Re: [PATCH v5 1/1] ceph: add getvxattr op

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On Mon, Jan 24, 2022 at 4:52 PM Jeff Layton <jlayton@xxxxxxxxxx> wrote:
>
> On Mon, 2022-01-24 at 09:00 +0000, Milind Changire wrote:
> > Problem:
> > Directory vxattr like ceph.dir.pin* may not be propagated to the
> > client as frequently to keep them updated. This creates vxattr
> > availability problems.
> > Also, the dir and file layout xattr is not reported for dirs and
> > files when a layout is not specifically set for the dir or file.
> >
> > Solution:
> > Adds new getvxattr op to fetch ceph.dir.pin*, ceph.dir.layout.json
> > and ceph.file.layout.json vxattrs.
> > If the entire layout for a dir or a file is being set, then it is
> > expected that the layout be set in standard JSON format. Individual
> > field value retrieval is not wrapped in JSON. The JSON format also
> > applies while setting the vxattr if the entire layout is being set in
> > one go.
> > ceph.(dir|file).layout.(pool_name|pool_id) are also supported as new
> > vxattrs to help disambiguate the pool name from pool_id when a digit
> > sequence is used as a pool name instead of an alphabetic sequence.
> >
> > As a temporary measure, setting a vxattr can also be done in the old
> > format. The old format will be deprecated in the future.
> >
> > URL: https://tracker.ceph.com/issues/51062
> > Signed-off-by: Milind Changire <mchangir@xxxxxxxxxx>
> > ---
> >  fs/ceph/inode.c              | 51 ++++++++++++++++++++++++++++++++++++
> >  fs/ceph/mds_client.c         | 27 ++++++++++++++++++-
> >  fs/ceph/mds_client.h         | 12 ++++++++-
> >  fs/ceph/strings.c            |  1 +
> >  fs/ceph/super.h              |  1 +
> >  fs/ceph/xattr.c              | 41 ++++++++++++++++++++++++++++-
> >  include/linux/ceph/ceph_fs.h |  1 +
> >  7 files changed, 131 insertions(+), 3 deletions(-)
> >
> > diff --git a/fs/ceph/inode.c b/fs/ceph/inode.c
> > index e3322fcb2e8d..efdce049b7f0 100644
> > --- a/fs/ceph/inode.c
> > +++ b/fs/ceph/inode.c
> > @@ -2291,6 +2291,57 @@ int __ceph_do_getattr(struct inode *inode, struct page *locked_page,
> >       return err;
> >  }
> >
> > +int ceph_do_getvxattr(struct inode *inode, const char *name, void *value,
> > +                   size_t size)
> > +{
> > +     struct ceph_fs_client *fsc = ceph_sb_to_client(inode->i_sb);
> > +     struct ceph_mds_client *mdsc = fsc->mdsc;
> > +     struct ceph_mds_request *req;
> > +     int mode = USE_AUTH_MDS;
> > +     int err;
> > +     char *xattr_value;
> > +     size_t xattr_value_len;
> > +
> > +     req = ceph_mdsc_create_request(mdsc, CEPH_MDS_OP_GETVXATTR, mode);
> > +     if (IS_ERR(req)) {
> > +             err = -ENOMEM;
> > +             goto out;
> > +     }
> > +
> > +     req->r_path2 = kstrdup(name, GFP_NOFS);
> > +     if (!req->r_path2) {
> > +             err = -ENOMEM;
> > +             goto put;
> > +     }
> > +
> > +     ihold(inode);
> > +     req->r_inode = inode;
> > +     err = ceph_mdsc_do_request(mdsc, NULL, req);
> > +     if (err < 0)
> > +             goto put;
> > +
> > +     xattr_value = req->r_reply_info.xattr_info.xattr_value;
> > +     xattr_value_len = req->r_reply_info.xattr_info.xattr_value_len;
> > +
> > +     dout("do_getvxattr xattr_value_len:%zu, size:%zu\n", xattr_value_len, size);
> > +
> > +     err = (int)xattr_value_len;
> > +     if (size == 0)
> > +             goto put;
> > +
> > +     if (xattr_value_len > size) {
> > +             err = -ERANGE;
> > +             goto put;
> > +     }
> > +
> > +     memcpy(value, xattr_value, xattr_value_len);
> > +put:
> > +     ceph_mdsc_put_request(req);
> > +out:
> > +     dout("do_getvxattr result=%d\n", err);
> > +     return err;
> > +}
> > +
> >
> >  /*
> >   * Check inode permissions.  We verify we have a valid value for
> > diff --git a/fs/ceph/mds_client.c b/fs/ceph/mds_client.c
> > index c30eefc0ac19..a5eafc71d976 100644
> > --- a/fs/ceph/mds_client.c
> > +++ b/fs/ceph/mds_client.c
> > @@ -555,6 +555,29 @@ static int parse_reply_info_create(void **p, void *end,
> >       return -EIO;
> >  }
> >
> > +static int parse_reply_info_getvxattr(void **p, void *end,
> > +                                   struct ceph_mds_reply_info_parsed *info,
> > +                                   u64 features)
> > +{
> > +     u8 struct_v, struct_compat;
> > +     u32 struct_len;
> > +     u32 value_len;
> > +
> > +     ceph_decode_8_safe(p, end, struct_v, bad);
> > +     ceph_decode_8_safe(p, end, struct_compat, bad);
> > +     ceph_decode_32_safe(p, end, struct_len, bad);
> > +     ceph_decode_32_safe(p, end, value_len, bad);
> > +
> > +     if (value_len == end - *p) {
> > +       info->xattr_info.xattr_value = *p;
> > +       info->xattr_info.xattr_value_len = end - *p;
> > +       *p = end;
> > +       return info->xattr_info.xattr_value_len;
> > +     }
> > +bad:
> > +     return -EIO;
> > +}
> > +
> >  /*
> >   * parse extra results
> >   */
> > @@ -570,6 +593,8 @@ static int parse_reply_info_extra(void **p, void *end,
> >               return parse_reply_info_readdir(p, end, info, features);
> >       else if (op == CEPH_MDS_OP_CREATE)
> >               return parse_reply_info_create(p, end, info, features, s);
> > +     else if (op == CEPH_MDS_OP_GETVXATTR)
> > +             return parse_reply_info_getvxattr(p, end, info, features);
> >       else
> >               return -EIO;
> >  }
> > @@ -615,7 +640,7 @@ static int parse_reply_info(struct ceph_mds_session *s, struct ceph_msg *msg,
> >
> >       if (p != end)
> >               goto bad;
> > -     return 0;
> > +     return err;
> >
> >  bad:
> >       err = -EIO;
> > diff --git a/fs/ceph/mds_client.h b/fs/ceph/mds_client.h
> > index 97c7f7bfa55f..f2a8e5af3c2e 100644
> > --- a/fs/ceph/mds_client.h
> > +++ b/fs/ceph/mds_client.h
> > @@ -29,8 +29,10 @@ enum ceph_feature_type {
> >       CEPHFS_FEATURE_MULTI_RECONNECT,
> >       CEPHFS_FEATURE_DELEG_INO,
> >       CEPHFS_FEATURE_METRIC_COLLECT,
> > +     CEPHFS_FEATURE_ALTERNATE_NAME,
> > +     CEPHFS_FEATURE_GETVXATTR,
> >
> > -     CEPHFS_FEATURE_MAX = CEPHFS_FEATURE_METRIC_COLLECT,
> > +     CEPHFS_FEATURE_MAX = CEPHFS_FEATURE_GETVXATTR,
> >  };
> >
> >  /*
> > @@ -45,6 +47,8 @@ enum ceph_feature_type {
> >       CEPHFS_FEATURE_MULTI_RECONNECT,         \
> >       CEPHFS_FEATURE_DELEG_INO,               \
> >       CEPHFS_FEATURE_METRIC_COLLECT,          \
> > +     CEPHFS_FEATURE_ALTERNATE_NAME,          \
> > +     CEPHFS_FEATURE_GETVXATTR,               \
> >                                               \
> >       CEPHFS_FEATURE_MAX,                     \
> >  }
> > @@ -100,6 +104,11 @@ struct ceph_mds_reply_dir_entry {
> >       loff_t                        offset;
> >  };
> >
> > +struct ceph_mds_reply_xattr {
> > +     char *xattr_value;
> > +     size_t xattr_value_len;
> > +};
> > +
> >  /*
> >   * parsed info about an mds reply, including information about
> >   * either: 1) the target inode and/or its parent directory and dentry,
> > @@ -115,6 +124,7 @@ struct ceph_mds_reply_info_parsed {
> >       char                          *dname;
> >       u32                           dname_len;
> >       struct ceph_mds_reply_lease   *dlease;
> > +     struct ceph_mds_reply_xattr   xattr_info;
> >
> >       /* extra */
> >       union {
> > diff --git a/fs/ceph/strings.c b/fs/ceph/strings.c
> > index 573bb9556fb5..e36e8948e728 100644
> > --- a/fs/ceph/strings.c
> > +++ b/fs/ceph/strings.c
> > @@ -60,6 +60,7 @@ const char *ceph_mds_op_name(int op)
> >       case CEPH_MDS_OP_LOOKUPINO:  return "lookupino";
> >       case CEPH_MDS_OP_LOOKUPNAME:  return "lookupname";
> >       case CEPH_MDS_OP_GETATTR:  return "getattr";
> > +     case CEPH_MDS_OP_GETVXATTR:  return "getvxattr";
> >       case CEPH_MDS_OP_SETXATTR: return "setxattr";
> >       case CEPH_MDS_OP_SETATTR: return "setattr";
> >       case CEPH_MDS_OP_RMXATTR: return "rmxattr";
> > diff --git a/fs/ceph/super.h b/fs/ceph/super.h
> > index ac331aa07cfa..a627fa69668e 100644
> > --- a/fs/ceph/super.h
> > +++ b/fs/ceph/super.h
> > @@ -1043,6 +1043,7 @@ static inline bool ceph_inode_is_shutdown(struct inode *inode)
> >
> >  /* xattr.c */
> >  int __ceph_setxattr(struct inode *, const char *, const void *, size_t, int);
> > +int ceph_do_getvxattr(struct inode *inode, const char *name, void *value, size_t size);
> >  ssize_t __ceph_getxattr(struct inode *, const char *, void *, size_t);
> >  extern ssize_t ceph_listxattr(struct dentry *, char *, size_t);
> >  extern struct ceph_buffer *__ceph_build_xattrs_blob(struct ceph_inode_info *ci);
> > diff --git a/fs/ceph/xattr.c b/fs/ceph/xattr.c
> > index fcf7dfdecf96..53ab1c38f1ff 100644
> > --- a/fs/ceph/xattr.c
> > +++ b/fs/ceph/xattr.c
> > @@ -918,6 +918,38 @@ static inline int __get_request_mask(struct inode *in) {
> >       return mask;
> >  }
> >
> > +/* check if the entire cluster supports the given feature */
> > +static inline bool ceph_cluster_has_feature(struct inode *inode, int feature_bit)
> > +{
> > +     int64_t i;
> > +     struct ceph_mds_client *mdsc = ceph_sb_to_mdsc(inode->i_sb);
> > +     struct ceph_mds_session **sessions = NULL;
> > +     int64_t num_sessions = 0;
> > +     bool found = false;
> > +
> > +     mutex_lock(&mdsc->mutex);
> > +     num_sessions = atomic_read(&mdsc->num_sessions);
> > +     sessions = mdsc->sessions;
> > +
> > +     if (mdsc->stopping)
> > +             goto unlock_out;
> > +
> > +     if (!sessions)
> > +             goto unlock_out;
> > +
>
> I don't think we can end up with a NULL sessions pointer w/o failing
> register_session(). You can probably drop this check.

okay; I'll drop that check

>
> > +     for (i = 0; i < num_sessions; i++) {
> > +             struct ceph_mds_session *session = sessions[i];
> > +             if (!session)
> > +                     goto unlock_out;
>
> I think you just want to continue here if there is no session for a
> particular index. This will make this return false if the client just
> happens to not have a session for this MDS at this time.

I want to send the request to the "auth mds" of the inode.
If there's a way to get that info, then I could just ensure that the
"auth mds" has the feature "getvxattr" and return true and ignore
other MDS'

>
> > +             if (!test_bit(feature_bit, &session->s_features))
> > +                     goto unlock_out;
> > +     }
> > +     found = true;
> > +unlock_out:
> > +     mutex_unlock(&mdsc->mutex);
> > +     return found;
> > +}
> > +
> >  ssize_t __ceph_getxattr(struct inode *inode, const char *name, void *value,
> >                     size_t size)
> >  {
> > @@ -978,8 +1010,15 @@ ssize_t __ceph_getxattr(struct inode *inode, const char *name, void *value,
> >
> >       err = -ENODATA;  /* == ENOATTR */
> >       xattr = __get_xattr(ci, name);
> > -     if (!xattr)
> > +     if (!xattr) {
> > +             if (!strncmp(name, XATTR_CEPH_PREFIX, XATTR_CEPH_PREFIX_LEN) &&
> > +                 ceph_cluster_has_feature(inode, CEPHFS_FEATURE_GETVXATTR)) {
> > +                     spin_unlock(&ci->i_ceph_lock);
> > +                     err = ceph_do_getvxattr(inode, name, value, size);
> > +                     spin_lock(&ci->i_ceph_lock);
> > +             }
> >               goto out;
> > +     }
>
> I think this is not quite the right spot to do this.
>
> This is occurring after the client has already issued a GETATTR to the
> MDS to fetch the xattr blob for the inode. However, we know that no
> ceph.* xattrs will be in that blob, so that call is of no value.
>
> I think you basically want logic like:
>
> 1/ test that the name starts with "ceph."
> 2/ if it does, then call ceph_match_vxattr
> 3/ if that doesn't match anything, then call ceph_do_getvxattr to ask
> the MDS about it

thanks for the suggestion

>
>
> >
> >       err = -ERANGE;
> >       if (size && size < xattr->val_len)
> > diff --git a/include/linux/ceph/ceph_fs.h b/include/linux/ceph/ceph_fs.h
> > index 7ad6c3d0db7d..66db21ac5f0c 100644
> > --- a/include/linux/ceph/ceph_fs.h
> > +++ b/include/linux/ceph/ceph_fs.h
> > @@ -328,6 +328,7 @@ enum {
> >       CEPH_MDS_OP_LOOKUPPARENT = 0x00103,
> >       CEPH_MDS_OP_LOOKUPINO  = 0x00104,
> >       CEPH_MDS_OP_LOOKUPNAME = 0x00105,
> > +     CEPH_MDS_OP_GETVXATTR  = 0x00106,
> >
> >       CEPH_MDS_OP_SETXATTR   = 0x01105,
> >       CEPH_MDS_OP_RMXATTR    = 0x01106,
>
> --
> Jeff Layton <jlayton@xxxxxxxxxx>



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