Linux 5.6 compat: struct proc_ops

The proc_ops structure was introduced to replace the use of of the
file_operations structure when registering proc handlers.  This
change creates a new kstat_proc_op_t typedef for compatibility
which can be used to pass around the correct structure.

This change additionally adds the 'const' keyword to all of the
existing proc operations structures.

Reviewed-by: Tony Hutter <hutter2@llnl.gov>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #9961

config/kernel-proc-operations.m4

@@ -0,0 +1,41 @@
+dnl #
+dnl # 5.6 API Change
+dnl # The proc_ops structure was introduced to replace the use of
+dnl # of the file_operations structure when registering proc handlers.
+dnl #
+AC_DEFUN([ZFS_AC_KERNEL_SRC_PROC_OPERATIONS], [
+	ZFS_LINUX_TEST_SRC([proc_ops_struct], [
+		#include <linux/proc_fs.h>
+
+		int test_open(struct inode *ip, struct file *fp) { return 0; }
+		ssize_t test_read(struct file *fp, char __user *ptr,
+		    size_t size, loff_t *offp) { return 0; }
+		ssize_t test_write(struct file *fp, const char __user *ptr,
+		    size_t size, loff_t *offp) { return 0; }
+		loff_t test_lseek(struct file *fp, loff_t off, int flag)
+		    { return 0; }
+		int test_release(struct inode *ip, struct file *fp)
+		    { return 0; }
+
+		const struct proc_ops test_ops __attribute__ ((unused)) = {
+			.proc_open      = test_open,
+			.proc_read      = test_read,
+			.proc_write	= test_write,
+			.proc_lseek     = test_lseek,
+			.proc_release   = test_release,
+		};
+	], [
+		struct proc_dir_entry *entry __attribute__ ((unused)) =
+		    proc_create_data("test", 0444, NULL, &test_ops, NULL);
+	])
+])
+
+AC_DEFUN([ZFS_AC_KERNEL_PROC_OPERATIONS], [
+	AC_MSG_CHECKING([whether proc_ops structure exists])
+	ZFS_LINUX_TEST_RESULT([proc_ops_struct], [
+		AC_MSG_RESULT(yes)
+		AC_DEFINE(HAVE_PROC_OPS_STRUCT, 1, [proc_ops structure exists])
+	], [
+		AC_MSG_RESULT(no)
+	])
+])

config/kernel.m4

@@ -52,6 +52,7 @@ AC_DEFUN([ZFS_AC_KERNEL_TEST_SRC], [
 	ZFS_AC_KERNEL_SRC_RW
 	ZFS_AC_KERNEL_SRC_TIMER_SETUP
 	ZFS_AC_KERNEL_SRC_SUPER_USER_NS
+	ZFS_AC_KERNEL_SRC_PROC_OPERATIONS
 	ZFS_AC_KERNEL_SRC_BLOCK_DEVICE_OPERATIONS
 	ZFS_AC_KERNEL_SRC_BIO
 	ZFS_AC_KERNEL_SRC_BLKDEV
@@ -145,6 +146,7 @@ AC_DEFUN([ZFS_AC_KERNEL_TEST_RESULT], [
 	ZFS_AC_KERNEL_RW
 	ZFS_AC_KERNEL_TIMER_SETUP
 	ZFS_AC_KERNEL_SUPER_USER_NS
+	ZFS_AC_KERNEL_PROC_OPERATIONS
 	ZFS_AC_KERNEL_BLOCK_DEVICE_OPERATIONS
 	ZFS_AC_KERNEL_BIO
 	ZFS_AC_KERNEL_BLKDEV

include/os/linux/spl/sys/kstat.h

@@ -152,6 +152,12 @@ typedef struct kstat_named_s {
 #define	KSTAT_NAMED_STR_PTR(knptr) ((knptr)->value.string.addr.ptr)
 #define	KSTAT_NAMED_STR_BUFLEN(knptr) ((knptr)->value.string.len)
 
+#ifdef HAVE_PROC_OPS_STRUCT
+typedef struct proc_ops kstat_proc_op_t;
+#else
+typedef struct file_operations kstat_proc_op_t;
+#endif
+
 typedef struct kstat_intr {
 	uint_t intrs[KSTAT_NUM_INTRS];
 } kstat_intr_t;
@@ -197,7 +203,7 @@ extern void kstat_proc_entry_init(kstat_proc_entry_t *kpep,
     const char *module, const char *name);
 extern void kstat_proc_entry_delete(kstat_proc_entry_t *kpep);
 extern void kstat_proc_entry_install(kstat_proc_entry_t *kpep, mode_t mode,
-    const struct file_operations *file_ops, void *data);
+    const kstat_proc_op_t *file_ops, void *data);
 
 extern void __kstat_install(kstat_t *ksp);
 extern void __kstat_delete(kstat_t *ksp);

module/os/linux/spl/spl-kstat.c

@@ -507,12 +507,20 @@ proc_kstat_write(struct file *filp, const char __user *buf, size_t len,
 	return (len);
 }
 
-static struct file_operations proc_kstat_operations = {
+static const kstat_proc_op_t proc_kstat_operations = {
+#ifdef HAVE_PROC_OPS_STRUCT
+	.proc_open	= proc_kstat_open,
+	.proc_write	= proc_kstat_write,
+	.proc_read	= seq_read,
+	.proc_lseek	= seq_lseek,
+	.proc_release	= seq_release,
+#else
 	.open		= proc_kstat_open,
 	.write		= proc_kstat_write,
 	.read		= seq_read,
 	.llseek		= seq_lseek,
 	.release	= seq_release,
+#endif
 };
 
 void
@@ -656,7 +664,7 @@ kstat_detect_collision(kstat_proc_entry_t *kpep)
  */
 void
 kstat_proc_entry_install(kstat_proc_entry_t *kpep, mode_t mode,
-    const struct file_operations *file_ops, void *data)
+    const kstat_proc_op_t *proc_ops, void *data)
 {
 	kstat_module_t *module;
 	kstat_proc_entry_t *tmp = NULL;
@@ -690,7 +698,7 @@ kstat_proc_entry_install(kstat_proc_entry_t *kpep, mode_t mode,
 
 	kpep->kpe_owner = module;
 	kpep->kpe_proc = proc_create_data(kpep->kpe_name, mode,
-	    module->ksm_proc, file_ops, data);
+	    module->ksm_proc, proc_ops, data);
 	if (kpep->kpe_proc == NULL) {
 		list_del_init(&kpep->kpe_list);
 		if (list_empty(&module->ksm_kstat_list))

module/os/linux/spl/spl-proc.c

@@ -532,11 +532,18 @@ proc_slab_open(struct inode *inode, struct file *filp)
 	return (seq_open(filp, &slab_seq_ops));
 }
 
-static struct file_operations proc_slab_operations = {
-	.open	   = proc_slab_open,
-	.read	   = seq_read,
-	.llseek	 = seq_lseek,
+static const kstat_proc_op_t proc_slab_operations = {
+#ifdef HAVE_PROC_OPS_STRUCT
+	.proc_open	= proc_slab_open,
+	.proc_read	= seq_read,
+	.proc_lseek	= seq_lseek,
+	.proc_release	= seq_release,
+#else
+	.open		= proc_slab_open,
+	.read		= seq_read,
+	.llseek		= seq_lseek,
 	.release	= seq_release,
+#endif
 };
 
 static void
@@ -571,18 +578,32 @@ proc_taskq_open(struct inode *inode, struct file *filp)
 	return (seq_open(filp, &taskq_seq_ops));
 }
 
-static struct file_operations proc_taskq_all_operations = {
+static const kstat_proc_op_t proc_taskq_all_operations = {
+#ifdef HAVE_PROC_OPS_STRUCT
+	.proc_open	= proc_taskq_all_open,
+	.proc_read	= seq_read,
+	.proc_lseek	= seq_lseek,
+	.proc_release	= seq_release,
+#else
 	.open		= proc_taskq_all_open,
 	.read		= seq_read,
 	.llseek		= seq_lseek,
 	.release	= seq_release,
+#endif
 };
 
-static struct file_operations proc_taskq_operations = {
+static const kstat_proc_op_t proc_taskq_operations = {
+#ifdef HAVE_PROC_OPS_STRUCT
+	.proc_open	= proc_taskq_open,
+	.proc_read	= seq_read,
+	.proc_lseek	= seq_lseek,
+	.proc_release	= seq_release,
+#else
 	.open		= proc_taskq_open,
 	.read		= seq_read,
 	.llseek		= seq_lseek,
 	.release	= seq_release,
+#endif
 };
 
 static struct ctl_table spl_kmem_table[] = {

module/os/linux/spl/spl-procfs-list.c

@@ -185,13 +185,20 @@ procfs_list_write(struct file *filp, const char __user *buf, size_t len,
 	return (len);
 }
 
-static struct file_operations procfs_list_operations = {
-	.owner		= THIS_MODULE,
+static const kstat_proc_op_t procfs_list_operations = {
+#ifdef HAVE_PROC_OPS_STRUCT
+	.proc_open	= procfs_list_open,
+	.proc_write	= procfs_list_write,
+	.proc_read	= seq_read,
+	.proc_lseek	= seq_lseek,
+	.proc_release	= seq_release_private,
+#else
 	.open		= procfs_list_open,
 	.write		= procfs_list_write,
 	.read		= seq_read,
 	.llseek		= seq_lseek,
 	.release	= seq_release_private,
+#endif
 };
 
 /*