[PATCH 5.19 106/717] fs: record I_DIRTY_TIME even if inode already has I_DIRTY_INODE

Greg Kroah-Hartman
2022-10-22T07:56:21Z

From: Lukas Czerner <lczerner@redhat.com>

commit cbfecb927f429a6fa613d74b998496bd71e4438a upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
Documentation/filesystems/vfs.rst | 3 +++
fs/fs-writeback.c | 37 +++++++++++++++++++++++++------------
fs/xfs/xfs_super.c | 10 ++++++++--
include/linux/fs.h | 9 +++++----
4 files changed, 41 insertions(+), 18 deletions(-)

--- a/Documentation/filesystems/vfs.rst
+++ b/Documentation/filesystems/vfs.rst
@@ -274,6 +274,9 @@ or bottom half).
This is specifically for the inode itself being marked dirty,
not its data. If the update needs to be persisted by fdatasync(),
then I_DIRTY_DATASYNC will be set in the flags argument.
+ I_DIRTY_TIME will be set in the flags in case lazytime is enabled
+ and struct inode has times updated since the last ->dirty_inode
+ call.

``write_inode``
this method is called when the VFS needs to write an inode to
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -1718,9 +1718,14 @@ static int writeback_single_inode(struct
*/
if (!(inode->i_state & I_DIRTY_ALL))
inode_cgwb_move_to_attached(inode, wb);
- else if (!(inode->i_state & I_SYNC_QUEUED) &&
- (inode->i_state & I_DIRTY))
- redirty_tail_locked(inode, wb);
+ else if (!(inode->i_state & I_SYNC_QUEUED)) {
+ if ((inode->i_state & I_DIRTY))
+ redirty_tail_locked(inode, wb);
+ else if (inode->i_state & I_DIRTY_TIME) {
+ inode->dirtied_when = jiffies;
+ inode_io_list_move_locked(inode, wb, &wb->b_dirty_time);
+ }
+ }

spin_unlock(&wb->list_lock);
inode_sync_complete(inode);
@@ -2370,6 +2375,20 @@ void __mark_inode_dirty(struct inode *in

if (flags & I_DIRTY_INODE) {
/*
+ * Inode timestamp update will piggback on this dirtying.
+ * We tell ->dirty_inode callback that timestamps need to
+ * be updated by setting I_DIRTY_TIME in flags.
+ */
+ if (inode->i_state & I_DIRTY_TIME) {
+ spin_lock(&inode->i_lock);
+ if (inode->i_state & I_DIRTY_TIME) {
+ inode->i_state &= ~I_DIRTY_TIME;
+ flags |= I_DIRTY_TIME;
+ }
+ spin_unlock(&inode->i_lock);
+ }
+
+ /*
* Notify the filesystem about the inode being dirtied, so that
* (if needed) it can update on-disk fields and journal the
* inode. This is only needed when the inode itself is being
@@ -2378,7 +2397,8 @@ void __mark_inode_dirty(struct inode *in
*/
trace_writeback_dirty_inode_start(inode, flags);
if (sb->s_op->dirty_inode)
- sb->s_op->dirty_inode(inode, flags & I_DIRTY_INODE);
+ sb->s_op->dirty_inode(inode,
+ flags & (I_DIRTY_INODE | I_DIRTY_TIME));
trace_writeback_dirty_inode(inode, flags);

/* I_DIRTY_INODE supersedes I_DIRTY_TIME. */
@@ -2399,21 +2419,15 @@ void __mark_inode_dirty(struct inode *in
*/
smp_mb();

- if (((inode->i_state & flags) == flags) ||
- (dirtytime && (inode->i_state & I_DIRTY_INODE)))
+ if ((inode->i_state & flags) == flags)
return;

spin_lock(&inode->i_lock);
- if (dirtytime && (inode->i_state & I_DIRTY_INODE))
- goto out_unlock_inode;
if ((inode->i_state & flags) != flags) {
const int was_dirty = inode->i_state & I_DIRTY;

inode_attach_wb(inode, NULL);

- /* I_DIRTY_INODE supersedes I_DIRTY_TIME. */
- if (flags & I_DIRTY_INODE)
- inode->i_state &= ~I_DIRTY_TIME;
inode->i_state |= flags;

/*
@@ -2486,7 +2500,6 @@ void __mark_inode_dirty(struct inode *in
out_unlock:
if (wb)
spin_unlock(&wb->list_lock);
-out_unlock_inode:
spin_unlock(&inode->i_lock);
}
EXPORT_SYMBOL(__mark_inode_dirty);
--- a/fs/xfs/xfs_super.c
+++ b/fs/xfs/xfs_super.c
@@ -650,7 +650,7 @@ xfs_fs_destroy_inode(
static void
xfs_fs_dirty_inode(
struct inode *inode,
- int flag)
+ int flags)
{
struct xfs_inode *ip = XFS_I(inode);
struct xfs_mount *mp = ip->i_mount;
@@ -658,7 +658,13 @@ xfs_fs_dirty_inode(

if (!(inode->i_sb->s_flags & SB_LAZYTIME))
return;
- if (flag != I_DIRTY_SYNC || !(inode->i_state & I_DIRTY_TIME))
+
+ /*
+ * Only do the timestamp update if the inode is dirty (I_DIRTY_SYNC)
+ * and has dirty timestamp (I_DIRTY_TIME). I_DIRTY_TIME can be passed
+ * in flags possibly together with I_DIRTY_SYNC.
+ */
+ if ((flags & ~I_DIRTY_TIME) != I_DIRTY_SYNC || !(flags & I_DIRTY_TIME))
return;

if (xfs_trans_alloc(mp, &M_RES(mp)->tr_fsyncts, 0, 0, 0, &tp))
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2241,13 +2241,14 @@ static inline void kiocb_clone(struct ki
* 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