Jeff Layton <jlayton@xxxxxxxxxx> writes:
> On Wed, 2020-11-11 at 15:39 +0000, Luis Henriques wrote:
>> When doing a rename across quota realms, there's a corner case that isn't
>> handled correctly. Here's a testcase:
>>
>> mkdir files limit
>> truncate files/file -s 10G
>> setfattr limit -n ceph.quota.max_bytes -v 1000000
>> mv files limit/
>>
>> The above will succeed because ftruncate(2) won't result in an immediate
>> notification of the MDSs with the new file size, and thus the quota realms
>> stats won't be updated.
>>
>> This patch forces a sync with the MDS every time there's an ATTR_SIZE that
>> sets a new i_size, even if we have Fx caps.
>>
>> Cc: stable@xxxxxxxxxxxxxxx
>> Fixes: dffdcd71458e ("ceph: allow rename operation under different quota realms")
>> URL: https://tracker.ceph.com/issues/36593
>> Signed-off-by: Luis Henriques <lhenriques@xxxxxxx>
>> ---
>> fs/ceph/inode.c | 11 ++---------
>> 1 file changed, 2 insertions(+), 9 deletions(-)
>>
>> diff --git a/fs/ceph/inode.c b/fs/ceph/inode.c
>> index 526faf4778ce..30e3f240ac96 100644
>> --- a/fs/ceph/inode.c
>> +++ b/fs/ceph/inode.c
>> @@ -2136,15 +2136,8 @@ int __ceph_setattr(struct inode *inode, struct iattr *attr)
>> if (ia_valid & ATTR_SIZE) {
>> dout("setattr %p size %lld -> %lld\n", inode,
>> inode->i_size, attr->ia_size);
>> - if ((issued & CEPH_CAP_FILE_EXCL) &&
>> - attr->ia_size > inode->i_size) {
>> - i_size_write(inode, attr->ia_size);
>> - inode->i_blocks = calc_inode_blocks(attr->ia_size);
>> - ci->i_reported_size = attr->ia_size;
>> - dirtied |= CEPH_CAP_FILE_EXCL;
>> - ia_valid |= ATTR_MTIME;
>> - } else if ((issued & CEPH_CAP_FILE_SHARED) == 0 ||
>> - attr->ia_size != inode->i_size) {
>> + if ((issued & (CEPH_CAP_FILE_EXCL|CEPH_CAP_FILE_SHARED)) ||
>> + (attr->ia_size != inode->i_size)) {
>> req->r_args.setattr.size = cpu_to_le64(attr->ia_size);
>> req->r_args.setattr.old_size =
>> cpu_to_le64(inode->i_size);
>
> Hmm...this makes truncates more expensive when we have caps. I'd rather
> not do that if we can help it.
Yeah, as I mentioned in the tracker, there's indeed a performance impact
with this fix. That's what made me add the RFC in the subject ;-)
> What about instead having the client mimic a fsync when there is a
> rename across quota realms? If we can't tell that reliably then we could
> also just do an effective fsync ahead of any cross-directory rename?
Ok, thanks for the suggestion. That may actually work, although it will
make the rename more expensive of course. I'll test that tomorrow and
eventually follow-up with a patch.
Cheers,
--
Luis
