linux-kernel - Re: [External] : [PATCH] ocfs2: retire ocfs2_drop_inode() and I_WILL

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Message-ID: <f9014fdb-95c8-4faa-8c42-c1ceea49cbd9@linux.alibaba.com>
Date: Mon, 8 Sep 2025 20:41:21 +0800
From: Joseph Qi <joseph.qi@...ux.alibaba.com>
To: Jan Kara <jack@...e.cz>
Cc: Mateusz Guzik <mjguzik@...il.com>,
 Mark Tinguely <mark.tinguely@...cle.com>, ocfs2-devel@...ts.linux.dev,
 viro@...iv.linux.org.uk, linux-kernel@...r.kernel.org,
 linux-fsdevel@...r.kernel.org, josef@...icpanda.com, jlbec@...lplan.org,
 mark@...heh.com, brauner@...nel.org, willy@...radead.org, david@...morbit.com
Subject: Re: [External] : [PATCH] ocfs2: retire ocfs2_drop_inode() and
 I_WILL_FREE usage



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@...cle.com> 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@...il.com>
>>>>> ---
>>>>>
>>>>> 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.

Thanks,
Joseph