XFS has #fiemap extent intervals limitted in kernel， so if we do not use seek_data, seek_hole. It will lead to getting a wrong fiemap (absence of some extents) from a large object. It is actually not security before Jewel with enabling filestore_seek_data_hole. Regards Ning Yao 2016-09-29 10:27 GMT+08:00 Haomai Wang <haomai@xxxxxxxx>: > On Thu, Sep 29, 2016 at 10:25 AM, Haomai Wang <haomai@xxxxxxxx> wrote: >> On Thu, Sep 29, 2016 at 12:26 AM, Ning Yao <zay11022@xxxxxxxxx> wrote: >>> Hi, >>> >>> As lots of fiemap issues in XFS, fiemap is default disabled now, >>> especially in Hammer, before seek_data, seek_hole is added. >>> >>> But disabling fiemap feature will cause a small sparse object become a >>> large full object during PushOps, which may lead to notably data >>> in-balance between OSD, especially on the new added OSD during data >>> rebalance. With those full objects, some OSDs may simultaneously >>> becomes full. >> >> Until now, I don't know existing problem with fiemap enabled in >> hammer. Although we find it maybe problem when clone to a existing >> overlap data range, but it won't exists in real case. > > Hmm, I can't guarantee this... I only means if you want to have sparse > object, you can enable this. .... > >> >>> >>> Furthermore, currently, it is impossible to make the full objects >>> sparse again if we enable the fiemap feature in the future. >>> >>> So I think if any solutions to make a full object back to a sparse >>> object again? One of the idea is to check whether the content in the >>> object contains consecutive zero and punch zeros for those object >>> during deep-scrub, is that possible and reasonable? >> >> Obviously it's a complex thing more than we get. >> >>> >>> >>> >>> Regards >>> Ning Yao >>> -- >>> To unsubscribe from this list: send the line "unsubscribe ceph-devel" in >>> the body of a message to majordomo@xxxxxxxxxxxxxxx >>> More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe ceph-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
