linux-ext4 - [PATCH 2/3] ext4: truncate complete range in pagecache before calling ext4_zero_partial

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Message-Id: <f7aaea4a59bc1c69f87e178dae34c38d2bcfee12.1695987265.git.ojaswin@linux.ibm.com>
Date:   Fri, 29 Sep 2023 19:40:44 +0530
From:   Ojaswin Mujoo <ojaswin@...ux.ibm.com>
To:     linux-ext4@...r.kernel.org, "Theodore Ts'o" <tytso@....edu>
Cc:     Ritesh Harjani <ritesh.list@...il.com>,
        linux-kernel@...r.kernel.org, Jan Kara <jack@...e.cz>
Subject: [PATCH 2/3] ext4: truncate complete range in pagecache before calling ext4_zero_partial_blocks()

In ext4_zero_range() and ext4_punch_hole(), the range passed could be unaligned
however we only zero out the pagecache range that is block aligned. These
functions are relying on ext4_zero_partial_blocks() ->
__ext4_block_zero_page_range() to take care of zeroing the unaligned edges in
the pageacache. However, the right thing to do is to properly zero out the whole
range in these functions before and not rely on a different function to do it
for us. Hence, modify ext4_zero_range() and ext4_punch_hole() to zero the
complete range.

This will also allow us to now exit early for unwritten buffer heads in
__ext4_block_zero_page_range(), in upcoming patch.

Signed-off-by: Ojaswin Mujoo <ojaswin@...ux.ibm.com>
---
 fs/ext4/extents.c | 17 +++++++++++------
 fs/ext4/inode.c   |  3 +--
 2 files changed, 12 insertions(+), 8 deletions(-)

diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index c79b4c25afc4..2dc681cab6a5 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -4582,9 +4582,6 @@ static long ext4_zero_range(struct file *file, loff_t offset,
 
 	/* Zero range excluding the unaligned edges */
 	if (max_blocks > 0) {
-		flags |= (EXT4_GET_BLOCKS_CONVERT_UNWRITTEN |
-			  EXT4_EX_NOCACHE);
-
 		/*
 		 * Prevent page faults from reinstantiating pages we have
 		 * released from page cache.
@@ -4609,17 +4606,25 @@ static long ext4_zero_range(struct file *file, loff_t offset,
 		 * disk in case of crash before zeroing trans is committed.
 		 */
 		if (ext4_should_journal_data(inode)) {
-			ret = filemap_write_and_wait_range(mapping, start, end - 1);
+			ret = filemap_write_and_wait_range(mapping, start,
+							   end - 1);
 			if (ret) {
 				filemap_invalidate_unlock(mapping);
 				goto out_mutex;
 			}
 		}
+	}
+
+	/*
+	 * Now truncate the pagecache and zero out non page aligned edges of the
+	 * range (if any)
+	 */
+	truncate_pagecache_range(inode, offset, offset + len - 1);
 
-		/* Now release the pages and zero block aligned part of pages */
-		truncate_pagecache_range(inode, start, end - 1);
+	if (max_blocks > 0) {
 		inode->i_mtime = inode->i_ctime = current_time(inode);
 
+		flags |= (EXT4_GET_BLOCKS_CONVERT_UNWRITTEN | EXT4_EX_NOCACHE);
 		ret = ext4_alloc_file_blocks(file, lblk, max_blocks, new_size,
 					     flags);
 		filemap_invalidate_unlock(mapping);
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 6c490f05e2ba..de8ea8430d30 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -3974,9 +3974,8 @@ 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);
 	}
+	truncate_pagecache_range(inode, offset, offset + length - 1);
 
 	if (ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS))
 		credits = ext4_writepage_trans_blocks(inode);
-- 
2.39.3