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From: David Howells <dhowells@redhat.com>
To: linux-fsdevel@vger.kernel.org
Cc: dhowells@redhat.com, Jeff Layton <jlayton@redhat.com>,
	"Matthew Wilcox (Oracle)" <willy@infradead.org>,
	Anna Schumaker <anna.schumaker@netapp.com>,
	Steve French <sfrench@samba.org>,
	Dominique Martinet <asmadeus@codewreck.org>,
	Mike Marshall <hubcap@omnibond.com>,
	David Wysochanski <dwysocha@redhat.com>,
	Shyam Prasad N <nspmangalore@gmail.com>,
	Miklos Szeredi <miklos@szeredi.hu>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	linux-cachefs@redhat.com, linux-afs@lists.infradead.org,
	linux-nfs@vger.kernel.org, linux-cifs@vger.kernel.org,
	ceph-devel@vger.kernel.org, v9fs-developer@lists.sourceforge.net,
	devel@lists.orangefs.org, linux-mm@kvack.org,
	linux-kernel@vger.kernel.org
Subject: [RFC PATCH 08/12] netfs: Keep dirty mark for pages with more than one dirty region
Date: Wed, 21 Jul 2021 14:46:28 +0100	[thread overview]
Message-ID: <162687518862.276387.262991356873597293.stgit@warthog.procyon.org.uk> (raw)
In-Reply-To: <162687506932.276387.14456718890524355509.stgit@warthog.procyon.org.uk>

If a page has more than one dirty region overlapping it, then we mustn't
clear the dirty mark when we want to flush one of them.

Make netfs_set_page_writeback() check the adjacent dirty regions to see if
they overlap the page(s) the region we're interested in, and if they do,
leave the page marked dirty.

NOTES:

 (1) Might want to discount the overlapping regions if they're being
     flushed (in which case they wouldn't normally want to hold the dirty
     bit).

 (2) Similarly, the writeback mark should not be cleared if the page is
     still being written back by another, overlapping region.

Signed-off-by: David Howells <dhowells@redhat.com>
---

 fs/netfs/write_back.c |   41 ++++++++++++++++++++++++++++++++++++++---
 1 file changed, 38 insertions(+), 3 deletions(-)

diff --git a/fs/netfs/write_back.c b/fs/netfs/write_back.c
index 9fcb2ac50ebb..5c779cb12345 100644
--- a/fs/netfs/write_back.c
+++ b/fs/netfs/write_back.c
@@ -135,12 +135,47 @@ static int netfs_lock_pages(struct address_space *mapping,
 	return ret;
 }
 
-static int netfs_set_page_writeback(struct page *page)
+static int netfs_set_page_writeback(struct page *page,
+				    struct netfs_i_context *ctx,
+				    struct netfs_write_request *wreq)
 {
+	struct netfs_dirty_region *region = wreq->region, *r;
+	loff_t pos = page_offset(page);
+	bool clear_dirty = true;
+
 	/* Now we need to clear the dirty flags on any page that's not shared
 	 * with any other dirty region.
 	 */
-	if (!clear_page_dirty_for_io(page))
+	spin_lock(&ctx->lock);
+	if (pos < region->dirty.start) {
+		r = region;
+		list_for_each_entry_continue_reverse(r, &ctx->dirty_regions, dirty_link) {
+			if (r->dirty.end <= pos)
+				break;
+			if (r->state < NETFS_REGION_IS_DIRTY)
+				continue;
+			kdebug("keep-dirty-b %lx reg=%x r=%x",
+			       page->index, region->debug_id, r->debug_id);
+			clear_dirty = false;
+		}
+	}
+
+	pos += thp_size(page);
+	if (pos > region->dirty.end) {
+		r = region;
+		list_for_each_entry_continue(r, &ctx->dirty_regions, dirty_link) {
+			if (r->dirty.start >= pos)
+				break;
+			if (r->state < NETFS_REGION_IS_DIRTY)
+				continue;
+			kdebug("keep-dirty-f %lx reg=%x r=%x",
+			       page->index, region->debug_id, r->debug_id);
+			clear_dirty = false;
+		}
+	}
+	spin_unlock(&ctx->lock);
+
+	if (clear_dirty && !clear_page_dirty_for_io(page))
 		BUG();
 
 	/* We set writeback unconditionally because a page may participate in
@@ -225,7 +260,7 @@ static int netfs_begin_write(struct address_space *mapping,
 	trace_netfs_wreq(wreq);
 
 	netfs_iterate_pages(mapping, wreq->first, wreq->last,
-			    netfs_set_page_writeback);
+			    netfs_set_page_writeback, ctx, wreq);
 	netfs_unlock_pages(mapping, wreq->first, wreq->last);
 	iov_iter_xarray(&wreq->source, WRITE, &wreq->mapping->i_pages,
 			wreq->start, wreq->len);



  parent reply	other threads:[~2021-07-21 13:47 UTC|newest]

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-21 13:44 David Howells
2021-07-21 13:44 ` [RFC PATCH 01/12] afs: Sort out symlink reading David Howells
2021-07-21 16:20   ` Jeff Layton
2021-07-26  9:44   ` David Howells
2021-07-21 13:44 ` [RFC PATCH 02/12] netfs: Add an iov_iter to the read subreq for the network fs/cache to use David Howells
2021-07-21 17:16   ` Jeff Layton
2021-07-21 17:20   ` David Howells
2021-07-21 13:45 ` [RFC PATCH 03/12] netfs: Remove netfs_read_subrequest::transferred David Howells
2021-07-21 17:43   ` Jeff Layton
2021-07-21 18:54   ` David Howells
2021-07-21 19:00     ` Jeff Layton
2021-07-21 13:45 ` [RFC PATCH 04/12] netfs: Use a buffer in netfs_read_request and add pages to it David Howells
2021-07-21 13:45 ` [RFC PATCH 05/12] netfs: Add a netfs inode context David Howells
2021-07-21 13:46 ` [RFC PATCH 06/12] netfs: Keep lists of pending, active, dirty and flushed regions David Howells
2021-07-21 13:46 ` [RFC PATCH 07/12] netfs: Initiate write request from a dirty region David Howells
2021-07-21 13:46 ` David Howells [this message]
2021-07-21 13:46 ` [RFC PATCH 09/12] netfs: Send write request to multiple destinations David Howells
2021-07-21 13:46 ` [RFC PATCH 10/12] netfs: Do encryption in write preparatory phase David Howells
2021-07-21 13:47 ` [RFC PATCH 11/12] netfs: Put a list of regions in /proc/fs/netfs/regions David Howells
2021-07-21 13:47 ` [RFC PATCH 12/12] netfs: Export some read-request ref functions David Howells
2021-07-21 14:00 ` [RFC PATCH 00/12] netfs: Experimental write helpers, fscrypt and compression David Howells
2021-07-21 18:42 ` [RFC PATCH 13/12] netfs: Do copy-to-cache-on-read through VM writeback David Howells

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