[PATCH] staging: lustre: fix sparse warnings related to lock context imbalance

[PATCH] staging: lustre: fix sparse warnings related to lock context imbalance

[Loic Pefferkorn]

Add __acquires() and __releases() function annotations, to fix sparse warnings related to lock context imbalance.

This fixes the following warnings:

drivers/staging/lustre/lustre/libcfs/linux/linux-tracefile.c:153:5: warning: context imbalance in 'cfs_trace_lock_tcd' - wrong count at exit
drivers/staging/lustre/lustre/libcfs/hash.c:128:1: warning: context imbalance in 'cfs_hash_spin_lock' - wrong count at exit
drivers/staging/lustre/lustre/libcfs/hash.c:142:9: warning: context imbalance in 'cfs_hash_rw_lock' - wrong count at exit
drivers/staging/lustre/lustre/ptlrpc/../../lustre/ldlm/l_lock.c:57:17: warning: context imbalance in 'lock_res_and_lock' - wrong count at exit
drivers/staging/lustre/lustre/libcfs/libcfs_lock.c:93:1: warning: context imbalance in 'cfs_percpt_lock' - wrong count at exit

Signed-off-by: Loic Pefferkorn <loic@loicp.eu>
---
 drivers/staging/lustre/lustre/libcfs/hash.c                  | 4 ++++
 drivers/staging/lustre/lustre/libcfs/libcfs_lock.c           | 2 ++
 drivers/staging/lustre/lustre/libcfs/linux/linux-tracefile.c | 2 ++
 drivers/staging/lustre/lustre/obdclass/cl_object.c           | 2 ++
 4 files changed, 10 insertions(+)

diff --git a/drivers/staging/lustre/lustre/libcfs/hash.c b/drivers/staging/lustre/lustre/libcfs/hash.c
index 32da783..7c6e2a3 100644
--- a/drivers/staging/lustre/lustre/libcfs/hash.c
+++ b/drivers/staging/lustre/lustre/libcfs/hash.c
@@ -126,18 +126,21 @@ cfs_hash_nl_unlock(union cfs_hash_lock *lock, int exclusive) {}
 
 static inline void
 cfs_hash_spin_lock(union cfs_hash_lock *lock, int exclusive)
+	__acquires(&lock->spin)
 {
 	spin_lock(&lock->spin);
 }
 
 static inline void
 cfs_hash_spin_unlock(union cfs_hash_lock *lock, int exclusive)
+	__releases(&lock->spin)
 {
 	spin_unlock(&lock->spin);
 }
 
 static inline void
 cfs_hash_rw_lock(union cfs_hash_lock *lock, int exclusive)
+	__acquires(&lock->rw)
 {
 	if (!exclusive)
 		read_lock(&lock->rw);
@@ -147,6 +150,7 @@ cfs_hash_rw_lock(union cfs_hash_lock *lock, int exclusive)
 
 static inline void
 cfs_hash_rw_unlock(union cfs_hash_lock *lock, int exclusive)
+	__releases(&lock->rw)
 {
 	if (!exclusive)
 		read_unlock(&lock->rw);
diff --git a/drivers/staging/lustre/lustre/libcfs/libcfs_lock.c b/drivers/staging/lustre/lustre/libcfs/libcfs_lock.c
index 2c199c7..1e529fc 100644
--- a/drivers/staging/lustre/lustre/libcfs/libcfs_lock.c
+++ b/drivers/staging/lustre/lustre/libcfs/libcfs_lock.c
@@ -91,6 +91,7 @@ EXPORT_SYMBOL(cfs_percpt_lock_alloc);
  */
 void
 cfs_percpt_lock(struct cfs_percpt_lock *pcl, int index)
+	__acquires(pcl->pcl_locks[index])
 {
 	int	ncpt = cfs_cpt_number(pcl->pcl_cptab);
 	int	i;
@@ -125,6 +126,7 @@ EXPORT_SYMBOL(cfs_percpt_lock);
 /** unlock a CPU partition */
 void
 cfs_percpt_unlock(struct cfs_percpt_lock *pcl, int index)
+	__releases(pcl->pcl_locks[index])
 {
 	int	ncpt = cfs_cpt_number(pcl->pcl_cptab);
 	int	i;
diff --git a/drivers/staging/lustre/lustre/libcfs/linux/linux-tracefile.c b/drivers/staging/lustre/lustre/libcfs/linux/linux-tracefile.c
index 976c61e..257669b 100644
--- a/drivers/staging/lustre/lustre/libcfs/linux/linux-tracefile.c
+++ b/drivers/staging/lustre/lustre/libcfs/linux/linux-tracefile.c
@@ -151,6 +151,7 @@ cfs_trace_buf_type_t cfs_trace_buf_idx_get(void)
  * for details.
  */
 int cfs_trace_lock_tcd(struct cfs_trace_cpu_data *tcd, int walking)
+	__acquires(&tcd->tc_lock)
 {
 	__LASSERT(tcd->tcd_type < CFS_TCD_TYPE_MAX);
 	if (tcd->tcd_type == CFS_TCD_TYPE_IRQ)
@@ -165,6 +166,7 @@ int cfs_trace_lock_tcd(struct cfs_trace_cpu_data *tcd, int walking)
 }
 
 void cfs_trace_unlock_tcd(struct cfs_trace_cpu_data *tcd, int walking)
+	__releases(&tcd->tcd_lock)
 {
 	__LASSERT(tcd->tcd_type < CFS_TCD_TYPE_MAX);
 	if (tcd->tcd_type == CFS_TCD_TYPE_IRQ)
diff --git a/drivers/staging/lustre/lustre/obdclass/cl_object.c b/drivers/staging/lustre/lustre/obdclass/cl_object.c
index ce96bd2..8577f97 100644
--- a/drivers/staging/lustre/lustre/obdclass/cl_object.c
+++ b/drivers/staging/lustre/lustre/obdclass/cl_object.c
@@ -193,6 +193,7 @@ static spinlock_t *cl_object_attr_guard(struct cl_object *o)
  * cl_object_attr_get(), cl_object_attr_set().
  */
 void cl_object_attr_lock(struct cl_object *o)
+	__acquires(cl_object_attr_guard(o))
 {
 	spin_lock(cl_object_attr_guard(o));
 }
@@ -202,6 +203,7 @@ EXPORT_SYMBOL(cl_object_attr_lock);
  * Releases data-attributes lock, acquired by cl_object_attr_lock().
  */
 void cl_object_attr_unlock(struct cl_object *o)
+	__releases(cl_object_attr_guard(o))
 {
 	spin_unlock(cl_object_attr_guard(o));
 }
-- 
2.1.2

Re: [PATCH] staging: lustre: fix sparse warnings related to lock context imbalance

[Greg KH]

On Wed, Nov 26, 2014 at 05:15:48PM +0100, Loic Pefferkorn wrote:
> Add __acquires() and __releases() function annotations, to fix sparse warnings related to lock context imbalance.
> 
> This fixes the following warnings:
> 
> drivers/staging/lustre/lustre/libcfs/linux/linux-tracefile.c:153:5: warning: context imbalance in 'cfs_trace_lock_tcd' - wrong count at exit
> drivers/staging/lustre/lustre/libcfs/hash.c:128:1: warning: context imbalance in 'cfs_hash_spin_lock' - wrong count at exit
> drivers/staging/lustre/lustre/libcfs/hash.c:142:9: warning: context imbalance in 'cfs_hash_rw_lock' - wrong count at exit
> drivers/staging/lustre/lustre/ptlrpc/../../lustre/ldlm/l_lock.c:57:17: warning: context imbalance in 'lock_res_and_lock' - wrong count at exit
> drivers/staging/lustre/lustre/libcfs/libcfs_lock.c:93:1: warning: context imbalance in 'cfs_percpt_lock' - wrong count at exit
> 
> Signed-off-by: Loic Pefferkorn <loic@loicp.eu>
> ---
>  drivers/staging/lustre/lustre/libcfs/hash.c                  | 4 ++++
>  drivers/staging/lustre/lustre/libcfs/libcfs_lock.c           | 2 ++
>  drivers/staging/lustre/lustre/libcfs/linux/linux-tracefile.c | 2 ++
>  drivers/staging/lustre/lustre/obdclass/cl_object.c           | 2 ++
>  4 files changed, 10 insertions(+)
> 
> diff --git a/drivers/staging/lustre/lustre/libcfs/hash.c b/drivers/staging/lustre/lustre/libcfs/hash.c
> index 32da783..7c6e2a3 100644
> --- a/drivers/staging/lustre/lustre/libcfs/hash.c
> +++ b/drivers/staging/lustre/lustre/libcfs/hash.c
> @@ -126,18 +126,21 @@ cfs_hash_nl_unlock(union cfs_hash_lock *lock, int exclusive) {}
>  
>  static inline void
>  cfs_hash_spin_lock(union cfs_hash_lock *lock, int exclusive)
> +	__acquires(&lock->spin)
>  {
>  	spin_lock(&lock->spin);
>  }
>  
>  static inline void
>  cfs_hash_spin_unlock(union cfs_hash_lock *lock, int exclusive)
> +	__releases(&lock->spin)
>  {
>  	spin_unlock(&lock->spin);
>  }

Ugh, how horrid, please just delete these functions and push down the
spin_lock/unlock calls down into the places these are called.

>  
>  static inline void
>  cfs_hash_rw_lock(union cfs_hash_lock *lock, int exclusive)
> +	__acquires(&lock->rw)
>  {
>  	if (!exclusive)
>  		read_lock(&lock->rw);
> @@ -147,6 +150,7 @@ cfs_hash_rw_lock(union cfs_hash_lock *lock, int exclusive)
>  
>  static inline void
>  cfs_hash_rw_unlock(union cfs_hash_lock *lock, int exclusive)
> +	__releases(&lock->rw)
>  {
>  	if (!exclusive)
>  		read_unlock(&lock->rw);


Same for these.

> diff --git a/drivers/staging/lustre/lustre/libcfs/libcfs_lock.c b/drivers/staging/lustre/lustre/libcfs/libcfs_lock.c
> index 2c199c7..1e529fc 100644
> --- a/drivers/staging/lustre/lustre/libcfs/libcfs_lock.c
> +++ b/drivers/staging/lustre/lustre/libcfs/libcfs_lock.c
> @@ -91,6 +91,7 @@ EXPORT_SYMBOL(cfs_percpt_lock_alloc);
>   */
>  void
>  cfs_percpt_lock(struct cfs_percpt_lock *pcl, int index)
> +	__acquires(pcl->pcl_locks[index])
>  {
>  	int	ncpt = cfs_cpt_number(pcl->pcl_cptab);
>  	int	i;
> @@ -125,6 +126,7 @@ EXPORT_SYMBOL(cfs_percpt_lock);
>  /** unlock a CPU partition */
>  void
>  cfs_percpt_unlock(struct cfs_percpt_lock *pcl, int index)
> +	__releases(pcl->pcl_locks[index])
>  {
>  	int	ncpt = cfs_cpt_number(pcl->pcl_cptab);
>  	int	i;
> diff --git a/drivers/staging/lustre/lustre/libcfs/linux/linux-tracefile.c b/drivers/staging/lustre/lustre/libcfs/linux/linux-tracefile.c
> index 976c61e..257669b 100644
> --- a/drivers/staging/lustre/lustre/libcfs/linux/linux-tracefile.c
> +++ b/drivers/staging/lustre/lustre/libcfs/linux/linux-tracefile.c
> @@ -151,6 +151,7 @@ cfs_trace_buf_type_t cfs_trace_buf_idx_get(void)
>   * for details.
>   */
>  int cfs_trace_lock_tcd(struct cfs_trace_cpu_data *tcd, int walking)
> +	__acquires(&tcd->tc_lock)
>  {
>  	__LASSERT(tcd->tcd_type < CFS_TCD_TYPE_MAX);
>  	if (tcd->tcd_type == CFS_TCD_TYPE_IRQ)
> @@ -165,6 +166,7 @@ int cfs_trace_lock_tcd(struct cfs_trace_cpu_data *tcd, int walking)
>  }
>  
>  void cfs_trace_unlock_tcd(struct cfs_trace_cpu_data *tcd, int walking)
> +	__releases(&tcd->tcd_lock)
>  {
>  	__LASSERT(tcd->tcd_type < CFS_TCD_TYPE_MAX);
>  	if (tcd->tcd_type == CFS_TCD_TYPE_IRQ)
> diff --git a/drivers/staging/lustre/lustre/obdclass/cl_object.c b/drivers/staging/lustre/lustre/obdclass/cl_object.c
> index ce96bd2..8577f97 100644
> --- a/drivers/staging/lustre/lustre/obdclass/cl_object.c
> +++ b/drivers/staging/lustre/lustre/obdclass/cl_object.c
> @@ -193,6 +193,7 @@ static spinlock_t *cl_object_attr_guard(struct cl_object *o)
>   * cl_object_attr_get(), cl_object_attr_set().
>   */
>  void cl_object_attr_lock(struct cl_object *o)
> +	__acquires(cl_object_attr_guard(o))
>  {
>  	spin_lock(cl_object_attr_guard(o));
>  }
> @@ -202,6 +203,7 @@ EXPORT_SYMBOL(cl_object_attr_lock);
>   * Releases data-attributes lock, acquired by cl_object_attr_lock().
>   */
>  void cl_object_attr_unlock(struct cl_object *o)
> +	__releases(cl_object_attr_guard(o))
>  {
>  	spin_unlock(cl_object_attr_guard(o));
>  }

Same thing here.

Re: [PATCH] staging: lustre: fix sparse warnings related to lock context imbalance

[Loïc Pefferkorn]

On Wed, Nov 26, 2014 at 12:54:43PM -0800, Greg KH wrote:
> 
> Ugh, how horrid, please just delete these functions and push down the
> spin_lock/unlock calls down into the places these are called.
>
> Same for these.
> 
> Same thing here.

Hello Greg,

Thanks for your comments, I will write a v2.

-- 
Cheers,
Loic

Re: [PATCH] staging: lustre: fix sparse warnings related to lock context imbalance

[Loïc Pefferkorn]

Hello Greg,

After some investigation, I think that removing these wrappers is not going to improve the code readability:

On Wed, Nov 26, 2014 at 12:54:43PM -0800, Greg KH wrote:
> On Wed, Nov 26, 2014 at 05:15:48PM +0100, Loic Pefferkorn wrote:
> > Add __acquires() and __releases() function annotations, to fix sparse warnings related to lock context imbalance.
> > 
> > This fixes the following warnings:
> > 
> > drivers/staging/lustre/lustre/libcfs/linux/linux-tracefile.c:153:5: warning: context imbalance in 'cfs_trace_lock_tcd' - wrong count at exit
> > drivers/staging/lustre/lustre/libcfs/hash.c:128:1: warning: context imbalance in 'cfs_hash_spin_lock' - wrong count at exit
> > drivers/staging/lustre/lustre/libcfs/hash.c:142:9: warning: context imbalance in 'cfs_hash_rw_lock' - wrong count at exit
> > drivers/staging/lustre/lustre/ptlrpc/../../lustre/ldlm/l_lock.c:57:17: warning: context imbalance in 'lock_res_and_lock' - wrong count at exit
> > drivers/staging/lustre/lustre/libcfs/libcfs_lock.c:93:1: warning: context imbalance in 'cfs_percpt_lock' - wrong count at exit
> > 
> > Signed-off-by: Loic Pefferkorn <loic@loicp.eu>
> > ---
> >  drivers/staging/lustre/lustre/libcfs/hash.c                  | 4 ++++
> >  drivers/staging/lustre/lustre/libcfs/libcfs_lock.c           | 2 ++
> >  drivers/staging/lustre/lustre/libcfs/linux/linux-tracefile.c | 2 ++
> >  drivers/staging/lustre/lustre/obdclass/cl_object.c           | 2 ++
> >  4 files changed, 10 insertions(+)
> > 
> > diff --git a/drivers/staging/lustre/lustre/libcfs/hash.c b/drivers/staging/lustre/lustre/libcfs/hash.c
> > index 32da783..7c6e2a3 100644
> > --- a/drivers/staging/lustre/lustre/libcfs/hash.c
> > +++ b/drivers/staging/lustre/lustre/libcfs/hash.c
> > @@ -126,18 +126,21 @@ cfs_hash_nl_unlock(union cfs_hash_lock *lock, int exclusive) {}
> >  
> >  static inline void
> >  cfs_hash_spin_lock(union cfs_hash_lock *lock, int exclusive)
> > +	__acquires(&lock->spin)
> >  {
> >  	spin_lock(&lock->spin);
> >  }
> >  
> >  static inline void
> >  cfs_hash_spin_unlock(union cfs_hash_lock *lock, int exclusive)
> > +	__releases(&lock->spin)
> >  {
> >  	spin_unlock(&lock->spin);
> >  }
> 
> Ugh, how horrid, please just delete these functions and push down the
> spin_lock/unlock calls down into the places these are called.

cfs_hash_spin_lock() and cfs_hash_spin_unlock() are referenced by function pointers later in the same file:

165 /** no bucket lock, one spinlock to protect everything */
166 static cfs_hash_lock_ops_t cfs_hash_nbl_lops = {
167     .hs_lock        = cfs_hash_spin_lock,
168     .hs_unlock      = cfs_hash_spin_unlock,
169     .hs_bkt_lock    = cfs_hash_nl_lock,
170     .hs_bkt_unlock  = cfs_hash_nl_unlock,
171 };
172 
173 /** spin bucket lock, rehash is enabled */
174 static cfs_hash_lock_ops_t cfs_hash_bkt_spin_lops = {
175     .hs_lock        = cfs_hash_rw_lock,
176     .hs_unlock      = cfs_hash_rw_unlock,
177     .hs_bkt_lock    = cfs_hash_spin_lock,
178     .hs_bkt_unlock  = cfs_hash_spin_unlock,
179 };

> 
> >  
> >  static inline void
> >  cfs_hash_rw_lock(union cfs_hash_lock *lock, int exclusive)
> > +	__acquires(&lock->rw)
> >  {
> >  	if (!exclusive)
> >  		read_lock(&lock->rw);
> > @@ -147,6 +150,7 @@ cfs_hash_rw_lock(union cfs_hash_lock *lock, int exclusive)
> >  
> >  static inline void
> >  cfs_hash_rw_unlock(union cfs_hash_lock *lock, int exclusive)
> > +	__releases(&lock->rw)
> >  {
> >  	if (!exclusive)
> >  		read_unlock(&lock->rw);
> 
> 
> Same for these.

Likewise for cfs_hash_rw_lock() and cfs_hash_rw_unlock():

173 /** spin bucket lock, rehash is enabled */
174 static cfs_hash_lock_ops_t cfs_hash_bkt_spin_lops = {
175         .hs_lock        = cfs_hash_rw_lock,
176         .hs_unlock      = cfs_hash_rw_unlock,
177         .hs_bkt_lock    = cfs_hash_spin_lock,
178         .hs_bkt_unlock  = cfs_hash_spin_unlock,
179 };
180 
181 /** rw bucket lock, rehash is enabled */
182 static cfs_hash_lock_ops_t cfs_hash_bkt_rw_lops = {
183         .hs_lock        = cfs_hash_rw_lock,
184         .hs_unlock      = cfs_hash_rw_unlock,
185         .hs_bkt_lock    = cfs_hash_rw_lock,
186         .hs_bkt_unlock  = cfs_hash_rw_unlock,
187 };

> 
> > diff --git a/drivers/staging/lustre/lustre/libcfs/libcfs_lock.c b/drivers/staging/lustre/lustre/libcfs/libcfs_lock.c
> > index 2c199c7..1e529fc 100644
> > --- a/drivers/staging/lustre/lustre/libcfs/libcfs_lock.c
> > +++ b/drivers/staging/lustre/lustre/libcfs/libcfs_lock.c
> > @@ -91,6 +91,7 @@ EXPORT_SYMBOL(cfs_percpt_lock_alloc);
> >   */
> >  void
> >  cfs_percpt_lock(struct cfs_percpt_lock *pcl, int index)
> > +	__acquires(pcl->pcl_locks[index])
> >  {
> >  	int	ncpt = cfs_cpt_number(pcl->pcl_cptab);
> >  	int	i;
> > @@ -125,6 +126,7 @@ EXPORT_SYMBOL(cfs_percpt_lock);
> >  /** unlock a CPU partition */
> >  void
> >  cfs_percpt_unlock(struct cfs_percpt_lock *pcl, int index)
> > +	__releases(pcl->pcl_locks[index])
> >  {
> >  	int	ncpt = cfs_cpt_number(pcl->pcl_cptab);
> >  	int	i;
> > diff --git a/drivers/staging/lustre/lustre/libcfs/linux/linux-tracefile.c b/drivers/staging/lustre/lustre/libcfs/linux/linux-tracefile.c
> > index 976c61e..257669b 100644
> > --- a/drivers/staging/lustre/lustre/libcfs/linux/linux-tracefile.c
> > +++ b/drivers/staging/lustre/lustre/libcfs/linux/linux-tracefile.c
> > @@ -151,6 +151,7 @@ cfs_trace_buf_type_t cfs_trace_buf_idx_get(void)
> >   * for details.
> >   */
> >  int cfs_trace_lock_tcd(struct cfs_trace_cpu_data *tcd, int walking)
> > +	__acquires(&tcd->tc_lock)
> >  {
> >  	__LASSERT(tcd->tcd_type < CFS_TCD_TYPE_MAX);
> >  	if (tcd->tcd_type == CFS_TCD_TYPE_IRQ)
> > @@ -165,6 +166,7 @@ int cfs_trace_lock_tcd(struct cfs_trace_cpu_data *tcd, int walking)
> >  }
> >  
> >  void cfs_trace_unlock_tcd(struct cfs_trace_cpu_data *tcd, int walking)
> > +	__releases(&tcd->tcd_lock)
> >  {
> >  	__LASSERT(tcd->tcd_type < CFS_TCD_TYPE_MAX);
> >  	if (tcd->tcd_type == CFS_TCD_TYPE_IRQ)
> > diff --git a/drivers/staging/lustre/lustre/obdclass/cl_object.c b/drivers/staging/lustre/lustre/obdclass/cl_object.c
> > index ce96bd2..8577f97 100644
> > --- a/drivers/staging/lustre/lustre/obdclass/cl_object.c
> > +++ b/drivers/staging/lustre/lustre/obdclass/cl_object.c
> > @@ -193,6 +193,7 @@ static spinlock_t *cl_object_attr_guard(struct cl_object *o)
> >   * cl_object_attr_get(), cl_object_attr_set().
> >   */
> >  void cl_object_attr_lock(struct cl_object *o)
> > +	__acquires(cl_object_attr_guard(o))
> >  {
> >  	spin_lock(cl_object_attr_guard(o));
> >  }
> > @@ -202,6 +203,7 @@ EXPORT_SYMBOL(cl_object_attr_lock);
> >   * Releases data-attributes lock, acquired by cl_object_attr_lock().
> >   */
> >  void cl_object_attr_unlock(struct cl_object *o)
> > +	__releases(cl_object_attr_guard(o))
> >  {
> >  	spin_unlock(cl_object_attr_guard(o));
> >  }
> 
> Same thing here.

These ones are easy to replace, but the naming scheme of all functions in cl_object.c is consistent,
from my point of view it ease code reading where they are called, for example in lustre/lustre/osc/osc_request.c:

before:

1827         if (valid != 0) {
1828             cl_object_attr_lock(obj);
1829             cl_object_attr_set(env, obj, attr, valid);
1830             cl_object_attr_unlock(obj);

after:

1827         if (valid != 0) {
1828             spin_lock(cl_object_attr_guard(obj));
1829             cl_object_attr_set(env, obj, attr, valid);
1830             spin_unlock(cl_object_attr_guard(obj));


But I'm here for learning, and I would be grateful to have your opinion.

-- 
Cheers,
Loic

Re: [PATCH] staging: lustre: fix sparse warnings related to lock context imbalance

[Dan Carpenter]

On Thu, Nov 27, 2014 at 07:34:10PM +0100, Loïc Pefferkorn wrote:
> 1827         if (valid != 0) {
> 1828             cl_object_attr_lock(obj);
> 1829             cl_object_attr_set(env, obj, attr, valid);
> 1830             cl_object_attr_unlock(obj);
> 
> after:
> 
> 1827         if (valid != 0) {
> 1828             spin_lock(cl_object_attr_guard(obj));
> 1829             cl_object_attr_set(env, obj, attr, valid);
> 1830             spin_unlock(cl_object_attr_guard(obj));

The word "_object" doesn't add any new information to the name.  If you
remove it then the code is improved.

		spin_lock(cl_attr_guard(obj));
		cl_attr_set(env, obj, attr, valid);
		spin_unlock(cl_attr_guard(obj));


regards,
dan carpenter

RE: [HPDD-discuss] [PATCH] staging: lustre: fix sparse warnings related to lock context imbalance

[Patrick Farrell]

Dan,

I disagree about the change suggested here.  In this particular code, 'object_attr' is distinct from 'attr', as in a 'setattr' call on an inode.  'cl_object' is a distinct thing from an inode/file on disk, and specifying it is the objects attr is helpful in understanding there is not a direct relationship to 'attr' in the general filesystem sense.  (cl_object attrs are used in determining actual on disk attributes, but there is not a one-to-one correspondence.)

I am willing to be corrected, but that is my first feeling here.

- Patrick
________________________________________
From: HPDD-discuss [hpdd-discuss-bounces@lists.01.org] on behalf of Dan Carpenter [dan.carpenter@oracle.com]
Sent: Friday, November 28, 2014 4:00 AM
To: Loïc Pefferkorn
Cc: devel@driverdev.osuosl.org; Greg KH; linux-kernel@vger.kernel.org; gdonald@gmail.com; HPDD-discuss@ml01.01.org
Subject: Re: [HPDD-discuss] [PATCH] staging: lustre: fix sparse warnings related to lock context imbalance

On Thu, Nov 27, 2014 at 07:34:10PM +0100, Loïc Pefferkorn wrote:
> 1827         if (valid != 0) {
> 1828             cl_object_attr_lock(obj);
> 1829             cl_object_attr_set(env, obj, attr, valid);
> 1830             cl_object_attr_unlock(obj);
>
> after:
>
> 1827         if (valid != 0) {
> 1828             spin_lock(cl_object_attr_guard(obj));
> 1829             cl_object_attr_set(env, obj, attr, valid);
> 1830             spin_unlock(cl_object_attr_guard(obj));

The word "_object" doesn't add any new information to the name.  If you
remove it then the code is improved.

                spin_lock(cl_attr_guard(obj));
                cl_attr_set(env, obj, attr, valid);
                spin_unlock(cl_attr_guard(obj));


regards,
dan carpenter

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Re: [HPDD-discuss] [PATCH] staging: lustre: fix sparse warnings related to lock context imbalance

[Dan Carpenter]

On Fri, Nov 28, 2014 at 03:45:24PM +0000, Patrick Farrell wrote:
> Dan,
> 
> I disagree about the change suggested here.  In this particular code,
> 'object_attr' is distinct from 'attr', as in a 'setattr' call on an
> inode.  'cl_object' is a distinct thing from an inode/file on disk,
> and specifying it is the objects attr is helpful in understanding
> there is not a direct relationship to 'attr' in the general filesystem
> sense.  (cl_object attrs are used in determining actual on disk
> attributes, but there is not a one-to-one correspondence.)
> 
> I am willing to be corrected, but that is my first feeling here.

I haven't looked at it deeply.  Loïc was suggesting that we need new
locking functions to deal with lustre's unwieldy naming schemes and I
think we should just fix the names...

We already have a cl_attr struct.  Is that different from what
we're locking here?  I don't think anyone will think this takes an inode
argument.

regards,
dan carpenter

Re: [PATCH] staging: lustre: fix sparse warnings related to lock context imbalance

[Greg KH]

On Thu, Nov 27, 2014 at 07:34:10PM +0100, Loïc Pefferkorn wrote:
> Hello Greg,
> 
> After some investigation, I think that removing these wrappers is not going to improve the code readability:
> 
> On Wed, Nov 26, 2014 at 12:54:43PM -0800, Greg KH wrote:
> > On Wed, Nov 26, 2014 at 05:15:48PM +0100, Loic Pefferkorn wrote:
> > > Add __acquires() and __releases() function annotations, to fix sparse warnings related to lock context imbalance.
> > > 
> > > This fixes the following warnings:
> > > 
> > > drivers/staging/lustre/lustre/libcfs/linux/linux-tracefile.c:153:5: warning: context imbalance in 'cfs_trace_lock_tcd' - wrong count at exit
> > > drivers/staging/lustre/lustre/libcfs/hash.c:128:1: warning: context imbalance in 'cfs_hash_spin_lock' - wrong count at exit
> > > drivers/staging/lustre/lustre/libcfs/hash.c:142:9: warning: context imbalance in 'cfs_hash_rw_lock' - wrong count at exit
> > > drivers/staging/lustre/lustre/ptlrpc/../../lustre/ldlm/l_lock.c:57:17: warning: context imbalance in 'lock_res_and_lock' - wrong count at exit
> > > drivers/staging/lustre/lustre/libcfs/libcfs_lock.c:93:1: warning: context imbalance in 'cfs_percpt_lock' - wrong count at exit
> > > 
> > > Signed-off-by: Loic Pefferkorn <loic@loicp.eu>
> > > ---
> > >  drivers/staging/lustre/lustre/libcfs/hash.c                  | 4 ++++
> > >  drivers/staging/lustre/lustre/libcfs/libcfs_lock.c           | 2 ++
> > >  drivers/staging/lustre/lustre/libcfs/linux/linux-tracefile.c | 2 ++
> > >  drivers/staging/lustre/lustre/obdclass/cl_object.c           | 2 ++
> > >  4 files changed, 10 insertions(+)
> > > 
> > > diff --git a/drivers/staging/lustre/lustre/libcfs/hash.c b/drivers/staging/lustre/lustre/libcfs/hash.c
> > > index 32da783..7c6e2a3 100644
> > > --- a/drivers/staging/lustre/lustre/libcfs/hash.c
> > > +++ b/drivers/staging/lustre/lustre/libcfs/hash.c
> > > @@ -126,18 +126,21 @@ cfs_hash_nl_unlock(union cfs_hash_lock *lock, int exclusive) {}
> > >  
> > >  static inline void
> > >  cfs_hash_spin_lock(union cfs_hash_lock *lock, int exclusive)
> > > +	__acquires(&lock->spin)
> > >  {
> > >  	spin_lock(&lock->spin);
> > >  }
> > >  
> > >  static inline void
> > >  cfs_hash_spin_unlock(union cfs_hash_lock *lock, int exclusive)
> > > +	__releases(&lock->spin)
> > >  {
> > >  	spin_unlock(&lock->spin);
> > >  }
> > 
> > Ugh, how horrid, please just delete these functions and push down the
> > spin_lock/unlock calls down into the places these are called.
> 
> cfs_hash_spin_lock() and cfs_hash_spin_unlock() are referenced by function pointers later in the same file:
> 
> 165 /** no bucket lock, one spinlock to protect everything */
> 166 static cfs_hash_lock_ops_t cfs_hash_nbl_lops = {
> 167     .hs_lock        = cfs_hash_spin_lock,
> 168     .hs_unlock      = cfs_hash_spin_unlock,
> 169     .hs_bkt_lock    = cfs_hash_nl_lock,
> 170     .hs_bkt_unlock  = cfs_hash_nl_unlock,
> 171 };
> 172 
> 173 /** spin bucket lock, rehash is enabled */
> 174 static cfs_hash_lock_ops_t cfs_hash_bkt_spin_lops = {
> 175     .hs_lock        = cfs_hash_rw_lock,
> 176     .hs_unlock      = cfs_hash_rw_unlock,
> 177     .hs_bkt_lock    = cfs_hash_spin_lock,
> 178     .hs_bkt_unlock  = cfs_hash_spin_unlock,
> 179 };

That's even worse than I imagined.  Putting sparse markings on these
function calls is just papering over nonsense.  Please work on unwinding
the mess so that you don't need callbacks for locks, that is an
abstraction that isn't needed.

> > >  static inline void
> > >  cfs_hash_rw_lock(union cfs_hash_lock *lock, int exclusive)
> > > +	__acquires(&lock->rw)
> > >  {
> > >  	if (!exclusive)
> > >  		read_lock(&lock->rw);
> > > @@ -147,6 +150,7 @@ cfs_hash_rw_lock(union cfs_hash_lock *lock, int exclusive)
> > >  
> > >  static inline void
> > >  cfs_hash_rw_unlock(union cfs_hash_lock *lock, int exclusive)
> > > +	__releases(&lock->rw)
> > >  {
> > >  	if (!exclusive)
> > >  		read_unlock(&lock->rw);
> > 
> > 
> > Same for these.
> 
> Likewise for cfs_hash_rw_lock() and cfs_hash_rw_unlock():
> 
> 173 /** spin bucket lock, rehash is enabled */
> 174 static cfs_hash_lock_ops_t cfs_hash_bkt_spin_lops = {
> 175         .hs_lock        = cfs_hash_rw_lock,
> 176         .hs_unlock      = cfs_hash_rw_unlock,
> 177         .hs_bkt_lock    = cfs_hash_spin_lock,
> 178         .hs_bkt_unlock  = cfs_hash_spin_unlock,
> 179 };
> 180 
> 181 /** rw bucket lock, rehash is enabled */
> 182 static cfs_hash_lock_ops_t cfs_hash_bkt_rw_lops = {
> 183         .hs_lock        = cfs_hash_rw_lock,
> 184         .hs_unlock      = cfs_hash_rw_unlock,
> 185         .hs_bkt_lock    = cfs_hash_rw_lock,
> 186         .hs_bkt_unlock  = cfs_hash_rw_unlock,
> 187 };

Same here, ick ick ick.

> > > diff --git a/drivers/staging/lustre/lustre/libcfs/libcfs_lock.c b/drivers/staging/lustre/lustre/libcfs/libcfs_lock.c
> > > index 2c199c7..1e529fc 100644
> > > --- a/drivers/staging/lustre/lustre/libcfs/libcfs_lock.c
> > > +++ b/drivers/staging/lustre/lustre/libcfs/libcfs_lock.c
> > > @@ -91,6 +91,7 @@ EXPORT_SYMBOL(cfs_percpt_lock_alloc);
> > >   */
> > >  void
> > >  cfs_percpt_lock(struct cfs_percpt_lock *pcl, int index)
> > > +	__acquires(pcl->pcl_locks[index])
> > >  {
> > >  	int	ncpt = cfs_cpt_number(pcl->pcl_cptab);
> > >  	int	i;
> > > @@ -125,6 +126,7 @@ EXPORT_SYMBOL(cfs_percpt_lock);
> > >  /** unlock a CPU partition */
> > >  void
> > >  cfs_percpt_unlock(struct cfs_percpt_lock *pcl, int index)
> > > +	__releases(pcl->pcl_locks[index])
> > >  {
> > >  	int	ncpt = cfs_cpt_number(pcl->pcl_cptab);
> > >  	int	i;
> > > diff --git a/drivers/staging/lustre/lustre/libcfs/linux/linux-tracefile.c b/drivers/staging/lustre/lustre/libcfs/linux/linux-tracefile.c
> > > index 976c61e..257669b 100644
> > > --- a/drivers/staging/lustre/lustre/libcfs/linux/linux-tracefile.c
> > > +++ b/drivers/staging/lustre/lustre/libcfs/linux/linux-tracefile.c
> > > @@ -151,6 +151,7 @@ cfs_trace_buf_type_t cfs_trace_buf_idx_get(void)
> > >   * for details.
> > >   */
> > >  int cfs_trace_lock_tcd(struct cfs_trace_cpu_data *tcd, int walking)
> > > +	__acquires(&tcd->tc_lock)
> > >  {
> > >  	__LASSERT(tcd->tcd_type < CFS_TCD_TYPE_MAX);
> > >  	if (tcd->tcd_type == CFS_TCD_TYPE_IRQ)
> > > @@ -165,6 +166,7 @@ int cfs_trace_lock_tcd(struct cfs_trace_cpu_data *tcd, int walking)
> > >  }
> > >  
> > >  void cfs_trace_unlock_tcd(struct cfs_trace_cpu_data *tcd, int walking)
> > > +	__releases(&tcd->tcd_lock)
> > >  {
> > >  	__LASSERT(tcd->tcd_type < CFS_TCD_TYPE_MAX);
> > >  	if (tcd->tcd_type == CFS_TCD_TYPE_IRQ)
> > > diff --git a/drivers/staging/lustre/lustre/obdclass/cl_object.c b/drivers/staging/lustre/lustre/obdclass/cl_object.c
> > > index ce96bd2..8577f97 100644
> > > --- a/drivers/staging/lustre/lustre/obdclass/cl_object.c
> > > +++ b/drivers/staging/lustre/lustre/obdclass/cl_object.c
> > > @@ -193,6 +193,7 @@ static spinlock_t *cl_object_attr_guard(struct cl_object *o)
> > >   * cl_object_attr_get(), cl_object_attr_set().
> > >   */
> > >  void cl_object_attr_lock(struct cl_object *o)
> > > +	__acquires(cl_object_attr_guard(o))
> > >  {
> > >  	spin_lock(cl_object_attr_guard(o));
> > >  }
> > > @@ -202,6 +203,7 @@ EXPORT_SYMBOL(cl_object_attr_lock);
> > >   * Releases data-attributes lock, acquired by cl_object_attr_lock().
> > >   */
> > >  void cl_object_attr_unlock(struct cl_object *o)
> > > +	__releases(cl_object_attr_guard(o))
> > >  {
> > >  	spin_unlock(cl_object_attr_guard(o));
> > >  }
> > 
> > Same thing here.
> 
> These ones are easy to replace, but the naming scheme of all functions in cl_object.c is consistent,
> from my point of view it ease code reading where they are called, for example in lustre/lustre/osc/osc_request.c:
> 
> before:
> 
> 1827         if (valid != 0) {
> 1828             cl_object_attr_lock(obj);
> 1829             cl_object_attr_set(env, obj, attr, valid);
> 1830             cl_object_attr_unlock(obj);
> 
> after:
> 
> 1827         if (valid != 0) {
> 1828             spin_lock(cl_object_attr_guard(obj));
> 1829             cl_object_attr_set(env, obj, attr, valid);
> 1830             spin_unlock(cl_object_attr_guard(obj));
> 
> 
> But I'm here for learning, and I would be grateful to have your opinion.

Don't hide "implementation of locks" in functions like this, it only
causes problems.  This code has layers of layers of layers of
abstractions due to it wanting to be originally ported to other
operating systems and lots of different kernel versions of Linux itself.
Unwinding and removing those layers is a good thing to do, don't paper
over the nonsense by putting sparse markings on pointless functions.

thanks,

greg k-h

Re: [PATCH] staging: lustre: fix sparse warnings related to lock context imbalance

[Loïc Pefferkorn]

On Fri, Nov 28, 2014 at 02:22:07PM -0800, Greg KH wrote:
> 
> That's even worse than I imagined.  Putting sparse markings on these
> function calls is just papering over nonsense.  Please work on unwinding
> the mess so that you don't need callbacks for locks, that is an
> abstraction that isn't needed.
> 
> Same here, ick ick ick.
> 
> 
> Don't hide "implementation of locks" in functions like this, it only
> causes problems.  This code has layers of layers of layers of
> abstractions due to it wanting to be originally ported to other
> operating systems and lots of different kernel versions of Linux itself.
> Unwinding and removing those layers is a good thing to do, don't paper
> over the nonsense by putting sparse markings on pointless functions.
> 
> thanks,

Hi guys,

Thanks for your reply. I'm going to write a v2.

-- 
Cheers,
Loïc