smb: client: add support for WSL reparse points

Add support for creating special files via WSL reparse points when
using 'reparse=wsl' mount option.  They're faster than NFS reparse
points because they don't require extra roundtrips to figure out what
->d_type a specific dirent is as such information is already stored in
query dir responses and then making getdents() calls faster.

Signed-off-by: Paulo Alcantara <pc@manguebit.com>
Signed-off-by: Steve French <stfrench@microsoft.com>

1 files changed, 165 insertions, 5 deletions

diff --git a/fs/smb/client/reparse.c b/fs/smb/client/reparse.c
index c405be47c84d..b240ccc9c887 100644
--- a/fs/smb/client/reparse.c
+++ b/fs/smb/client/reparse.c
@@ -11,6 +11,7 @@
 #include "cifsproto.h"
 #include "cifs_unicode.h"
 #include "cifs_debug.h"
+#include "fs_context.h"
 #include "reparse.h"
 
 int smb2_create_reparse_symlink(const unsigned int xid, struct inode *inode,
@@ -68,7 +69,7 @@ int smb2_create_reparse_symlink(const unsigned int xid, struct inode *inode,
 	iov.iov_base = buf;
 	iov.iov_len = len;
 	new = smb2_get_reparse_inode(&data, inode->i_sb, xid,
-				     tcon, full_path, &iov);
+				     tcon, full_path, &iov, NULL);
 	if (!IS_ERR(new))
 		d_instantiate(dentry, new);
 	else
@@ -114,9 +115,9 @@ static int nfs_set_reparse_buf(struct reparse_posix_data *buf,
 	return 0;
 }
 
-int smb2_make_nfs_node(unsigned int xid, struct inode *inode,
-		       struct dentry *dentry, struct cifs_tcon *tcon,
-		       const char *full_path, umode_t mode, dev_t dev)
+static int mknod_nfs(unsigned int xid, struct inode *inode,
+		     struct dentry *dentry, struct cifs_tcon *tcon,
+		     const char *full_path, umode_t mode, dev_t dev)
 {
 	struct cifs_open_info_data data;
 	struct reparse_posix_data *p;
@@ -136,12 +137,171 @@ int smb2_make_nfs_node(unsigned int xid, struct inode *inode,
 	};
 
 	new = smb2_get_reparse_inode(&data, inode->i_sb, xid,
-				     tcon, full_path, &iov);
+				     tcon, full_path, &iov, NULL);
+	if (!IS_ERR(new))
+		d_instantiate(dentry, new);
+	else
+		rc = PTR_ERR(new);
+	cifs_free_open_info(&data);
+	return rc;
+}
+
+static int wsl_set_reparse_buf(struct reparse_data_buffer *buf,
+			       mode_t mode, struct kvec *iov)
+{
+	u32 tag;
+
+	switch ((tag = reparse_mode_wsl_tag(mode))) {
+	case IO_REPARSE_TAG_LX_BLK:
+	case IO_REPARSE_TAG_LX_CHR:
+	case IO_REPARSE_TAG_LX_FIFO:
+	case IO_REPARSE_TAG_AF_UNIX:
+		break;
+	default:
+		return -EOPNOTSUPP;
+	}
+
+	buf->ReparseTag = cpu_to_le32(tag);
+	buf->Reserved = 0;
+	buf->ReparseDataLength = 0;
+	iov->iov_base = buf;
+	iov->iov_len = sizeof(*buf);
+	return 0;
+}
+
+static struct smb2_create_ea_ctx *ea_create_context(u32 dlen, size_t *cc_len)
+{
+	struct smb2_create_ea_ctx *cc;
+
+	*cc_len = round_up(sizeof(*cc) + dlen, 8);
+	cc = kzalloc(*cc_len, GFP_KERNEL);
+	if (!cc)
+		return ERR_PTR(-ENOMEM);
+
+	cc->ctx.NameOffset = cpu_to_le16(offsetof(struct smb2_create_ea_ctx,
+						  name));
+	cc->ctx.NameLength = cpu_to_le16(4);
+	memcpy(cc->name, SMB2_CREATE_EA_BUFFER, strlen(SMB2_CREATE_EA_BUFFER));
+	cc->ctx.DataOffset = cpu_to_le16(offsetof(struct smb2_create_ea_ctx, ea));
+	cc->ctx.DataLength = cpu_to_le32(dlen);
+	return cc;
+}
+
+struct wsl_xattr {
+	const char	*name;
+	__le64		value;
+	u16		size;
+	u32		next;
+};
+
+static int wsl_set_xattrs(struct inode *inode, umode_t _mode,
+			  dev_t _dev, struct kvec *iov)
+{
+	struct smb2_file_full_ea_info *ea;
+	struct smb2_create_ea_ctx *cc;
+	struct smb3_fs_context *ctx = CIFS_SB(inode->i_sb)->ctx;
+	__le64 uid = cpu_to_le64(from_kuid(current_user_ns(), ctx->linux_uid));
+	__le64 gid = cpu_to_le64(from_kgid(current_user_ns(), ctx->linux_gid));
+	__le64 dev = cpu_to_le64(((u64)MINOR(_dev) << 32) | MAJOR(_dev));
+	__le64 mode = cpu_to_le64(_mode);
+	struct wsl_xattr xattrs[] = {
+		{ .name = "$LXUID", .value = uid, .size = 4, },
+		{ .name = "$LXGID", .value = gid, .size = 4, },
+		{ .name = "$LXMOD", .value = mode, .size = 4, },
+		{ .name = "$LXDEV", .value = dev, .size = 8, },
+	};
+	size_t cc_len;
+	u32 dlen = 0, next = 0;
+	int i, num_xattrs;
+	u8 name_size = strlen(xattrs[0].name) + 1;
+
+	memset(iov, 0, sizeof(*iov));
+
+	/* Exclude $LXDEV xattr for sockets and fifos */
+	if (S_ISSOCK(_mode) || S_ISFIFO(_mode))
+		num_xattrs = ARRAY_SIZE(xattrs) - 1;
+	else
+		num_xattrs = ARRAY_SIZE(xattrs);
+
+	for (i = 0; i < num_xattrs; i++) {
+		xattrs[i].next = ALIGN(sizeof(*ea) + name_size +
+				       xattrs[i].size, 4);
+		dlen += xattrs[i].next;
+	}
+
+	cc = ea_create_context(dlen, &cc_len);
+	if (!cc)
+		return PTR_ERR(cc);
+
+	ea = &cc->ea;
+	for (i = 0; i < num_xattrs; i++) {
+		ea = (void *)((u8 *)ea + next);
+		next = xattrs[i].next;
+		ea->next_entry_offset = cpu_to_le32(next);
+
+		ea->ea_name_length = name_size - 1;
+		ea->ea_value_length = cpu_to_le16(xattrs[i].size);
+		memcpy(ea->ea_data, xattrs[i].name, name_size);
+		memcpy(&ea->ea_data[name_size],
+		       &xattrs[i].value, xattrs[i].size);
+	}
+	ea->next_entry_offset = 0;
+
+	iov->iov_base = cc;
+	iov->iov_len = cc_len;
+	return 0;
+}
+
+static int mknod_wsl(unsigned int xid, struct inode *inode,
+		     struct dentry *dentry, struct cifs_tcon *tcon,
+		     const char *full_path, umode_t mode, dev_t dev)
+{
+	struct cifs_open_info_data data;
+	struct reparse_data_buffer buf;
+	struct inode *new;
+	struct kvec reparse_iov, xattr_iov;
+	int rc;
+
+	rc = wsl_set_reparse_buf(&buf, mode, &reparse_iov);
+	if (rc)
+		return rc;
+
+	rc = wsl_set_xattrs(inode, mode, dev, &xattr_iov);
+	if (rc)
+		return rc;
+
+	data = (struct cifs_open_info_data) {
+		.reparse_point = true,
+		.reparse = { .tag = le32_to_cpu(buf.ReparseTag), .buf = &buf, },
+	};
+
+	new = smb2_get_reparse_inode(&data, inode->i_sb,
+				     xid, tcon, full_path,
+				     &reparse_iov, &xattr_iov);
 	if (!IS_ERR(new))
 		d_instantiate(dentry, new);
 	else
 		rc = PTR_ERR(new);
 	cifs_free_open_info(&data);
+	kfree(xattr_iov.iov_base);
+	return rc;
+}
+
+int smb2_mknod_reparse(unsigned int xid, struct inode *inode,
+		       struct dentry *dentry, struct cifs_tcon *tcon,
+		       const char *full_path, umode_t mode, dev_t dev)
+{
+	struct smb3_fs_context *ctx = CIFS_SB(inode->i_sb)->ctx;
+	int rc = -EOPNOTSUPP;
+
+	switch (ctx->reparse_type) {
+	case CIFS_REPARSE_TYPE_NFS:
+		rc = mknod_nfs(xid, inode, dentry, tcon, full_path, mode, dev);
+		break;
+	case CIFS_REPARSE_TYPE_WSL:
+		rc = mknod_wsl(xid, inode, dentry, tcon, full_path, mode, dev);
+		break;
+	}
 	return rc;
 }