Re: [PATCH 3/3] ceph: rework trim caps code

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On Fri, 23 Aug 2013, Gregory Farnum wrote:
> Did this patch get dropped on purpose? I also don't see it in our
> testing branch.

We fixed d_prune to be less lame instead.  That patch is waiting for Al's 
attention on -fsdevel.

sage


> -Greg
> Software Engineer #42 @ http://inktank.com | http://ceph.com
> 
> 
> On Sun, Aug 4, 2013 at 11:10 PM, Yan, Zheng <zheng.z.yan@xxxxxxxxx> wrote:
> > From: "Yan, Zheng" <zheng.z.yan@xxxxxxxxx>
> >
> > The trim caps code that handles SESSION_RECALL_STATE message has
> > two issues. First, it uses d_prune_aliases() to prune dentries.
> > This confuses our 'dir complete' check, because d_prune_aliases()
> > unhashes dentries before calling our d_prune() callback. Second,
> > it only prune dentries, inodes with zero reference are still in
> > the icache unless there is memory pressure.
> >
> > The fix is adding d_delete() and drop_inode() VFS callback. VFS
> > calls our d_delete()/drop_inode() callback when a dentry/inode's
> > last reference is dropped. If true is returned, VFS drop the
> > dentry/inode from the cache. When handling SESSION_RECALL_STATE
> > message, we mark inode with CEPH_I_TRIMCAPS flag. Our callbacks
> > check the flag and session->s_trim_caps to decide if VFS should
> > drop a dentry/inode. To trim an inode, we just need to reference
> > dentries associated with the inode, then release them.
> >
> > Signed-off-by: Yan, Zheng <zheng.z.yan@xxxxxxxxx>
> > ---
> >  fs/ceph/caps.c       | 30 ++++++++++++++++++++++++++++++
> >  fs/ceph/dir.c        | 12 ++++++++++++
> >  fs/ceph/inode.c      | 11 +++++++++++
> >  fs/ceph/mds_client.c | 37 ++++++++++++++++++++++++++++++-------
> >  fs/ceph/mds_client.h |  4 ++--
> >  fs/ceph/super.c      |  1 +
> >  fs/ceph/super.h      |  3 +++
> >  7 files changed, 89 insertions(+), 9 deletions(-)
> >
> > diff --git a/fs/ceph/caps.c b/fs/ceph/caps.c
> > index 49590a0..332dc8d 100644
> > --- a/fs/ceph/caps.c
> > +++ b/fs/ceph/caps.c
> > @@ -882,6 +882,36 @@ int __ceph_caps_mds_wanted(struct ceph_inode_info *ci)
> >  }
> >
> >  /*
> > + * Used by ceph_d_delete()/ceph_drop_inode(). check if we should drop
> > + * the inode.
> > + */
> > +int ceph_trim_caps(struct ceph_inode_info *ci, int drop_inode)
> > +{
> > +       struct ceph_cap *cap;
> > +       struct rb_node *p;
> > +       int ret = 0;
> > +
> > +       if (!spin_trylock(&ci->i_ceph_lock))
> > +               return 0;
> > +
> > +       if (ci->i_ceph_flags & CEPH_I_TRIMCAPS) {
> > +               for (p = rb_first(&ci->i_caps); p; p = rb_next(p)) {
> > +                       cap = rb_entry(p, struct ceph_cap, ci_node);
> > +                       if (atomic_read(&cap->session->s_trim_caps) <= 0)
> > +                               continue;
> > +                       if (drop_inode)
> > +                               atomic_dec(&cap->session->s_trim_caps);
> > +                       ret = 1;
> > +               }
> > +               if (!ret)
> > +                       ci->i_ceph_flags &= ~CEPH_I_TRIMCAPS;
> > +       }
> > +
> > +       spin_unlock(&ci->i_ceph_lock);
> > +       return ret;
> > +}
> > +
> > +/*
> >   * called under i_ceph_lock
> >   */
> >  static int __ceph_is_any_caps(struct ceph_inode_info *ci)
> > diff --git a/fs/ceph/dir.c b/fs/ceph/dir.c
> > index 0e4da4a..9741f34 100644
> > --- a/fs/ceph/dir.c
> > +++ b/fs/ceph/dir.c
> > @@ -1043,6 +1043,17 @@ static int ceph_d_revalidate(struct dentry *dentry, unsigned int flags)
> >         return valid;
> >  }
> >
> > +static int ceph_d_delete(const struct dentry *dentry)
> > +{
> > +       if (dentry->d_inode) {
> > +               struct ceph_inode_info *ci = ceph_inode(dentry->d_inode);
> > +               /* need trim caps? */
> > +               if (ci->i_ceph_flags & CEPH_I_TRIMCAPS)
> > +                       return ceph_trim_caps(ci, false);
> > +       }
> > +       return 0;
> > +}
> > +
> >  /*
> >   * Release our ceph_dentry_info.
> >   */
> > @@ -1300,6 +1311,7 @@ const struct inode_operations ceph_dir_iops = {
> >
> >  const struct dentry_operations ceph_dentry_ops = {
> >         .d_revalidate = ceph_d_revalidate,
> > +       .d_delete = ceph_d_delete,
> >         .d_release = ceph_d_release,
> >         .d_prune = ceph_d_prune,
> >  };
> > diff --git a/fs/ceph/inode.c b/fs/ceph/inode.c
> > index 01e4db1..371590a 100644
> > --- a/fs/ceph/inode.c
> > +++ b/fs/ceph/inode.c
> > @@ -431,6 +431,17 @@ void ceph_destroy_inode(struct inode *inode)
> >         call_rcu(&inode->i_rcu, ceph_i_callback);
> >  }
> >
> > +int ceph_drop_inode(struct inode *inode)
> > +{
> > +       struct ceph_inode_info *ci = ceph_inode(inode);
> > +       int ret = generic_drop_inode(inode);
> > +
> > +       /* need trim caps? */
> > +       if (!ret && (ci->i_ceph_flags & CEPH_I_TRIMCAPS))
> > +               ret = ceph_trim_caps(ci, true);
> > +
> > +       return ret ;
> > +}
> >
> >  /*
> >   * Helpers to fill in size, ctime, mtime, and atime.  We have to be
> > diff --git a/fs/ceph/mds_client.c b/fs/ceph/mds_client.c
> > index 2a42b5f..7c2b8d6 100644
> > --- a/fs/ceph/mds_client.c
> > +++ b/fs/ceph/mds_client.c
> > @@ -435,7 +435,7 @@ static struct ceph_mds_session *register_session(struct ceph_mds_client *mdsc,
> >         s->s_renew_seq = 0;
> >         INIT_LIST_HEAD(&s->s_caps);
> >         s->s_nr_caps = 0;
> > -       s->s_trim_caps = 0;
> > +       atomic_set(&s->s_trim_caps, 0);
> >         atomic_set(&s->s_ref, 1);
> >         INIT_LIST_HEAD(&s->s_waiting);
> >         INIT_LIST_HEAD(&s->s_unsafe);
> > @@ -1207,9 +1207,10 @@ static int trim_caps_cb(struct inode *inode, struct ceph_cap *cap, void *arg)
> >  {
> >         struct ceph_mds_session *session = arg;
> >         struct ceph_inode_info *ci = ceph_inode(inode);
> > +       struct dentry *dentry;
> >         int used, oissued, mine;
> >
> > -       if (session->s_trim_caps <= 0)
> > +       if (atomic_read(&session->s_trim_caps) <= 0)
> >                 return -1;
> >
> >         spin_lock(&ci->i_ceph_lock);
> > @@ -1225,16 +1226,39 @@ static int trim_caps_cb(struct inode *inode, struct ceph_cap *cap, void *arg)
> >         if ((used & ~oissued) & mine)
> >                 goto out;   /* we need these caps */
> >
> > -       session->s_trim_caps--;
> >         if (oissued) {
> >                 /* we aren't the only cap.. just remove us */
> >                 __queue_cap_release(session, ceph_ino(inode), cap->cap_id,
> >                                     cap->mseq, cap->issue_seq);
> >                 __ceph_remove_cap(cap);
> > +               atomic_dec(&session->s_trim_caps);
> >         } else {
> >                 /* try to drop referring dentries */
> > +               ci->i_ceph_flags |= CEPH_I_TRIMCAPS;
> >                 spin_unlock(&ci->i_ceph_lock);
> > -               d_prune_aliases(inode);
> > +               /*
> > +                * can't use d_prune_aliases(), because it unhashes dentries
> > +                * before calling ceph_d_prune().
> > +                */
> > +restart:
> > +               spin_lock(&inode->i_lock);
> > +               hlist_for_each_entry(dentry, &inode->i_dentry, d_alias) {
> > +                       spin_lock(&dentry->d_lock);
> > +                       if (!dentry->d_count) {
> > +                               dget_dlock(dentry);
> > +                               spin_unlock(&dentry->d_lock);
> > +                               spin_unlock(&inode->i_lock);
> > +                               /*
> > +                                * our d_delete callback returns true when
> > +                                * CEPH_I_TRIMCAPS is set. This makes VFS
> > +                                * drop the dentry.
> > +                                */
> > +                               dput(dentry);
> > +                               goto restart;
> > +                       }
> > +                       spin_unlock(&dentry->d_lock);
> > +               }
> > +               spin_unlock(&inode->i_lock);
> >                 dout("trim_caps_cb %p cap %p  pruned, count now %d\n",
> >                      inode, cap, atomic_read(&inode->i_count));
> >                 return 0;
> > @@ -1257,12 +1281,11 @@ static int trim_caps(struct ceph_mds_client *mdsc,
> >         dout("trim_caps mds%d start: %d / %d, trim %d\n",
> >              session->s_mds, session->s_nr_caps, max_caps, trim_caps);
> >         if (trim_caps > 0) {
> > -               session->s_trim_caps = trim_caps;
> > +               atomic_set(&session->s_trim_caps, trim_caps);
> >                 iterate_session_caps(session, trim_caps_cb, session);
> >                 dout("trim_caps mds%d done: %d / %d, trimmed %d\n",
> >                      session->s_mds, session->s_nr_caps, max_caps,
> > -                       trim_caps - session->s_trim_caps);
> > -               session->s_trim_caps = 0;
> > +                    trim_caps - atomic_read(&session->s_trim_caps));
> >         }
> >         return 0;
> >  }
> > diff --git a/fs/ceph/mds_client.h b/fs/ceph/mds_client.h
> > index c2a19fb..d0e6566 100644
> > --- a/fs/ceph/mds_client.h
> > +++ b/fs/ceph/mds_client.h
> > @@ -130,8 +130,8 @@ struct ceph_mds_session {
> >         /* protected by s_cap_lock */
> >         spinlock_t        s_cap_lock;
> >         struct list_head  s_caps;     /* all caps issued by this session */
> > -       int               s_nr_caps, s_trim_caps;
> > -       int               s_num_cap_releases;
> > +       int               s_nr_caps, s_num_cap_releases;
> > +       atomic_t          s_trim_caps;
> >         struct list_head  s_cap_releases; /* waiting cap_release messages */
> >         struct list_head  s_cap_releases_done; /* ready to send */
> >         struct ceph_cap  *s_cap_iterator;
> > diff --git a/fs/ceph/super.c b/fs/ceph/super.c
> > index 6627b26..bcf26bf 100644
> > --- a/fs/ceph/super.c
> > +++ b/fs/ceph/super.c
> > @@ -655,6 +655,7 @@ static const struct super_operations ceph_super_ops = {
> >         .alloc_inode    = ceph_alloc_inode,
> >         .destroy_inode  = ceph_destroy_inode,
> >         .write_inode    = ceph_write_inode,
> > +       .drop_inode     = ceph_drop_inode,
> >         .sync_fs        = ceph_sync_fs,
> >         .put_super      = ceph_put_super,
> >         .show_options   = ceph_show_options,
> > diff --git a/fs/ceph/super.h b/fs/ceph/super.h
> > index e81c0b6..b87691a 100644
> > --- a/fs/ceph/super.h
> > +++ b/fs/ceph/super.h
> > @@ -421,6 +421,7 @@ static inline struct inode *ceph_find_inode(struct super_block *sb,
> >  /*
> >   * Ceph inode.
> >   */
> > +#define CEPH_I_TRIMCAPS  1  /* trim caps when possible */
> >  #define CEPH_I_NODELAY   4  /* do not delay cap release */
> >  #define CEPH_I_FLUSH     8  /* do not delay flush of dirty metadata */
> >  #define CEPH_I_NOFLUSH  16  /* do not flush dirty caps */
> > @@ -487,6 +488,7 @@ extern int __ceph_caps_issued(struct ceph_inode_info *ci, int *implemented);
> >  extern int __ceph_caps_issued_mask(struct ceph_inode_info *ci, int mask, int t);
> >  extern int __ceph_caps_issued_other(struct ceph_inode_info *ci,
> >                                     struct ceph_cap *cap);
> > +extern int ceph_trim_caps(struct ceph_inode_info *ci, int drop_inode);
> >
> >  static inline int ceph_caps_issued(struct ceph_inode_info *ci)
> >  {
> > @@ -675,6 +677,7 @@ extern const struct inode_operations ceph_file_iops;
> >
> >  extern struct inode *ceph_alloc_inode(struct super_block *sb);
> >  extern void ceph_destroy_inode(struct inode *inode);
> > +extern int ceph_drop_inode(struct inode *inode);
> >
> >  extern struct inode *ceph_get_inode(struct super_block *sb,
> >                                     struct ceph_vino vino);
> > --
> > 1.8.1.4
> >
> > --
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> 
> 
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