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ext4: don't use the orphan list when migrating an inode 

We probably want to remove the indirect block to extents migration
feature after a deprecation window, but until then, let's fix a
potential data loss problem caused by the fact that we put the
tmp_inode on the orphan list.  In the unlikely case where we crash and
do a journal recovery, the data blocks belonging to the inode being
migrated are also represented in the tmp_inode on the orphan list ---
and so its data blocks will get marked unallocated, and available for
reuse.

Instead, stop putting the tmp_inode on the oprhan list.  So in the
case where we crash while migrating the inode, we'll leak an inode,
which is not a disaster.  It will be easily fixed the next time we run
fsck, and it's better than potentially having blocks getting claimed
by two different files, and losing data as a result.

Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Reviewed-by: Lukas Czerner <lczerner@redhat.com>
Cc: stable@kernel.org
This commit is contained in:
Theodore Ts'o 2022-01-05 23:59:56 -05:00
parent a2e3965df4
commit 6eeaf88fd5
1 changed files with 4 additions and 15 deletions
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19
fs/ext4/migrate.c
View File

@ -437,12 +437,12 @@ int ext4_ext_migrate(struct inode *inode)
percpu_down_write(&sbi->s_writepages_rwsem);
/*
* Worst case we can touch the allocation bitmaps, a bgd
* block, and a block to link in the orphan list. We do need
* need to worry about credits for modifying the quota inode.
* Worst case we can touch the allocation bitmaps and a block
* group descriptor block. We do need need to worry about
* credits for modifying the quota inode.
*/
handle = ext4_journal_start(inode, EXT4_HT_MIGRATE,
4 + EXT4_MAXQUOTAS_TRANS_BLOCKS(inode->i_sb));
3 + EXT4_MAXQUOTAS_TRANS_BLOCKS(inode->i_sb));
if (IS_ERR(handle)) {
retval = PTR_ERR(handle);
@ -463,10 +463,6 @@ int ext4_ext_migrate(struct inode *inode)
* 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;
@ -478,7 +474,6 @@ int ext4_ext_migrate(struct inode *inode)
clear_nlink(tmp_inode);
ext4_ext_tree_init(handle, tmp_inode);
ext4_orphan_add(handle, tmp_inode);
ext4_journal_stop(handle);
/*
@ -503,12 +498,6 @@ int ext4_ext_migrate(struct inode *inode)
handle = ext4_journal_start(inode, EXT4_HT_MIGRATE, 1);
if (IS_ERR(handle)) {
/*
* It is impossible to update on-disk structures without
* a handle, so just rollback in-core changes and live other
* work to orphan_list_cleanup()
*/
ext4_orphan_del(NULL, tmp_inode);
retval = PTR_ERR(handle);
goto out_tmp_inode;
}