ubifs: Rework ubifs_assert()

With having access to struct ubifs_info in ubifs_assert() we can
give more information when an assert is failing.
By using ubifs_err() we can tell which UBIFS instance failed.

Also multiple actions can be taken now.
We support:
 - report: This is what UBIFS did so far, just report the failure and go
   on.
 - read-only: Switch to read-only mode.
 - panic: shoot the kernel in the head.
Signed-off-by: Richard Weinberger <richard@nod.at>

fs/ubifs/debug.c

@@ -3081,6 +3081,28 @@ void dbg_debugfs_exit(void)
 		debugfs_remove_recursive(dfs_rootdir);
 }
 
+void ubifs_assert_failed(struct ubifs_info *c, const char *expr,
+			 const char *file, int line)
+{
+	ubifs_err(c, "UBIFS assert failed: %s, in %s:%u", expr, file, line);
+
+	switch (c->assert_action) {
+		case ASSACT_PANIC:
+		BUG();
+		break;
+
+		case ASSACT_RO:
+		ubifs_ro_mode(c, -EINVAL);
+		break;
+
+		case ASSACT_REPORT:
+		default:
+		dump_stack();
+		break;
+
+	}
+}
+
 /**
  * ubifs_debugging_init - initialize UBIFS debugging.
  * @c: UBIFS file-system description object

fs/ubifs/debug.h

@@ -148,18 +148,20 @@ struct ubifs_global_debug_info {
 	unsigned int tst_rcvry:1;
 };
 
+void ubifs_assert_failed(struct ubifs_info *c, const char *expr,
+	const char *file, int line);
+
 #define ubifs_assert(c, expr) do {                                             \
 	if (unlikely(!(expr))) {                                               \
-		pr_crit("UBIFS assert failed in %s at %u (pid %d)\n",          \
-		       __func__, __LINE__, current->pid);                      \
-		dump_stack();                                                  \
+		ubifs_assert_failed((struct ubifs_info *)c, #expr, __FILE__,   \
+		 __LINE__);                                                    \
 	}                                                                      \
 } while (0)
 
 #define ubifs_assert_cmt_locked(c) do {                                        \
 	if (unlikely(down_write_trylock(&(c)->commit_sem))) {                  \
 		up_write(&(c)->commit_sem);                                    \
-		pr_crit("commit lock is not locked!\n");                       \
+		ubifs_err(c, "commit lock is not locked!\n");                  \
 		ubifs_assert(c, 0);                                            \
 	}                                                                      \
 } while (0)

fs/ubifs/ubifs.h

@@ -258,6 +258,18 @@ enum {
 	LEB_RETAINED,
 };
 
+/*
+ * Action taken upon a failed ubifs_assert().
+ * @ASSACT_REPORT: just report the failed assertion
+ * @ASSACT_RO: switch to read-only mode
+ * @ASSACT_PANIC: call BUG() and possible panic the kernel
+ */
+enum {
+	ASSACT_REPORT = 0,
+	ASSACT_RO,
+	ASSACT_PANIC,
+};
+
 /**
  * struct ubifs_old_idx - index node obsoleted since last commit start.
  * @rb: rb-tree node
@@ -1015,6 +1027,7 @@ struct ubifs_debug_info;
  * @bulk_read: enable bulk-reads
  * @default_compr: default compression algorithm (%UBIFS_COMPR_LZO, etc)
  * @rw_incompat: the media is not R/W compatible
+ * @assert_action: action to take when a ubifs_assert() fails
  *
  * @tnc_mutex: protects the Tree Node Cache (TNC), @zroot, @cnext, @enext, and
  *             @calc_idx_sz
@@ -1256,6 +1269,7 @@ struct ubifs_info {
 	unsigned int bulk_read:1;
 	unsigned int default_compr:2;
 	unsigned int rw_incompat:1;
+	unsigned int assert_action:2;
 
 	struct mutex tnc_mutex;
 	struct ubifs_zbranch zroot;