[PATCH v4] ceph: correctly release memory from capsnap

[PATCH v4] ceph: correctly release memory from capsnap

[xiubli]

From: Xiubo Li <xiubli@redhat.com>

When force umounting, it will try to remove all the session caps.
If there has any capsnap is in the flushing list, the remove session
caps callback will try to release the capsnap->flush_cap memory to
"ceph_cap_flush_cachep" slab cache, while which is allocated from
kmalloc-256 slab cache.

At the same time switch to list_del_init() because just in case the
force umount has removed it from the lists and the
handle_cap_flushsnap_ack() comes then the seconds list_del_init()
won't crash the kernel.

URL: https://tracker.ceph.com/issues/52283
Signed-off-by: Xiubo Li <xiubli@redhat.com>
---

Changed in V4:
- add a new is_capsnap field in ceph_cap_flush struct.


 fs/ceph/caps.c       | 19 ++++++++++++-------
 fs/ceph/mds_client.c |  7 ++++---
 fs/ceph/snap.c       |  1 +
 fs/ceph/super.h      |  3 ++-
 4 files changed, 19 insertions(+), 11 deletions(-)

diff --git a/fs/ceph/caps.c b/fs/ceph/caps.c
index 4663ab830614..52c7026fd0d1 100644
--- a/fs/ceph/caps.c
+++ b/fs/ceph/caps.c
@@ -1712,7 +1712,11 @@ int __ceph_mark_dirty_caps(struct ceph_inode_info *ci, int mask,
 
 struct ceph_cap_flush *ceph_alloc_cap_flush(void)
 {
-	return kmem_cache_alloc(ceph_cap_flush_cachep, GFP_KERNEL);
+	struct ceph_cap_flush *cf;
+
+	cf = kmem_cache_alloc(ceph_cap_flush_cachep, GFP_KERNEL);
+	cf->is_capsnap = false;
+	return cf;
 }
 
 void ceph_free_cap_flush(struct ceph_cap_flush *cf)
@@ -1747,7 +1751,7 @@ static bool __detach_cap_flush_from_mdsc(struct ceph_mds_client *mdsc,
 		prev->wake = true;
 		wake = false;
 	}
-	list_del(&cf->g_list);
+	list_del_init(&cf->g_list);
 	return wake;
 }
 
@@ -1762,7 +1766,7 @@ static bool __detach_cap_flush_from_ci(struct ceph_inode_info *ci,
 		prev->wake = true;
 		wake = false;
 	}
-	list_del(&cf->i_list);
+	list_del_init(&cf->i_list);
 	return wake;
 }
 
@@ -2400,7 +2404,7 @@ static void __kick_flushing_caps(struct ceph_mds_client *mdsc,
 	ci->i_ceph_flags &= ~CEPH_I_KICK_FLUSH;
 
 	list_for_each_entry_reverse(cf, &ci->i_cap_flush_list, i_list) {
-		if (!cf->caps) {
+		if (cf->is_capsnap) {
 			last_snap_flush = cf->tid;
 			break;
 		}
@@ -2419,7 +2423,7 @@ static void __kick_flushing_caps(struct ceph_mds_client *mdsc,
 
 		first_tid = cf->tid + 1;
 
-		if (cf->caps) {
+		if (!cf->is_capsnap) {
 			struct cap_msg_args arg;
 
 			dout("kick_flushing_caps %p cap %p tid %llu %s\n",
@@ -3568,7 +3572,7 @@ static void handle_cap_flush_ack(struct inode *inode, u64 flush_tid,
 			cleaned = cf->caps;
 
 		/* Is this a capsnap? */
-		if (cf->caps == 0)
+		if (cf->is_capsnap)
 			continue;
 
 		if (cf->tid <= flush_tid) {
@@ -3642,7 +3646,8 @@ static void handle_cap_flush_ack(struct inode *inode, u64 flush_tid,
 		cf = list_first_entry(&to_remove,
 				      struct ceph_cap_flush, i_list);
 		list_del(&cf->i_list);
-		ceph_free_cap_flush(cf);
+		if (!cf->is_capsnap)
+			ceph_free_cap_flush(cf);
 	}
 
 	if (wake_ci)
diff --git a/fs/ceph/mds_client.c b/fs/ceph/mds_client.c
index dcb5f34a084b..b9e6a69cc058 100644
--- a/fs/ceph/mds_client.c
+++ b/fs/ceph/mds_client.c
@@ -1656,7 +1656,7 @@ static int remove_session_caps_cb(struct inode *inode, struct ceph_cap *cap,
 		spin_lock(&mdsc->cap_dirty_lock);
 
 		list_for_each_entry(cf, &to_remove, i_list)
-			list_del(&cf->g_list);
+			list_del_init(&cf->g_list);
 
 		if (!list_empty(&ci->i_dirty_item)) {
 			pr_warn_ratelimited(
@@ -1710,8 +1710,9 @@ static int remove_session_caps_cb(struct inode *inode, struct ceph_cap *cap,
 		struct ceph_cap_flush *cf;
 		cf = list_first_entry(&to_remove,
 				      struct ceph_cap_flush, i_list);
-		list_del(&cf->i_list);
-		ceph_free_cap_flush(cf);
+		list_del_init(&cf->i_list);
+		if (!cf->is_capsnap)
+			ceph_free_cap_flush(cf);
 	}
 
 	wake_up_all(&ci->i_cap_wq);
diff --git a/fs/ceph/snap.c b/fs/ceph/snap.c
index af502a8245f0..62fab59bbf96 100644
--- a/fs/ceph/snap.c
+++ b/fs/ceph/snap.c
@@ -487,6 +487,7 @@ static void ceph_queue_cap_snap(struct ceph_inode_info *ci)
 		pr_err("ENOMEM allocating ceph_cap_snap on %p\n", inode);
 		return;
 	}
+	capsnap->cap_flush.is_capsnap = true;
 
 	spin_lock(&ci->i_ceph_lock);
 	used = __ceph_caps_used(ci);
diff --git a/fs/ceph/super.h b/fs/ceph/super.h
index 106ddfd1ce92..336350861791 100644
--- a/fs/ceph/super.h
+++ b/fs/ceph/super.h
@@ -186,8 +186,9 @@ struct ceph_cap {
 
 struct ceph_cap_flush {
 	u64 tid;
-	int caps; /* 0 means capsnap */
+	int caps;
 	bool wake; /* wake up flush waiters when finish ? */
+	bool is_capsnap; /* true means capsnap */
 	struct list_head g_list; // global
 	struct list_head i_list; // per inode
 	struct ceph_inode_info *ci;
-- 
2.27.0

Re: [PATCH v4] ceph: correctly release memory from capsnap

[Jeff Layton]

On Wed, 2021-08-18 at 21:38 +0800, xiubli@redhat.com wrote:
> From: Xiubo Li <xiubli@redhat.com>
> 
> When force umounting, it will try to remove all the session caps.
> If there has any capsnap is in the flushing list, the remove session
> caps callback will try to release the capsnap->flush_cap memory to
> "ceph_cap_flush_cachep" slab cache, while which is allocated from
> kmalloc-256 slab cache.
> 
> At the same time switch to list_del_init() because just in case the
> force umount has removed it from the lists and the
> handle_cap_flushsnap_ack() comes then the seconds list_del_init()
> won't crash the kernel.
> 
> URL: https://tracker.ceph.com/issues/52283
> Signed-off-by: Xiubo Li <xiubli@redhat.com>
> ---
> 
> Changed in V4:
> - add a new is_capsnap field in ceph_cap_flush struct.
> 
> 
>  fs/ceph/caps.c       | 19 ++++++++++++-------
>  fs/ceph/mds_client.c |  7 ++++---
>  fs/ceph/snap.c       |  1 +
>  fs/ceph/super.h      |  3 ++-
>  4 files changed, 19 insertions(+), 11 deletions(-)
> 
> diff --git a/fs/ceph/caps.c b/fs/ceph/caps.c
> index 4663ab830614..52c7026fd0d1 100644
> --- a/fs/ceph/caps.c
> +++ b/fs/ceph/caps.c
> @@ -1712,7 +1712,11 @@ int __ceph_mark_dirty_caps(struct ceph_inode_info *ci, int mask,
>  
>  struct ceph_cap_flush *ceph_alloc_cap_flush(void)
>  {
> -	return kmem_cache_alloc(ceph_cap_flush_cachep, GFP_KERNEL);
> +	struct ceph_cap_flush *cf;
> +
> +	cf = kmem_cache_alloc(ceph_cap_flush_cachep, GFP_KERNEL);
> +	cf->is_capsnap = false;
> +	return cf;
>  }
>  
>  void ceph_free_cap_flush(struct ceph_cap_flush *cf)
> @@ -1747,7 +1751,7 @@ static bool __detach_cap_flush_from_mdsc(struct ceph_mds_client *mdsc,
>  		prev->wake = true;
>  		wake = false;
>  	}
> -	list_del(&cf->g_list);
> +	list_del_init(&cf->g_list);
>  	return wake;
>  }
>  
> @@ -1762,7 +1766,7 @@ static bool __detach_cap_flush_from_ci(struct ceph_inode_info *ci,
>  		prev->wake = true;
>  		wake = false;
>  	}
> -	list_del(&cf->i_list);
> +	list_del_init(&cf->i_list);
>  	return wake;
>  }
>  
> @@ -2400,7 +2404,7 @@ static void __kick_flushing_caps(struct ceph_mds_client *mdsc,
>  	ci->i_ceph_flags &= ~CEPH_I_KICK_FLUSH;
>  
>  	list_for_each_entry_reverse(cf, &ci->i_cap_flush_list, i_list) {
> -		if (!cf->caps) {
> +		if (cf->is_capsnap) {
>  			last_snap_flush = cf->tid;
>  			break;
>  		}
> @@ -2419,7 +2423,7 @@ static void __kick_flushing_caps(struct ceph_mds_client *mdsc,
>  
>  		first_tid = cf->tid + 1;
>  
> -		if (cf->caps) {
> +		if (!cf->is_capsnap) {
>  			struct cap_msg_args arg;
>  
>  			dout("kick_flushing_caps %p cap %p tid %llu %s\n",
> @@ -3568,7 +3572,7 @@ static void handle_cap_flush_ack(struct inode *inode, u64 flush_tid,
>  			cleaned = cf->caps;
>  
>  		/* Is this a capsnap? */
> -		if (cf->caps == 0)
> +		if (cf->is_capsnap)
>  			continue;
>  
>  		if (cf->tid <= flush_tid) {
> @@ -3642,7 +3646,8 @@ static void handle_cap_flush_ack(struct inode *inode, u64 flush_tid,
>  		cf = list_first_entry(&to_remove,
>  				      struct ceph_cap_flush, i_list);
>  		list_del(&cf->i_list);
> -		ceph_free_cap_flush(cf);
> +		if (!cf->is_capsnap)
> +			ceph_free_cap_flush(cf);
>  	}
>  
>  	if (wake_ci)
> diff --git a/fs/ceph/mds_client.c b/fs/ceph/mds_client.c
> index dcb5f34a084b..b9e6a69cc058 100644
> --- a/fs/ceph/mds_client.c
> +++ b/fs/ceph/mds_client.c
> @@ -1656,7 +1656,7 @@ static int remove_session_caps_cb(struct inode *inode, struct ceph_cap *cap,
>  		spin_lock(&mdsc->cap_dirty_lock);
>  
>  		list_for_each_entry(cf, &to_remove, i_list)
> -			list_del(&cf->g_list);
> +			list_del_init(&cf->g_list);
>  
>  		if (!list_empty(&ci->i_dirty_item)) {
>  			pr_warn_ratelimited(
> @@ -1710,8 +1710,9 @@ static int remove_session_caps_cb(struct inode *inode, struct ceph_cap *cap,
>  		struct ceph_cap_flush *cf;
>  		cf = list_first_entry(&to_remove,
>  				      struct ceph_cap_flush, i_list);
> -		list_del(&cf->i_list);
> -		ceph_free_cap_flush(cf);
> +		list_del_init(&cf->i_list);
> +		if (!cf->is_capsnap)
> +			ceph_free_cap_flush(cf);
>  	}
>  
>  	wake_up_all(&ci->i_cap_wq);
> diff --git a/fs/ceph/snap.c b/fs/ceph/snap.c
> index af502a8245f0..62fab59bbf96 100644
> --- a/fs/ceph/snap.c
> +++ b/fs/ceph/snap.c
> @@ -487,6 +487,7 @@ static void ceph_queue_cap_snap(struct ceph_inode_info *ci)
>  		pr_err("ENOMEM allocating ceph_cap_snap on %p\n", inode);
>  		return;
>  	}
> +	capsnap->cap_flush.is_capsnap = true;
>  
>  	spin_lock(&ci->i_ceph_lock);
>  	used = __ceph_caps_used(ci);
> diff --git a/fs/ceph/super.h b/fs/ceph/super.h
> index 106ddfd1ce92..336350861791 100644
> --- a/fs/ceph/super.h
> +++ b/fs/ceph/super.h
> @@ -186,8 +186,9 @@ struct ceph_cap {
>  
>  struct ceph_cap_flush {
>  	u64 tid;
> -	int caps; /* 0 means capsnap */
> +	int caps;
>  	bool wake; /* wake up flush waiters when finish ? */
> +	bool is_capsnap; /* true means capsnap */
>  	struct list_head g_list; // global
>  	struct list_head i_list; // per inode
>  	struct ceph_inode_info *ci;

Looks good, Xiubo. I'll merge into testing after a bit of local testing
on my part.

I'll plan to mark this one for stable too, but I'll need to look at the
prerequisites as there may be merge conflicts with earlier kernels.
-- 
Jeff Layton <jlayton@kernel.org>

Re: [PATCH v4] ceph: correctly release memory from capsnap

[Xiubo Li]

On 8/19/21 12:06 AM, Jeff Layton wrote:
> On Wed, 2021-08-18 at 21:38 +0800, xiubli@redhat.com wrote:
>> From: Xiubo Li <xiubli@redhat.com>
>>
>> When force umounting, it will try to remove all the session caps.
>> If there has any capsnap is in the flushing list, the remove session
>> caps callback will try to release the capsnap->flush_cap memory to
>> "ceph_cap_flush_cachep" slab cache, while which is allocated from
>> kmalloc-256 slab cache.
>>
>> At the same time switch to list_del_init() because just in case the
>> force umount has removed it from the lists and the
>> handle_cap_flushsnap_ack() comes then the seconds list_del_init()
>> won't crash the kernel.
>>
>> URL: https://tracker.ceph.com/issues/52283
>> Signed-off-by: Xiubo Li <xiubli@redhat.com>
>> ---
>>
>> Changed in V4:
>> - add a new is_capsnap field in ceph_cap_flush struct.
>>
>>
>>   fs/ceph/caps.c       | 19 ++++++++++++-------
>>   fs/ceph/mds_client.c |  7 ++++---
>>   fs/ceph/snap.c       |  1 +
>>   fs/ceph/super.h      |  3 ++-
>>   4 files changed, 19 insertions(+), 11 deletions(-)
>>
>> diff --git a/fs/ceph/caps.c b/fs/ceph/caps.c
>> index 4663ab830614..52c7026fd0d1 100644
>> --- a/fs/ceph/caps.c
>> +++ b/fs/ceph/caps.c
>> @@ -1712,7 +1712,11 @@ int __ceph_mark_dirty_caps(struct ceph_inode_info *ci, int mask,
>>   
>>   struct ceph_cap_flush *ceph_alloc_cap_flush(void)
>>   {
>> -	return kmem_cache_alloc(ceph_cap_flush_cachep, GFP_KERNEL);
>> +	struct ceph_cap_flush *cf;
>> +
>> +	cf = kmem_cache_alloc(ceph_cap_flush_cachep, GFP_KERNEL);
>> +	cf->is_capsnap = false;
>> +	return cf;
>>   }
>>   
>>   void ceph_free_cap_flush(struct ceph_cap_flush *cf)
>> @@ -1747,7 +1751,7 @@ static bool __detach_cap_flush_from_mdsc(struct ceph_mds_client *mdsc,
>>   		prev->wake = true;
>>   		wake = false;
>>   	}
>> -	list_del(&cf->g_list);
>> +	list_del_init(&cf->g_list);
>>   	return wake;
>>   }
>>   
>> @@ -1762,7 +1766,7 @@ static bool __detach_cap_flush_from_ci(struct ceph_inode_info *ci,
>>   		prev->wake = true;
>>   		wake = false;
>>   	}
>> -	list_del(&cf->i_list);
>> +	list_del_init(&cf->i_list);
>>   	return wake;
>>   }
>>   
>> @@ -2400,7 +2404,7 @@ static void __kick_flushing_caps(struct ceph_mds_client *mdsc,
>>   	ci->i_ceph_flags &= ~CEPH_I_KICK_FLUSH;
>>   
>>   	list_for_each_entry_reverse(cf, &ci->i_cap_flush_list, i_list) {
>> -		if (!cf->caps) {
>> +		if (cf->is_capsnap) {
>>   			last_snap_flush = cf->tid;
>>   			break;
>>   		}
>> @@ -2419,7 +2423,7 @@ static void __kick_flushing_caps(struct ceph_mds_client *mdsc,
>>   
>>   		first_tid = cf->tid + 1;
>>   
>> -		if (cf->caps) {
>> +		if (!cf->is_capsnap) {
>>   			struct cap_msg_args arg;
>>   
>>   			dout("kick_flushing_caps %p cap %p tid %llu %s\n",
>> @@ -3568,7 +3572,7 @@ static void handle_cap_flush_ack(struct inode *inode, u64 flush_tid,
>>   			cleaned = cf->caps;
>>   
>>   		/* Is this a capsnap? */
>> -		if (cf->caps == 0)
>> +		if (cf->is_capsnap)
>>   			continue;
>>   
>>   		if (cf->tid <= flush_tid) {
>> @@ -3642,7 +3646,8 @@ static void handle_cap_flush_ack(struct inode *inode, u64 flush_tid,
>>   		cf = list_first_entry(&to_remove,
>>   				      struct ceph_cap_flush, i_list);
>>   		list_del(&cf->i_list);
>> -		ceph_free_cap_flush(cf);
>> +		if (!cf->is_capsnap)
>> +			ceph_free_cap_flush(cf);
>>   	}
>>   
>>   	if (wake_ci)
>> diff --git a/fs/ceph/mds_client.c b/fs/ceph/mds_client.c
>> index dcb5f34a084b..b9e6a69cc058 100644
>> --- a/fs/ceph/mds_client.c
>> +++ b/fs/ceph/mds_client.c
>> @@ -1656,7 +1656,7 @@ static int remove_session_caps_cb(struct inode *inode, struct ceph_cap *cap,
>>   		spin_lock(&mdsc->cap_dirty_lock);
>>   
>>   		list_for_each_entry(cf, &to_remove, i_list)
>> -			list_del(&cf->g_list);
>> +			list_del_init(&cf->g_list);
>>   
>>   		if (!list_empty(&ci->i_dirty_item)) {
>>   			pr_warn_ratelimited(
>> @@ -1710,8 +1710,9 @@ static int remove_session_caps_cb(struct inode *inode, struct ceph_cap *cap,
>>   		struct ceph_cap_flush *cf;
>>   		cf = list_first_entry(&to_remove,
>>   				      struct ceph_cap_flush, i_list);
>> -		list_del(&cf->i_list);
>> -		ceph_free_cap_flush(cf);
>> +		list_del_init(&cf->i_list);
>> +		if (!cf->is_capsnap)
>> +			ceph_free_cap_flush(cf);
>>   	}
>>   
>>   	wake_up_all(&ci->i_cap_wq);
>> diff --git a/fs/ceph/snap.c b/fs/ceph/snap.c
>> index af502a8245f0..62fab59bbf96 100644
>> --- a/fs/ceph/snap.c
>> +++ b/fs/ceph/snap.c
>> @@ -487,6 +487,7 @@ static void ceph_queue_cap_snap(struct ceph_inode_info *ci)
>>   		pr_err("ENOMEM allocating ceph_cap_snap on %p\n", inode);
>>   		return;
>>   	}
>> +	capsnap->cap_flush.is_capsnap = true;
>>   
>>   	spin_lock(&ci->i_ceph_lock);
>>   	used = __ceph_caps_used(ci);
>> diff --git a/fs/ceph/super.h b/fs/ceph/super.h
>> index 106ddfd1ce92..336350861791 100644
>> --- a/fs/ceph/super.h
>> +++ b/fs/ceph/super.h
>> @@ -186,8 +186,9 @@ struct ceph_cap {
>>   
>>   struct ceph_cap_flush {
>>   	u64 tid;
>> -	int caps; /* 0 means capsnap */
>> +	int caps;
>>   	bool wake; /* wake up flush waiters when finish ? */
>> +	bool is_capsnap; /* true means capsnap */
>>   	struct list_head g_list; // global
>>   	struct list_head i_list; // per inode
>>   	struct ceph_inode_info *ci;
> Looks good, Xiubo. I'll merge into testing after a bit of local testing
> on my part.
>
> I'll plan to mark this one for stable too, but I'll need to look at the
> prerequisites as there may be merge conflicts with earlier kernels.

I tried it but not all, for some old kernels it may conflict with the 
code only in `__detach_cap_flush_from_mdsc()` and 
`__detach_cap_flush_from_ci()`, which will fold these two funcs into 
__finish_cap_flush().

Thanks

BRs

Re: [PATCH v4] ceph: correctly release memory from capsnap

[Jeff Layton]

On Thu, 2021-08-19 at 07:43 +0800, Xiubo Li wrote:
> On 8/19/21 12:06 AM, Jeff Layton wrote:
> > On Wed, 2021-08-18 at 21:38 +0800, xiubli@redhat.com wrote:
> > > From: Xiubo Li <xiubli@redhat.com>
> > > 
> > > When force umounting, it will try to remove all the session caps.
> > > If there has any capsnap is in the flushing list, the remove session
> > > caps callback will try to release the capsnap->flush_cap memory to
> > > "ceph_cap_flush_cachep" slab cache, while which is allocated from
> > > kmalloc-256 slab cache.
> > > 
> > > At the same time switch to list_del_init() because just in case the
> > > force umount has removed it from the lists and the
> > > handle_cap_flushsnap_ack() comes then the seconds list_del_init()
> > > won't crash the kernel.
> > > 
> > > URL: https://tracker.ceph.com/issues/52283
> > > Signed-off-by: Xiubo Li <xiubli@redhat.com>
> > > ---
> > > 
> > > Changed in V4:
> > > - add a new is_capsnap field in ceph_cap_flush struct.
> > > 
> > > 
> > >   fs/ceph/caps.c       | 19 ++++++++++++-------
> > >   fs/ceph/mds_client.c |  7 ++++---
> > >   fs/ceph/snap.c       |  1 +
> > >   fs/ceph/super.h      |  3 ++-
> > >   4 files changed, 19 insertions(+), 11 deletions(-)
> > > 
> > > diff --git a/fs/ceph/caps.c b/fs/ceph/caps.c
> > > index 4663ab830614..52c7026fd0d1 100644
> > > --- a/fs/ceph/caps.c
> > > +++ b/fs/ceph/caps.c
> > > @@ -1712,7 +1712,11 @@ int __ceph_mark_dirty_caps(struct ceph_inode_info *ci, int mask,
> > >   
> > >   struct ceph_cap_flush *ceph_alloc_cap_flush(void)
> > >   {
> > > -	return kmem_cache_alloc(ceph_cap_flush_cachep, GFP_KERNEL);
> > > +	struct ceph_cap_flush *cf;
> > > +
> > > +	cf = kmem_cache_alloc(ceph_cap_flush_cachep, GFP_KERNEL);
> > > +	cf->is_capsnap = false;
> > > +	return cf;
> > >   }
> > >   
> > >   void ceph_free_cap_flush(struct ceph_cap_flush *cf)
> > > @@ -1747,7 +1751,7 @@ static bool __detach_cap_flush_from_mdsc(struct ceph_mds_client *mdsc,
> > >   		prev->wake = true;
> > >   		wake = false;
> > >   	}
> > > -	list_del(&cf->g_list);
> > > +	list_del_init(&cf->g_list);
> > >   	return wake;
> > >   }
> > >   
> > > @@ -1762,7 +1766,7 @@ static bool __detach_cap_flush_from_ci(struct ceph_inode_info *ci,
> > >   		prev->wake = true;
> > >   		wake = false;
> > >   	}
> > > -	list_del(&cf->i_list);
> > > +	list_del_init(&cf->i_list);
> > >   	return wake;
> > >   }
> > >   
> > > @@ -2400,7 +2404,7 @@ static void __kick_flushing_caps(struct ceph_mds_client *mdsc,
> > >   	ci->i_ceph_flags &= ~CEPH_I_KICK_FLUSH;
> > >   
> > >   	list_for_each_entry_reverse(cf, &ci->i_cap_flush_list, i_list) {
> > > -		if (!cf->caps) {
> > > +		if (cf->is_capsnap) {
> > >   			last_snap_flush = cf->tid;
> > >   			break;
> > >   		}
> > > @@ -2419,7 +2423,7 @@ static void __kick_flushing_caps(struct ceph_mds_client *mdsc,
> > >   
> > >   		first_tid = cf->tid + 1;
> > >   
> > > -		if (cf->caps) {
> > > +		if (!cf->is_capsnap) {
> > >   			struct cap_msg_args arg;
> > >   
> > >   			dout("kick_flushing_caps %p cap %p tid %llu %s\n",
> > > @@ -3568,7 +3572,7 @@ static void handle_cap_flush_ack(struct inode *inode, u64 flush_tid,
> > >   			cleaned = cf->caps;
> > >   
> > >   		/* Is this a capsnap? */
> > > -		if (cf->caps == 0)
> > > +		if (cf->is_capsnap)
> > >   			continue;
> > >   
> > >   		if (cf->tid <= flush_tid) {
> > > @@ -3642,7 +3646,8 @@ static void handle_cap_flush_ack(struct inode *inode, u64 flush_tid,
> > >   		cf = list_first_entry(&to_remove,
> > >   				      struct ceph_cap_flush, i_list);
> > >   		list_del(&cf->i_list);
> > > -		ceph_free_cap_flush(cf);
> > > +		if (!cf->is_capsnap)
> > > +			ceph_free_cap_flush(cf);
> > >   	}
> > >   
> > >   	if (wake_ci)
> > > diff --git a/fs/ceph/mds_client.c b/fs/ceph/mds_client.c
> > > index dcb5f34a084b..b9e6a69cc058 100644
> > > --- a/fs/ceph/mds_client.c
> > > +++ b/fs/ceph/mds_client.c
> > > @@ -1656,7 +1656,7 @@ static int remove_session_caps_cb(struct inode *inode, struct ceph_cap *cap,
> > >   		spin_lock(&mdsc->cap_dirty_lock);
> > >   
> > >   		list_for_each_entry(cf, &to_remove, i_list)
> > > -			list_del(&cf->g_list);
> > > +			list_del_init(&cf->g_list);
> > >   
> > >   		if (!list_empty(&ci->i_dirty_item)) {
> > >   			pr_warn_ratelimited(
> > > @@ -1710,8 +1710,9 @@ static int remove_session_caps_cb(struct inode *inode, struct ceph_cap *cap,
> > >   		struct ceph_cap_flush *cf;
> > >   		cf = list_first_entry(&to_remove,
> > >   				      struct ceph_cap_flush, i_list);
> > > -		list_del(&cf->i_list);
> > > -		ceph_free_cap_flush(cf);
> > > +		list_del_init(&cf->i_list);
> > > +		if (!cf->is_capsnap)
> > > +			ceph_free_cap_flush(cf);
> > >   	}
> > >   
> > >   	wake_up_all(&ci->i_cap_wq);
> > > diff --git a/fs/ceph/snap.c b/fs/ceph/snap.c
> > > index af502a8245f0..62fab59bbf96 100644
> > > --- a/fs/ceph/snap.c
> > > +++ b/fs/ceph/snap.c
> > > @@ -487,6 +487,7 @@ static void ceph_queue_cap_snap(struct ceph_inode_info *ci)
> > >   		pr_err("ENOMEM allocating ceph_cap_snap on %p\n", inode);
> > >   		return;
> > >   	}
> > > +	capsnap->cap_flush.is_capsnap = true;
> > >   
> > >   	spin_lock(&ci->i_ceph_lock);
> > >   	used = __ceph_caps_used(ci);
> > > diff --git a/fs/ceph/super.h b/fs/ceph/super.h
> > > index 106ddfd1ce92..336350861791 100644
> > > --- a/fs/ceph/super.h
> > > +++ b/fs/ceph/super.h
> > > @@ -186,8 +186,9 @@ struct ceph_cap {
> > >   
> > >   struct ceph_cap_flush {
> > >   	u64 tid;
> > > -	int caps; /* 0 means capsnap */
> > > +	int caps;
> > >   	bool wake; /* wake up flush waiters when finish ? */
> > > +	bool is_capsnap; /* true means capsnap */
> > >   	struct list_head g_list; // global
> > >   	struct list_head i_list; // per inode
> > >   	struct ceph_inode_info *ci;
> > Looks good, Xiubo. I'll merge into testing after a bit of local testing
> > on my part.
> > 
> > I'll plan to mark this one for stable too, but I'll need to look at the
> > prerequisites as there may be merge conflicts with earlier kernels.
> 
> I tried it but not all, for some old kernels it may conflict with the 
> code only in `__detach_cap_flush_from_mdsc()` and 
> `__detach_cap_flush_from_ci()`, which will fold these two funcs into 
> __finish_cap_flush().
> 

Yeah, there are quite a few merge conflicts on older kernels and pulling
in earlier patches to eliminate them just brings in more conflicts. We
may have to do a custom backport on this one for some of the older
stable kernels.

-- 
Jeff Layton <jlayton@kernel.org>

Re: [PATCH v4] ceph: correctly release memory from capsnap

[Xiubo Li]

On 8/19/21 6:59 PM, Jeff Layton wrote:
> On Thu, 2021-08-19 at 07:43 +0800, Xiubo Li wrote:
>> On 8/19/21 12:06 AM, Jeff Layton wrote:
>>> On Wed, 2021-08-18 at 21:38 +0800, xiubli@redhat.com wrote:
>>>> From: Xiubo Li <xiubli@redhat.com>
>>>>
>>>> When force umounting, it will try to remove all the session caps.
>>>> If there has any capsnap is in the flushing list, the remove session
>>>> caps callback will try to release the capsnap->flush_cap memory to
>>>> "ceph_cap_flush_cachep" slab cache, while which is allocated from
>>>> kmalloc-256 slab cache.
>>>>
>>>> At the same time switch to list_del_init() because just in case the
>>>> force umount has removed it from the lists and the
>>>> handle_cap_flushsnap_ack() comes then the seconds list_del_init()
>>>> won't crash the kernel.
>>>>
>>>> URL: https://tracker.ceph.com/issues/52283
>>>> Signed-off-by: Xiubo Li <xiubli@redhat.com>
>>>> ---
>>>>
>>>> Changed in V4:
>>>> - add a new is_capsnap field in ceph_cap_flush struct.
>>>>
>>>>
>>>>    fs/ceph/caps.c       | 19 ++++++++++++-------
>>>>    fs/ceph/mds_client.c |  7 ++++---
>>>>    fs/ceph/snap.c       |  1 +
>>>>    fs/ceph/super.h      |  3 ++-
>>>>    4 files changed, 19 insertions(+), 11 deletions(-)
>>>>
>>>> diff --git a/fs/ceph/caps.c b/fs/ceph/caps.c
>>>> index 4663ab830614..52c7026fd0d1 100644
>>>> --- a/fs/ceph/caps.c
>>>> +++ b/fs/ceph/caps.c
>>>> @@ -1712,7 +1712,11 @@ int __ceph_mark_dirty_caps(struct ceph_inode_info *ci, int mask,
>>>>    
>>>>    struct ceph_cap_flush *ceph_alloc_cap_flush(void)
>>>>    {
>>>> -	return kmem_cache_alloc(ceph_cap_flush_cachep, GFP_KERNEL);
>>>> +	struct ceph_cap_flush *cf;
>>>> +
>>>> +	cf = kmem_cache_alloc(ceph_cap_flush_cachep, GFP_KERNEL);
>>>> +	cf->is_capsnap = false;
>>>> +	return cf;
>>>>    }
>>>>    
>>>>    void ceph_free_cap_flush(struct ceph_cap_flush *cf)
>>>> @@ -1747,7 +1751,7 @@ static bool __detach_cap_flush_from_mdsc(struct ceph_mds_client *mdsc,
>>>>    		prev->wake = true;
>>>>    		wake = false;
>>>>    	}
>>>> -	list_del(&cf->g_list);
>>>> +	list_del_init(&cf->g_list);
>>>>    	return wake;
>>>>    }
>>>>    
>>>> @@ -1762,7 +1766,7 @@ static bool __detach_cap_flush_from_ci(struct ceph_inode_info *ci,
>>>>    		prev->wake = true;
>>>>    		wake = false;
>>>>    	}
>>>> -	list_del(&cf->i_list);
>>>> +	list_del_init(&cf->i_list);
>>>>    	return wake;
>>>>    }
>>>>    
>>>> @@ -2400,7 +2404,7 @@ static void __kick_flushing_caps(struct ceph_mds_client *mdsc,
>>>>    	ci->i_ceph_flags &= ~CEPH_I_KICK_FLUSH;
>>>>    
>>>>    	list_for_each_entry_reverse(cf, &ci->i_cap_flush_list, i_list) {
>>>> -		if (!cf->caps) {
>>>> +		if (cf->is_capsnap) {
>>>>    			last_snap_flush = cf->tid;
>>>>    			break;
>>>>    		}
>>>> @@ -2419,7 +2423,7 @@ static void __kick_flushing_caps(struct ceph_mds_client *mdsc,
>>>>    
>>>>    		first_tid = cf->tid + 1;
>>>>    
>>>> -		if (cf->caps) {
>>>> +		if (!cf->is_capsnap) {
>>>>    			struct cap_msg_args arg;
>>>>    
>>>>    			dout("kick_flushing_caps %p cap %p tid %llu %s\n",
>>>> @@ -3568,7 +3572,7 @@ static void handle_cap_flush_ack(struct inode *inode, u64 flush_tid,
>>>>    			cleaned = cf->caps;
>>>>    
>>>>    		/* Is this a capsnap? */
>>>> -		if (cf->caps == 0)
>>>> +		if (cf->is_capsnap)
>>>>    			continue;
>>>>    
>>>>    		if (cf->tid <= flush_tid) {
>>>> @@ -3642,7 +3646,8 @@ static void handle_cap_flush_ack(struct inode *inode, u64 flush_tid,
>>>>    		cf = list_first_entry(&to_remove,
>>>>    				      struct ceph_cap_flush, i_list);
>>>>    		list_del(&cf->i_list);
>>>> -		ceph_free_cap_flush(cf);
>>>> +		if (!cf->is_capsnap)
>>>> +			ceph_free_cap_flush(cf);
>>>>    	}
>>>>    
>>>>    	if (wake_ci)
>>>> diff --git a/fs/ceph/mds_client.c b/fs/ceph/mds_client.c
>>>> index dcb5f34a084b..b9e6a69cc058 100644
>>>> --- a/fs/ceph/mds_client.c
>>>> +++ b/fs/ceph/mds_client.c
>>>> @@ -1656,7 +1656,7 @@ static int remove_session_caps_cb(struct inode *inode, struct ceph_cap *cap,
>>>>    		spin_lock(&mdsc->cap_dirty_lock);
>>>>    
>>>>    		list_for_each_entry(cf, &to_remove, i_list)
>>>> -			list_del(&cf->g_list);
>>>> +			list_del_init(&cf->g_list);
>>>>    
>>>>    		if (!list_empty(&ci->i_dirty_item)) {
>>>>    			pr_warn_ratelimited(
>>>> @@ -1710,8 +1710,9 @@ static int remove_session_caps_cb(struct inode *inode, struct ceph_cap *cap,
>>>>    		struct ceph_cap_flush *cf;
>>>>    		cf = list_first_entry(&to_remove,
>>>>    				      struct ceph_cap_flush, i_list);
>>>> -		list_del(&cf->i_list);
>>>> -		ceph_free_cap_flush(cf);
>>>> +		list_del_init(&cf->i_list);
>>>> +		if (!cf->is_capsnap)
>>>> +			ceph_free_cap_flush(cf);
>>>>    	}
>>>>    
>>>>    	wake_up_all(&ci->i_cap_wq);
>>>> diff --git a/fs/ceph/snap.c b/fs/ceph/snap.c
>>>> index af502a8245f0..62fab59bbf96 100644
>>>> --- a/fs/ceph/snap.c
>>>> +++ b/fs/ceph/snap.c
>>>> @@ -487,6 +487,7 @@ static void ceph_queue_cap_snap(struct ceph_inode_info *ci)
>>>>    		pr_err("ENOMEM allocating ceph_cap_snap on %p\n", inode);
>>>>    		return;
>>>>    	}
>>>> +	capsnap->cap_flush.is_capsnap = true;
>>>>    
>>>>    	spin_lock(&ci->i_ceph_lock);
>>>>    	used = __ceph_caps_used(ci);
>>>> diff --git a/fs/ceph/super.h b/fs/ceph/super.h
>>>> index 106ddfd1ce92..336350861791 100644
>>>> --- a/fs/ceph/super.h
>>>> +++ b/fs/ceph/super.h
>>>> @@ -186,8 +186,9 @@ struct ceph_cap {
>>>>    
>>>>    struct ceph_cap_flush {
>>>>    	u64 tid;
>>>> -	int caps; /* 0 means capsnap */
>>>> +	int caps;
>>>>    	bool wake; /* wake up flush waiters when finish ? */
>>>> +	bool is_capsnap; /* true means capsnap */
>>>>    	struct list_head g_list; // global
>>>>    	struct list_head i_list; // per inode
>>>>    	struct ceph_inode_info *ci;
>>> Looks good, Xiubo. I'll merge into testing after a bit of local testing
>>> on my part.
>>>
>>> I'll plan to mark this one for stable too, but I'll need to look at the
>>> prerequisites as there may be merge conflicts with earlier kernels.
>> I tried it but not all, for some old kernels it may conflict with the
>> code only in `__detach_cap_flush_from_mdsc()` and
>> `__detach_cap_flush_from_ci()`, which will fold these two funcs into
>> __finish_cap_flush().
>>
> Yeah, there are quite a few merge conflicts on older kernels and pulling
> in earlier patches to eliminate them just brings in more conflicts. We
> may have to do a custom backport on this one for some of the older
> stable kernels.
>
Yeah, agree.