linux-ext4 - [PATCH AUTOSEL 4.14 76/95] ext4: cleanup pagecache before swap i

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Date:   Tue,  7 May 2019 01:38:05 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     yangerkun <yangerkun@...wei.com>, Theodore Ts'o <tytso@....edu>,
        stable@...nel.org, Sasha Levin <alexander.levin@...rosoft.com>,
        linux-ext4@...r.kernel.org
Subject: [PATCH AUTOSEL 4.14 76/95] ext4: cleanup pagecache before swap i_data

From: yangerkun <yangerkun@...wei.com>

[ Upstream commit a46c68a318b08f819047843abf349aeee5d10ac2 ]

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@...wei.com>
Signed-off-by: Theodore Ts'o <tytso@....edu>
Cc: stable@...nel.org
Signed-off-by: Sasha Levin <alexander.levin@...rosoft.com>
---
 fs/ext4/ioctl.c | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/fs/ext4/ioctl.c b/fs/ext4/ioctl.c
index 3dbf4e414706..ca6d27bfcdd8 100644
--- a/fs/ext4/ioctl.c
+++ b/fs/ext4/ioctl.c
@@ -116,9 +116,6 @@ static long swap_inode_boot_loader(struct super_block *sb,
 		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);
@@ -126,6 +123,15 @@ static long swap_inode_boot_loader(struct super_block *sb,
 	truncate_inode_pages(&inode->i_data, 0);
 	truncate_inode_pages(&inode_bl->i_data, 0);
 
+	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);
@@ -135,7 +141,7 @@ static long swap_inode_boot_loader(struct super_block *sb,
 	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 */
@@ -190,6 +196,8 @@ static long swap_inode_boot_loader(struct super_block *sb,
 	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);
-- 
2.20.1