From: =?utf-8?q?Lu=C3=ADs_Henriques_=3Clhenriques=40suse=2Ede=3E?=
Date: Tue, 14 Dec 2021 17:50:58 +0000
Subject: ext4: set csum seed in tmp inode while migrating to extents
Mime-version: 1.0
Content-type: text/plain; charset=UTF-8
Content-transfer-encoding: 8bit
Git-commit: e81c9302a6c3c008f5c30beb73b38adb0170ff2d
Patch-mainline: v5.17-rc1
References: bsc#1195272

When migrating to extents, the temporary inode will have it's own checksum
seed.  This means that, when swapping the inodes data, the inode checksums
will be incorrect.

This can be fixed by recalculating the extents checksums again.  Or simply
by copying the seed into the temporary inode.

Link: https://bugzilla.kernel.org/show_bug.cgi?id=213357
Reported-by: Jeroen van Wolffelaar <jeroen@wolffelaar.nl>
Signed-off-by: Luís Henriques <lhenriques@suse.de>
Link: https://lore.kernel.org/r/20211214175058.19511-1-lhenriques@suse.de
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: stable@kernel.org

---
 fs/ext4/migrate.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/fs/ext4/migrate.c b/fs/ext4/migrate.c
index 7e0b4f81c6c0..36dfc88ce05b 100644
--- a/fs/ext4/migrate.c
+++ b/fs/ext4/migrate.c
@@ -459,6 +459,17 @@ int ext4_ext_migrate(struct inode *inode)
 		ext4_journal_stop(handle);
 		goto out_unlock;
 	}
+	/*
+	 * Use the correct seed for checksum (i.e. the seed from 'inode').  This
+	 * is so that the metadata blocks will have the correct checksum after
+	 * the migration.
+	 *
+	 * Note however that, if a crash occurs during the migration process,
+	 * the recovery process is broken because the tmp_inode checksums will
+	 * be wrong and the orphans cleanup will fail.
+	 */
+	ei = EXT4_I(inode);
+	EXT4_I(tmp_inode)->i_csum_seed = ei->i_csum_seed;
 	i_size_write(tmp_inode, i_size_read(inode));
 	/*
 	 * Set the i_nlink to zero so it will be deleted later
@@ -502,7 +513,6 @@ int ext4_ext_migrate(struct inode *inode)
 		goto out_tmp_inode;
 	}
 
-	ei = EXT4_I(inode);
 	i_data = ei->i_data;
 	memset(&lb, 0, sizeof(lb));