linux-kernel - Re: [RFC PATCH 2/2] ceph: quota: fix quota subdir mounts

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Date:   Sun, 03 Mar 2019 10:59:12 +0000
From:   Luis Henriques <lhenriques@...e.com>
To:     Jeff Layton <jlayton@...hat.com>
Cc:     "Yan\, Zheng" <zyan@...hat.com>, Sage Weil <sage@...hat.com>,
        Ilya Dryomov <idryomov@...il.com>, ceph-devel@...r.kernel.org,
        linux-kernel@...r.kernel.org, Hendrik Peyerl <hpeyerl@...sline.net>
Subject: Re: [RFC PATCH 2/2] ceph: quota: fix quota subdir mounts

Jeff Layton <jlayton@...hat.com> writes:

> On Fri, 2019-03-01 at 17:57 +0000, Luis Henriques wrote:
>> The CephFS kernel client doesn't enforce quotas that are set in a
>> directory that isn't visible in the mount point.  For example, given the
>> path '/dir1/dir2', if quotas are set in 'dir1' and the mount is done in with
>> 
>>   mount -t ceph <server>:<port>:/dir1/ /mnt
>> 
>> then the client can't access the 'dir1' inode from the quota realm dir2
>> belongs to.
>> 
>> This patch fixes this by simply doing an MDS LOOKUPINO Op and grabbing a
>> reference to it (so that it doesn't disappear again).  This also requires an
>> extra field in ceph_snap_realm so that we know we have to release that
>> reference when destroying the realm.
>> 
>> Links: https://tracker.ceph.com/issues/3848
>
> This bug looks unrelated to the patch description. Are you sure it's
> correct?

Ups!  Looks like I truncated the bug number.  Sorry about that, here's
the correct link:

 https://tracker.ceph.com/issues/38482

Cheers,
-- 
Luis


>> Reported-by: Hendrik Peyerl <hpeyerl@...sline.net>
>> Signed-off-by: Luis Henriques <lhenriques@...e.com>
>> ---
>>  fs/ceph/caps.c  |  2 +-
>>  fs/ceph/quota.c | 30 +++++++++++++++++++++++++++---
>>  fs/ceph/snap.c  |  3 +++
>>  fs/ceph/super.h |  2 ++
>>  4 files changed, 33 insertions(+), 4 deletions(-)
>> 
>> diff --git a/fs/ceph/caps.c b/fs/ceph/caps.c
>> index bba28a5034ba..e79994ff53d6 100644
>> --- a/fs/ceph/caps.c
>> +++ b/fs/ceph/caps.c
>> @@ -1035,7 +1035,7 @@ static void drop_inode_snap_realm(struct ceph_inode_info *ci)
>>  	list_del_init(&ci->i_snap_realm_item);
>>  	ci->i_snap_realm_counter++;
>>  	ci->i_snap_realm = NULL;
>> -	if (realm->ino == ci->i_vino.ino)
>> +	if ((realm->ino == ci->i_vino.ino) && !realm->own_inode)
>>  		realm->inode = NULL;
>>  	spin_unlock(&realm->inodes_with_caps_lock);
>>  	ceph_put_snap_realm(ceph_sb_to_client(ci->vfs_inode.i_sb)->mdsc,
>> diff --git a/fs/ceph/quota.c b/fs/ceph/quota.c
>> index 9455d3aef0c3..f6b972d222e4 100644
>> --- a/fs/ceph/quota.c
>> +++ b/fs/ceph/quota.c
>> @@ -22,7 +22,16 @@ void ceph_adjust_quota_realms_count(struct inode *inode, bool inc)
>>  static inline bool ceph_has_realms_with_quotas(struct inode *inode)
>>  {
>>  	struct ceph_mds_client *mdsc = ceph_inode_to_client(inode)->mdsc;
>> -	return atomic64_read(&mdsc->quotarealms_count) > 0;
>> +	struct super_block *sb = mdsc->fsc->sb;
>> +
>> +	if (atomic64_read(&mdsc->quotarealms_count) > 0)
>> +		return true;
>> +	/* if root is the real CephFS root, we don't have quota realms */
>> +	if (sb->s_root->d_inode &&
>> +	    (sb->s_root->d_inode->i_ino == CEPH_INO_ROOT))
>> +		return false;
>> +	/* otherwise, we can't know for sure */
>> +	return true;
>>  }
>>  
>>  void ceph_handle_quota(struct ceph_mds_client *mdsc,
>> @@ -166,6 +175,7 @@ static bool check_quota_exceeded(struct inode *inode, enum quota_check_op op,
>>  		return false;
>>  
>>  	down_read(&mdsc->snap_rwsem);
>> +restart:
>>  	realm = ceph_inode(inode)->i_snap_realm;
>>  	if (realm)
>>  		ceph_get_snap_realm(mdsc, realm);
>> @@ -176,8 +186,22 @@ static bool check_quota_exceeded(struct inode *inode, enum quota_check_op op,
>>  		spin_lock(&realm->inodes_with_caps_lock);
>>  		in = realm->inode ? igrab(realm->inode) : NULL;
>>  		spin_unlock(&realm->inodes_with_caps_lock);
>> -		if (!in)
>> -			break;
>> +		if (!in) {
>> +			up_read(&mdsc->snap_rwsem);
>> +			in = ceph_lookup_inode(inode->i_sb, realm->ino);
>> +			down_read(&mdsc->snap_rwsem);
>> +			if (IS_ERR(in)) {
>> +				pr_warn("Can't lookup inode %llx (err: %ld)\n",
>> +					realm->ino, PTR_ERR(in));
>> +				break;
>> +			}
>> +			spin_lock(&realm->inodes_with_caps_lock);
>> +			realm->inode = in;
>> +			realm->own_inode = true;
>> +			spin_unlock(&realm->inodes_with_caps_lock);
>> +			ceph_put_snap_realm(mdsc, realm);
>> +			goto restart;
>> +		}
>>  
>>  		ci = ceph_inode(in);
>>  		spin_lock(&ci->i_ceph_lock);
>> diff --git a/fs/ceph/snap.c b/fs/ceph/snap.c
>> index f74193da0e09..c84ed8e8526a 100644
>> --- a/fs/ceph/snap.c
>> +++ b/fs/ceph/snap.c
>> @@ -117,6 +117,7 @@ static struct ceph_snap_realm *ceph_create_snap_realm(
>>  
>>  	atomic_set(&realm->nref, 1);    /* for caller */
>>  	realm->ino = ino;
>> +	realm->own_inode = false;
>>  	INIT_LIST_HEAD(&realm->children);
>>  	INIT_LIST_HEAD(&realm->child_item);
>>  	INIT_LIST_HEAD(&realm->empty_item);
>> @@ -184,6 +185,8 @@ static void __destroy_snap_realm(struct ceph_mds_client *mdsc,
>>  	kfree(realm->prior_parent_snaps);
>>  	kfree(realm->snaps);
>>  	ceph_put_snap_context(realm->cached_context);
>> +	if (realm->own_inode && realm->inode)
>> +		iput(realm->inode);
>>  	kfree(realm);
>>  }
>>  
>> diff --git a/fs/ceph/super.h b/fs/ceph/super.h
>> index ce51e98b08ec..3f0d74d2150f 100644
>> --- a/fs/ceph/super.h
>> +++ b/fs/ceph/super.h
>> @@ -764,6 +764,8 @@ struct ceph_snap_realm {
>>  	atomic_t nref;
>>  	struct rb_node node;
>>  
>> +	bool own_inode;     /* true if we hold a ref to the inode */
>> +
>>  	u64 created, seq;
>>  	u64 parent_ino;
>>  	u64 parent_since;   /* snapid when our current parent became so */