Linux 6.1 compat: open inside tmpfile()

Linux 863f144 modified the .tmpfile interface to pass a struct file,
rather than a struct dentry, and expect the tmpfile implementation to
open inside of tmpfile().

This patch implements a configuration test that checks for this new API
and appropriately sets a HAVE_TMPFILE_DENTRY flag that tracks this old
API.  Contingent on this flag, the appropriate API is implemented.

Reviewed-by: Richard Yao <richard.yao@alumni.stonybrook.edu>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Antonio Russo <aerusso@aerusso.net>
Closes #14301
Closes #14343

config/kernel-tmpfile.m4

@@ -3,11 +3,25 @@ dnl # 3.11 API change
 dnl # Add support for i_op->tmpfile
 dnl #
 AC_DEFUN([ZFS_AC_KERNEL_SRC_TMPFILE], [
+	dnl #
+	dnl # 6.1 API change
+	dnl # use struct file instead of struct dentry
+	dnl #
+	ZFS_LINUX_TEST_SRC([inode_operations_tmpfile], [
+		#include <linux/fs.h>
+		int tmpfile(struct user_namespace *userns,
+		    struct inode *inode, struct file *file,
+		    umode_t mode) { return 0; }
+		static struct inode_operations
+		    iops __attribute__ ((unused)) = {
+			.tmpfile = tmpfile,
+		};
+	],[])
 	dnl #
 	dnl # 5.11 API change
 	dnl # add support for userns parameter to tmpfile
 	dnl #
-	ZFS_LINUX_TEST_SRC([inode_operations_tmpfile_userns], [
+	ZFS_LINUX_TEST_SRC([inode_operations_tmpfile_dentry_userns], [
 		#include <linux/fs.h>
 		int tmpfile(struct user_namespace *userns,
 		    struct inode *inode, struct dentry *dentry,
@@ -17,7 +31,7 @@ AC_DEFUN([ZFS_AC_KERNEL_SRC_TMPFILE], [
 			.tmpfile = tmpfile,
 		};
 	],[])
-	ZFS_LINUX_TEST_SRC([inode_operations_tmpfile], [
+	ZFS_LINUX_TEST_SRC([inode_operations_tmpfile_dentry], [
 			#include <linux/fs.h>
 			int tmpfile(struct inode *inode, struct dentry *dentry,
 			    umode_t mode) { return 0; }
@@ -30,16 +44,24 @@ AC_DEFUN([ZFS_AC_KERNEL_SRC_TMPFILE], [
 
 AC_DEFUN([ZFS_AC_KERNEL_TMPFILE], [
 	AC_MSG_CHECKING([whether i_op->tmpfile() exists])
-	ZFS_LINUX_TEST_RESULT([inode_operations_tmpfile_userns], [
+	ZFS_LINUX_TEST_RESULT([inode_operations_tmpfile], [
 		AC_MSG_RESULT(yes)
 		AC_DEFINE(HAVE_TMPFILE, 1, [i_op->tmpfile() exists])
 		AC_DEFINE(HAVE_TMPFILE_USERNS, 1, [i_op->tmpfile() has userns])
 	],[
-		ZFS_LINUX_TEST_RESULT([inode_operations_tmpfile], [
+		ZFS_LINUX_TEST_RESULT([inode_operations_tmpfile_dentry_userns], [
 			AC_MSG_RESULT(yes)
 			AC_DEFINE(HAVE_TMPFILE, 1, [i_op->tmpfile() exists])
+			AC_DEFINE(HAVE_TMPFILE_USERNS, 1, [i_op->tmpfile() has userns])
+			AC_DEFINE(HAVE_TMPFILE_DENTRY, 1, [i_op->tmpfile() uses old dentry signature])
+		],[
+			ZFS_LINUX_TEST_RESULT([inode_operations_tmpfile_dentry], [
+				AC_MSG_RESULT(yes)
+				AC_DEFINE(HAVE_TMPFILE, 1, [i_op->tmpfile() exists])
+				AC_DEFINE(HAVE_TMPFILE_DENTRY, 1, [i_op->tmpfile() uses old dentry signature])
 			],[
 				AC_MSG_RESULT(no)
 			])
 		])
+	])
 ])

module/os/linux/zfs/zpl_inode.c

@@ -234,12 +234,17 @@ zpl_mknod(struct inode *dir, struct dentry *dentry, umode_t mode,
 
 #ifdef HAVE_TMPFILE
 static int
+#ifndef HAVE_TMPFILE_DENTRY
+zpl_tmpfile(struct user_namespace *userns, struct inode *dir,
+    struct file *file, umode_t mode)
+#else
 #ifdef HAVE_TMPFILE_USERNS
 zpl_tmpfile(struct user_namespace *userns, struct inode *dir,
     struct dentry *dentry, umode_t mode)
 #else
 zpl_tmpfile(struct inode *dir, struct dentry *dentry, umode_t mode)
 #endif
+#endif
 {
 	cred_t *cr = CRED();
 	struct inode *ip;
@@ -265,11 +270,21 @@ zpl_tmpfile(struct inode *dir, struct dentry *dentry, umode_t mode)
 	if (error == 0) {
 		/* d_tmpfile will do drop_nlink, so we should set it first */
 		set_nlink(ip, 1);
+#ifndef HAVE_TMPFILE_DENTRY
+		d_tmpfile(file, ip);
+
+		error = zpl_xattr_security_init(ip, dir,
+		    &file->f_path.dentry->d_name);
+#else
 		d_tmpfile(dentry, ip);
 
 		error = zpl_xattr_security_init(ip, dir, &dentry->d_name);
+#endif
 		if (error == 0)
 			error = zpl_init_acl(ip, dir);
+#ifndef HAVE_TMPFILE_DENTRY
+		error = finish_open_simple(file, error);
+#endif
 		/*
 		 * don't need to handle error here, file is already in
 		 * unlinked set.