mtd: Add several functions to the fail_function list

add mtd_read(), mtd_write(), mtd_erase(), mtd_block_markbad() to
fail_function list for testing purpose

- Specify the function to inject the fault
echo mtd_read > /sys/kernel/debug/fail_function/inject

- Specifies the return value of the function to inject the fault
printf %#x -12 > /sys/kernel/debug/fail_function/mtd_read/retval

- Specify other fault injection configuration parameters.
echo -1 > /sys/kernel/debug/fail_function/times
echo 100 > /sys/kernel/debug/fail_function/probability
echo 15 > /sys/kernel/debug/fail_function/space

Signed-off-by: ZhaoLong Wang <wangzhaolong1@huawei.com>
Reviewed-by: Zhihao Cheng <chengzhihao1@huawei.com>
Signed-off-by: Richard Weinberger <richard@nod.at>

Author: ZhaoLong Wang

drivers/mtd/mtdcore.c

@@ -30,6 +30,7 @@
 #include <linux/debugfs.h>
 #include <linux/nvmem-provider.h>
 #include <linux/root_dev.h>
+#include <linux/error-injection.h>
 
 #include <linux/mtd/mtd.h>
 #include <linux/mtd/partitions.h>
@@ -1412,6 +1413,7 @@ int mtd_erase(struct mtd_info *mtd, struct erase_info *instr)
 	return ret;
 }
 EXPORT_SYMBOL_GPL(mtd_erase);
+ALLOW_ERROR_INJECTION(mtd_erase, ERRNO);
 
 /*
  * This stuff for eXecute-In-Place. phys is optional and may be set to NULL.
@@ -1511,6 +1513,7 @@ int mtd_read(struct mtd_info *mtd, loff_t from, size_t len, size_t *retlen,
 	return ret;
 }
 EXPORT_SYMBOL_GPL(mtd_read);
+ALLOW_ERROR_INJECTION(mtd_read, ERRNO);
 
 int mtd_write(struct mtd_info *mtd, loff_t to, size_t len, size_t *retlen,
 	      const u_char *buf)
@@ -1527,6 +1530,7 @@ int mtd_write(struct mtd_info *mtd, loff_t to, size_t len, size_t *retlen,
 	return ret;
 }
 EXPORT_SYMBOL_GPL(mtd_write);
+ALLOW_ERROR_INJECTION(mtd_write, ERRNO);
 
 /*
  * In blackbox flight recorder like scenarios we want to make successful writes
@@ -2347,6 +2351,7 @@ int mtd_block_markbad(struct mtd_info *mtd, loff_t ofs)
 	return 0;
 }
 EXPORT_SYMBOL_GPL(mtd_block_markbad);
+ALLOW_ERROR_INJECTION(mtd_block_markbad, ERRNO);
 
 /*
  * default_mtd_writev - the default writev method