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Date:   Mon, 4 Mar 2019 15:40:22 +0800
From:   "Yan, Zheng" <ukernel@...il.com>
To:     Luis Henriques <lhenriques@...e.com>
Cc:     "Yan, Zheng" <zyan@...hat.com>, Sage Weil <sage@...hat.com>,
        Ilya Dryomov <idryomov@...il.com>,
        ceph-devel <ceph-devel@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Hendrik Peyerl <hpeyerl@...sline.net>
Subject: Re: [RFC PATCH 2/2] ceph: quota: fix quota subdir mounts

On Sat, Mar 2, 2019 at 3:13 AM Luis Henriques <lhenriques@...e.com> 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.
>

This may cause circle reference if somehow an inode owned by snaprealm
get moved into mount subdir (other clients do rename).  how about
holding these inodes in mds_client?

> Links: https://tracker.ceph.com/issues/3848
> 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 */

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