UBIFS: add re-mount debugging checks

We observe space corrupted accounting when re-mounting. So add some
debbugging checks to catch problems like this.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>

fs/ubifs/budget.c

@@ -689,7 +689,7 @@ long long ubifs_reported_space(const struct ubifs_info *c, long long free)
 }
 
 /**
- * ubifs_get_free_space - return amount of free space.
+ * ubifs_get_free_space_nolock - return amount of free space.
  * @c: UBIFS file-system description object
  *
  * This function calculates amount of free space to report to user-space.
@@ -704,16 +704,14 @@ long long ubifs_reported_space(const struct ubifs_info *c, long long free)
  * traditional file-systems, because they have way less overhead than UBIFS.
  * So, to keep users happy, UBIFS tries to take the overhead into account.
  */
-long long ubifs_get_free_space(struct ubifs_info *c)
+long long ubifs_get_free_space_nolock(struct ubifs_info *c)
 {
-	int min_idx_lebs, rsvd_idx_lebs, lebs;
+	int rsvd_idx_lebs, lebs;
 	long long available, outstanding, free;
 
-	spin_lock(&c->space_lock);
-	min_idx_lebs = c->min_idx_lebs;
-	ubifs_assert(min_idx_lebs == ubifs_calc_min_idx_lebs(c));
+	ubifs_assert(c->min_idx_lebs == ubifs_calc_min_idx_lebs(c));
 	outstanding = c->budg_data_growth + c->budg_dd_growth;
-	available = ubifs_calc_available(c, min_idx_lebs);
+	available = ubifs_calc_available(c, c->min_idx_lebs);
 
 	/*
 	 * When reporting free space to user-space, UBIFS guarantees that it is
@@ -726,15 +724,14 @@ long long ubifs_get_free_space(struct ubifs_info *c)
 	 * Note, the calculations below are similar to what we have in
 	 * 'do_budget_space()', so refer there for comments.
 	 */
-	if (min_idx_lebs > c->lst.idx_lebs)
-		rsvd_idx_lebs = min_idx_lebs - c->lst.idx_lebs;
+	if (c->min_idx_lebs > c->lst.idx_lebs)
+		rsvd_idx_lebs = c->min_idx_lebs - c->lst.idx_lebs;
 	else
 		rsvd_idx_lebs = 0;
 	lebs = c->lst.empty_lebs + c->freeable_cnt + c->idx_gc_cnt -
 	       c->lst.taken_empty_lebs;
 	lebs -= rsvd_idx_lebs;
 	available += lebs * (c->dark_wm - c->leb_overhead);
-	spin_unlock(&c->space_lock);
 
 	if (available > outstanding)
 		free = ubifs_reported_space(c, available - outstanding);
@@ -742,3 +739,21 @@ long long ubifs_get_free_space(struct ubifs_info *c)
 		free = 0;
 	return free;
 }
+
+/**
+ * ubifs_get_free_space - return amount of free space.
+ * @c: UBIFS file-system description object
+ *
+ * This function calculates and retuns amount of free space to report to
+ * user-space.
+ */
+long long ubifs_get_free_space(struct ubifs_info *c)
+{
+	long long free;
+
+	spin_lock(&c->space_lock);
+	free = ubifs_get_free_space_nolock(c);
+	spin_unlock(&c->space_lock);
+
+	return free;
+}

fs/ubifs/debug.c

@@ -620,9 +620,11 @@ void dbg_dump_budg(struct ubifs_info *c)
 	       c->dark_wm, c->dead_wm, c->max_idx_node_sz);
 	printk(KERN_DEBUG "\tgc_lnum %d, ihead_lnum %d\n",
 	       c->gc_lnum, c->ihead_lnum);
-	for (i = 0; i < c->jhead_cnt; i++)
-		printk(KERN_DEBUG "\tjhead %d\t LEB %d\n",
-		       c->jheads[i].wbuf.jhead, c->jheads[i].wbuf.lnum);
+	/* If we are in R/O mode, journal heads do not exist */
+	if (c->jheads)
+		for (i = 0; i < c->jhead_cnt; i++)
+			printk(KERN_DEBUG "\tjhead %d\t LEB %d\n",
+			       c->jheads[i].wbuf.jhead, c->jheads[i].wbuf.lnum);
 	for (rb = rb_first(&c->buds); rb; rb = rb_next(rb)) {
 		bud = rb_entry(rb, struct ubifs_bud, rb);
 		printk(KERN_DEBUG "\tbud LEB %d\n", bud->lnum);
@@ -637,10 +639,7 @@ void dbg_dump_budg(struct ubifs_info *c)
 	/* Print budgeting predictions */
 	available = ubifs_calc_available(c, c->min_idx_lebs);
 	outstanding = c->budg_data_growth + c->budg_dd_growth;
-	if (available > outstanding)
-		free = ubifs_reported_space(c, available - outstanding);
-	else
-		free = 0;
+	free = ubifs_get_free_space_nolock(c);
 	printk(KERN_DEBUG "Budgeting predictions:\n");
 	printk(KERN_DEBUG "\tavailable: %lld, outstanding %lld, free %lld\n",
 	       available, outstanding, free);
@@ -860,6 +859,65 @@ void dbg_dump_index(struct ubifs_info *c)
 	dbg_walk_index(c, NULL, dump_znode, NULL);
 }
 
+/**
+ * dbg_save_space_info - save information about flash space.
+ * @c: UBIFS file-system description object
+ *
+ * This function saves information about UBIFS free space, dirty space, etc, in
+ * order to check it later.
+ */
+void dbg_save_space_info(struct ubifs_info *c)
+{
+	struct ubifs_debug_info *d = c->dbg;
+
+	ubifs_get_lp_stats(c, &d->saved_lst);
+
+	spin_lock(&c->space_lock);
+	d->saved_free = ubifs_get_free_space_nolock(c);
+	spin_unlock(&c->space_lock);
+}
+
+/**
+ * dbg_check_space_info - check flash space information.
+ * @c: UBIFS file-system description object
+ *
+ * This function compares current flash space information with the information
+ * which was saved when the 'dbg_save_space_info()' function was called.
+ * Returns zero if the information has not changed, and %-EINVAL it it has
+ * changed.
+ */
+int dbg_check_space_info(struct ubifs_info *c)
+{
+	struct ubifs_debug_info *d = c->dbg;
+	struct ubifs_lp_stats lst;
+	long long avail, free;
+
+	spin_lock(&c->space_lock);
+	avail = ubifs_calc_available(c, c->min_idx_lebs);
+	spin_unlock(&c->space_lock);
+	free = ubifs_get_free_space(c);
+
+	if (free != d->saved_free) {
+		ubifs_err("free space changed from %lld to %lld",
+			  d->saved_free, free);
+		goto out;
+	}
+
+	return 0;
+
+out:
+	ubifs_msg("saved lprops statistics dump");
+	dbg_dump_lstats(&d->saved_lst);
+	ubifs_get_lp_stats(c, &lst);
+	ubifs_msg("current lprops statistics dump");
+	dbg_dump_lstats(&d->saved_lst);
+	spin_lock(&c->space_lock);
+	dbg_dump_budg(c);
+	spin_unlock(&c->space_lock);
+	dump_stack();
+	return -EINVAL;
+}
+
 /**
  * dbg_check_synced_i_size - check synchronized inode size.
  * @inode: inode to check
@@ -2409,7 +2467,7 @@ void ubifs_debugging_exit(struct ubifs_info *c)
  * Root directory for UBIFS stuff in debugfs. Contains sub-directories which
  * contain the stuff specific to particular file-system mounts.
  */
-static struct dentry *debugfs_rootdir;
+static struct dentry *dfs_rootdir;
 
 /**
  * dbg_debugfs_init - initialize debugfs file-system.
@@ -2421,9 +2479,9 @@ static struct dentry *debugfs_rootdir;
  */
 int dbg_debugfs_init(void)
 {
-	debugfs_rootdir = debugfs_create_dir("ubifs", NULL);
-	if (IS_ERR(debugfs_rootdir)) {
-		int err = PTR_ERR(debugfs_rootdir);
+	dfs_rootdir = debugfs_create_dir("ubifs", NULL);
+	if (IS_ERR(dfs_rootdir)) {
+		int err = PTR_ERR(dfs_rootdir);
 		ubifs_err("cannot create \"ubifs\" debugfs directory, "
 			  "error %d\n", err);
 		return err;
@@ -2437,7 +2495,7 @@ int dbg_debugfs_init(void)
  */
 void dbg_debugfs_exit(void)
 {
-	debugfs_remove(debugfs_rootdir);
+	debugfs_remove(dfs_rootdir);
 }
 
 static int open_debugfs_file(struct inode *inode, struct file *file)
@@ -2452,13 +2510,13 @@ static ssize_t write_debugfs_file(struct file *file, const char __user *buf,
 	struct ubifs_info *c = file->private_data;
 	struct ubifs_debug_info *d = c->dbg;
 
-	if (file->f_path.dentry == d->dump_lprops)
+	if (file->f_path.dentry == d->dfs_dump_lprops)
 		dbg_dump_lprops(c);
-	else if (file->f_path.dentry == d->dump_budg) {
+	else if (file->f_path.dentry == d->dfs_dump_budg) {
 		spin_lock(&c->space_lock);
 		dbg_dump_budg(c);
 		spin_unlock(&c->space_lock);
-	} else if (file->f_path.dentry == d->dump_tnc) {
+	} else if (file->f_path.dentry == d->dfs_dump_tnc) {
 		mutex_lock(&c->tnc_mutex);
 		dbg_dump_tnc(c);
 		mutex_unlock(&c->tnc_mutex);
@@ -2469,7 +2527,7 @@ static ssize_t write_debugfs_file(struct file *file, const char __user *buf,
 	return count;
 }
 
-static const struct file_operations debugfs_fops = {
+static const struct file_operations dfs_fops = {
 	.open = open_debugfs_file,
 	.write = write_debugfs_file,
 	.owner = THIS_MODULE,
@@ -2494,36 +2552,32 @@ int dbg_debugfs_init_fs(struct ubifs_info *c)
 	struct dentry *dent;
 	struct ubifs_debug_info *d = c->dbg;
 
-	sprintf(d->debugfs_dir_name, "ubi%d_%d", c->vi.ubi_num, c->vi.vol_id);
-	d->debugfs_dir = debugfs_create_dir(d->debugfs_dir_name,
-					      debugfs_rootdir);
-	if (IS_ERR(d->debugfs_dir)) {
-		err = PTR_ERR(d->debugfs_dir);
+	sprintf(d->dfs_dir_name, "ubi%d_%d", c->vi.ubi_num, c->vi.vol_id);
+	d->dfs_dir = debugfs_create_dir(d->dfs_dir_name, dfs_rootdir);
+	if (IS_ERR(d->dfs_dir)) {
+		err = PTR_ERR(d->dfs_dir);
 		ubifs_err("cannot create \"%s\" debugfs directory, error %d\n",
-			  d->debugfs_dir_name, err);
+			  d->dfs_dir_name, err);
 		goto out;
 	}
 
 	fname = "dump_lprops";
-	dent = debugfs_create_file(fname, S_IWUGO, d->debugfs_dir, c,
-				   &debugfs_fops);
+	dent = debugfs_create_file(fname, S_IWUGO, d->dfs_dir, c, &dfs_fops);
 	if (IS_ERR(dent))
 		goto out_remove;
-	d->dump_lprops = dent;
+	d->dfs_dump_lprops = dent;
 
 	fname = "dump_budg";
-	dent = debugfs_create_file(fname, S_IWUGO, d->debugfs_dir, c,
-				   &debugfs_fops);
+	dent = debugfs_create_file(fname, S_IWUGO, d->dfs_dir, c, &dfs_fops);
 	if (IS_ERR(dent))
 		goto out_remove;
-	d->dump_budg = dent;
+	d->dfs_dump_budg = dent;
 
 	fname = "dump_tnc";
-	dent = debugfs_create_file(fname, S_IWUGO, d->debugfs_dir, c,
-				   &debugfs_fops);
+	dent = debugfs_create_file(fname, S_IWUGO, d->dfs_dir, c, &dfs_fops);
 	if (IS_ERR(dent))
 		goto out_remove;
-	d->dump_tnc = dent;
+	d->dfs_dump_tnc = dent;
 
 	return 0;
 
@@ -2531,7 +2585,7 @@ out_remove:
 	err = PTR_ERR(dent);
 	ubifs_err("cannot create \"%s\" debugfs directory, error %d\n",
 		  fname, err);
-	debugfs_remove_recursive(d->debugfs_dir);
+	debugfs_remove_recursive(d->dfs_dir);
 out:
 	return err;
 }
@@ -2542,7 +2596,7 @@ out:
  */
 void dbg_debugfs_exit_fs(struct ubifs_info *c)
 {
-	debugfs_remove_recursive(c->dbg->debugfs_dir);
+	debugfs_remove_recursive(c->dbg->dfs_dir);
 }
 
 #endif /* CONFIG_UBIFS_FS_DEBUG */

fs/ubifs/debug.h

@@ -41,15 +41,17 @@
  * @chk_lpt_wastage: used by LPT tree size checker
  * @chk_lpt_lebs: used by LPT tree size checker
  * @new_nhead_offs: used by LPT tree size checker
- * @new_ihead_lnum: used by debugging to check ihead_lnum
- * @new_ihead_offs: used by debugging to check ihead_offs
+ * @new_ihead_lnum: used by debugging to check @c->ihead_lnum
+ * @new_ihead_offs: used by debugging to check @c->ihead_offs
  *
- * debugfs_dir_name: name of debugfs directory containing this file-system's
- *                   files
- * debugfs_dir: direntry object of the file-system debugfs directory
- * dump_lprops: "dump lprops" debugfs knob
- * dump_budg: "dump budgeting information" debugfs knob
- * dump_tnc: "dump TNC" debugfs knob
+ * @saved_lst: saved lprops statistics (used by 'dbg_save_space_info()')
+ * @saved_free: saved free space (used by 'dbg_save_space_info()')
+ *
+ * dfs_dir_name: name of debugfs directory containing this file-system's files
+ * dfs_dir: direntry object of the file-system debugfs directory
+ * dfs_dump_lprops: "dump lprops" debugfs knob
+ * dfs_dump_budg: "dump budgeting information" debugfs knob
+ * dfs_dump_tnc: "dump TNC" debugfs knob
  */
 struct ubifs_debug_info {
 	void *buf;
@@ -69,11 +71,14 @@ struct ubifs_debug_info {
 	int new_ihead_lnum;
 	int new_ihead_offs;
 
-	char debugfs_dir_name[100];
-	struct dentry *debugfs_dir;
-	struct dentry *dump_lprops;
-	struct dentry *dump_budg;
-	struct dentry *dump_tnc;
+	struct ubifs_lp_stats saved_lst;
+	long long saved_free;
+
+	char dfs_dir_name[100];
+	struct dentry *dfs_dir;
+	struct dentry *dfs_dump_lprops;
+	struct dentry *dfs_dump_budg;
+	struct dentry *dfs_dump_tnc;
 };
 
 #define ubifs_assert(expr) do {                                                \
@@ -297,7 +302,8 @@ int dbg_walk_index(struct ubifs_info *c, dbg_leaf_callback leaf_cb,
 		   dbg_znode_callback znode_cb, void *priv);
 
 /* Checking functions */
-
+void dbg_save_space_info(struct ubifs_info *c);
+int dbg_check_space_info(struct ubifs_info *c);
 int dbg_check_lprops(struct ubifs_info *c);
 int dbg_old_index_check_init(struct ubifs_info *c, struct ubifs_zbranch *zroot);
 int dbg_check_old_index(struct ubifs_info *c, struct ubifs_zbranch *zroot);
@@ -439,6 +445,8 @@ void dbg_debugfs_exit_fs(struct ubifs_info *c);
 
 #define dbg_walk_index(c, leaf_cb, znode_cb, priv) 0
 #define dbg_old_index_check_init(c, zroot)         0
+#define dbg_save_space_info(c)                     ({})
+#define dbg_check_space_info(c)                    0
 #define dbg_check_old_index(c, zroot)              0
 #define dbg_check_cats(c)                          0
 #define dbg_check_ltab(c)                          0

fs/ubifs/file.c

@@ -432,7 +432,6 @@ static int ubifs_write_begin(struct file *file, struct address_space *mapping,
 	int uninitialized_var(err), appending = !!(pos + len > inode->i_size);
 	struct page *page;
 
-
 	ubifs_assert(ubifs_inode(inode)->ui_size == inode->i_size);
 
 	if (unlikely(c->ro_media))

fs/ubifs/lprops.c

@@ -635,10 +635,10 @@ const struct ubifs_lprops *ubifs_change_lp(struct ubifs_info *c,
  * @c: UBIFS file-system description object
  * @st: return statistics
  */
-void ubifs_get_lp_stats(struct ubifs_info *c, struct ubifs_lp_stats *st)
+void ubifs_get_lp_stats(struct ubifs_info *c, struct ubifs_lp_stats *lst)
 {
 	spin_lock(&c->space_lock);
-	memcpy(st, &c->lst, sizeof(struct ubifs_lp_stats));
+	memcpy(lst, &c->lst, sizeof(struct ubifs_lp_stats));
 	spin_unlock(&c->space_lock);
 }
 

fs/ubifs/super.c

@@ -1470,6 +1470,7 @@ static int ubifs_remount_rw(struct ubifs_info *c)
 	int err, lnum;
 
 	mutex_lock(&c->umount_mutex);
+	dbg_save_space_info(c);
 	c->remounting_rw = 1;
 	c->always_chk_crc = 1;
 
@@ -1573,8 +1574,9 @@ static int ubifs_remount_rw(struct ubifs_info *c)
 	c->vfs_sb->s_flags &= ~MS_RDONLY;
 	c->remounting_rw = 0;
 	c->always_chk_crc = 0;
+	err = dbg_check_space_info(c);
 	mutex_unlock(&c->umount_mutex);
-	return 0;
+	return err;
 
 out:
 	vfree(c->orph_buf);
@@ -1629,8 +1631,8 @@ static void commit_on_unmount(struct ubifs_info *c)
  * ubifs_remount_ro - re-mount in read-only mode.
  * @c: UBIFS file-system description object
  *
- * We rely on VFS to have stopped writing. Possibly the background thread could
- * be running a commit, however kthread_stop will wait in that case.
+ * We assume VFS has stopped writing. Possibly the background thread could be
+ * running a commit, however kthread_stop will wait in that case.
  */
 static void ubifs_remount_ro(struct ubifs_info *c)
 {
@@ -1640,13 +1642,14 @@ static void ubifs_remount_ro(struct ubifs_info *c)
 	ubifs_assert(!c->ro_media);
 
 	commit_on_unmount(c);
-
 	mutex_lock(&c->umount_mutex);
 	if (c->bgt) {
 		kthread_stop(c->bgt);
 		c->bgt = NULL;
 	}
 
+	dbg_save_space_info(c);
+
 	for (i = 0; i < c->jhead_cnt; i++) {
 		ubifs_wbuf_sync(&c->jheads[i].wbuf);
 		del_timer_sync(&c->jheads[i].wbuf.timer);
@@ -1669,6 +1672,9 @@ static void ubifs_remount_ro(struct ubifs_info *c)
 	vfree(c->ileb_buf);
 	c->ileb_buf = NULL;
 	ubifs_lpt_free(c, 1);
+	err = dbg_check_space_info(c);
+	if (err)
+		ubifs_ro_mode(c, err);
 	mutex_unlock(&c->umount_mutex);
 }
 

fs/ubifs/ubifs.h

@@ -1495,6 +1495,7 @@ void ubifs_release_ino_dirty(struct ubifs_info *c, struct inode *inode,
 void ubifs_cancel_ino_op(struct ubifs_info *c, struct inode *inode,
 			 struct ubifs_budget_req *req);
 long long ubifs_get_free_space(struct ubifs_info *c);
+long long ubifs_get_free_space_nolock(struct ubifs_info *c);
 int ubifs_calc_min_idx_lebs(struct ubifs_info *c);
 void ubifs_convert_page_budget(struct ubifs_info *c);
 long long ubifs_reported_space(const struct ubifs_info *c, long long free);
@@ -1646,7 +1647,7 @@ const struct ubifs_lprops *ubifs_change_lp(struct ubifs_info *c,
 					   const struct ubifs_lprops *lp,
 					   int free, int dirty, int flags,
 					   int idx_gc_cnt);
-void ubifs_get_lp_stats(struct ubifs_info *c, struct ubifs_lp_stats *stats);
+void ubifs_get_lp_stats(struct ubifs_info *c, struct ubifs_lp_stats *lst);
 void ubifs_add_to_cat(struct ubifs_info *c, struct ubifs_lprops *lprops,
 		      int cat);
 void ubifs_replace_cat(struct ubifs_info *c, struct ubifs_lprops *old_lprops,