linux-kernel - [PATCH v5 03/10] ext4: don't write back data before punch hole in nojournal mode

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Message-ID: <20241220011637.1157197-4-yi.zhang@huaweicloud.com>
Date: Fri, 20 Dec 2024 09:16:30 +0800
From: Zhang Yi <yi.zhang@...weicloud.com>
To: linux-ext4@...r.kernel.org
Cc: linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	tytso@....edu,
	adilger.kernel@...ger.ca,
	jack@...e.cz,
	ojaswin@...ux.ibm.com,
	yi.zhang@...wei.com,
	yi.zhang@...weicloud.com,
	chengzhihao1@...wei.com,
	yukuai3@...wei.com,
	yangerkun@...wei.com
Subject: [PATCH v5 03/10] ext4: don't write back data before punch hole in nojournal mode

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

There is no need to write back all data before punching a hole in
non-journaled mode since it will be dropped soon after removing space.
Therefore, the call to filemap_write_and_wait_range() can be eliminated.
Besides, similar to ext4_zero_range(), we must address the case of
partially punched folios when block size < page size. It is essential to
remove writable userspace mappings to ensure that the folio can be
faulted again during subsequent mmap write access.

In journaled mode, we need to write dirty pages out before discarding
page cache in case of crash before committing the freeing data
transaction, which could expose old, stale data, even if synchronization
has been performed.

Signed-off-by: Zhang Yi <yi.zhang@...wei.com>
Reviewed-by: Jan Kara <jack@...e.cz>
Reviewed-by: Ojaswin Mujoo <ojaswin@...ux.ibm.com>
---
 fs/ext4/inode.c | 18 +++++-------------
 1 file changed, 5 insertions(+), 13 deletions(-)

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index b94cbdb82692..33f1a28177cf 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -4019,17 +4019,6 @@ int ext4_punch_hole(struct file *file, loff_t offset, loff_t length)
 
 	trace_ext4_punch_hole(inode, offset, length, 0);
 
-	/*
-	 * Write out all dirty pages to avoid race conditions
-	 * Then release them.
-	 */
-	if (mapping_tagged(mapping, PAGECACHE_TAG_DIRTY)) {
-		ret = filemap_write_and_wait_range(mapping, offset,
-						   offset + length - 1);
-		if (ret)
-			return ret;
-	}
-
 	inode_lock(inode);
 
 	/* No need to punch hole beyond i_size */
@@ -4091,8 +4080,11 @@ int ext4_punch_hole(struct file *file, loff_t offset, loff_t length)
 		ret = ext4_update_disksize_before_punch(inode, offset, length);
 		if (ret)
 			goto out_dio;
-		truncate_pagecache_range(inode, first_block_offset,
-					 last_block_offset);
+
+		ret = ext4_truncate_page_cache_block_range(inode,
+				first_block_offset, last_block_offset + 1);
+		if (ret)
+			goto out_dio;
 	}
 
 	if (ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS))
-- 
2.46.1