David Disseldorp <ddiss@xxxxxxx> writes:
> Hi Luís,
>
> On Thu, 9 Jun 2022 11:53:42 +0100, Luís Henriques wrote:
>
>> CephFS doesn't have a maximum xattr size. Instead, it imposes a maximum
>> size for the full set of xattrs names+values, which by default is 64K.
>>
>> This patch fixes the max_attrval_size so that it is slightly < 64K in
>> order to accommodate any already existing xattrs in the file.
>>
>> Signed-off-by: Luís Henriques <lhenriques@xxxxxxx>
>> ---
>> tests/generic/020 | 10 +++++++++-
>> 1 file changed, 9 insertions(+), 1 deletion(-)
>>
>> diff --git a/tests/generic/020 b/tests/generic/020
>> index d8648e96286e..76f13220fe85 100755
>> --- a/tests/generic/020
>> +++ b/tests/generic/020
>> @@ -128,7 +128,7 @@ _attr_get_max()
>> pvfs2)
>> max_attrval_size=8192
>> ;;
>> - xfs|udf|9p|ceph)
>> + xfs|udf|9p)
>> max_attrval_size=65536
>> ;;
>> bcachefs)
>> @@ -139,6 +139,14 @@ _attr_get_max()
>> # the underlying filesystem, so just use the lowest value above.
>> max_attrval_size=1024
>> ;;
>> + ceph)
>> + # CephFS does not have a maximum value for attributes. Instead,
>> + # it imposes a maximum size for the full set of xattrs
>> + # names+values, which by default is 64K. Set this to a value
>> + # that is slightly smaller than 64K so that it can accommodate
>> + # already existing xattrs.
>> + max_attrval_size=65000
>> + ;;
>
> I take it a more exact calculation would be something like:
> (64K - $max_attrval_namelen - sizeof(user.snrub="fish2\012"))?
>
> Perhaps you could calculate this on the fly for CephFS by passing in the
> filename and subtracting the `getfattr -d $filename` results... That
> said, it'd probably get a bit ugly, expecially if encoding needs to be
> taken into account.
In fact, this is *exactly* what I had before Dave suggested to keep it
simple. After moving the code back into common/attr, where's how the
generic code would look like:
+ ceph)
+ # CephFS does have a limit for the whole set of names+values
+ # attributes in a file. Thus, it is necessary to get the sizes
+ # of all names and values already existent and subtract them to
+ # the (default) maximum, which is 64k.
+ local len=0
+ while read line; do
+ # skip 1st line
+ [ "$line" != "${line#'#'}" ] && continue
+ n=$(echo $line | awk -F"=0x" '{print $1}')
+ v=$(echo $line | awk -F"=0x" '{print $2}')
+ nlen=${#n}
+ vlen=${#v}
+ # total is the sum of the name len and the value len
+ # divided by 2 because we're dumping them in hex format
+ t=$(($nlen + $vlen / 2))
+ len=$(($len + $t))
+ done <<< $(_getfattr -d -e hex $file 2> /dev/null)
+ echo $((65536 - $max_attrval_namelen - $len))
+ ;;
so... yeah, I'm not particularly gifted on shell, it could probably be
done in more clever/cleaner ways. Anyway, I'm open to revisit this if
this is the preferred solution.
> Reviewed-by: David Disseldorp <ddiss@xxxxxxx>
Thanks David. (And sorry! I completely forgot to include you on CC as I
had promised.)
Cheers,
--
Luís
