NFS: Add support for fallocate(FALLOC_FL_ZERO_RANGE)

This implements a suggestion from Trond that we can mimic
FALLOC_FL_ZERO_RANGE by sending a compound that first does a DEALLOCATE
to punch a hole in a file, and then an ALLOCATE to fill the hole with
zeroes. There might technically be a race here, but once the DEALLOCATE
finishes any reads from the region would return zeroes anyway, so I
don't expect it to cause problems.

Signed-off-by: Anna Schumaker <[email protected]>

Author: Anna Schumaker

fs/nfs/nfs42.h

@@ -21,6 +21,7 @@ int nfs42_proc_allocate(struct file *, loff_t, loff_t);
 ssize_t nfs42_proc_copy(struct file *, loff_t, struct file *, loff_t, size_t,
 			struct nl4_server *, nfs4_stateid *, bool);
 int nfs42_proc_deallocate(struct file *, loff_t, loff_t);
+int nfs42_proc_zero_range(struct file *, loff_t, loff_t);
 loff_t nfs42_proc_llseek(struct file *, loff_t, int);
 int nfs42_proc_layoutstats_generic(struct nfs_server *,
 				   struct nfs42_layoutstat_data *);

fs/nfs/nfs42proc.c

@@ -146,7 +146,8 @@ int nfs42_proc_allocate(struct file *filep, loff_t offset, loff_t len)
 
 	err = nfs42_proc_fallocate(&msg, filep, offset, len);
 	if (err == -EOPNOTSUPP)
-		NFS_SERVER(inode)->caps &= ~NFS_CAP_ALLOCATE;
+		NFS_SERVER(inode)->caps &= ~(NFS_CAP_ALLOCATE |
+					     NFS_CAP_ZERO_RANGE);
 
 	inode_unlock(inode);
 	return err;
@@ -169,7 +170,31 @@ int nfs42_proc_deallocate(struct file *filep, loff_t offset, loff_t len)
 	if (err == 0)
 		truncate_pagecache_range(inode, offset, (offset + len) -1);
 	if (err == -EOPNOTSUPP)
-		NFS_SERVER(inode)->caps &= ~NFS_CAP_DEALLOCATE;
+		NFS_SERVER(inode)->caps &= ~(NFS_CAP_DEALLOCATE |
+					     NFS_CAP_ZERO_RANGE);
+
+	inode_unlock(inode);
+	return err;
+}
+
+int nfs42_proc_zero_range(struct file *filep, loff_t offset, loff_t len)
+{
+	struct rpc_message msg = {
+		.rpc_proc = &nfs4_procedures[NFSPROC4_CLNT_ZERO_RANGE],
+	};
+	struct inode *inode = file_inode(filep);
+	int err;
+
+	if (!nfs_server_capable(inode, NFS_CAP_ZERO_RANGE))
+		return -EOPNOTSUPP;
+
+	inode_lock(inode);
+
+	err = nfs42_proc_fallocate(&msg, filep, offset, len);
+	if (err == 0)
+		truncate_pagecache_range(inode, offset, (offset + len) -1);
+	if (err == -EOPNOTSUPP)
+		NFS_SERVER(inode)->caps &= ~NFS_CAP_ZERO_RANGE;
 
 	inode_unlock(inode);
 	return err;

fs/nfs/nfs42xdr.c

@@ -174,6 +174,18 @@
 					 decode_putfh_maxsz + \
 					 decode_deallocate_maxsz + \
 					 decode_getattr_maxsz)
+#define NFS4_enc_zero_range_sz		(compound_encode_hdr_maxsz + \
+					 encode_sequence_maxsz + \
+					 encode_putfh_maxsz + \
+					 encode_deallocate_maxsz + \
+					 encode_allocate_maxsz + \
+					 encode_getattr_maxsz)
+#define NFS4_dec_zero_range_sz		(compound_decode_hdr_maxsz + \
+					 decode_sequence_maxsz + \
+					 decode_putfh_maxsz + \
+					 decode_deallocate_maxsz + \
+					 decode_allocate_maxsz + \
+					 decode_getattr_maxsz)
 #define NFS4_enc_read_plus_sz		(compound_encode_hdr_maxsz + \
 					 encode_sequence_maxsz + \
 					 encode_putfh_maxsz + \
@@ -648,6 +660,27 @@ static void nfs4_xdr_enc_deallocate(struct rpc_rqst *req,
 	encode_nops(&hdr);
 }
 
+/*
+ * Encode ZERO_RANGE request
+ */
+static void nfs4_xdr_enc_zero_range(struct rpc_rqst *req,
+				    struct xdr_stream *xdr,
+				    const void *data)
+{
+	const struct nfs42_falloc_args *args = data;
+	struct compound_hdr hdr = {
+		.minorversion = nfs4_xdr_minorversion(&args->seq_args),
+	};
+
+	encode_compound_hdr(xdr, req, &hdr);
+	encode_sequence(xdr, &args->seq_args, &hdr);
+	encode_putfh(xdr, args->falloc_fh, &hdr);
+	encode_deallocate(xdr, args, &hdr);
+	encode_allocate(xdr, args, &hdr);
+	encode_getfattr(xdr, args->falloc_bitmask, &hdr);
+	encode_nops(&hdr);
+}
+
 /*
  * Encode READ_PLUS request
  */
@@ -1510,6 +1543,37 @@ static int nfs4_xdr_dec_deallocate(struct rpc_rqst *rqstp,
 	return status;
 }
 
+/*
+ * Decode ZERO_RANGE request
+ */
+static int nfs4_xdr_dec_zero_range(struct rpc_rqst *rqstp,
+				   struct xdr_stream *xdr,
+				   void *data)
+{
+	struct nfs42_falloc_res *res = data;
+	struct compound_hdr hdr;
+	int status;
+
+	status = decode_compound_hdr(xdr, &hdr);
+	if (status)
+		goto out;
+	status = decode_sequence(xdr, &res->seq_res, rqstp);
+	if (status)
+		goto out;
+	status = decode_putfh(xdr);
+	if (status)
+		goto out;
+	status = decode_deallocate(xdr, res);
+	if (status)
+		goto out;
+	status = decode_allocate(xdr, res);
+	if (status)
+		goto out;
+	decode_getfattr(xdr, res->falloc_fattr, res->falloc_server);
+out:
+	return status;
+}
+
 /*
  * Decode READ_PLUS request
  */

fs/nfs/nfs4file.c

@@ -225,15 +225,23 @@ static long nfs42_fallocate(struct file *filep, int mode, loff_t offset, loff_t
 	if (!S_ISREG(inode->i_mode))
 		return -EOPNOTSUPP;
 
-	if ((mode != 0) && (mode != (FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE)))
+	switch (mode) {
+	case 0:
+	case FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE:
+	case FALLOC_FL_ZERO_RANGE:
+		break;
+	default:
 		return -EOPNOTSUPP;
+	}
 
 	ret = inode_newsize_ok(inode, offset + len);
 	if (ret < 0)
 		return ret;
 
 	if (mode & FALLOC_FL_PUNCH_HOLE)
 		return nfs42_proc_deallocate(filep, offset, len);
+	else if (mode & FALLOC_FL_ZERO_RANGE)
+		return nfs42_proc_zero_range(filep, offset ,len);
 	return nfs42_proc_allocate(filep, offset, len);
 }
 

fs/nfs/nfs4proc.c

@@ -10822,6 +10822,7 @@ static const struct nfs4_minor_version_ops nfs_v4_2_minor_ops = {
 		| NFS_CAP_OFFLOAD_CANCEL
 		| NFS_CAP_COPY_NOTIFY
 		| NFS_CAP_DEALLOCATE
+		| NFS_CAP_ZERO_RANGE
 		| NFS_CAP_SEEK
 		| NFS_CAP_LAYOUTSTATS
 		| NFS_CAP_CLONE

fs/nfs/nfs4xdr.c

@@ -7711,6 +7711,7 @@ const struct rpc_procinfo nfs4_procedures[] = {
 	PROC42(LISTXATTRS,	enc_listxattrs,		dec_listxattrs),
 	PROC42(REMOVEXATTR,	enc_removexattr,	dec_removexattr),
 	PROC42(READ_PLUS,	enc_read_plus,		dec_read_plus),
+	PROC42(ZERO_RANGE,	enc_zero_range,		dec_zero_range),
 };
 
 static unsigned int nfs_version4_counts[ARRAY_SIZE(nfs4_procedures)];

include/linux/nfs4.h

@@ -678,6 +678,7 @@ enum {
 	NFSPROC4_CLNT_SEEK,
 	NFSPROC4_CLNT_ALLOCATE,
 	NFSPROC4_CLNT_DEALLOCATE,
+	NFSPROC4_CLNT_ZERO_RANGE,
 	NFSPROC4_CLNT_LAYOUTSTATS,
 	NFSPROC4_CLNT_CLONE,
 	NFSPROC4_CLNT_COPY,

include/linux/nfs_fs_sb.h

@@ -304,6 +304,7 @@ struct nfs_server {
 #define NFS_CAP_CASE_PRESERVING	(1U << 7)
 #define NFS_CAP_REBOOT_LAYOUTRETURN	(1U << 8)
 #define NFS_CAP_OFFLOAD_STATUS	(1U << 9)
+#define NFS_CAP_ZERO_RANGE	(1U << 10)
 #define NFS_CAP_OPEN_XOR	(1U << 12)
 #define NFS_CAP_DELEGTIME	(1U << 13)
 #define NFS_CAP_POSIX_LOCK	(1U << 14)