From a46c68a318b08f819047843abf349aeee5d10ac2 Mon Sep 17 00:00:00 2001
From: yangerkun <yangerkun@huawei.com>
Date: Mon, 11 Feb 2019 00:05:24 -0500
Subject: [PATCH] ext4: cleanup pagecache before swap i_data
Git-commit: a46c68a318b08f819047843abf349aeee5d10ac2
Patch-mainline: v5.1-rc1
References: bsc#1131178

While do swap, we should make sure there has no new dirty page since we
should swap i_data between two inode:
1.We should lock i_mmap_sem with write to avoid new pagecache from mmap
read/write;
2.Change filemap_flush to filemap_write_and_wait and move them to the
space protected by inode lock to avoid new pagecache from buffer read/write.

Signed-off-by: yangerkun <yangerkun@huawei.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: stable@kernel.org
Acked-by: Jan Kara <jack@suse.cz>

---
 fs/ext4/ioctl.c |   16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

--- a/fs/ext4/ioctl.c
+++ b/fs/ext4/ioctl.c
@@ -122,9 +122,6 @@ static long swap_inode_boot_loader(struc
 		return PTR_ERR(inode_bl);
 	ei_bl = EXT4_I(inode_bl);
 
-	filemap_flush(inode->i_mapping);
-	filemap_flush(inode_bl->i_mapping);
-
 	/* Protect orig inodes against a truncate and make sure,
 	 * that only 1 swap_inode_boot_loader is running. */
 	lock_two_nondirectories(inode, inode_bl);
@@ -142,6 +139,15 @@ static long swap_inode_boot_loader(struc
 		goto journal_err_out;
 	}
 
+	down_write(&EXT4_I(inode)->i_mmap_sem);
+	err = filemap_write_and_wait(inode->i_mapping);
+	if (err)
+		goto err_out;
+
+	err = filemap_write_and_wait(inode_bl->i_mapping);
+	if (err)
+		goto err_out;
+
 	/* Wait for all existing dio workers */
 	ext4_inode_block_unlocked_dio(inode);
 	ext4_inode_block_unlocked_dio(inode_bl);
@@ -154,7 +160,7 @@ static long swap_inode_boot_loader(struc
 	handle = ext4_journal_start(inode_bl, EXT4_HT_MOVE_EXTENTS, 2);
 	if (IS_ERR(handle)) {
 		err = -EINVAL;
-		goto journal_err_out;
+		goto err_out;
 	}
 
 	/* Protect extent tree against block allocations via delalloc */
@@ -214,6 +220,8 @@ static long swap_inode_boot_loader(struc
 	ext4_journal_stop(handle);
 	ext4_double_up_write_data_sem(inode, inode_bl);
 
+err_out:
+	up_write(&EXT4_I(inode)->i_mmap_sem);
 journal_err_out:
 	ext4_inode_resume_unlocked_dio(inode);
 	ext4_inode_resume_unlocked_dio(inode_bl);