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From: Xiubo Li <xiubli@redhat.com>
To: Jeff Layton <jlayton@kernel.org>
Cc: idryomov@gmail.com, pdonnell@redhat.com, ceph-devel@vger.kernel.org
Subject: Re: [PATCH v4] ceph: correctly release memory from capsnap
Date: Thu, 19 Aug 2021 07:43:48 +0800	[thread overview]
Message-ID: <f2bf8537-41a5-c406-ec11-c11a40d79a42@redhat.com> (raw)
In-Reply-To: <007becbddbb928e7cb52feb5ffafb4f254dd5ba0.camel@kernel.org>


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



  reply	other threads:[~2021-08-18 23:43 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-18 13:38 [PATCH v4] ceph: correctly release memory from capsnap xiubli
2021-08-18 16:06 ` Jeff Layton
2021-08-18 23:43   ` Xiubo Li [this message]
2021-08-19 10:59     ` Jeff Layton
2021-08-19 12:40       ` Xiubo Li

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