9p: add 9P2000.L statfs operation

I made a V2 of this patch on top of my patches for VFS switches. The
change was adding v9fs_statfs pointer to v9fs_super_ops_dotl
instead of v9fs_super_ops.

statfs - get file system statistics

size[4] Tstatfs tag[2] fid[4]
size[4] Rstatfs tag[2] type[4] bsize[4] blocks[8] bfree[8] bavail[8]
                files[8] ffree[8] fsid[8] namelen[4]

The statfs message is used to request file system information returned
by the statfs(2) system call, which is used by df(1) to report file
system and disk space usage.
Signed-off-by: Jim Garlick <garlick@llnl.gov>
Signed-off-by: Sripathi Kodi <sripathik@in.ibm.com>
Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>

fs/9p/vfs_super.c

@@ -38,6 +38,7 @@
 #include <linux/idr.h>
 #include <linux/sched.h>
 #include <linux/slab.h>
+#include <linux/statfs.h>
 #include <net/9p/9p.h>
 #include <net/9p/client.h>
 
@@ -214,6 +215,42 @@ v9fs_umount_begin(struct super_block *sb)
 	v9fs_session_begin_cancel(v9ses);
 }
 
+static int v9fs_statfs(struct dentry *dentry, struct kstatfs *buf)
+{
+	struct v9fs_session_info *v9ses;
+	struct p9_fid *fid;
+	struct p9_rstatfs rs;
+	int res;
+
+	fid = v9fs_fid_lookup(dentry);
+	if (IS_ERR(fid)) {
+		res = PTR_ERR(fid);
+		goto done;
+	}
+
+	v9ses = v9fs_inode2v9ses(dentry->d_inode);
+	if (v9fs_proto_dotl(v9ses)) {
+		res = p9_client_statfs(fid, &rs);
+		if (res == 0) {
+			buf->f_type = rs.type;
+			buf->f_bsize = rs.bsize;
+			buf->f_blocks = rs.blocks;
+			buf->f_bfree = rs.bfree;
+			buf->f_bavail = rs.bavail;
+			buf->f_files = rs.files;
+			buf->f_ffree = rs.ffree;
+			buf->f_fsid.val[0] = rs.fsid & 0xFFFFFFFFUL;
+			buf->f_fsid.val[1] = (rs.fsid >> 32) & 0xFFFFFFFFUL;
+			buf->f_namelen = rs.namelen;
+		}
+		if (res != -ENOSYS)
+			goto done;
+	}
+	res = simple_statfs(dentry, buf);
+done:
+	return res;
+}
+
 static const struct super_operations v9fs_super_ops = {
 #ifdef CONFIG_9P_FSCACHE
 	.alloc_inode = v9fs_alloc_inode,
@@ -230,7 +267,7 @@ static const struct super_operations v9fs_super_ops_dotl = {
 	.alloc_inode = v9fs_alloc_inode,
 	.destroy_inode = v9fs_destroy_inode,
 #endif
-	.statfs = simple_statfs,
+	.statfs = v9fs_statfs,
 	.clear_inode = v9fs_clear_inode,
 	.show_options = generic_show_options,
 	.umount_begin = v9fs_umount_begin,

include/net/9p/9p.h

@@ -86,6 +86,8 @@ do { \
 
 /**
  * enum p9_msg_t - 9P message types
+ * @P9_TSTATFS: file system status request
+ * @P9_RSTATFS: file system status response
  * @P9_TVERSION: version handshake request
  * @P9_RVERSION: version handshake response
  * @P9_TAUTH: request to establish authentication channel
@@ -125,6 +127,8 @@ do { \
  */
 
 enum p9_msg_t {
+	P9_TSTATFS = 8,
+	P9_RSTATFS,
 	P9_TVERSION = 100,
 	P9_RVERSION,
 	P9_TAUTH = 102,
@@ -350,6 +354,22 @@ struct p9_wstat {
 };
 
 /* Structures for Protocol Operations */
+struct p9_tstatfs {
+	u32 fid;
+};
+
+struct p9_rstatfs {
+	u32 type;
+	u32 bsize;
+	u64 blocks;
+	u64 bfree;
+	u64 bavail;
+	u64 files;
+	u64 ffree;
+	u64 fsid;
+	u32 namelen;
+};
+
 struct p9_tversion {
 	u32 msize;
 	struct p9_str version;

include/net/9p/client.h

@@ -195,6 +195,7 @@ struct p9_fid {
 	struct list_head dlist;	/* list of all fids attached to a dentry */
 };
 
+int p9_client_statfs(struct p9_fid *fid, struct p9_rstatfs *sb);
 int p9_client_version(struct p9_client *);
 struct p9_client *p9_client_create(const char *dev_name, char *options);
 void p9_client_destroy(struct p9_client *clnt);

net/9p/client.c

@@ -1365,3 +1365,42 @@ int p9_client_wstat(struct p9_fid *fid, struct p9_wstat *wst)
 	return err;
 }
 EXPORT_SYMBOL(p9_client_wstat);
+
+int p9_client_statfs(struct p9_fid *fid, struct p9_rstatfs *sb)
+{
+	int err;
+	struct p9_req_t *req;
+	struct p9_client *clnt;
+
+	err = 0;
+	clnt = fid->clnt;
+
+	P9_DPRINTK(P9_DEBUG_9P, ">>> TSTATFS fid %d\n", fid->fid);
+
+	req = p9_client_rpc(clnt, P9_TSTATFS, "d", fid->fid);
+	if (IS_ERR(req)) {
+		err = PTR_ERR(req);
+		goto error;
+	}
+
+	err = p9pdu_readf(req->rc, clnt->proto_version, "ddqqqqqqd", &sb->type,
+		&sb->bsize, &sb->blocks, &sb->bfree, &sb->bavail,
+		&sb->files, &sb->ffree, &sb->fsid, &sb->namelen);
+	if (err) {
+		p9pdu_dump(1, req->rc);
+		p9_free_req(clnt, req);
+		goto error;
+	}
+
+	P9_DPRINTK(P9_DEBUG_9P, "<<< RSTATFS fid %d type 0x%lx bsize %ld "
+		"blocks %llu bfree %llu bavail %llu files %llu ffree %llu "
+		"fsid %llu namelen %ld\n",
+		fid->fid, (long unsigned int)sb->type, (long int)sb->bsize,
+		sb->blocks, sb->bfree, sb->bavail, sb->files,  sb->ffree,
+		sb->fsid, (long int)sb->namelen);
+
+	p9_free_req(clnt, req);
+error:
+	return err;
+}
+EXPORT_SYMBOL(p9_client_statfs);