Re: [PATCH] fs/nfsd: fix update of inode attrs in CB_GETATTR

[Jeff Layton <jlayton@kernel.org>]

On Mon, 2024-08-26 at 08:31 -0700, Dai Ngo wrote:
> 
> On 8/24/24 5:46 AM, Jeff Layton wrote:
> > Currently, we copy the mtime and ctime to the in-core inode and then
> > mark the inode dirty. This is fine for certain types of filesystems, but
> > not all. Some require a real setattr to properly change these values
> > (e.g. ceph or reexported NFS).
> > 
> > Fix this code to call notify_change() instead, which is the proper way
> > to effect a setattr. There is one problem though:
> > 
> > In this case, the client is holding a write delegation and has sent us
> > attributes to update our cache. We don't want to break the delegation
> > for this since that would defeat the purpose.
> 
> I think this won't happen with NFS since nfsd_breaker_owns_lease detects
> its own lease and won't break the delegation.
> 

I don't think that works here. In this case, we've gotten a GETATTR
request from a different client than the lease holder. So the breaker
in this case does _not_ own the lease.

> 
> >   Add a new ATTR_DELEG flag
> > that makes notify_change bypass the try_break_deleg call.
> > 
> > Fixes: c5967721e106 ("NFSD: handle GETATTR conflict with write delegation")
> > Signed-off-by: Jeff Layton <jlayton@kernel.org>
> > ---
> > One more CB_GETATTR fix. This one involves a little change at the VFS
> > layer to avoid breaking the delegation.
> > 
> > Christian, unless you have objections, this should probably go in
> > via Chuck's tree as this patch depends on a nfsd patch [1] that I sent
> > yesterday. An A-b or R-b would be welcome though.
> > 
> > [1]: https://lore.kernel.org/linux-nfs/20240823-nfsd-fixes-v1-1-fc99aa16f6a0@kernel.org/T/#u
> > ---
> >   fs/attr.c           |  9 ++++++---
> >   fs/nfsd/nfs4state.c | 18 +++++++++++++-----
> >   fs/nfsd/nfs4xdr.c   |  2 +-
> >   fs/nfsd/state.h     |  2 +-
> >   include/linux/fs.h  |  1 +
> >   5 files changed, 22 insertions(+), 10 deletions(-)
> > 
> > diff --git a/fs/attr.c b/fs/attr.c
> > index 960a310581eb..a40a2fb406f0 100644
> > --- a/fs/attr.c
> > +++ b/fs/attr.c
> > @@ -489,9 +489,12 @@ int notify_change(struct mnt_idmap *idmap, struct dentry *dentry,
> >   	error = security_inode_setattr(idmap, dentry, attr);
> >   	if (error)
> >   		return error;
> > -	error = try_break_deleg(inode, delegated_inode);
> > -	if (error)
> > -		return error;
> > +
> > +	if (!(ia_valid & ATTR_DELEG)) {
> > +		error = try_break_deleg(inode, delegated_inode);
> > +		if (error)
> > +			return error;
> > +	}
> >   
> >   	if (inode->i_op->setattr)
> >   		error = inode->i_op->setattr(idmap, dentry, attr);
> > diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
> > index dafff707e23a..e0e3d3ca0d45 100644
> > --- a/fs/nfsd/nfs4state.c
> > +++ b/fs/nfsd/nfs4state.c
> > @@ -8815,7 +8815,7 @@ nfsd4_get_writestateid(struct nfsd4_compound_state *cstate,
> >   /**
> >    * nfsd4_deleg_getattr_conflict - Recall if GETATTR causes conflict
> >    * @rqstp: RPC transaction context
> > - * @inode: file to be checked for a conflict
> > + * @dentry: dentry of inode to be checked for a conflict
> >    * @modified: return true if file was modified
> >    * @size: new size of file if modified is true
> >    *
> > @@ -8830,7 +8830,7 @@ nfsd4_get_writestateid(struct nfsd4_compound_state *cstate,
> >    * code is returned.
> >    */
> >   __be32
> > -nfsd4_deleg_getattr_conflict(struct svc_rqst *rqstp, struct inode *inode,
> > +nfsd4_deleg_getattr_conflict(struct svc_rqst *rqstp, struct dentry *dentry,
> >   				bool *modified, u64 *size)
> >   {
> >   	__be32 status;
> > @@ -8840,6 +8840,7 @@ nfsd4_deleg_getattr_conflict(struct svc_rqst *rqstp, struct inode *inode,
> >   	struct nfs4_delegation *dp;
> >   	struct iattr attrs;
> >   	struct nfs4_cb_fattr *ncf;
> > +	struct inode *inode = d_inode(dentry);
> >   
> >   	*modified = false;
> >   	ctx = locks_inode_context(inode);
> > @@ -8887,15 +8888,22 @@ nfsd4_deleg_getattr_conflict(struct svc_rqst *rqstp, struct inode *inode,
> >   					ncf->ncf_cur_fsize != ncf->ncf_cb_fsize))
> >   				ncf->ncf_file_modified = true;
> >   			if (ncf->ncf_file_modified) {
> > +				int err;
> > +
> >   				/*
> >   				 * Per section 10.4.3 of RFC 8881, the server would
> >   				 * not update the file's metadata with the client's
> >   				 * modified size
> >   				 */
> >   				attrs.ia_mtime = attrs.ia_ctime = current_time(inode);
> > -				attrs.ia_valid = ATTR_MTIME | ATTR_CTIME;
> > -				setattr_copy(&nop_mnt_idmap, inode, &attrs);
> > -				mark_inode_dirty(inode);
> > +				attrs.ia_valid = ATTR_MTIME | ATTR_CTIME | ATTR_DELEG;
> > +				inode_lock(inode);
> > +				err = notify_change(&nop_mnt_idmap, dentry, &attrs, NULL);
> > +				inode_unlock(inode);
> > +				if (err) {
> > +					nfs4_put_stid(&dp->dl_stid);
> > +					return nfserrno(err);
> > +				}
> >   				ncf->ncf_cur_fsize = ncf->ncf_cb_fsize;
> >   				*size = ncf->ncf_cur_fsize;
> >   				*modified = true;
> > diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
> > index 43ccf6119cf1..97f583777972 100644
> > --- a/fs/nfsd/nfs4xdr.c
> > +++ b/fs/nfsd/nfs4xdr.c
> > @@ -3565,7 +3565,7 @@ nfsd4_encode_fattr4(struct svc_rqst *rqstp, struct xdr_stream *xdr,
> >   	}
> >   	args.size = 0;
> >   	if (attrmask[0] & (FATTR4_WORD0_CHANGE | FATTR4_WORD0_SIZE)) {
> > -		status = nfsd4_deleg_getattr_conflict(rqstp, d_inode(dentry),
> > +		status = nfsd4_deleg_getattr_conflict(rqstp, dentry,
> >   					&file_modified, &size);
> >   		if (status)
> >   			goto out;
> > diff --git a/fs/nfsd/state.h b/fs/nfsd/state.h
> > index ffc217099d19..ec4559ecd193 100644
> > --- a/fs/nfsd/state.h
> > +++ b/fs/nfsd/state.h
> > @@ -781,5 +781,5 @@ static inline bool try_to_expire_client(struct nfs4_client *clp)
> >   }
> >   
> >   extern __be32 nfsd4_deleg_getattr_conflict(struct svc_rqst *rqstp,
> > -		struct inode *inode, bool *file_modified, u64 *size);
> > +		struct dentry *dentry, bool *file_modified, u64 *size);
> >   #endif   /* NFSD4_STATE_H */
> > diff --git a/include/linux/fs.h b/include/linux/fs.h
> > index 0283cf366c2a..3fe289c74869 100644
> > --- a/include/linux/fs.h
> > +++ b/include/linux/fs.h
> > @@ -208,6 +208,7 @@ typedef int (dio_iodone_t)(struct kiocb *iocb, loff_t offset,
> >   #define ATTR_OPEN	(1 << 15) /* Truncating from open(O_TRUNC) */
> >   #define ATTR_TIMES_SET	(1 << 16)
> >   #define ATTR_TOUCH	(1 << 17)
> > +#define ATTR_DELEG	(1 << 18) /* Delegated attrs (don't break) */
> >   
> >   /*
> >    * Whiteout is represented by a char device.  The following constants define the
> > 
> > ---
> > base-commit: a204501e1743d695ca2930ed25a2be9f8ced96d3
> > change-id: 20240823-nfsd-fixes-61f0c785d125
> > 
> > Best regards,

-- 
Jeff Layton <jlayton@kernel.org>