[PATCH 10/11] btrfs: don't split nocow extent_maps in btrfs_extract_ordered_extent

From: Christoph Hellwig <hch@lst.de>
To: Chris Mason <clm@fb.com>, Josef Bacik <josef@toxicpanda.com>,
	David Sterba <dsterba@suse.com>
Cc: Boris Burkov <boris@bur.io>,
	Johannes Thumshirn <Johannes.Thumshirn@wdc.com>,
	Naohiro Aota <Naohiro.Aota@wdc.com>,
	linux-btrfs@vger.kernel.org
Subject: [PATCH 10/11] btrfs: don't split nocow extent_maps in btrfs_extract_ordered_extent
Date: Fri, 24 Mar 2023 10:32:06 +0800	[thread overview]
Message-ID: <20230324023207.544800-11-hch@lst.de> (raw)
In-Reply-To: <20230324023207.544800-1-hch@lst.de>

From: Boris Burkov <boris@bur.io>

Nocow writes just overwrite an existing extent map, which thus should
not be split in btrfs_extract_ordered_extent.  The nocow case can't
currently happen as btrfs_extract_ordered_extent is only used on zoned
devices that do not support nocow writes, but this will change soon.

Signed-off-by: Boris Burkov <boris@bur.io>
[hch: split from a larger patch, wrote a commit log]
Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 fs/btrfs/inode.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 2abbedfd31c2c2..f72ba14dcda55e 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -2622,6 +2622,14 @@ int btrfs_extract_ordered_extent(struct btrfs_bio *bbio,
 	ret = btrfs_split_ordered_extent(ordered, len);
 	if (ret)
 		return ret;
+
+	/*
+	 * Don't split the extent_map for nocow extents, as we're writing
+	 * into a pre-existing one.
+	 */
+	if (test_bit(BTRFS_ORDERED_NOCOW, &ordered->flags))
+		return 0;
+
 	return split_extent_map(inode, bbio->file_offset, ordered_len, len);
 }
 
-- 
2.39.2

