[PATCH 1/6] NFSD: Add per-export read/write I/O mode settings

[Jeff Layton <jlayton@kernel.org>]

Add ex_riomode/ex_wiomode to struct svc_export along with a
kernel-internal NFSD_IO_DEFAULT value meaning "follow the global debugfs
knob".

Add an io-mode enum to the nfsd netlink spec so the mode values are
uAPI (NFSD_IO_MODE_*), and define NFSD_IO_BUFFERED/DONTCACHE/DIRECT in
terms of it. The generated NLA_POLICY_MAX policy range-checks the new
read-iomode/write-iomode attributes.

Parse those attributes, copy the settings on cache update, and report
them in nfsd.export/content. The new options are netlink-only.

Signed-off-by: Jeff Layton <jlayton@kernel.org>
---
 Documentation/netlink/specs/nfsd.yaml | 24 ++++++++++++++++++++++++
 fs/nfsd/export.c                      | 28 ++++++++++++++++++++++++++--
 fs/nfsd/export.h                      |  2 ++
 fs/nfsd/netlink.c                     |  4 +++-
 fs/nfsd/netlink.h                     |  2 +-
 fs/nfsd/nfsd.h                        | 17 +++++++++++++----
 include/uapi/linux/nfsd_netlink.h     | 12 ++++++++++++
 7 files changed, 81 insertions(+), 8 deletions(-)

diff --git a/Documentation/netlink/specs/nfsd.yaml b/Documentation/netlink/specs/nfsd.yaml
index a4991206b45e..eb42ba65619d 100644
--- a/Documentation/netlink/specs/nfsd.yaml
+++ b/Documentation/netlink/specs/nfsd.yaml
@@ -56,6 +56,16 @@ definitions:
     name: nfsclnt-idmax
     value: 1024
     header: linux/nfsd/export.h
+  -
+    type: enum
+    name: io-mode
+    doc: >-
+      NFS READ/WRITE I/O mode. These values match the global io_cache_read
+      and io_cache_write debugfs settings.
+    entries:
+      - buffered
+      - dontcache
+      - direct
 
 attribute-sets:
   -
@@ -302,6 +312,20 @@ attribute-sets:
       -
         name: fsid
         type: s32
+      -
+        name: read-iomode
+        type: u32
+        enum: io-mode
+        doc: >-
+          Per-export NFS READ I/O mode. When absent, the export follows
+          the global io_cache_read setting.
+      -
+        name: write-iomode
+        type: u32
+        enum: io-mode
+        doc: >-
+          Per-export NFS WRITE I/O mode. When absent, the export follows
+          the global io_cache_write setting.
   -
     name: svc-export-reqs
     attributes:
diff --git a/fs/nfsd/export.c b/fs/nfsd/export.c
index 265ea8fd31c6..c71350965789 100644
--- a/fs/nfsd/export.c
+++ b/fs/nfsd/export.c
@@ -838,14 +838,14 @@ static int check_export(const struct path *path, int *flags,
 static int nfsd_nl_parse_one_export(struct cache_detail *cd,
 				    struct nlattr *attr)
 {
-	struct nlattr *tb[NFSD_A_SVC_EXPORT_FSID + 1];
+	struct nlattr *tb[NFSD_A_SVC_EXPORT_WRITE_IOMODE + 1];
 	struct auth_domain *dom = NULL;
 	struct svc_export exp = {}, *expp;
 	struct nlattr *secinfo_attr;
 	struct timespec64 boot;
 	int err, rem;
 
-	err = nla_parse_nested(tb, NFSD_A_SVC_EXPORT_FSID, attr,
+	err = nla_parse_nested(tb, NFSD_A_SVC_EXPORT_WRITE_IOMODE, attr,
 			       nfsd_svc_export_nl_policy, NULL);
 	if (err)
 		return err;
@@ -873,6 +873,8 @@ static int nfsd_nl_parse_one_export(struct cache_detail *cd,
 	exp.cd = cd;
 	exp.ex_devid_map = NULL;
 	exp.ex_xprtsec_modes = NFSEXP_XPRTSEC_ALL;
+	exp.ex_riomode = NFSD_IO_DEFAULT;
+	exp.ex_wiomode = NFSD_IO_DEFAULT;
 
 	/* expiry (required, wallclock seconds) */
 	if (!tb[NFSD_A_SVC_EXPORT_EXPIRY]) {
@@ -986,6 +988,12 @@ static int nfsd_nl_parse_one_export(struct cache_detail *cd,
 			}
 		}
 
+		/* read-iomode / write-iomode (optional u32) */
+		if (tb[NFSD_A_SVC_EXPORT_READ_IOMODE])
+			exp.ex_riomode = nla_get_u32(tb[NFSD_A_SVC_EXPORT_READ_IOMODE]);
+		if (tb[NFSD_A_SVC_EXPORT_WRITE_IOMODE])
+			exp.ex_wiomode = nla_get_u32(tb[NFSD_A_SVC_EXPORT_WRITE_IOMODE]);
+
 		err = check_export(&exp.ex_path, &exp.ex_flags,
 				   exp.ex_uuid);
 		if (err)
@@ -1342,6 +1350,8 @@ static int svc_export_parse(struct cache_detail *cd, char *mesg, int mlen)
 	exp.cd = cd;
 	exp.ex_devid_map = NULL;
 	exp.ex_xprtsec_modes = NFSEXP_XPRTSEC_ALL;
+	exp.ex_riomode = NFSD_IO_DEFAULT;
+	exp.ex_wiomode = NFSD_IO_DEFAULT;
 
 	/* expiry */
 	err = get_expiry(&mesg, &exp.h.expiry_time);
@@ -1462,6 +1472,12 @@ static int is_export_stats_file(struct seq_file *m)
 	return !strcmp(m->file->f_path.dentry->d_name.name, "export_stats");
 }
 
+static const char * const nfsd_iomode_names[] = {
+	[NFSD_IO_BUFFERED]	= "buffered",
+	[NFSD_IO_DONTCACHE]	= "dontcache",
+	[NFSD_IO_DIRECT]	= "direct",
+};
+
 static int svc_export_show(struct seq_file *m,
 			   struct cache_detail *cd,
 			   struct cache_head *h)
@@ -1498,6 +1514,12 @@ static int svc_export_show(struct seq_file *m,
 	    !test_bit(CACHE_NEGATIVE, &h->flags)) {
 		exp_flags(m, exp->ex_flags, exp->ex_fsid,
 			  exp->ex_anon_uid, exp->ex_anon_gid, &exp->ex_fslocs);
+		if (exp->ex_riomode != NFSD_IO_DEFAULT)
+			seq_printf(m, ",riomode=%s",
+				   nfsd_iomode_names[exp->ex_riomode]);
+		if (exp->ex_wiomode != NFSD_IO_DEFAULT)
+			seq_printf(m, ",wiomode=%s",
+				   nfsd_iomode_names[exp->ex_wiomode]);
 		if (exp->ex_uuid) {
 			int i;
 			seq_puts(m, ",uuid=");
@@ -1564,6 +1586,8 @@ static void export_update(struct cache_head *cnew, struct cache_head *citem)
 		new->ex_flavors[i] = item->ex_flavors[i];
 	}
 	new->ex_xprtsec_modes = item->ex_xprtsec_modes;
+	new->ex_riomode = item->ex_riomode;
+	new->ex_wiomode = item->ex_wiomode;
 }
 
 static struct cache_head *svc_export_alloc(void)
diff --git a/fs/nfsd/export.h b/fs/nfsd/export.h
index 117fb28db1e0..0e832990a12c 100644
--- a/fs/nfsd/export.h
+++ b/fs/nfsd/export.h
@@ -77,6 +77,8 @@ struct svc_export {
 	struct cache_detail	*cd;
 	struct rcu_head		ex_rcu;
 	unsigned long		ex_xprtsec_modes;
+	s8			ex_riomode;
+	s8			ex_wiomode;
 	struct export_stats	*ex_stats;
 };
 
diff --git a/fs/nfsd/netlink.c b/fs/nfsd/netlink.c
index 4ea6a7c1ce7f..5c35764e62d1 100644
--- a/fs/nfsd/netlink.c
+++ b/fs/nfsd/netlink.c
@@ -42,7 +42,7 @@ const struct nla_policy nfsd_sock_nl_policy[NFSD_A_SOCK_TRANSPORT_NAME + 1] = {
 	[NFSD_A_SOCK_TRANSPORT_NAME] = { .type = NLA_NUL_STRING, },
 };
 
-const struct nla_policy nfsd_svc_export_nl_policy[NFSD_A_SVC_EXPORT_FSID + 1] = {
+const struct nla_policy nfsd_svc_export_nl_policy[NFSD_A_SVC_EXPORT_WRITE_IOMODE + 1] = {
 	[NFSD_A_SVC_EXPORT_SEQNO] = { .type = NLA_U64, },
 	[NFSD_A_SVC_EXPORT_CLIENT] = { .type = NLA_NUL_STRING, },
 	[NFSD_A_SVC_EXPORT_PATH] = { .type = NLA_NUL_STRING, },
@@ -56,6 +56,8 @@ const struct nla_policy nfsd_svc_export_nl_policy[NFSD_A_SVC_EXPORT_FSID + 1] =
 	[NFSD_A_SVC_EXPORT_XPRTSEC] = NLA_POLICY_MASK(NLA_U32, 0x7),
 	[NFSD_A_SVC_EXPORT_FLAGS] = NLA_POLICY_MASK(NLA_U32, 0x3ffff),
 	[NFSD_A_SVC_EXPORT_FSID] = { .type = NLA_S32, },
+	[NFSD_A_SVC_EXPORT_READ_IOMODE] = NLA_POLICY_MAX(NLA_U32, 2),
+	[NFSD_A_SVC_EXPORT_WRITE_IOMODE] = NLA_POLICY_MAX(NLA_U32, 2),
 };
 
 const struct nla_policy nfsd_version_nl_policy[NFSD_A_VERSION_ENABLED + 1] = {
diff --git a/fs/nfsd/netlink.h b/fs/nfsd/netlink.h
index 57fc86c63b1d..db00e06de15c 100644
--- a/fs/nfsd/netlink.h
+++ b/fs/nfsd/netlink.h
@@ -19,7 +19,7 @@ extern const struct nla_policy nfsd_expkey_nl_policy[NFSD_A_EXPKEY_PATH + 1];
 extern const struct nla_policy nfsd_fslocation_nl_policy[NFSD_A_FSLOCATION_PATH + 1];
 extern const struct nla_policy nfsd_fslocations_nl_policy[NFSD_A_FSLOCATIONS_LOCATION + 1];
 extern const struct nla_policy nfsd_sock_nl_policy[NFSD_A_SOCK_TRANSPORT_NAME + 1];
-extern const struct nla_policy nfsd_svc_export_nl_policy[NFSD_A_SVC_EXPORT_FSID + 1];
+extern const struct nla_policy nfsd_svc_export_nl_policy[NFSD_A_SVC_EXPORT_WRITE_IOMODE + 1];
 extern const struct nla_policy nfsd_version_nl_policy[NFSD_A_VERSION_ENABLED + 1];
 
 int nfsd_nl_rpc_status_get_dumpit(struct sk_buff *skb,
diff --git a/fs/nfsd/nfsd.h b/fs/nfsd/nfsd.h
index b520b51692b0..8b4bed37b46b 100644
--- a/fs/nfsd/nfsd.h
+++ b/fs/nfsd/nfsd.h
@@ -16,6 +16,7 @@
 #include <linux/sunrpc/svc_xprt.h>
 
 #include <uapi/linux/nfsd/debug.h>
+#include <uapi/linux/nfsd_netlink.h>
 
 #undef ifdebug
 #ifdef CONFIG_SUNRPC_DEBUG
@@ -134,10 +135,18 @@ extern bool nfsd_disable_splice_read __read_mostly;
 extern bool nfsd_delegts_enabled __read_mostly;
 
 enum {
-	/* Any new NFSD_IO enum value must be added at the end */
-	NFSD_IO_BUFFERED,
-	NFSD_IO_DONTCACHE,
-	NFSD_IO_DIRECT,
+	/* Values are uAPI: per-export modes are sent over netlink */
+	NFSD_IO_BUFFERED	= NFSD_IO_MODE_BUFFERED,
+	NFSD_IO_DONTCACHE	= NFSD_IO_MODE_DONTCACHE,
+	NFSD_IO_DIRECT		= NFSD_IO_MODE_DIRECT,
+	/*
+	 * Kernel-internal only: a per-export mode of NFSD_IO_DEFAULT
+	 * means "follow the global nfsd_io_cache_read/write knob".
+	 * It is never sent across the kernel-userspace interface.
+	 * It is -1 so that it stays distinct from all present and
+	 * future mode values.
+	 */
+	NFSD_IO_DEFAULT = -1,
 };
 
 extern u64 nfsd_io_cache_read __read_mostly;
diff --git a/include/uapi/linux/nfsd_netlink.h b/include/uapi/linux/nfsd_netlink.h
index dcd2126d848b..6628ed7c0922 100644
--- a/include/uapi/linux/nfsd_netlink.h
+++ b/include/uapi/linux/nfsd_netlink.h
@@ -59,6 +59,16 @@ enum nfsd_rpcbind_flags {
 	NFSD_RPCBIND_FLAGS_NO_UDP = 1,
 };
 
+/*
+ * NFS READ/WRITE I/O mode. These values match the global io_cache_read and
+ * io_cache_write debugfs settings.
+ */
+enum nfsd_io_mode {
+	NFSD_IO_MODE_BUFFERED,
+	NFSD_IO_MODE_DONTCACHE,
+	NFSD_IO_MODE_DIRECT,
+};
+
 enum {
 	NFSD_A_CACHE_NOTIFY_CACHE_TYPE = 1,
 
@@ -185,6 +195,8 @@ enum {
 	NFSD_A_SVC_EXPORT_XPRTSEC,
 	NFSD_A_SVC_EXPORT_FLAGS,
 	NFSD_A_SVC_EXPORT_FSID,
+	NFSD_A_SVC_EXPORT_READ_IOMODE,
+	NFSD_A_SVC_EXPORT_WRITE_IOMODE,
 
 	__NFSD_A_SVC_EXPORT_MAX,
 	NFSD_A_SVC_EXPORT_MAX = (__NFSD_A_SVC_EXPORT_MAX - 1)

-- 
2.56.0