ext4: recover csum seed of tmp_inode after migrating to extents

[ Upstream commit 07ea7a617d6b278fb7acedb5cbe1a81ce2de7d0c ]

When migrating to extents, the checksum seed of temporary inode
need to be replaced by inode's, otherwise the inode checksums
will be incorrect when swapping the inodes data.

However, the temporary inode can not match it's checksum to
itself since it has lost it's own checksum seed.

mkfs.ext4 -F /dev/sdc
mount /dev/sdc /mnt/sdc
xfs_io -fc "pwrite 4k 4k" -c "fsync" /mnt/sdc/testfile
chattr -e /mnt/sdc/testfile
chattr +e /mnt/sdc/testfile
umount /dev/sdc
fsck -fn /dev/sdc

========
...
Pass 1: Checking inodes, blocks, and sizes
Inode 13 passes checks, but checksum does not match inode.  Fix? no
...
========

The fix is simple, save the checksum seed of temporary inode, and
recover it after migrating to extents.

Fixes: e81c9302a6c3 ("ext4: set csum seed in tmp inode while migrating to extents")
Signed-off-by: Li Lingfeng <lilingfeng3@huawei.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20220617062515.2113438-1-lilingfeng3@huawei.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/fs/ext4/migrate.c b/fs/ext4/migrate.c
index ff8916e1d38e9195e399cd825f3e2705873429a8..af5a75a89e6e133bb5f51c75aff103458d436c06 100644 (file)
--- a/fs/ext4/migrate.c
+++ b/fs/ext4/migrate.c
@@ -417,7 +417,7 @@ int ext4_ext_migrate(struct inode *inode)
        struct inode *tmp_inode = NULL;
        struct migrate_struct lb;
        unsigned long max_entries;
-       __u32 goal;
+       __u32 goal, tmp_csum_seed;
        uid_t owner[2];
 
        /*
@@ -465,6 +465,7 @@ int ext4_ext_migrate(struct inode *inode)
         * the migration.
         */
        ei = EXT4_I(inode);
+       tmp_csum_seed = EXT4_I(tmp_inode)->i_csum_seed;
        EXT4_I(tmp_inode)->i_csum_seed = ei->i_csum_seed;
        i_size_write(tmp_inode, i_size_read(inode));
        /*
@@ -575,6 +576,7 @@ err_out:
         * the inode is not visible to user space.
         */
        tmp_inode->i_blocks = 0;
+       EXT4_I(tmp_inode)->i_csum_seed = tmp_csum_seed;
 
        /* Reset the extent details */
        ext4_ext_tree_init(handle, tmp_inode);