linux-kernel - [PATCH 1/2] ext4: use ext4_ext_remove_space() for fast commit replay delete range

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Date:   Thu, 23 Dec 2021 11:23:36 +0800
From:   Xin Yin <yinxin.x@...edance.com>
To:     harshadshirwadkar@...il.com, tytso@....edu,
        adilger.kernel@...ger.ca
Cc:     linux-ext4@...r.kernel.org, linux-kernel@...r.kernel.org,
        Xin Yin <yinxin.x@...edance.com>
Subject: [PATCH 1/2] ext4: use ext4_ext_remove_space() for fast commit replay delete range

For now ,we use ext4_punch_hole() during fast commit replay delete range
procedure. But it will be affected by inode->i_size, which may not
correct during fast commit replay procedure. The following test will
failed.

-create & write foo (len 1000K)
-falloc FALLOC_FL_ZERO_RANGE foo (range 400K - 600K)
-create & fsync bar
-falloc FALLOC_FL_PUNCH_HOLE foo (range 300K-500K)
-fsync foo
-crash before a full commit

After the fast_commit reply procedure, the range 400K-500K will not be
removed. Because in this case, when calling ext4_punch_hole() the
inode->i_size is 0, and it just retruns with doing nothing.

Change to use ext4_ext_remove_space() instead of ext4_punch_hole()
to remove blocks of inode directly.

Signed-off-by: Xin Yin <yinxin.x@...edance.com>
---
 fs/ext4/fast_commit.c | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/fs/ext4/fast_commit.c b/fs/ext4/fast_commit.c
index aa05b23f9c14..3deb97b22ca4 100644
--- a/fs/ext4/fast_commit.c
+++ b/fs/ext4/fast_commit.c
@@ -1708,11 +1708,14 @@ ext4_fc_replay_del_range(struct super_block *sb, struct ext4_fc_tl *tl,
 		}
 	}
 
-	ret = ext4_punch_hole(inode,
-		le32_to_cpu(lrange.fc_lblk) << sb->s_blocksize_bits,
-		le32_to_cpu(lrange.fc_len) <<  sb->s_blocksize_bits);
-	if (ret)
-		jbd_debug(1, "ext4_punch_hole returned %d", ret);
+	down_write(&EXT4_I(inode)->i_data_sem);
+	ret = ext4_ext_remove_space(inode, lrange.fc_lblk,
+				lrange.fc_lblk + lrange.fc_len - 1);
+	up_write(&EXT4_I(inode)->i_data_sem);
+	if (ret) {
+		iput(inode);
+		return 0;
+	}
 	ext4_ext_replay_shrink_inode(inode,
 		i_size_read(inode) >> sb->s_blocksize_bits);
 	ext4_mark_inode_dirty(NULL, inode);
-- 
2.20.1