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>

7 files changed, 148 insertions, 65 deletions

diff --git a/fs/ubifs/budget.c b/fs/ubifs/budget.c
index 175f9c590b77..f393620890ee 100644
--- a/fs/ubifs/budget.c
+++ b/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;
+}
diff --git a/fs/ubifs/debug.c b/fs/ubifs/debug.c
index 792c5a16c182..9a41f6f245b7 100644
--- a/fs/ubifs/debug.c
+++ b/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);
@@ -861,6 +860,65 @@ void dbg_dump_index(struct ubifs_info *c)
 }
 
 /**
+ * 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 */
diff --git a/fs/ubifs/debug.h b/fs/ubifs/debug.h
index 9820d6999f7e..c1cd73b2e06e 100644
--- a/fs/ubifs/debug.h
+++ b/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
diff --git a/fs/ubifs/file.c b/fs/ubifs/file.c
index 17443d97e6f1..93b6de51f261 100644
--- a/fs/ubifs/file.c
+++ b/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))
diff --git a/fs/ubifs/lprops.c b/fs/ubifs/lprops.c
index 68328c59762b..4cdd284dea56 100644
--- a/fs/ubifs/lprops.c
+++ b/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);
 }
 
diff --git a/fs/ubifs/super.c b/fs/ubifs/super.c
index 807bbd3c8b4b..5c814a71f33a 100644
--- a/fs/ubifs/super.c
+++ b/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);
 }
 
diff --git a/fs/ubifs/ubifs.h b/fs/ubifs/ubifs.h
index ee9517a7b024..f1754354029f 100644
--- a/fs/ubifs/ubifs.h
+++ b/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,