Re: [PATCH] ocfs2: add journal NULL check in ocfs2_checkpoint_inode()

[Heming Zhao <heming.zhao@suse.com>]

On Mon, Jun 01, 2026 at 02:50:56PM +0800, Joseph Qi wrote:
> 
> 
> On 6/1/26 11:32 AM, Heming Zhao wrote:
> > On Sun, May 31, 2026 at 09:16:45PM +0800, Joseph Qi wrote:
> >> During unmount, ocfs2_journal_shutdown() frees the journal and sets
> >> osb->journal to NULL. Later, when VFS evicts remaining cached inodes,
> >> ocfs2_evict_inode() -> ocfs2_clear_inode() -> ocfs2_checkpoint_inode()
> >> -> ocfs2_ci_fully_checkpointed() dereferences osb->journal, causing a
> >> NULL pointer dereference.
> >>
> >> Fix this by adding a NULL check for osb->journal in
> >> ocfs2_checkpoint_inode(). If the journal is NULL, it has already been
> >> fully flushed and destroyed during shutdown, so there is nothing to
> >> checkpoint.
> >>
> >> Reported-by: Farhad Alemi <farhad.alemi@berkeley.edu>
> >> Fixes: da5e7c87827e ("ocfs2: cleanup journal init and shutdown")
> >> Signed-off-by: Joseph Qi <joseph.qi@linux.alibaba.com>
> >> Tested-by: Farhad Alemi <farhad.alemi@berkeley.edu>
> >> ---
> >>  fs/ocfs2/journal.h | 3 +++
> >>  1 file changed, 3 insertions(+)
> >>
> >> diff --git a/fs/ocfs2/journal.h b/fs/ocfs2/journal.h
> >> index 6397170f302f..f8b3b2a3d630 100644
> >> --- a/fs/ocfs2/journal.h
> >> +++ b/fs/ocfs2/journal.h
> >> @@ -196,6 +196,9 @@ static inline void ocfs2_checkpoint_inode(struct inode *inode)
> >>  	if (ocfs2_mount_local(osb))
> >>  		return;
> >>  
> >> +	if (!osb->journal)
> >> +		return;
> >> +
> > 
> > In my view, the code is correct for this bug.
> > However, the if condition is insufficient if ocfs2_journal_shutdown() sets
> > "journal = NULL" immediately after this line.
> > 
> During unmount, journal shutdown happens before final inode eviction is 
> triggered by generic_shutdown_super() -> evict_inodes(). That means they
> run sequentially in the unmount path (same thread context).
> 
> Thanks,
> Joseph
> 

Thanks for the explanation. I will provide my Reviewed-by tag.

Based on the call stack in Farhad's email attachment, it seems the test case
triggered the if (osb->slot_num != OCFS2_INVALID_SLOT) condition in
ocfs2_dismount_volume() to skip the released slot_inode.

Thanks,
Heming