Messages in this thread | | | Date | Mon, 3 Oct 2022 21:12:46 -0700 | Subject | Re: [PATCH] xfs: fail dax mount if reflink is enabled on a partition | From | Gotou, Yasunori/五島 康文 <> |
| |
On 2022/10/03 17:12, Darrick J. Wong wrote: > On Fri, Sep 30, 2022 at 09:56:41AM +0900, Gotou, Yasunori/五島 康文 wrote: >> Hello everyone, >> >> On 2022/09/20 11:38, Yang, Xiao/杨 晓 wrote: >>> Hi Darrick, Brian and Christoph >>> >>> Ping. I hope to get your feedback. >>> >>> 1) I have confirmed that the following patch set did not change the test >>> result of generic/470 with thin-volume. Besides, I didn't see any >>> failure when running generic/470 based on normal PMEM device instaed of >>> thin-volume. >>> https://lore.kernel.org/linux-xfs/20211129102203.2243509-1-hch@lst.de/ >>> >>> 2) I can reproduce the failure of generic/482 without thin-volume. >>> >>> 3) Is it necessary to make thin-volume support DAX. Is there any use >>> case for the requirement? >> >> >> Though I asked other place(*), I really want to know the usecase of >> dm-thin-volume with DAX and reflink. >> >> >> In my understanding, dm-thin-volume seems to provide similar feature like >> reflink of xfs. Both feature provide COW update to reduce usage of >> its region, and snapshot feature, right? >> >> I found that docker seems to select one of them (or other feature which >> supports COW). Then user don't need to use thin-volume and reflink at same >> time. >> >> Database which uses FS-DAX may want to use snapshot for its data of FS-DAX, >> its user seems to be satisfied with reflink or thin-volume. >> >> So I could not find on what use-case user would like to use dm-thin-volume >> and reflink at same time. >> >> The only possibility is that the user has mistakenly configured dm-thinpool >> and reflink to be used at the same time, but if that is the case, it seems >> to be better for the user to disable one or the other. >> >> I really wander why dm-thin-volume must be used with reflik and FS-DAX. > > There isn't a hard requirement between fsdax and dm-thinp. The /test/ > needs dm-logwrites to check that write page faults on a MAP_SYNC > mmapping are persisted directly to disk. dm-logwrites requires a fast > way to zero an entire device for correct operation of the replay step, > and thinp is the only way to guarantee that.
Thank you for your answer. But I still feel something is strange. Though dm-thinp may be good way to execute the test correctly, I suppose it seems to be likely a kind of workaround to pass the test, it may not be really required for actual users.
Could you tell me why passing test by workaround is so necessary?
Thanks,
> > --D > >> If my understanding is something wrong, please correct me. >> >> (*)https://lore.kernel.org/all/TYWPR01MB1008258F474CA2295B4CD3D9B90549@TYWPR01MB10082.jpnprd01.prod.outlook.com/
| |