UBIFS: use EROFS when emulating failures

When the debugging failure emulation is enabled and UBIFS decides to
emulate an I/O error, it uses EIO error code. In which case UBIFS
switches into R/O mode later on. The for the user-space is that when
a failure is emulated, the file-system sometimes returns EIO and
sometimes EROFS. This makes it more difficult to implement user-space
tests for the failure mode. Let's be consistent and return EROFS in
all the cases.

This patch is an improvement for the debugging code and does not affect
the functionality at all.
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>

fs/ubifs/debug.c

@@ -2650,7 +2650,7 @@ int dbg_leb_read(struct ubi_volume_desc *desc, int lnum, char *buf, int offset,
 		 int len, int check)
 {
 	if (in_failure_mode(desc))
-		return -EIO;
+		return -EROFS;
 	return ubi_leb_read(desc, lnum, buf, offset, len, check);
 }
 
@@ -2660,7 +2660,7 @@ int dbg_leb_write(struct ubi_volume_desc *desc, int lnum, const void *buf,
 	int err, failing;
 
 	if (in_failure_mode(desc))
-		return -EIO;
+		return -EROFS;
 	failing = do_fail(desc, lnum, 1);
 	if (failing)
 		cut_data(buf, len);
@@ -2668,7 +2668,7 @@ int dbg_leb_write(struct ubi_volume_desc *desc, int lnum, const void *buf,
 	if (err)
 		return err;
 	if (failing)
-		return -EIO;
+		return -EROFS;
 	return 0;
 }
 
@@ -2678,12 +2678,12 @@ int dbg_leb_change(struct ubi_volume_desc *desc, int lnum, const void *buf,
 	int err;
 
 	if (do_fail(desc, lnum, 1))
-		return -EIO;
+		return -EROFS;
 	err = ubi_leb_change(desc, lnum, buf, len, dtype);
 	if (err)
 		return err;
 	if (do_fail(desc, lnum, 1))
-		return -EIO;
+		return -EROFS;
 	return 0;
 }
 
@@ -2692,12 +2692,12 @@ int dbg_leb_erase(struct ubi_volume_desc *desc, int lnum)
 	int err;
 
 	if (do_fail(desc, lnum, 0))
-		return -EIO;
+		return -EROFS;
 	err = ubi_leb_erase(desc, lnum);
 	if (err)
 		return err;
 	if (do_fail(desc, lnum, 0))
-		return -EIO;
+		return -EROFS;
 	return 0;
 }
 
@@ -2706,19 +2706,19 @@ int dbg_leb_unmap(struct ubi_volume_desc *desc, int lnum)
 	int err;
 
 	if (do_fail(desc, lnum, 0))
-		return -EIO;
+		return -EROFS;
 	err = ubi_leb_unmap(desc, lnum);
 	if (err)
 		return err;
 	if (do_fail(desc, lnum, 0))
-		return -EIO;
+		return -EROFS;
 	return 0;
 }
 
 int dbg_is_mapped(struct ubi_volume_desc *desc, int lnum)
 {
 	if (in_failure_mode(desc))
-		return -EIO;
+		return -EROFS;
 	return ubi_is_mapped(desc, lnum);
 }
 
@@ -2727,12 +2727,12 @@ int dbg_leb_map(struct ubi_volume_desc *desc, int lnum, int dtype)
 	int err;
 
 	if (do_fail(desc, lnum, 0))
-		return -EIO;
+		return -EROFS;
 	err = ubi_leb_map(desc, lnum, dtype);
 	if (err)
 		return err;
 	if (do_fail(desc, lnum, 0))
-		return -EIO;
+		return -EROFS;
 	return 0;
 }