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

[Dai Ngo <dai.ngo@xxxxxxxxxx>]

On 8/26/24 9:13 AM, Jeff Layton wrote:
> 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.

Oh yes, the lease breaker in nfsd_breaker_owns_lease is the client
that sends the GETATTR so it is not the same as the lease's owner.

Thanks,
-Dai

> > >    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@xxxxxxxxxx>
> > > ---
> > > 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@xxxxxxxxxx/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,