[PATCH AUTOSEL 4.14 76/95] ext4: cleanup pagecache before swap i_data

Sasha Levin
2019-05-07T05:40:47Z

From: yangerkun <yangerkun@huawei.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@huawei.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: stable@kernel.org
Signed-off-by: Sasha Levin <alexander.levin@microsoft.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