kernel: compat: inline iterate_dir -> vfs_readdir compat

I'll just copy what I put in comments:

this is backported on msm-3.10 though SO YEAH WE STILL USE IT IF ITS THERE !! (ref: Makefile)
but we have to try to follow what upstream linux is, and it is only added on 3.11
need to inline struct dir_context since this doesnt exist pre-iterate_dir era!

ref: torvalds/linux@5c0ba4e
analysis:

int kernel_iterate_dir(struct file *file, struct dir_context *ctx) -> res = readdir(file, ctx, ctx->actor);  ++++ file, struct -> file, struct, struct->member
int vfs_readdir(struct file *file, filldir_t filler, void *buf) -> res = readdir(file, buf, filler); file, ??, ?? +++ 1 3 2

Signed-off-by: backslashxx <[email protected]>

Author: backslashxx

kernel/Makefile

@@ -56,6 +56,12 @@ $(info -- KernelSU Manager signature hash: $(KSU_EXPECTED_HASH))
 ccflags-y += -DEXPECTED_SIZE=$(KSU_EXPECTED_SIZE)
 ccflags-y += -DEXPECTED_HASH=\"$(KSU_EXPECTED_HASH)\"
 
+# UL, look for iterate_dir on ‎fs/readdir.c
+ifeq ($(shell grep -q "^int iterate_dir" $(srctree)/fs/readdir.c 2>/dev/null; echo $$?),0)
+$(info -- KernelSU/compat: iterate_dir found!)
+ccflags-y += -DKSU_HAS_ITERATE_DIR
+endif
+
 # UL, look for read_iter on f_op struct
 ifeq ($(shell grep -q "read_iter" $(srctree)/include/linux/fs.h 2>/dev/null; echo $$?),0)
 $(info -- KernelSU/compat: f_op->read_iter found!)

kernel/kernel_compat.h

@@ -24,4 +24,23 @@ extern ssize_t ksu_kernel_write_compat(struct file *p, const void *buf,
 
 extern int ksu_access_ok(const void *addr, unsigned long size);
 
+// this is backported on msm-3.10 though SO YEAH WE STILL USE IT IF ITS THERE !! (ref: Makefile)
+// but we have to try to follow what upstream linux is, and it is only added on 3.11
+// need to inline struct dir_context since this doesnt exist pre-iterate_dir era!
+#if LINUX_VERSION_CODE < KERNEL_VERSION(3, 11, 0) && !defined(KSU_HAS_ITERATE_DIR)
+struct dir_context {
+	const filldir_t actor;
+	loff_t pos;
+};
+
+// ref: https://github.com/torvalds/linux/commit/5c0ba4e0762e6dabd14a5c276652e2defec38de7
+// analysis: 
+// int kernel_iterate_dir(struct file *file, struct dir_context *ctx) -> res = readdir(file, ctx, ctx->actor);  ++++ file, struct -> file, struct, struct->member
+// int vfs_readdir(struct file *file, filldir_t filler, void *buf) -> res = readdir(file, buf, filler); file, ??, ?? +++ 1 3 2
+static int iterate_dir(struct file *file, struct dir_context *ctx)
+{
+	return vfs_readdir(file, ctx->actor, ctx);
+}
+#endif // CONFIG_KSU_HAS_ITERATE_DIR
+
 #endif