Re: [External] : [PATCH] ocfs2: retire ocfs2_drop_inode() and I_WILL_FREE usage

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On Tue 09-09-25 09:23:56, Joseph Qi wrote:
> On 2025/9/8 21:54, Jan Kara wrote:
> > On Mon 08-09-25 20:41:21, Joseph Qi wrote:
> >>
> >>
> >> On 2025/9/8 18:23, Jan Kara wrote:
> >>> On Mon 08-09-25 09:51:36, Joseph Qi wrote:
> >>>> On 2025/9/5 00:22, Mateusz Guzik wrote:
> >>>>> On Thu, Sep 4, 2025 at 6:15 PM Mark Tinguely <mark.tinguely@xxxxxxxxxx> wrote:
> >>>>>>
> >>>>>> On 9/4/25 10:42 AM, Mateusz Guzik wrote:
> >>>>>>> This postpones the writeout to ocfs2_evict_inode(), which I'm told is
> >>>>>>> fine (tm).
> >>>>>>>
> >>>>>>> The intent is to retire the I_WILL_FREE flag.
> >>>>>>>
> >>>>>>> Signed-off-by: Mateusz Guzik <mjguzik@xxxxxxxxx>
> >>>>>>> ---
> >>>>>>>
> >>>>>>> ACHTUNG: only compile-time tested. Need an ocfs2 person to ack it.
> >>>>>>>
> >>>>>>> btw grep shows comments referencing ocfs2_drop_inode() which are already
> >>>>>>> stale on the stock kernel, I opted to not touch them.
> >>>>>>>
> >>>>>>> This ties into an effort to remove the I_WILL_FREE flag, unblocking
> >>>>>>> other work. If accepted would be probably best taken through vfs
> >>>>>>> branches with said work, see https://urldefense.com/v3/__https://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs.git/log/?h=vfs-6.18.inode.refcount.preliminaries__;!!ACWV5N9M2RV99hQ!OLwk8DVo7uvC-Pd6XVTiUCgP6MUDMKBMEyuV27h_yPGXOjaq078-kMdC9ILFoYQh-4WX93yb0nMfBDFFY_0$
> >>>>>>>
> >>>>>>>   fs/ocfs2/inode.c       | 23 ++---------------------
> >>>>>>>   fs/ocfs2/inode.h       |  1 -
> >>>>>>>   fs/ocfs2/ocfs2_trace.h |  2 --
> >>>>>>>   fs/ocfs2/super.c       |  2 +-
> >>>>>>>   4 files changed, 3 insertions(+), 25 deletions(-)
> >>>>>>>
> >>>>>>> diff --git a/fs/ocfs2/inode.c b/fs/ocfs2/inode.c
> >>>>>>> index 6c4f78f473fb..5f4a2cbc505d 100644
> >>>>>>> --- a/fs/ocfs2/inode.c
> >>>>>>> +++ b/fs/ocfs2/inode.c
> >>>>>>> @@ -1290,6 +1290,8 @@ static void ocfs2_clear_inode(struct inode *inode)
> >>>>>>>
> >>>>>>>   void ocfs2_evict_inode(struct inode *inode)
> >>>>>>>   {
> >>>>>>> +     write_inode_now(inode, 1);
> >>>>>>> +
> >>>>>>>       if (!inode->i_nlink ||
> >>>>>>>           (OCFS2_I(inode)->ip_flags & OCFS2_INODE_MAYBE_ORPHANED)) {
> >>>>>>>               ocfs2_delete_inode(inode);
> >>>>>>> @@ -1299,27 +1301,6 @@ void ocfs2_evict_inode(struct inode *inode)
> >>>>>>>       ocfs2_clear_inode(inode);
> >>>>>>>   }
> >>>>>>>
> >>>>>>> -/* Called under inode_lock, with no more references on the
> >>>>>>> - * struct inode, so it's safe here to check the flags field
> >>>>>>> - * and to manipulate i_nlink without any other locks. */
> >>>>>>> -int ocfs2_drop_inode(struct inode *inode)
> >>>>>>> -{
> >>>>>>> -     struct ocfs2_inode_info *oi = OCFS2_I(inode);
> >>>>>>> -
> >>>>>>> -     trace_ocfs2_drop_inode((unsigned long long)oi->ip_blkno,
> >>>>>>> -                             inode->i_nlink, oi->ip_flags);
> >>>>>>> -
> >>>>>>> -     assert_spin_locked(&inode->i_lock);
> >>>>>>> -     inode->i_state |= I_WILL_FREE;
> >>>>>>> -     spin_unlock(&inode->i_lock);
> >>>>>>> -     write_inode_now(inode, 1);
> >>>>>>> -     spin_lock(&inode->i_lock);
> >>>>>>> -     WARN_ON(inode->i_state & I_NEW);
> >>>>>>> -     inode->i_state &= ~I_WILL_FREE;
> >>>>>>> -
> >>>>>>> -     return 1;
> >>>>>>> -}
> >>>>>>> -
> >>>>>>>   /*
> >>>>>>>    * This is called from our getattr.
> >>>>>>>    */
> >>>>>>> diff --git a/fs/ocfs2/inode.h b/fs/ocfs2/inode.h
> >>>>>>> index accf03d4765e..07bd838e7843 100644
> >>>>>>> --- a/fs/ocfs2/inode.h
> >>>>>>> +++ b/fs/ocfs2/inode.h
> >>>>>>> @@ -116,7 +116,6 @@ static inline struct ocfs2_caching_info *INODE_CACHE(struct inode *inode)
> >>>>>>>   }
> >>>>>>>
> >>>>>>>   void ocfs2_evict_inode(struct inode *inode);
> >>>>>>> -int ocfs2_drop_inode(struct inode *inode);
> >>>>>>>
> >>>>>>>   /* Flags for ocfs2_iget() */
> >>>>>>>   #define OCFS2_FI_FLAG_SYSFILE               0x1
> >>>>>>> diff --git a/fs/ocfs2/ocfs2_trace.h b/fs/ocfs2/ocfs2_trace.h
> >>>>>>> index 54ed1495de9a..4b32fb5658ad 100644
> >>>>>>> --- a/fs/ocfs2/ocfs2_trace.h
> >>>>>>> +++ b/fs/ocfs2/ocfs2_trace.h
> >>>>>>> @@ -1569,8 +1569,6 @@ DEFINE_OCFS2_ULL_ULL_UINT_EVENT(ocfs2_delete_inode);
> >>>>>>>
> >>>>>>>   DEFINE_OCFS2_ULL_UINT_EVENT(ocfs2_clear_inode);
> >>>>>>>
> >>>>>>> -DEFINE_OCFS2_ULL_UINT_UINT_EVENT(ocfs2_drop_inode);
> >>>>>>> -
> >>>>>>>   TRACE_EVENT(ocfs2_inode_revalidate,
> >>>>>>>       TP_PROTO(void *inode, unsigned long long ino,
> >>>>>>>                unsigned int flags),
> >>>>>>> diff --git a/fs/ocfs2/super.c b/fs/ocfs2/super.c
> >>>>>>> index 53daa4482406..e4b0d25f4869 100644
> >>>>>>> --- a/fs/ocfs2/super.c
> >>>>>>> +++ b/fs/ocfs2/super.c
> >>>>>>> @@ -129,7 +129,7 @@ static const struct super_operations ocfs2_sops = {
> >>>>>>>       .statfs         = ocfs2_statfs,
> >>>>>>>       .alloc_inode    = ocfs2_alloc_inode,
> >>>>>>>       .free_inode     = ocfs2_free_inode,
> >>>>>>> -     .drop_inode     = ocfs2_drop_inode,
> >>>>>>> +     .drop_inode     = generic_delete_inode,
> >>>>>>>       .evict_inode    = ocfs2_evict_inode,
> >>>>>>>       .sync_fs        = ocfs2_sync_fs,
> >>>>>>>       .put_super      = ocfs2_put_super,
> >>>>>>
> >>>>>>
> >>>>>> I agree, fileystems should not use I_FREEING/I_WILL_FREE.
> >>>>>> Doing the sync write_inode_now() should be fine in ocfs_evict_inode().
> >>>>>>
> >>>>>> Question is ocfs_drop_inode. In commit 513e2dae9422:
> >>>>>>   ocfs2: flush inode data to disk and free inode when i_count becomes zero
> >>>>>> the return of 1 drops immediate to fix a memory caching issue.
> >>>>>> Shouldn't .drop_inode() still return 1?
> >>>>>
> >>>>> generic_delete_inode is a stub doing just that.
> >>>>>
> >>>> In case of "drop = 0", it may return directly without calling evict().
> >>>> This seems break the expectation of commit 513e2dae9422.
> >>>
> >>> generic_delete_inode() always returns 1 so evict() will be called.
> >>> ocfs2_drop_inode() always returns 1 as well after 513e2dae9422. So I'm not
> >>> sure which case of "drop = 0" do you see...
> >>>
> >> I don't see a real case, just in theory.
> >> As I described before, if we make sure write_inode_now() will be called
> >> in iput_final(), it would be fine.
> > 
> > I'm sorry but I still don't quite understand what you are proposing. If
> > ->drop() returns 1, the filesystem wants to remove the inode from cache
> > (perhaps because it was deleted). Hence iput_final() doesn't bother with
> > writing out such inodes. This doesn't work well with ocfs2 wanting to
> > always drop inodes hence ocfs2 needs to write the inode itself in
> > ocfs2_evice_inode(). Perhaps you have some modification to iput_final() in
> > mind but I'm not sure how that would work so can you perhaps suggest a
> > patch if you think iput_final() should work differently? Thanks!
> > 
> I'm just discussing if generic_delete_inode() will always returns 1. And
> if it is, I'm fine with this change. Sorry for the confusion.

generic_delete_inode() is defined as:

int generic_delete_inode(struct inode *inode)
{               
        return 1;
}

So the return is pretty much guaranteed :). But I agree with Mateusz the
function name could be less confusing.

								Honza
-- 
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR




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