f2fs: add mount option to select fault injection ratio

This patch adds a mount option to select fault ratio.

Signed-off-by: Jaegeuk Kim <[e-mail]>

fs/f2fs/Kconfig

···
 	  information and block IO patterns in the filesystem level.
 
 	  If unsure, say N.
+
+config F2FS_FAULT_INJECTION
+	bool "F2FS fault injection facility"
+	depends on F2FS_FS
+	help
+	  Test F2FS to inject faults such as ENOMEM, ENOSPC, and so on.
+
+	  If unsure, say N.

fs/f2fs/f2fs.h

···
 #define F2FS_MOUNT_EXTENT_CACHE		0x00002000
 #define F2FS_MOUNT_FORCE_FG_GC		0x00004000
 #define F2FS_MOUNT_DATA_FLUSH		0x00008000
+#define F2FS_MOUNT_FAULT_INJECTION	0x00010000
 
 #define clear_opt(sbi, option)	(sbi->mount_opt.opt &= ~F2FS_MOUNT_##option)
 #define set_opt(sbi, option)	(sbi->mount_opt.opt |= F2FS_MOUNT_##option)

fs/f2fs/super.c

···
 static struct kmem_cache *f2fs_inode_cachep;
 static struct kset *f2fs_kset;
 
+#ifdef CONFIG_F2FS_FAULT_INJECTION
+u32 f2fs_fault_rate = 0;
+#endif
+
 /* f2fs-wide shrinker description */
 static struct shrinker f2fs_shrinker_info = {
 	.scan_objects = f2fs_shrink_scan,
···
 	Opt_noextent_cache,
 	Opt_noinline_data,
 	Opt_data_flush,
+	Opt_fault_injection,
 	Opt_err,
 };
 
···
 	{Opt_noextent_cache, "noextent_cache"},
 	{Opt_noinline_data, "noinline_data"},
 	{Opt_data_flush, "data_flush"},
+	{Opt_fault_injection, "fault_injection=%u"},
 	{Opt_err, NULL},
 };
 
···
 	char *p, *name;
 	int arg = 0;
 
+#ifdef CONFIG_F2FS_FAULT_INJECTION
+	f2fs_fault_rate = 0;
+#endif
 	if (!options)
 		return 0;
 
···
 			break;
 		case Opt_data_flush:
 			set_opt(sbi, DATA_FLUSH);
+			break;
+		case Opt_fault_injection:
+			if (args->from && match_int(args, &arg))
+				return -EINVAL;
+#ifdef CONFIG_F2FS_FAULT_INJECTION
+			f2fs_fault_rate = arg;
+#else
+			f2fs_msg(sb, KERN_INFO,
+				"FAULT_INJECTION was not selected");
+#endif
 			break;
 		default:
 			f2fs_msg(sb, KERN_ERR,