implement generic_file_buffered_write()

This function is removed in el8 therefore we need to implement
it ourselves now. Copy it.

Signed-off-by: Auke Kok <auke.kok@versity.com>

kmod/src/Makefile.kernelcompat

@@ -204,3 +204,12 @@ endif
 ifneq (,$(shell grep 'define register_hotcpu_notifier' include/linux/cpu.h))
 ccflags-y += -DKC_CPU_NOTIFIER
 endif
+
+#
+# v3.14-rc8-130-gccad2365668f
+#
+# generic_file_buffered_write is removed, backport it
+#
+ifneq (,$(shell grep 'extern ssize_t generic_file_buffered_write' include/linux/fs.h))
+ccflags-y += -DKC_GENERIC_FILE_BUFFERED_WRITE=1
+endif

kmod/src/kernelcompat.c

@@ -1,4 +1,6 @@
 
+#include <linux/uio.h>
+
 #include "kernelcompat.h"
 
 #ifdef KC_SHRINKER_SHRINK
@@ -58,3 +60,25 @@ struct timespec64 kc_current_time(struct inode *inode)
 	return now;
 }
 #endif
+
+#ifndef KC_GENERIC_FILE_BUFFERED_WRITE
+ssize_t
+kc_generic_file_buffered_write(struct kiocb *iocb, const struct iovec *iov,
+			       unsigned long nr_segs, loff_t pos, loff_t *ppos,
+			       size_t count, ssize_t written)
+{
+	struct file *file = iocb->ki_filp;
+	ssize_t status;
+	struct iov_iter i;
+
+	iov_iter_init(&i, WRITE, iov, nr_segs, count);
+	status = generic_perform_write(file, &i, pos);
+
+	if (likely(status >= 0)) {
+		written += status;
+		*ppos = pos + status;
+	}
+
+	return written ? written : status;
+}
+#endif

kmod/src/kernelcompat.h

@@ -266,4 +266,11 @@ static inline int kc_kernel_getpeername(struct socket *sock, struct sockaddr *ad
 #define kc_sock_create_kern sock_create_kern
 #endif
 
+#ifndef KC_GENERIC_FILE_BUFFERED_WRITE
+ssize_t kc_generic_file_buffered_write(struct kiocb *iocb, const struct iovec *iov,
+               unsigned long nr_segs, loff_t pos, loff_t *ppos,
+               size_t count, ssize_t written);
+#define generic_file_buffered_write kc_generic_file_buffered_write
+#endif
+
 #endif