UBIFS: lessen the size of debugging info data structure

This patch lessens the 'struct ubifs_debug_info' size by 90 bytes by
allocating less bytes for the debugfs root directory name. It introduces macros
for the name patter an length instead of hard-coding 100 bytes. It also makes
UBIFS use 'snprintf()' and teaches it to gracefully catch situations when the
name array is too short.

Additionally, this patch makes 2 unrelated changes - I just thought they do not
deserve separate commits: simplifies 'ubifs_assert()' for non-debugging case
and makes 'dbg_debugfs_init()' properly verify debugfs return code which may be
an error code or NULL, so we should you 'IS_ERR_OR_NULL()' instead of
'IS_ERR()'.

Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>

2 files changed, 22 insertions, 7 deletions

diff --git a/fs/ubifs/debug.c b/fs/ubifs/debug.c
index 0bb2bcef0de9..c9609a63512e 100644
--- a/fs/ubifs/debug.c
+++ b/fs/ubifs/debug.c
@@ -2815,8 +2815,8 @@ static struct dentry *dfs_rootdir;
 int dbg_debugfs_init(void)
 {
         dfs_rootdir = debugfs_create_dir("ubifs", NULL);
-        if (IS_ERR(dfs_rootdir)) {
-                int err = PTR_ERR(dfs_rootdir);
+        if (IS_ERR_OR_NULL(dfs_rootdir)) {
+                int err = dfs_rootdir ? PTR_ERR(dfs_rootdir) : -ENODEV;
                 ubifs_err("cannot create \"ubifs\" debugfs directory, "
                           "error %d\n", err);
                 return err;
@@ -2880,12 +2880,20 @@ static const struct file_operations dfs_fops = {
  */
 int dbg_debugfs_init_fs(struct ubifs_info *c)
 {
-        int err;
+        int err, n;
         const char *fname;
         struct dentry *dent;
         struct ubifs_debug_info *d = c->dbg;
 
-        sprintf(d->dfs_dir_name, "ubi%d_%d", c->vi.ubi_num, c->vi.vol_id);
+        n = snprintf(d->dfs_dir_name, UBIFS_DFS_DIR_LEN + 1, UBIFS_DFS_DIR_NAME,
+                     c->vi.ubi_num, c->vi.vol_id);
+        if (n == UBIFS_DFS_DIR_LEN) {
+                /* The array size is too small */
+                fname = UBIFS_DFS_DIR_NAME;
+                dent = ERR_PTR(-EINVAL);
+                goto out;
+        }
+
         fname = d->dfs_dir_name;
         dent = debugfs_create_dir(fname, dfs_rootdir);
         if (IS_ERR_OR_NULL(dent))
@@ -2916,7 +2924,7 @@ out_remove:
         debugfs_remove_recursive(d->dfs_dir);
 out:
         err = dent ? PTR_ERR(dent) : -ENODEV;
-        ubifs_err("cannot create \"%s\" debugfs directory, error %d\n",
+        ubifs_err("cannot create \"%s\" debugfs filr or directory, error %d\n",
                   fname, err);
         return err;
 }
diff --git a/fs/ubifs/debug.h b/fs/ubifs/debug.h
index a811ac4a26bb..b59c43a4149c 100644
--- a/fs/ubifs/debug.h
+++ b/fs/ubifs/debug.h
@@ -33,6 +33,13 @@ typedef int (*dbg_znode_callback)(struct ubifs_info *c,
 
 #include <linux/random.h>
 
+/*
+ * The UBIFS debugfs directory name pattern and maximum name length (3 for "ubi"
+ * + 1 for "_" and plus 2x2 for 2 UBI numbers and 1 for the trailing zero byte.
+ */
+#define UBIFS_DFS_DIR_NAME "ubi%d_%d"
+#define UBIFS_DFS_DIR_LEN  (3 + 1 + 2*2 + 1)
+
 /**
  * ubifs_debug_info - per-FS debugging information.
  * @old_zroot: old index root - used by 'dbg_check_old_index()'
@@ -84,7 +91,7 @@ struct ubifs_debug_info {
         long long saved_free;
         int saved_idx_gc_cnt;
 
-        char dfs_dir_name[100];
+        char dfs_dir_name[UBIFS_DFS_DIR_LEN + 1];
         struct dentry *dfs_dir;
         struct dentry *dfs_dump_lprops;
         struct dentry *dfs_dump_budg;
@@ -313,7 +320,7 @@ void dbg_debugfs_exit_fs(struct ubifs_info *c);
 
 /* Use "if (0)" to make compiler check arguments even if debugging is off */
 #define ubifs_assert(expr)  do {                                               \
-        if (0 && (expr))                                                       \
+        if (0)                                                                 \
                 printk(KERN_CRIT "UBIFS assert failed in %s at %u (pid %d)\n", \
                        __func__, __LINE__, current->pid);                      \
 } while (0)