Re: [PATCH v5 0/2] ceph: metrics for opened files, pinned caps and opened inodes

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On 2020/9/11 19:49, Jeff Layton wrote:
On Fri, 2020-09-11 at 11:43 +0800, Xiubo Li wrote:
On 2020/9/10 20:13, Jeff Layton wrote:
On Thu, 2020-09-10 at 08:00 +0200, Ilya Dryomov wrote:
On Thu, Sep 10, 2020 at 2:59 AM Xiubo Li <xiubli@xxxxxxxxxx> wrote:
On 2020/9/10 4:34, Ilya Dryomov wrote:
On Thu, Sep 3, 2020 at 4:22 PM Xiubo Li <xiubli@xxxxxxxxxx> wrote:
On 2020/9/3 22:18, Jeff Layton wrote:
On Thu, 2020-09-03 at 09:01 -0400, xiubli@xxxxxxxxxx wrote:
From: Xiubo Li <xiubli@xxxxxxxxxx>

Changed in V5:
- Remove mdsc parsing helpers except the ceph_sb_to_mdsc()
- Remove the is_opened member.

Changed in V4:
- A small fix about the total_inodes.

Changed in V3:
- Resend for V2 just forgot one patch, which is adding some helpers
support to simplify the code.

Changed in V2:
- Add number of inodes that have opened files.
- Remove the dir metrics and fold into files.



Xiubo Li (2):
      ceph: add ceph_sb_to_mdsc helper support to parse the mdsc
      ceph: metrics for opened files, pinned caps and opened inodes

     fs/ceph/caps.c    | 41 +++++++++++++++++++++++++++++++++++++----
     fs/ceph/debugfs.c | 11 +++++++++++
     fs/ceph/dir.c     | 20 +++++++-------------
     fs/ceph/file.c    | 13 ++++++-------
     fs/ceph/inode.c   | 11 ++++++++---
     fs/ceph/locks.c   |  2 +-
     fs/ceph/metric.c  | 14 ++++++++++++++
     fs/ceph/metric.h  |  7 +++++++
     fs/ceph/quota.c   | 10 +++++-----
     fs/ceph/snap.c    |  2 +-
     fs/ceph/super.h   |  6 ++++++
     11 files changed, 103 insertions(+), 34 deletions(-)

Looks good. I went ahead and merge this into testing.

Small merge conflict in quota.c, which I guess is probably due to not
basing this on testing branch. I also dropped what looks like an
unrelated hunk in the second patch.

In the future, if you can be sure that patches you post apply cleanly to
testing branch then that would make things easier.
Okay, will do it.
Hi Xiubo,

There is a problem with lifetimes here.  mdsc isn't guaranteed to exist
when ->free_inode() is called.  This can lead to crashes on a NULL mdsc
in ceph_free_inode() in case of e.g. "umount -f".  I know it was Jeff's
suggestion to move the decrement of total_inodes into ceph_free_inode(),
but it doesn't look like it can be easily deferred past ->evict_inode().
Okay, I will take a look.
Given that it's just a counter which we don't care about if the
mount is going away, some form of "if (mdsc)" check might do, but
need to make sure that it covers possible races, if any.

Good catch, Ilya.

What may be best is to move the increment out of ceph_alloc_inode and
instead put it in ceph_set_ino_cb. Then the decrement can go back into
ceph_evict_inode.
Hi Jeff, Ilya

Checked the code, it seems in the ceph_evict_inode() we will also hit
the same issue .

With the '-f' options when umounting, it will skip the inodes whose
i_count ref > 0. And then free the fsc/mdsc in ceph. And later the
iput_final() will call the ceph_evict_inode() and then ceph_free_inode().

Could we just check if !!(sb->s_flags & SB_ACTIVE) is false will we skip
the counting ?

Note that umount -f (MNT_FORCE) just means that ceph_umount_begin is
called before unmounting.

Yeah, right.

I misread the SB_FORCE and the MNT_FORCE.


If what you're saying it true, then we have bigger problems.
ceph_evict_inode does this today when ci->i_snap_realm is set:

     struct ceph_mds_client *mdsc = ceph_inode_to_client(inode)->mdsc;

...and then goes on to use that mdsc pointer.

I wonder if we ought to be moving move some of the operations in
ceph_kill_sb into ceph_put_super... particularly the call to
destroy_fs_client()?





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