Re: [PATCH 2/5 v3] locks: Copy all infomation for conflock

[Kinglong Mee <kinglongmee-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>]

On 8/15/2014 22:33, Kinglong Mee wrote:
> On 8/15/2014 19:14, Jeff Layton wrote:
>> On Fri, 15 Aug 2014 08:07:12 +0800
>> Kinglong Mee <kinglongmee-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
>>
>>> Commit d5b9026a67 ([PATCH] knfsd: locks: flag NFSv4-owned locks) using
>>> fl_lmops field in file_lock for checking nfsd4 lockowner.
>>>
>>> But, commit 1a747ee0cc (locks: don't call ->copy_lock methods on return
>>> of conflicting locks) causes the fl_lmops of conflock always be NULL.
>>>
>>> Also, commit 0996905f93 (lockd: posix_test_lock() should not call
>>> locks_copy_lock()) caused the fl_lmops of conflock always be NULL too.
>>>
>>> Make sure copy the private information by fl_copy_lock() in struct
>>> file_lock_operations, merge __locks_copy_lock() to fl_copy_lock().
>>>
>>> v3: Update based on Joe and Jeff's patch.
>>>
>>> Signed-off-by: Kinglong Mee <kinglongmee-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
>>> ---
>>>  fs/locks.c         | 24 +++++++-----------------
>>>  include/linux/fs.h |  6 ------
>>>  2 files changed, 7 insertions(+), 23 deletions(-)
>>>
>>> diff --git a/fs/locks.c b/fs/locks.c
>>> index cb66fb0..fe52abb 100644
>>> --- a/fs/locks.c
>>> +++ b/fs/locks.c
>>> @@ -281,33 +281,23 @@ static void locks_copy_private(struct file_lock *new, struct file_lock *fl)
>>>  /*
>>>   * Initialize a new lock from an existing file_lock structure.
>>>   */
>>> -void __locks_copy_lock(struct file_lock *new, const struct file_lock *fl)
>>> +void locks_copy_lock(struct file_lock *new, struct file_lock *fl)
>>>  {
>>> +	/* "new" must be a freshly-initialized lock */
>>> +	WARN_ON_ONCE(new->fl_ops);
>>> +
>>>  	new->fl_owner = fl->fl_owner;
>>>  	new->fl_pid = fl->fl_pid;
>>> -	new->fl_file = NULL;
>>> +	new->fl_file = fl->fl_file;
>>>  	new->fl_flags = fl->fl_flags;
>>>  	new->fl_type = fl->fl_type;
>>>  	new->fl_start = fl->fl_start;
>>>  	new->fl_end = fl->fl_end;
>>>  	new->fl_ops = NULL;
>>>  	new->fl_lmops = NULL;
>>> -}
>>> -EXPORT_SYMBOL(__locks_copy_lock);
>>> -
>>> -void locks_copy_lock(struct file_lock *new, struct file_lock *fl)
>>> -{
>>> -	/* "new" must be a freshly-initialized lock */
>>> -	WARN_ON_ONCE(new->fl_ops);
>>> -
>>> -	__locks_copy_lock(new, fl);
>>> -	new->fl_file = fl->fl_file;
>>> -	new->fl_ops = fl->fl_ops;
>>> -	new->fl_lmops = fl->fl_lmops;
>>>  
>>>  	locks_copy_private(new, fl);
>>>  }
>>> -
>>>  EXPORT_SYMBOL(locks_copy_lock);
>>>  
>>>  static inline int flock_translate_cmd(int cmd) {
>>> @@ -735,7 +725,7 @@ posix_test_lock(struct file *filp, struct file_lock *fl)
>>>  			break;
>>>  	}
>>>  	if (cfl) {
>>> -		__locks_copy_lock(fl, cfl);
>>> +		locks_copy_lock(fl, cfl);
>>>  		if (cfl->fl_nspid)
>>>  			fl->fl_pid = pid_vnr(cfl->fl_nspid);
>>>  	} else
>>> @@ -941,7 +931,7 @@ static int __posix_lock_file(struct inode *inode, struct file_lock *request, str
>>>  			if (!posix_locks_conflict(request, fl))
>>>  				continue;
>>>  			if (conflock)
>>> -				__locks_copy_lock(conflock, fl);
>>> +				locks_copy_lock(conflock, fl);
>>>  			error = -EAGAIN;
>>>  			if (!(request->fl_flags & FL_SLEEP))
>>>  				goto out;
>>> diff --git a/include/linux/fs.h b/include/linux/fs.h
>>> index 908af4f..a383a30 100644
>>> --- a/include/linux/fs.h
>>> +++ b/include/linux/fs.h
>>> @@ -966,7 +966,6 @@ void locks_free_lock(struct file_lock *fl);
>>>  extern void locks_init_lock(struct file_lock *);
>>>  extern struct file_lock * locks_alloc_lock(void);
>>>  extern void locks_copy_lock(struct file_lock *, struct file_lock *);
>>> -extern void __locks_copy_lock(struct file_lock *, const struct file_lock *);
>>>  extern void locks_remove_posix(struct file *, fl_owner_t);
>>>  extern void locks_remove_file(struct file *);
>>>  extern void locks_release_private(struct file_lock *);
>>> @@ -1026,11 +1025,6 @@ static inline void locks_init_lock(struct file_lock *fl)
>>>  	return;
>>>  }
>>>  
>>> -static inline void __locks_copy_lock(struct file_lock *new, struct file_lock *fl)
>>> -{
>>> -	return;
>>> -}
>>> -
>>>  static inline void locks_copy_lock(struct file_lock *new, struct file_lock *fl)
>>>  {
>>>  	return;
>>
>> I'm not sure this is really what you want to do. Calling fl_copy_lock
>> for a conflock looks relatively harmless for nfs and nlm. AFS though
>> seems to add the lock to a list associated with the inode. That seems a
>> little suspicious for a conflock and could be problematic. It may be
>> best to avoid dealing with fl_ops for a conflock.
>>
>> Also in the case of fcntl_getlk, the struct file_lock lives on the
>> stack, and locks_release_private is never called on it. You'll need to
>> audit all of the current callers of __locks_copy_lock to ensure that
>> any resources you end up taking references on when copying the conflock
>> are eventually released.
> 
> Sorry for my no further think about it.
> I will check that again next day.

I think we should not change the logical of coping lock,
leave fl_ops and fl_lmops as private data as right now.

I have plan to,
1. move fl_owner assign from __locks_copy_lock() to locks_copy_private(),
   I think it should be a private data, am I right?
2. call locks_copy_private() coping private data specifically.
   a. add an argument for posix_test_lock() and __posix_lock_file() and etc,
      to point whether coping private data.
   b. hack the conflock's fl_flags to do the same thing as a,
      adds FL_NEED_PRIV fl_flags only valid for conflock.

I don't think 2.a is a nice resolve, because it changes the interface
and many caller don't care the private data (I think contains fl_owner)
for conflock except nfsd.

So, I'd like *2.b*. A draft is appended as following,

thanks,
Kinglong Mee

------------------snip--------------------------

diff --git a/fs/locks.c b/fs/locks.c
index be1858e..5f0349d 100644
--- a/fs/locks.c
+++ b/fs/locks.c
@@ -282,6 +282,8 @@ static void locks_copy_private(struct file_lock *new, struct file_lock *fl)
 	if (fl->fl_lmops) {
 		if (fl->fl_lmops->lm_copy_owner)
 			fl->fl_lmops->lm_copy_owner(new, fl);
+		else
+			new->fl_owner = fl->fl_owner;
 		new->fl_lmops = fl->fl_lmops;
 	}
 }
@@ -291,7 +293,7 @@ static void locks_copy_private(struct file_lock *new, struct file_lock *fl)
  */
 void __locks_copy_lock(struct file_lock *new, const struct file_lock *fl)
 {
-	new->fl_owner = fl->fl_owner;
+	new->fl_owner = NULL;
 	new->fl_pid = fl->fl_pid;
 	new->fl_file = NULL;
 	new->fl_flags = fl->fl_flags;
@@ -734,6 +736,7 @@ posix_test_lock(struct file *filp, struct file_lock *fl)
 {
 	struct file_lock *cfl;
 	struct inode *inode = file_inode(filp);
+	bool need_priv = !!(fl->fl_flags & FL_NEED_PRIV);
 
 	spin_lock(&inode->i_lock);
 	for (cfl = file_inode(filp)->i_flock; cfl; cfl = cfl->fl_next) {
@@ -746,6 +749,8 @@ posix_test_lock(struct file *filp, struct file_lock *fl)
 		__locks_copy_lock(fl, cfl);
 		if (cfl->fl_nspid)
 			fl->fl_pid = pid_vnr(cfl->fl_nspid);
+		if (need_priv)
+			locks_copy_private(fl, cfl);
 	} else
 		fl->fl_type = F_UNLCK;
 	spin_unlock(&inode->i_lock);
@@ -919,7 +924,7 @@ static int __posix_lock_file(struct inode *inode, struct file_lock *request, str
 	struct file_lock *right = NULL;
 	struct file_lock **before;
 	int error;
-	bool added = false;
+	bool added = false, need_priv = false;
 	LIST_HEAD(dispose);
 
 	/*
@@ -948,8 +953,12 @@ static int __posix_lock_file(struct inode *inode, struct file_lock *request, str
 				continue;
 			if (!posix_locks_conflict(request, fl))
 				continue;
-			if (conflock)
+			if (conflock) {
+				need_priv = !!(conflock->fl_flags & FL_NEED_PRIV);
 				__locks_copy_lock(conflock, fl);
+				if (need_priv)
+					locks_copy_private(conflock, fl);
+			}
 			error = -EAGAIN;
 			if (!(request->fl_flags & FL_SLEEP))
 				goto out;
diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
index 5076497..3db43f9 100644
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -5275,6 +5275,7 @@ nfsd4_lock(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
 		goto out;
 	}
 
+	conflock->fl_flags = FL_NEED_PRIV;
 	err = vfs_lock_file(filp, F_SETLK, file_lock, conflock);
 	switch (-err) {
 	case 0: /* success! */
@@ -5396,7 +5397,7 @@ nfsd4_lockt(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
 	if (lo)
 		file_lock->fl_owner = (fl_owner_t)lo;
 	file_lock->fl_pid = current->tgid;
-	file_lock->fl_flags = FL_POSIX;
+	file_lock->fl_flags = FL_POSIX | FL_NEED_PRIV;
 
 	file_lock->fl_start = lockt->lt_offset;
 	file_lock->fl_end = last_byte_offset(lockt->lt_offset, lockt->lt_length);
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 56f2acd..f257d0d 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -844,6 +844,7 @@ static inline struct file *get_file(struct file *f)
 #define FL_DOWNGRADE_PENDING	256 /* Lease is being downgraded */
 #define FL_UNLOCK_PENDING	512 /* Lease is being broken */
 #define FL_OFDLCK	1024	/* lock is "owned" by struct file */
+#define FL_NEED_PRIV	2048	/* Need copy private data from conflock */
 
 /*
  * Special return value from posix_lock_file() and vfs_lock_file() for
--
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