Jan Kara <jack@xxxxxxx> writes:
> 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?
Jan,
Looking back at the email from Amir, I realize I misunderstood his
original suggestion. Amir suggested it be FILEID_INVALID with 0-len OR
FILEID_INO32_GEN with zeroed fields. I mixed the two suggestions.
The advantage of doing FILEID_INO32_GEN with zeroed field is to avoid
special casing the test program. But I don't have a good reason to use
FILEID_INVALID with a len > 0.
I'm sending a v6 with everything, including this, addressed. testcase
and man pages will be updated as well.
--
Gabriel Krisman Bertazi
