linux-ext4 - [RFC PATCH v2 21/25] ext4: writeback partial blocks before zero range

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Message-Id: <20240102123918.799062-22-yi.zhang@huaweicloud.com>
Date: Tue,  2 Jan 2024 20:39:14 +0800
From: Zhang Yi <yi.zhang@...weicloud.com>
To: linux-ext4@...r.kernel.org
Cc: linux-fsdevel@...r.kernel.org,
	tytso@....edu,
	adilger.kernel@...ger.ca,
	jack@...e.cz,
	ritesh.list@...il.com,
	hch@...radead.org,
	djwong@...nel.org,
	willy@...radead.org,
	yi.zhang@...wei.com,
	yi.zhang@...weicloud.com,
	chengzhihao1@...wei.com,
	yukuai3@...wei.com,
	wangkefeng.wang@...wei.com
Subject: [RFC PATCH v2 21/25] ext4: writeback partial blocks before zero range

From: Zhang Yi <yi.zhang@...wei.com>

If we zero partial blocks, iomap_zero_iter() will skip zeroing out if
the srcmap is IOMAP_UNWRITTEN, it works fine in xfs because this type
means the block is pure unwritten, doesn't contain any delayed data,
but in ext4, IOMAP_UNWRITTEN may contain delayed data. For now we cannot
simply change the meaning of this flag in ext4, so just writeback
partial blocks from the beginning, make sure it becomes IOMAP_MAPPED
before zeroing out.

Signed-off-by: Zhang Yi <yi.zhang@...wei.com>
---
 fs/ext4/extents.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index 67ff75108cd1..d98c50472a42 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -4606,6 +4606,15 @@ static long ext4_zero_range(struct file *file, loff_t offset,
 		if (ret)
 			goto out_mutex;
 
+		ret = filemap_write_and_wait_range(mapping,
+				round_down(offset, 1 << blkbits), offset);
+		if (ret)
+			goto out_mutex;
+
+		ret = filemap_write_and_wait_range(mapping, offset + len,
+				round_up((offset + len), 1 << blkbits));
+		if (ret)
+			goto out_mutex;
 	}
 
 	/* Zero range excluding the unaligned edges */
-- 
2.39.2