[v3,1/3] ceph: remove the capsnaps when removing the caps

From: Xiubo Li <xiubli@redhat.com>

The capsnaps will ihold the inodes when queuing to flush, so when
force umounting it will close the sessions first and if the MDSes
respond very fast and the session connections are closed just
before killing the superblock, which will flush the msgr queue,
then the flush capsnap callback won't ever be called, which will
lead the memory leak bug for the ceph_inode_info.

URL: https://tracker.ceph.com/issues/52295
Signed-off-by: Xiubo Li <xiubli@redhat.com>
---
 fs/ceph/caps.c       | 67 +++++++++++++++++++++++++++++++++-----------
 fs/ceph/mds_client.c | 31 +++++++++++++++++++-
 fs/ceph/super.h      |  6 ++++
 3 files changed, 86 insertions(+), 18 deletions(-)

On 8/25/21 10:25 PM, Jeff Layton wrote:
> On Wed, 2021-08-25 at 21:45 +0800, xiubli@redhat.com wrote:

>> From: Xiubo Li <xiubli@redhat.com>

>>

>> The capsnaps will ihold the inodes when queuing to flush, so when

>> force umounting it will close the sessions first and if the MDSes

>> respond very fast and the session connections are closed just

>> before killing the superblock, which will flush the msgr queue,

>> then the flush capsnap callback won't ever be called, which will

>> lead the memory leak bug for the ceph_inode_info.

>>

>> URL: https://tracker.ceph.com/issues/52295

>> Signed-off-by: Xiubo Li <xiubli@redhat.com>

>> ---

>>   fs/ceph/caps.c       | 67 +++++++++++++++++++++++++++++++++-----------

>>   fs/ceph/mds_client.c | 31 +++++++++++++++++++-

>>   fs/ceph/super.h      |  6 ++++

>>   3 files changed, 86 insertions(+), 18 deletions(-)

>>

>> diff --git a/fs/ceph/caps.c b/fs/ceph/caps.c

>> index 1e6261a16fb5..61326b490b2b 100644

>> --- a/fs/ceph/caps.c

>> +++ b/fs/ceph/caps.c

>> @@ -3162,7 +3162,15 @@ void ceph_put_wrbuffer_cap_refs(struct ceph_inode_info *ci, int nr,

>>   				break;

>>   			}

>>   		}

>> -		BUG_ON(!found);

>> +

>> +		/*

>> +		 * The capsnap should already be removed when

>> +		 * removing auth cap in case likes force unmount.

>> +		 */

>> +		BUG_ON(!found && ci->i_auth_cap);

>> +		if (!found)

>> +			goto unlock;

>> +

>>   		capsnap->dirty_pages -= nr;

>>   		if (capsnap->dirty_pages == 0) {

>>   			complete_capsnap = true;

>> @@ -3184,6 +3192,7 @@ void ceph_put_wrbuffer_cap_refs(struct ceph_inode_info *ci, int nr,

>>   		     complete_capsnap ? " (complete capsnap)" : "");

>>   	}

>>   

>> +unlock:

>>   	spin_unlock(&ci->i_ceph_lock);

>>   

>>   	if (last) {

>> @@ -3658,6 +3667,43 @@ static void handle_cap_flush_ack(struct inode *inode, u64 flush_tid,

>>   		iput(inode);

>>   }

>>   

>> +void __ceph_remove_capsnap(struct inode *inode, struct ceph_cap_snap *capsnap,

>> +			   bool *wake_ci, bool *wake_mdsc)

>> +{

>> +	struct ceph_inode_info *ci = ceph_inode(inode);

>> +	struct ceph_mds_client *mdsc = ceph_sb_to_client(inode->i_sb)->mdsc;

>> +	bool ret;

>> +

>> +	lockdep_assert_held(&ci->i_ceph_lock);

> Hmm, your earlier patch had a note saying that the s_mutex needed to he

> held here too. Is that not the case?


The s_mutex is not needed here, I meant the i_ceph_lock and the comment 
was just copied from somewhere and forgot to modify it.



>

>> +

>> +	dout("removing capsnap %p, inode %p ci %p\n", capsnap, inode, ci);

>> +

>> +	list_del_init(&capsnap->ci_item);

>> +	ret = __detach_cap_flush_from_ci(ci, &capsnap->cap_flush);

>> +	if (wake_ci)

>> +		*wake_ci = ret;

>> +

>> +	spin_lock(&mdsc->cap_dirty_lock);

>> +	if (list_empty(&ci->i_cap_flush_list))

>> +		list_del_init(&ci->i_flushing_item);

>> +

>> +	ret = __detach_cap_flush_from_mdsc(mdsc, &capsnap->cap_flush);

>> +	if (wake_mdsc)

>> +		*wake_mdsc = ret;

>> +	spin_unlock(&mdsc->cap_dirty_lock);

>> +}

>> +

>> +void ceph_remove_capsnap(struct inode *inode, struct ceph_cap_snap *capsnap,

>> +			 bool *wake_ci, bool *wake_mdsc)

>> +{

>> +	struct ceph_inode_info *ci = ceph_inode(inode);

>> +

>> +	lockdep_assert_held(&ci->i_ceph_lock);

>> +

>> +	WARN_ON_ONCE(capsnap->dirty_pages || capsnap->writing);

>> +	__ceph_remove_capsnap(inode, capsnap, wake_ci, wake_mdsc);

>> +}

>> +

>>   /*

>>    * Handle FLUSHSNAP_ACK.  MDS has flushed snap data to disk and we can

>>    * throw away our cap_snap.

>> @@ -3695,23 +3741,10 @@ static void handle_cap_flushsnap_ack(struct inode *inode, u64 flush_tid,

>>   			     capsnap, capsnap->follows);

>>   		}

>>   	}

>> -	if (flushed) {

>> -		WARN_ON(capsnap->dirty_pages || capsnap->writing);

>> -		dout(" removing %p cap_snap %p follows %lld\n",

>> -		     inode, capsnap, follows);

>> -		list_del(&capsnap->ci_item);

>> -		wake_ci |= __detach_cap_flush_from_ci(ci, &capsnap->cap_flush);

>> -

>> -		spin_lock(&mdsc->cap_dirty_lock);

>> -

>> -		if (list_empty(&ci->i_cap_flush_list))

>> -			list_del_init(&ci->i_flushing_item);

>> -

>> -		wake_mdsc |= __detach_cap_flush_from_mdsc(mdsc,

>> -							  &capsnap->cap_flush);

>> -		spin_unlock(&mdsc->cap_dirty_lock);

>> -	}

>> +	if (flushed)

>> +		ceph_remove_capsnap(inode, capsnap, &wake_ci, &wake_mdsc);

>>   	spin_unlock(&ci->i_ceph_lock);

>> +

>>   	if (flushed) {

>>   		ceph_put_snap_context(capsnap->context);

>>   		ceph_put_cap_snap(capsnap);

>> diff --git a/fs/ceph/mds_client.c b/fs/ceph/mds_client.c

>> index df3a735f7837..36ad0ebb2295 100644

>> --- a/fs/ceph/mds_client.c

>> +++ b/fs/ceph/mds_client.c

>> @@ -1604,14 +1604,39 @@ int ceph_iterate_session_caps(struct ceph_mds_session *session,

>>   	return ret;

>>   }

>>   

>> +static int remove_capsnaps(struct ceph_mds_client *mdsc, struct inode *inode)

>> +{

>> +	struct ceph_inode_info *ci = ceph_inode(inode);

>> +	struct ceph_cap_snap *capsnap;

>> +	int capsnap_release = 0;

>> +

>> +	lockdep_assert_held(&ci->i_ceph_lock);

>> +

>> +	dout("removing capsnaps, ci is %p, inode is %p\n", ci, inode);

>> +

>> +	while (!list_empty(&ci->i_cap_snaps)) {

>> +		capsnap = list_first_entry(&ci->i_cap_snaps,

>> +					   struct ceph_cap_snap, ci_item);

>> +		__ceph_remove_capsnap(inode, capsnap, NULL, NULL);

>> +		ceph_put_snap_context(capsnap->context);

>> +		ceph_put_cap_snap(capsnap);

>> +		capsnap_release++;

>> +	}

>> +	wake_up_all(&ci->i_cap_wq);

>> +	wake_up_all(&mdsc->cap_flushing_wq);

>> +	return capsnap_release;

>> +}

>> +

>>   static int remove_session_caps_cb(struct inode *inode, struct ceph_cap *cap,

>>   				  void *arg)

>>   {

>>   	struct ceph_fs_client *fsc = (struct ceph_fs_client *)arg;

>> +	struct ceph_mds_client *mdsc = fsc->mdsc;

>>   	struct ceph_inode_info *ci = ceph_inode(inode);

>>   	LIST_HEAD(to_remove);

>>   	bool dirty_dropped = false;

>>   	bool invalidate = false;

>> +	int capsnap_release = 0;

>>   

>>   	dout("removing cap %p, ci is %p, inode is %p\n",

>>   	     cap, ci, &ci->vfs_inode);

>> @@ -1619,7 +1644,6 @@ static int remove_session_caps_cb(struct inode *inode, struct ceph_cap *cap,

>>   	__ceph_remove_cap(cap, false);

>>   	if (!ci->i_auth_cap) {

>>   		struct ceph_cap_flush *cf;

>> -		struct ceph_mds_client *mdsc = fsc->mdsc;

>>   

>>   		if (READ_ONCE(fsc->mount_state) >= CEPH_MOUNT_SHUTDOWN) {

>>   			if (inode->i_data.nrpages > 0)

>> @@ -1683,6 +1707,9 @@ static int remove_session_caps_cb(struct inode *inode, struct ceph_cap *cap,

>>   			list_add(&ci->i_prealloc_cap_flush->i_list, &to_remove);

>>   			ci->i_prealloc_cap_flush = NULL;

>>   		}

>> +

>> +		if (!list_empty(&ci->i_cap_snaps))

>> +			capsnap_release = remove_capsnaps(mdsc, inode);

>>   	}

>>   	spin_unlock(&ci->i_ceph_lock);

>>   	while (!list_empty(&to_remove)) {

>> @@ -1699,6 +1726,8 @@ static int remove_session_caps_cb(struct inode *inode, struct ceph_cap *cap,

>>   		ceph_queue_invalidate(inode);

>>   	if (dirty_dropped)

>>   		iput(inode);

>> +	while (capsnap_release--)

>> +		iput(inode);

>>   	return 0;

>>   }

>>   

>> diff --git a/fs/ceph/super.h b/fs/ceph/super.h

>> index 8f4f2747be65..445d13d760d1 100644

>> --- a/fs/ceph/super.h

>> +++ b/fs/ceph/super.h

>> @@ -1169,6 +1169,12 @@ extern void ceph_put_cap_refs_no_check_caps(struct ceph_inode_info *ci,

>>   					    int had);

>>   extern void ceph_put_wrbuffer_cap_refs(struct ceph_inode_info *ci, int nr,

>>   				       struct ceph_snap_context *snapc);

>> +extern void __ceph_remove_capsnap(struct inode *inode,

>> +				  struct ceph_cap_snap *capsnap,

>> +				  bool *wake_ci, bool *wake_mdsc);

>> +extern void ceph_remove_capsnap(struct inode *inode,

>> +				struct ceph_cap_snap *capsnap,

>> +				bool *wake_ci, bool *wake_mdsc);

>>   extern void ceph_flush_snaps(struct ceph_inode_info *ci,

>>   			     struct ceph_mds_session **psession);

>>   extern bool __ceph_should_report_size(struct ceph_inode_info *ci);