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From:   Trond Myklebust <trondmy@gmail.com>
To:     "J. Bruce Fields" <bfields@redhat.com>
Cc:     linux-nfs@vger.kernel.org
Subject: [PATCH 9/9] nfsd: Ensure sampling of the write verifier is atomic with the write
Date:   Mon,  6 Jan 2020 13:40:37 -0500
Message-Id: <20200106184037.563557-10-trond.myklebust@hammerspace.com>
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When doing an unstable write, we need to ensure that we sample the
write verifier before releasing the lock, and allowing a commit to
the same file to proceed.

Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
---
 fs/nfsd/nfs3proc.c |  2 +-
 fs/nfsd/nfs3xdr.c  |  8 ++------
 fs/nfsd/nfs4proc.c |  4 ++--
 fs/nfsd/nfsproc.c  |  2 +-
 fs/nfsd/vfs.c      | 12 +++++++++---
 fs/nfsd/vfs.h      |  5 +++--
 fs/nfsd/xdr3.h     |  1 +
 7 files changed, 19 insertions(+), 15 deletions(-)

diff --git a/fs/nfsd/nfs3proc.c b/fs/nfsd/nfs3proc.c
index ffdc592868a6..288bc76b4574 100644
--- a/fs/nfsd/nfs3proc.c
+++ b/fs/nfsd/nfs3proc.c
@@ -203,7 +203,7 @@ nfsd3_proc_write(struct svc_rqst *rqstp)
 		RETURN_STATUS(nfserr_io);
 	nfserr = nfsd_write(rqstp, &resp->fh, argp->offset,
 			    rqstp->rq_vec, nvecs, &cnt,
-			    resp->committed);
+			    resp->committed, resp->verf);
 	resp->count = cnt;
 	RETURN_STATUS(nfserr);
 }
diff --git a/fs/nfsd/nfs3xdr.c b/fs/nfsd/nfs3xdr.c
index 4aaa85f42da2..e1f6c65049b3 100644
--- a/fs/nfsd/nfs3xdr.c
+++ b/fs/nfsd/nfs3xdr.c
@@ -751,17 +751,13 @@ int
 nfs3svc_encode_writeres(struct svc_rqst *rqstp, __be32 *p)
 {
 	struct nfsd3_writeres *resp = rqstp->rq_resp;
-	struct nfsd_net *nn = net_generic(SVC_NET(rqstp), nfsd_net_id);
-	__be32 verf[2];
 
 	p = encode_wcc_data(rqstp, p, &resp->fh);
 	if (resp->status == 0) {
 		*p++ = htonl(resp->count);
 		*p++ = htonl(resp->committed);
-		/* unique identifier, y2038 overflow can be ignored */
-		nfsd_copy_boot_verifier(verf, nn);
-		*p++ = verf[0];
-		*p++ = verf[1];
+		*p++ = resp->verf[0];
+		*p++ = resp->verf[1];
 	}
 	return xdr_ressize_check(rqstp, p);
 }
diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c
index c24a4f96c973..af2cb7dcb74c 100644
--- a/fs/nfsd/nfs4proc.c
+++ b/fs/nfsd/nfs4proc.c
@@ -1006,7 +1006,6 @@ nfsd4_write(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
 	}
 
 	write->wr_how_written = write->wr_stable_how;
-	gen_boot_verifier(&write->wr_verifier, SVC_NET(rqstp));
 
 	nvecs = svc_fill_write_vector(rqstp, write->wr_pagelist,
 				      &write->wr_head, write->wr_buflen);
@@ -1014,7 +1013,8 @@ nfsd4_write(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
 
 	status = nfsd_vfs_write(rqstp, &cstate->current_fh, nf,
 				write->wr_offset, rqstp->rq_vec, nvecs, &cnt,
-				write->wr_how_written);
+				write->wr_how_written,
+				(__be32 *)write->wr_verifier.data);
 	nfsd_file_put(nf);
 
 	write->wr_bytes_written = cnt;
diff --git a/fs/nfsd/nfsproc.c b/fs/nfsd/nfsproc.c
index c83ddac22f38..bb1fbb67f697 100644
--- a/fs/nfsd/nfsproc.c
+++ b/fs/nfsd/nfsproc.c
@@ -226,7 +226,7 @@ nfsd_proc_write(struct svc_rqst *rqstp)
 		return nfserr_io;
 	nfserr = nfsd_write(rqstp, fh_copy(&resp->fh, &argp->fh),
 			    argp->offset, rqstp->rq_vec, nvecs,
-			    &cnt, NFS_DATA_SYNC);
+			    &cnt, NFS_DATA_SYNC, NULL);
 	return nfsd_return_attrs(nfserr, resp);
 }
 
diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
index 1d69a1e78b03..8beed0fbf93a 100644
--- a/fs/nfsd/vfs.c
+++ b/fs/nfsd/vfs.c
@@ -962,7 +962,8 @@ static int wait_for_concurrent_writes(struct file *file)
 __be32
 nfsd_vfs_write(struct svc_rqst *rqstp, struct svc_fh *fhp, struct nfsd_file *nf,
 				loff_t offset, struct kvec *vec, int vlen,
-				unsigned long *cnt, int stable)
+				unsigned long *cnt, int stable,
+				__be32 *verf)
 {
 	struct file		*file = nf->nf_file;
 	struct svc_export	*exp;
@@ -1004,6 +1005,10 @@ nfsd_vfs_write(struct svc_rqst *rqstp, struct svc_fh *fhp, struct nfsd_file *nf,
 		up_write(&nf->nf_rwsem);
 	} else {
 		down_read(&nf->nf_rwsem);
+		if (verf)
+			nfsd_copy_boot_verifier(verf,
+					net_generic(SVC_NET(rqstp),
+					nfsd_net_id));
 		host_err = vfs_iter_write(file, &iter, &pos, flags);
 		up_read(&nf->nf_rwsem);
 	}
@@ -1074,7 +1079,8 @@ __be32 nfsd_read(struct svc_rqst *rqstp, struct svc_fh *fhp,
  */
 __be32
 nfsd_write(struct svc_rqst *rqstp, struct svc_fh *fhp, loff_t offset,
-	   struct kvec *vec, int vlen, unsigned long *cnt, int stable)
+	   struct kvec *vec, int vlen, unsigned long *cnt, int stable,
+	   __be32 *verf)
 {
 	struct nfsd_file *nf;
 	__be32 err;
@@ -1086,7 +1092,7 @@ nfsd_write(struct svc_rqst *rqstp, struct svc_fh *fhp, loff_t offset,
 		goto out;
 
 	err = nfsd_vfs_write(rqstp, fhp, nf, offset, vec,
-			vlen, cnt, stable);
+			vlen, cnt, stable, verf);
 	nfsd_file_put(nf);
 out:
 	trace_nfsd_write_done(rqstp, fhp, offset, *cnt);
diff --git a/fs/nfsd/vfs.h b/fs/nfsd/vfs.h
index 29e30688ccfb..11a112617e91 100644
--- a/fs/nfsd/vfs.h
+++ b/fs/nfsd/vfs.h
@@ -94,11 +94,12 @@ __be32 		nfsd_read(struct svc_rqst *, struct svc_fh *,
 				loff_t, struct kvec *, int, unsigned long *,
 				u32 *eof);
 __be32 		nfsd_write(struct svc_rqst *, struct svc_fh *, loff_t,
-				struct kvec *, int, unsigned long *, int);
+				struct kvec *, int, unsigned long *,
+				int stable, __be32 *verf);
 __be32		nfsd_vfs_write(struct svc_rqst *rqstp, struct svc_fh *fhp,
 				struct nfsd_file *nf, loff_t offset,
 				struct kvec *vec, int vlen, unsigned long *cnt,
-				int stable);
+				int stable, __be32 *verf);
 __be32		nfsd_readlink(struct svc_rqst *, struct svc_fh *,
 				char *, int *);
 __be32		nfsd_symlink(struct svc_rqst *, struct svc_fh *,
diff --git a/fs/nfsd/xdr3.h b/fs/nfsd/xdr3.h
index 21fc1f14bcad..fed959a809e8 100644
--- a/fs/nfsd/xdr3.h
+++ b/fs/nfsd/xdr3.h
@@ -159,6 +159,7 @@ struct nfsd3_writeres {
 	struct svc_fh		fh;
 	unsigned long		count;
 	int			committed;
+	__be32			verf[2];
 };
 
 struct nfsd3_renameres {
-- 
2.24.1