba21..374707df6575 100644 --- a/fs/netfs/buffered_read.c +++ b/fs/netfs/buffered_read.c @@ -16,6 +16,7 @@ void netfs_rreq_unlock_folios(struct netfs_io_request *rreq) { struct netfs_io_subrequest *subreq; + struct netfs_folio *finfo; struct folio *folio; pgoff_t start_page = rreq->start / PAGE_SIZE; pgoff_t last_page = ((rreq->start + rreq->len) / PAGE_SIZE) - 1; @@ -86,6 +87,15 @@ void netfs_rreq_unlock_folios(struct netfs_io_request *rreq) if (!pg_failed) { flush_dcache_folio(folio); + finfo = netfs_folio_info(folio); + if (finfo) { + trace_netfs_folio(folio, netfs_folio_trace_filled_gaps); + if (finfo->netfs_group) + folio_change_private(folio, finfo->netfs_group); + else + folio_detach_private(folio); + kfree(finfo); + } folio_mark_uptodate(folio); } @@ -245,6 +255,7 @@ int netfs_read_folio(struct file *file, struct folio *folio) struct address_space *mapping = folio_file_mapping(folio); struct netfs_io_request *rreq; struct netfs_inode *ctx = netfs_inode(mapping->host); + struct folio *sink = NULL; int ret; _enter("%lx", folio_index(folio)); @@ -265,12 +276,56 @@ int netfs_read_folio(struct file *file, struct folio *folio) trace_netfs_read(rreq, rreq->start, rreq->len, netfs_read_trace_readpage); /* Set up the output buffer */ - iov_iter_xarray(&rreq->iter, ITER_DEST, &mapping->i_pages, - rreq->start, rreq->len); + if (folio_test_dirty(folio)) { + /* Handle someone trying to read from an unflushed streaming + * write. We fiddle the buffer so that a gap at the beginning + * and/or a gap at the end get copied to, but the middle is + * discarded. + */ + struct netfs_folio *finfo = netfs_folio_info(folio); + struct bio_vec *bvec; + unsigned int from = finfo->dirty_offset; + unsigned int to = from + finfo->dirty_len; + unsigned int off = 0, i = 0; + size_t flen = folio_size(folio); + size_t nr_bvec = flen / PAGE_SIZE + 2; + size_t part; + + ret = -ENOMEM; + bvec = kmalloc_array(nr_bvec, sizeof(*bvec), GFP_KERNEL); + if (!bvec) + goto discard; + + sink = folio_alloc(GFP_KERNEL, 0); + if (!sink) + goto discard; + + trace_netfs_folio(folio, netfs_folio_trace_read_gaps); + + rreq->direct_bv = bvec; + rreq->direct_bv_count = nr_bvec; + if (from > 0) { + bvec_set_folio(&bvec[i++], folio, from, 0); + off = from; + } + while (off < to) { + part = min_t(size_t, to - off, PAGE_SIZE); + bvec_set_folio(&bvec[i++], sink, part, 0); + off += part; + } + if (to < flen) + bvec_set_folio(&bvec[i++], folio, flen - to, to); + iov_iter_bvec(&rreq->iter, ITER_DEST, bvec, i, rreq->len); + } else { + iov_iter_xarray(&rreq->iter, ITER_DEST, &mapping->i_pages, + rreq->start, rreq->len); + } ret = netfs_begin_read(rreq, true); + if (sink) + folio_put(sink); netfs_put_request(rreq, false, netfs_rreq_trace_put_return); - return ret; + return ret < 0 ? ret : 0; discard: netfs_put_request(rreq, false, netfs_rreq_trace_put_discard); diff --git a/include/trace/events/netfs.h b/include/trace/events/netfs.h index 94793f842000..b7426f455086 100644 --- a/include/trace/events/netfs.h +++ b/include/trace/events/netfs.h @@ -115,9 +115,11 @@ EM(netfs_folio_trace_clear, "clear") \ EM(netfs_folio_trace_clear_s, "clear-s") \ EM(netfs_folio_trace_clear_g, "clear-g") \ + EM(netfs_folio_trace_filled_gaps, "filled-gaps") \ EM(netfs_folio_trace_kill, "kill") \ EM(netfs_folio_trace_mkwrite, "mkwrite") \ EM(netfs_folio_trace_mkwrite_plus, "mkwrite+") \ + EM(netfs_folio_trace_read_gaps, "read-gaps") \ EM(netfs_folio_trace_redirty, "redirty") \ EM(netfs_folio_trace_redirtied, "redirtied") \ EM(netfs_folio_trace_store, "store") \