Hi Darrick, On Thu, 2019-05-30 at 08:26 -0700, Darrick J. Wong wrote: > On Thu, May 30, 2019 at 05:41:47PM +0800, Murphy Zhou wrote: > > NFSv4.2 could pass _require_scratch_dedupe, since the test offset > > and > > size are aligned, while generic/517 is performing unaligned dedupe. > > NFS does not support unaligned dedupe now, returns EINVAL. > > > > Signed-off-by: Murphy Zhou <xzhou@xxxxxxxxxx> > > --- > > tests/generic/517 | 1 + > > 1 file changed, 1 insertion(+) > > > > diff --git a/tests/generic/517 b/tests/generic/517 > > index 601bb24e..23665782 100755 > > --- a/tests/generic/517 > > +++ b/tests/generic/517 > > @@ -30,6 +30,7 @@ _cleanup() > > _supported_fs generic > > _supported_os Linux > > _require_scratch_dedupe > > +$FSTYP == "nfs" && _notrun "NFS can't handle unaligned > > deduplication" > > Uh... NFS supports dedupe?? > > Let's see, we pass REMAP_FILE_DEDUP to nfs42_remap_file_range via > @remap_flags. That function checks remap_flags but never touches it > again. It's not passed to nfs42_proc_clone, which (AFAICT) means > that > the nfs client sends a CLONE request to the server on behalf of a > FS_IOC_EXTENT_SAME ioctl. That seems suspicious to me... > > The nfs client also doesn't lock and compare the file contents itself > (the server should be doing that anyway, right?) which means that > dedupe > doesn't fail if the file contents are different? > > Oh, I see... Xiaoli Feng turned on dedupe for cifs (b073a08016a10f0) > and > nfs (ce96e888fe48e) even though (the last I heard) neither protocol > supports dedupe and now will corrupt data in doing so. > > Let's hold off on this for now while I go email Anna & Steve about > whether or not nfs and cifs support dedupe. > What is the VFS requirement for dedup support? According to the RFC7862 spec for CLONE: "If SAVED_FH and CURRENT_FH refer to the same file and the source and target ranges overlap, the operation MUST fail with NFS4ERR_INVAL." So clearly we may not support dedup if there is a requirement that we be able to clone between overlapping ranges on the same file. However I can find no restriction on using CLONE for non-overlapping ranges. -- Trond Myklebust Linux NFS client maintainer, Hammerspace trond.myklebust@xxxxxxxxxxxxxxx
