smb: client: set symlink type as native for POSIX mounts

JIRA: https://issues.redhat.com/browse/RHEL-109507

commit a967e75
Author: Paulo Alcantara <pc@manguebit.org>
Date:   Thu Jul 31 20:46:41 2025 -0300

    smb: client: set symlink type as native for POSIX mounts

    SMB3.1.1 POSIX mounts require symlinks to be created natively with
    IO_REPARSE_TAG_SYMLINK reparse point.

    Cc: linux-cifs@vger.kernel.org
    Cc: Ralph Boehme <slow@samba.org>
    Cc: David Howells <dhowells@redhat.com>
    Cc: <stable@vger.kernel.org>
    Reported-by: Matthew Richardson <m.richardson@ed.ac.uk>
    Closes: https://marc.info/?i=1124e7cd-6a46-40a6-9f44-b7664a66654b@ed.ac.uk
    Signed-off-by: Paulo Alcantara (Red Hat) <pc@manguebit.org>
    Signed-off-by: Steve French <stfrench@microsoft.com>

Signed-off-by: Paulo Alcantara <paalcant@redhat.com>

Author: pcacjr

fs/smb/client/cifsfs.c

@@ -717,7 +717,7 @@ cifs_show_options(struct seq_file *s, struct dentry *root)
 	else
 		seq_puts(s, ",nativesocket");
 	seq_show_option(s, "symlink",
-			cifs_symlink_type_str(get_cifs_symlink_type(cifs_sb)));
+			cifs_symlink_type_str(cifs_symlink_type(cifs_sb)));
 
 	seq_printf(s, ",rsize=%u", cifs_sb->ctx->rsize);
 	seq_printf(s, ",wsize=%u", cifs_sb->ctx->wsize);

fs/smb/client/fs_context.c

@@ -1844,24 +1844,6 @@ static int smb3_fs_context_parse_param(struct fs_context *fc,
 	return -EINVAL;
 }
 
-enum cifs_symlink_type get_cifs_symlink_type(struct cifs_sb_info *cifs_sb)
-{
-	if (cifs_sb->ctx->symlink_type == CIFS_SYMLINK_TYPE_DEFAULT) {
-		if (cifs_sb->ctx->mfsymlinks)
-			return CIFS_SYMLINK_TYPE_MFSYMLINKS;
-		else if (cifs_sb->ctx->sfu_emul)
-			return CIFS_SYMLINK_TYPE_SFU;
-		else if (cifs_sb->ctx->linux_ext && !cifs_sb->ctx->no_linux_ext)
-			return CIFS_SYMLINK_TYPE_UNIX;
-		else if (cifs_sb->ctx->reparse_type != CIFS_REPARSE_TYPE_NONE)
-			return CIFS_SYMLINK_TYPE_NATIVE;
-		else
-			return CIFS_SYMLINK_TYPE_NONE;
-	} else {
-		return cifs_sb->ctx->symlink_type;
-	}
-}
-
 int smb3_init_fs_context(struct fs_context *fc)
 {
 	struct smb3_fs_context *ctx;

fs/smb/client/fs_context.h

@@ -341,7 +341,23 @@ struct smb3_fs_context {
 
 extern const struct fs_parameter_spec smb3_fs_parameters[];
 
-extern enum cifs_symlink_type get_cifs_symlink_type(struct cifs_sb_info *cifs_sb);
+static inline enum cifs_symlink_type cifs_symlink_type(struct cifs_sb_info *cifs_sb)
+{
+	bool posix = cifs_sb_master_tcon(cifs_sb)->posix_extensions;
+
+	if (cifs_sb->ctx->symlink_type != CIFS_SYMLINK_TYPE_DEFAULT)
+		return cifs_sb->ctx->symlink_type;
+
+	if (cifs_sb->ctx->mfsymlinks)
+		return CIFS_SYMLINK_TYPE_MFSYMLINKS;
+	else if (cifs_sb->ctx->sfu_emul)
+		return CIFS_SYMLINK_TYPE_SFU;
+	else if (cifs_sb->ctx->linux_ext && !cifs_sb->ctx->no_linux_ext)
+		return posix ? CIFS_SYMLINK_TYPE_NATIVE : CIFS_SYMLINK_TYPE_UNIX;
+	else if (cifs_sb->ctx->reparse_type != CIFS_REPARSE_TYPE_NONE)
+		return CIFS_SYMLINK_TYPE_NATIVE;
+	return CIFS_SYMLINK_TYPE_NONE;
+}
 
 extern int smb3_init_fs_context(struct fs_context *fc);
 extern void smb3_cleanup_fs_context_contents(struct smb3_fs_context *ctx);

fs/smb/client/link.c

@@ -605,14 +605,7 @@ cifs_symlink(struct mnt_idmap *idmap, struct inode *inode,
 
 	/* BB what if DFS and this volume is on different share? BB */
 	rc = -EOPNOTSUPP;
-	switch (get_cifs_symlink_type(cifs_sb)) {
-	case CIFS_SYMLINK_TYPE_DEFAULT:
-		/* should not happen, get_cifs_symlink_type() resolves the default */
-		break;
-
-	case CIFS_SYMLINK_TYPE_NONE:
-		break;
-
+	switch (cifs_symlink_type(cifs_sb)) {
 	case CIFS_SYMLINK_TYPE_UNIX:
 #ifdef CONFIG_CIFS_ALLOW_INSECURE_LEGACY
 		if (pTcon->unix_ext) {
@@ -648,6 +641,8 @@ cifs_symlink(struct mnt_idmap *idmap, struct inode *inode,
 			goto symlink_exit;
 		}
 		break;
+	default:
+		break;
 	}
 
 	if (rc == 0) {

fs/smb/client/reparse.c

@@ -38,7 +38,7 @@ int create_reparse_symlink(const unsigned int xid, struct inode *inode,
 				struct dentry *dentry, struct cifs_tcon *tcon,
 				const char *full_path, const char *symname)
 {
-	switch (get_cifs_symlink_type(CIFS_SB(inode->i_sb))) {
+	switch (cifs_symlink_type(CIFS_SB(inode->i_sb))) {
 	case CIFS_SYMLINK_TYPE_NATIVE:
 		return create_native_symlink(xid, inode, dentry, tcon, full_path, symname);
 	case CIFS_SYMLINK_TYPE_NFS: