cifs: use a refcount to protect open/closing the cached file handle

Signed-off-by: Ronnie Sahlberg <lsahlber@redhat.com>
---
 fs/cifs/cifsglob.h  |  1 +
 fs/cifs/smb2inode.c |  4 +++-
 fs/cifs/smb2ops.c   | 31 ++++++++++++++++++++++++++-----
 fs/cifs/smb2proto.h |  1 +
 4 files changed, 31 insertions(+), 6 deletions(-)

2018-07-30 15:48 GMT-07:00 Ronnie Sahlberg <lsahlber@redhat.com>:
> Signed-off-by: Ronnie Sahlberg <lsahlber@redhat.com>
> ---
>  fs/cifs/cifsglob.h  |  1 +
>  fs/cifs/smb2inode.c |  4 +++-
>  fs/cifs/smb2ops.c   | 31 ++++++++++++++++++++++++++-----
>  fs/cifs/smb2proto.h |  1 +
>  4 files changed, 31 insertions(+), 6 deletions(-)
>
> diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h
> index 658d1230566d..05458826fc69 100644
> --- a/fs/cifs/cifsglob.h
> +++ b/fs/cifs/cifsglob.h
> @@ -907,6 +907,7 @@ cap_unix(struct cifs_ses *ses)
>
>  struct cached_fid {
>         bool is_valid:1;        /* Do we have a useable root fid */
> +       struct kref refcount;
>         struct cifs_fid *fid;
>         struct mutex fid_mutex;
>         struct cifs_tcon *tcon;
> diff --git a/fs/cifs/smb2inode.c b/fs/cifs/smb2inode.c
> index d01ad706d7fc..f22cbc0d1869 100644
> --- a/fs/cifs/smb2inode.c
> +++ b/fs/cifs/smb2inode.c
> @@ -120,7 +120,9 @@ smb2_open_op_close(const unsigned int xid, struct cifs_tcon *tcon,
>                 break;
>         }
>
> -       if (use_cached_root_handle == false)
> +       if (use_cached_root_handle)
> +               close_shroot(&tcon->crfid);
> +       else
>                 rc = SMB2_close(xid, tcon, fid.persistent_fid, fid.volatile_fid);
>         if (tmprc)
>                 rc = tmprc;
> diff --git a/fs/cifs/smb2ops.c b/fs/cifs/smb2ops.c
> index b7eefb6429d1..03ca37ef484e 100644
> --- a/fs/cifs/smb2ops.c
> +++ b/fs/cifs/smb2ops.c
> @@ -470,21 +470,36 @@ SMB3_request_interfaces(const unsigned int xid, struct cifs_tcon *tcon)
>         return rc;
>  }
>
> -void
> -smb2_cached_lease_break(struct work_struct *work)
> +static void
> +smb2_close_cached_fid(struct kref *ref)
>  {
> -       struct cached_fid *cfid = container_of(work,
> -                               struct cached_fid, lease_break);
> -       mutex_lock(&cfid->fid_mutex);
> +       struct cached_fid *cfid = container_of(ref, struct cached_fid,
> +                                              refcount);
> +
>         if (cfid->is_valid) {
>                 cifs_dbg(FYI, "clear cached root file handle\n");
>                 SMB2_close(0, cfid->tcon, cfid->fid->persistent_fid,
>                            cfid->fid->volatile_fid);
>                 cfid->is_valid = false;
>         }
> +}
> +
> +void close_shroot(struct cached_fid *cfid)
> +{
> +       mutex_lock(&cfid->fid_mutex);
> +       kref_put(&cfid->refcount, smb2_close_cached_fid);
>         mutex_unlock(&cfid->fid_mutex);
>  }
>
> +void
> +smb2_cached_lease_break(struct work_struct *work)
> +{
> +       struct cached_fid *cfid = container_of(work,
> +                               struct cached_fid, lease_break);
> +
> +       close_shroot(cfid);
> +}
> +
>  /*
>   * Open the directory at the root of a share
>   */
> @@ -499,6 +514,7 @@ int open_shroot(unsigned int xid, struct cifs_tcon *tcon, struct cifs_fid *pfid)
>         if (tcon->crfid.is_valid) {
>                 cifs_dbg(FYI, "found a cached root file handle\n");
>                 memcpy(pfid, tcon->crfid.fid, sizeof(struct cifs_fid));
> +               kref_get(&tcon->crfid.refcount);
>                 mutex_unlock(&tcon->crfid.fid_mutex);
>                 return 0;
>         }
> @@ -515,6 +531,8 @@ int open_shroot(unsigned int xid, struct cifs_tcon *tcon, struct cifs_fid *pfid)
>                 memcpy(tcon->crfid.fid, pfid, sizeof(struct cifs_fid));
>                 tcon->crfid.tcon = tcon;
>                 tcon->crfid.is_valid = true;
> +               kref_init(&tcon->crfid.refcount);
> +               kref_get(&tcon->crfid.refcount);
>         }
>         mutex_unlock(&tcon->crfid.fid_mutex);
>         return rc;
> @@ -558,6 +576,9 @@ smb3_qfs_tcon(const unsigned int xid, struct cifs_tcon *tcon)
>                         FS_SECTOR_SIZE_INFORMATION); /* SMB3 specific */
>         if (no_cached_open)
>                 SMB2_close(xid, tcon, fid.persistent_fid, fid.volatile_fid);
> +       else
> +               close_shroot(&tcon->crfid);
> +
>         return;
>  }
>
> diff --git a/fs/cifs/smb2proto.h b/fs/cifs/smb2proto.h
> index 51c52fe50b95..b4076577eeb7 100644
> --- a/fs/cifs/smb2proto.h
> +++ b/fs/cifs/smb2proto.h
> @@ -68,6 +68,7 @@ extern int smb3_handle_read_data(struct TCP_Server_Info *server,
>
>  extern int open_shroot(unsigned int xid, struct cifs_tcon *tcon,
>                         struct cifs_fid *pfid);
> +extern void close_shroot(struct cached_fid *cfid);
>  extern void move_smb2_info_to_cifs(FILE_ALL_INFO *dst,
>                                    struct smb2_file_all_info *src);
>  extern int smb2_query_path_info(const unsigned int xid, struct cifs_tcon *tcon,
> --

Looks good.

Reviewed-by: Pavel Shilovsky <pshilov@microsoft.com>

--
Best regards,
Pavel Shilovsky
--
To unsubscribe from this list: send the line "unsubscribe linux-cifs" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html