On Wed 11-08-21 17:12:05, Gabriel Krisman Bertazi wrote:
> Jan Kara <jack@xxxxxxx> writes:
> >> @@ -376,14 +371,24 @@ static int fanotify_encode_fh(struct fanotify_fh *fh, struct inode *inode,
> >> fh->flags |= FANOTIFY_FH_FLAG_EXT_BUF;
> >> }
> >>
> >> - dwords = fh_len >> 2;
> >> - type = exportfs_encode_inode_fh(inode, buf, &dwords, NULL);
> >> - err = -EINVAL;
> >> - if (!type || type == FILEID_INVALID || fh_len != dwords << 2)
> >> - goto out_err;
> >> -
> >> - fh->type = type;
> >> - fh->len = fh_len;
> >> + if (inode) {
> >> + dwords = fh_len >> 2;
> >> + type = exportfs_encode_inode_fh(inode, buf, &dwords, NULL);
> >> + err = -EINVAL;
> >> + if (!type || type == FILEID_INVALID || fh_len != dwords << 2)
> >> + goto out_err;
> >> + fh->type = type;
> >> + fh->len = fh_len;
> >> + } else {
> >> + /*
> >> + * Invalid FHs are used on FAN_FS_ERROR for errors not
> >> + * linked to any inode. Caller needs to guarantee the fh
> >> + * has at least FANOTIFY_NULL_FH_LEN bytes of space.
> >> + */
> >> + fh->type = FILEID_INVALID;
> >> + fh->len = FANOTIFY_NULL_FH_LEN;
> >> + memset(buf, 0, FANOTIFY_NULL_FH_LEN);
> >> + }
> >
> > Maybe it will become clearer later during the series but why do you set
> > fh->len to FANOTIFY_NULL_FH_LEN and not 0?
>
> Jan,
>
> That is how we encode a NULL file handle (i.e. superblock error). Amir
> suggested it would be an invalid FILEID_INVALID, with a zeroed handle of
> size 8. I will improve the comment on the next iteration.
Thanks for info. Then I have a question for Amir I guess :) Amir, what's
the advantage of zeroed handle of size 8 instead of just 0 length file
handle?
Honza
--
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR
