On Wed, 2023-08-02 at 13:15 -0700, dai.ngo@xxxxxxxxxx wrote: > On 8/2/23 11:15 AM, Jeff Layton wrote: > > On Wed, 2023-08-02 at 09:29 -0700, dai.ngo@xxxxxxxxxx wrote: > > > On 8/1/23 6:33 AM, Jeff Layton wrote: > > > > I noticed that xfstests generic/001 was failing against linux-next nfsd. > > > > > > > > The client would request a OPEN4_SHARE_ACCESS_WRITE open, and the server > > > > would hand out a write delegation. The client would then try to use that > > > > write delegation as the source stateid in a COPY > > > not sure why the client opens the source file of a COPY operation with > > > OPEN4_SHARE_ACCESS_WRITE? > > > > > It doesn't. The original open is to write the data for the file being > > copied. It then opens the file again for READ, but since it has a write > > delegation, it doesn't need to talk to the server at all -- it can just > > use that stateid for later operations. > > > > > > or CLONE operation, and > > > > the server would respond with NFS4ERR_STALE. > > > If the server does not allow client to use write delegation for the > > > READ, should the correct error return be NFS4ERR_OPENMODE? > > > > > The server must allow the client to use a write delegation for read > > operations. It's required by the spec, AFAIU. > > > > The error in this case was just bogus. The vfs copy routine would return > > -EBADF since the file didn't have FMODE_READ, and the nfs server would > > translate that into NFS4ERR_STALE. > > > > Probably there is a better v4 error code that we could translate EBADF > > to, but with this patch it shouldn't be a problem any longer. > > > > > > The problem is that the struct file associated with the delegation does > > > > not necessarily have read permissions. It's handing out a write > > > > delegation on what is effectively an O_WRONLY open. RFC 8881 states: > > > > > > > > "An OPEN_DELEGATE_WRITE delegation allows the client to handle, on its > > > > own, all opens." > > > > > > > > Given that the client didn't request any read permissions, and that nfsd > > > > didn't check for any, it seems wrong to give out a write delegation. > > > > > > > > Only hand out a write delegation if we have a O_RDWR descriptor > > > > available. If it fails to find an appropriate write descriptor, go > > > > ahead and try for a read delegation if NFS4_SHARE_ACCESS_READ was > > > > requested. > > > > > > > > This fixes xfstest generic/001. > > > > > > > > Closes: https://bugzilla.linux-nfs.org/show_bug.cgi?id=412 > > > > Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx> > > > > --- > > > > Changes in v2: > > > > - Rework the logic when finding struct file for the delegation. The > > > > earlier patch might still have attached a O_WRONLY file to the deleg > > > > in some cases, and could still have handed out a write delegation on > > > > an O_WRONLY OPEN request in some cases. > > > > --- > > > > fs/nfsd/nfs4state.c | 29 ++++++++++++++++++----------- > > > > 1 file changed, 18 insertions(+), 11 deletions(-) > > > > > > > > diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c > > > > index ef7118ebee00..e79d82fd05e7 100644 > > > > --- a/fs/nfsd/nfs4state.c > > > > +++ b/fs/nfsd/nfs4state.c > > > > @@ -5449,7 +5449,7 @@ nfs4_set_delegation(struct nfsd4_open *open, struct nfs4_ol_stateid *stp, > > > > struct nfs4_file *fp = stp->st_stid.sc_file; > > > > struct nfs4_clnt_odstate *odstate = stp->st_clnt_odstate; > > > > struct nfs4_delegation *dp; > > > > - struct nfsd_file *nf; > > > > + struct nfsd_file *nf = NULL; > > > > struct file_lock *fl; > > > > u32 dl_type; > > > > > > > > @@ -5461,21 +5461,28 @@ nfs4_set_delegation(struct nfsd4_open *open, struct nfs4_ol_stateid *stp, > > > > if (fp->fi_had_conflict) > > > > return ERR_PTR(-EAGAIN); > > > > > > > > - if (open->op_share_access & NFS4_SHARE_ACCESS_WRITE) { > > > > - nf = find_writeable_file(fp); > > > > + /* > > > > + * Try for a write delegation first. We need an O_RDWR file > > > > + * since a write delegation allows the client to perform any open > > > > + * from its cache. > > > > + */ > > > > + if ((open->op_share_access & NFS4_SHARE_ACCESS_BOTH) == NFS4_SHARE_ACCESS_BOTH) { > > > > + nf = nfsd_file_get(fp->fi_fds[O_RDWR]); > > > > dl_type = NFS4_OPEN_DELEGATE_WRITE; > > > > - } else { > > > Does this mean OPEN4_SHARE_ACCESS_WRITE do not get a write delegation? > > > It does not seem right. > > > > > > -Dai > > > > > Why? Per RFC 8881: > > > > "An OPEN_DELEGATE_WRITE delegation allows the client to handle, on its > > own, all opens." > > > > All opens. That includes read opens. > > > > An OPEN4_SHARE_ACCESS_WRITE open will succeed on a file to which the > > user has no read permissions. Therefore, we can't grant a write > > delegation since can't guarantee that the user is allowed to do that. > > If the server grants the write delegation on an OPEN with > OPEN4_SHARE_ACCESS_WRITE on the file with WR-only access mode then > why can't the server checks and denies the subsequent READ? > > Per RFC 8881, section 9.1.2: > > For delegation stateids, the access mode is based on the type of > delegation. > > When a READ, WRITE, or SETATTR (that specifies the size attribute) > operation is done, the operation is subject to checking against the > access mode to verify that the operation is appropriate given the > stateid with which the operation is associated. > > In the case of WRITE-type operations (i.e., WRITEs and SETATTRs that > set size), the server MUST verify that the access mode allows writing > and MUST return an NFS4ERR_OPENMODE error if it does not. In the case > of READ, the server may perform the corresponding check on the access > mode, or it may choose to allow READ on OPENs for OPEN4_SHARE_ACCESS_WRITE, > to accommodate clients whose WRITE implementation may unavoidably do > reads (e.g., due to buffer cache constraints). However, even if READs > are allowed in these circumstances, the server MUST still check for > locks that conflict with the READ (e.g., another OPEN specified > OPEN4_SHARE_DENY_READ or OPEN4_SHARE_DENY_BOTH). Note that a server > that does enforce the access mode check on READs need not explicitly > check for conflicting share reservations since the existence of OPEN > for OPEN4_SHARE_ACCESS_READ guarantees that no conflicting share > reservation can exist. > > FWIW, The Solaris server grants write delegation on OPEN with > OPEN4_SHARE_ACCESS_WRITE on file with access mode either RW or > WR-only. Maybe this is a bug? or the spec is not clear? > I don't think that's necessarily a bug. It's not that the spec demands that we only hand out delegations on BOTH opens. This is more of a quirk of the Linux implementation. Linux' write delegations require an open O_RDWR file descriptor because we may be called upon to do a read on its behalf. Technically, we could probably just have it check for OPEN4_SHARE_ACCESS_WRITE, but in the case where READ isn't also set, then you're unlikely to get a delegation. Either the O_RDWR descriptor will be NULL, or there are other, conflicting opens already present. Solaris may have a completely different design that doesn't require this. I haven't looked at its code to know. > It'd would be interesting to know how ONTAP server behaves in > this scenario. > Indeed. Most likely it behaves more like Solaris does, but it'd nice to know. > > > > > > > > > + } > > > > + > > > > + /* > > > > + * If the file is being opened O_RDONLY or we couldn't get a O_RDWR > > > > + * file for some reason, then try for a read deleg instead. > > > > + */ > > > > + if (!nf && (open->op_share_access & NFS4_SHARE_ACCESS_READ)) { > > > > nf = find_readable_file(fp); > > > > dl_type = NFS4_OPEN_DELEGATE_READ; > > > > } > > > > - if (!nf) { > > > > - /* > > > > - * We probably could attempt another open and get a read > > > > - * delegation, but for now, don't bother until the > > > > - * client actually sends us one. > > > > - */ > > > > + > > > > + if (!nf) > > > > return ERR_PTR(-EAGAIN); > > > > - } > > > > + > > > > spin_lock(&state_lock); > > > > spin_lock(&fp->fi_lock); > > > > if (nfs4_delegation_exists(clp, fp)) > > > > > > > > --- > > > > base-commit: a734662572708cf062e974f659ae50c24fc1ad17 > > > > change-id: 20230731-wdeleg-bbdb6b25a3c6 > > > > > > > > Best regards, -- Jeff Layton <jlayton@xxxxxxxxxx>
