Patch "ext4: recover csum seed of tmp_inode after migrating to extents" has been added to the 5.4-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    ext4: recover csum seed of tmp_inode after migrating to extents

to the 5.4-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     ext4-recover-csum-seed-of-tmp_inode-after-migrating-.patch
and it can be found in the queue-5.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 3ac2abadcc8d6dba64af190b12743c2f7ec7b285
Author: Li Lingfeng <lilingfeng3@xxxxxxxxxx>
Date:   Fri Jun 17 14:25:15 2022 +0800

    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@xxxxxxxxxx>
    Reviewed-by: Jan Kara <jack@xxxxxxx>
    Link: https://lore.kernel.org/r/20220617062515.2113438-1-lilingfeng3@xxxxxxxxxx
    Signed-off-by: Theodore Ts'o <tytso@xxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/fs/ext4/migrate.c b/fs/ext4/migrate.c
index c5b2ea1a9372..1faa8e4ffb9d 100644
--- a/fs/ext4/migrate.c
+++ b/fs/ext4/migrate.c
@@ -435,7 +435,7 @@ 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];
 
 	/*
@@ -483,6 +483,7 @@ 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));
 	/*
@@ -593,6 +594,7 @@ int ext4_ext_migrate(struct inode *inode)
 	 * 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);