[PATCH v2] NFSD: Disallow layoutget during grace period

[Sergey Bashirov <sergeybashirov@gmail.com>]

When the block/scsi layout server is recovering from a reboot and is in a
grace period, any operation that may result in deletion or reallocation of
block extents should not be allowed. See RFC 8881, section 18.43.3.

If multiple clients write data to the same file, rebooting the server
during writing can result in the file corruption. Observed this behavior
while testing pNFS block volume setup.

Co-developed-by: Konstantin Evtushenko <koevtushenko@yandex.com>
Signed-off-by: Konstantin Evtushenko <koevtushenko@yandex.com>
Signed-off-by: Sergey Bashirov <sergeybashirov@gmail.com>
---
Changes in v2:
 - Push down the check to layout driver level

 fs/nfsd/blocklayout.c    | 8 +++++++-
 fs/nfsd/flexfilelayout.c | 2 +-
 fs/nfsd/nfs4proc.c       | 3 ++-
 fs/nfsd/pnfs.h           | 2 +-
 4 files changed, 11 insertions(+), 4 deletions(-)

diff --git a/fs/nfsd/blocklayout.c b/fs/nfsd/blocklayout.c
index 0822d8a119c6..1fbc5bbde07f 100644
--- a/fs/nfsd/blocklayout.c
+++ b/fs/nfsd/blocklayout.c
@@ -19,7 +19,7 @@
 
 static __be32
 nfsd4_block_proc_layoutget(struct inode *inode, const struct svc_fh *fhp,
-		struct nfsd4_layoutget *args)
+		struct nfsd4_layoutget *args, bool in_grace)
 {
 	struct nfsd4_layout_seg *seg = &args->lg_seg;
 	struct super_block *sb = inode->i_sb;
@@ -34,6 +34,9 @@ nfsd4_block_proc_layoutget(struct inode *inode, const struct svc_fh *fhp,
 		goto out_layoutunavailable;
 	}
 
+	if (in_grace)
+		goto out_grace;
+
 	/*
 	 * Some clients barf on non-zero block numbers for NONE or INVALID
 	 * layouts, so make sure to zero the whole structure.
@@ -111,6 +114,9 @@ nfsd4_block_proc_layoutget(struct inode *inode, const struct svc_fh *fhp,
 out_layoutunavailable:
 	seg->length = 0;
 	return nfserr_layoutunavailable;
+out_grace:
+	seg->length = 0;
+	return nfserr_grace;
 }
 
 static __be32
diff --git a/fs/nfsd/flexfilelayout.c b/fs/nfsd/flexfilelayout.c
index 3ca5304440ff..274a1e9bb596 100644
--- a/fs/nfsd/flexfilelayout.c
+++ b/fs/nfsd/flexfilelayout.c
@@ -21,7 +21,7 @@
 
 static __be32
 nfsd4_ff_proc_layoutget(struct inode *inode, const struct svc_fh *fhp,
-		struct nfsd4_layoutget *args)
+		struct nfsd4_layoutget *args, bool in_grace)
 {
 	struct nfsd4_layout_seg *seg = &args->lg_seg;
 	u32 device_generation = 0;
diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c
index d7c58aa64f06..5d1d343a4e23 100644
--- a/fs/nfsd/nfs4proc.c
+++ b/fs/nfsd/nfs4proc.c
@@ -2435,6 +2435,7 @@ static __be32
 nfsd4_layoutget(struct svc_rqst *rqstp,
 		struct nfsd4_compound_state *cstate, union nfsd4_op_u *u)
 {
+	struct net *net = SVC_NET(rqstp);
 	struct nfsd4_layoutget *lgp = &u->layoutget;
 	struct svc_fh *current_fh = &cstate->current_fh;
 	const struct nfsd4_layout_ops *ops;
@@ -2498,7 +2499,7 @@ nfsd4_layoutget(struct svc_rqst *rqstp,
 		goto out_put_stid;
 
 	nfserr = ops->proc_layoutget(d_inode(current_fh->fh_dentry),
-				     current_fh, lgp);
+				     current_fh, lgp, locks_in_grace(net));
 	if (nfserr)
 		goto out_put_stid;
 
diff --git a/fs/nfsd/pnfs.h b/fs/nfsd/pnfs.h
index dfd411d1f363..61c2528ef077 100644
--- a/fs/nfsd/pnfs.h
+++ b/fs/nfsd/pnfs.h
@@ -30,7 +30,7 @@ struct nfsd4_layout_ops {
 			const struct nfsd4_getdeviceinfo *gdevp);
 
 	__be32 (*proc_layoutget)(struct inode *, const struct svc_fh *fhp,
-			struct nfsd4_layoutget *lgp);
+			struct nfsd4_layoutget *lgp, bool in_grace);
 	__be32 (*encode_layoutget)(struct xdr_stream *xdr,
 			const struct nfsd4_layoutget *lgp);
 
-- 
2.43.0