fs: record I_DIRTY_TIME even if inode already has I_DIRTY_INODE

Currently the I_DIRTY_TIME will never get set if the inode already has
I_DIRTY_INODE with assumption that it supersedes I_DIRTY_TIME.  That's
true, however ext4 will only update the on-disk inode in
->dirty_inode(), not on actual writeback. As a result if the inode
already has I_DIRTY_INODE state by the time we get to
__mark_inode_dirty() only with I_DIRTY_TIME, the time was already filled
into on-disk inode and will not get updated until the next I_DIRTY_INODE
update, which might never come if we crash or get a power failure.

The problem can be reproduced on ext4 by running xfstest generic/622
with -o iversion mount option.

Fix it by allowing I_DIRTY_TIME to be set even if the inode already has
I_DIRTY_INODE. Also make sure that the case is properly handled in
writeback_single_inode() as well. Additionally changes in
xfs_fs_dirty_inode() was made to accommodate for I_DIRTY_TIME in flag.

Thanks Jan Kara for suggestions on how to make this work properly.

Cc: Dave Chinner <david@fromorbit.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: stable@kernel.org
Signed-off-by: Lukas Czerner <lczerner@redhat.com>
Suggested-by: Jan Kara <jack@suse.cz>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20220825100657.44217-1-lczerner@redhat.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

1 files changed, 5 insertions, 4 deletions

diff --git a/include/linux/fs.h b/include/linux/fs.h
index 9eced4cc286e..56a4b4b02477 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2371,13 +2371,14 @@ static inline void kiocb_clone(struct kiocb *kiocb, struct kiocb *kiocb_src,
  *			don't have to write inode on fdatasync() when only
  *			e.g. the timestamps have changed.
  * I_DIRTY_PAGES	Inode has dirty pages.  Inode itself may be clean.
- * I_DIRTY_TIME		The inode itself only has dirty timestamps, and the
+ * I_DIRTY_TIME		The inode itself has dirty timestamps, and the
  *			lazytime mount option is enabled.  We keep track of this
  *			separately from I_DIRTY_SYNC in order to implement
  *			lazytime.  This gets cleared if I_DIRTY_INODE
- *			(I_DIRTY_SYNC and/or I_DIRTY_DATASYNC) gets set.  I.e.
- *			either I_DIRTY_TIME *or* I_DIRTY_INODE can be set in
- *			i_state, but not both.  I_DIRTY_PAGES may still be set.
+ *			(I_DIRTY_SYNC and/or I_DIRTY_DATASYNC) gets set. But
+ *			I_DIRTY_TIME can still be set if I_DIRTY_SYNC is already
+ *			in place because writeback might already be in progress
+ *			and we don't want to lose the time update
  * I_NEW		Serves as both a mutex and completion notification.
  *			New inodes set I_NEW.  If two processes both create
  *			the same inode, one of them will release its inode and