UBIFS: introduce debugfs helpers

Separate out pieces of code from the debugfs file read/write functions and
create separate 'interpret_user_input()'/'provide_user_output()' helpers. These
helpers will be needed in one of the following patches, so this is just a
preparational change.

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

1 files changed, 56 insertions, 20 deletions

diff --git a/fs/ubifs/debug.c b/fs/ubifs/debug.c
index 24a85073ac6c..b98638eb0fcb 100644
--- a/fs/ubifs/debug.c
+++ b/fs/ubifs/debug.c
@@ -2820,13 +2820,39 @@ static int dfs_file_open(struct inode *inode, struct file *file)
         return nonseekable_open(inode, file);
 }
 
+/**
+ * provide_user_output - provide output to the user reading a debugfs file.
+ * @val: boolean value for the answer
+ * @u: the buffer to store the answer at
+ * @count: size of the buffer
+ * @ppos: position in the @u output buffer
+ *
+ * This is a simple helper function which stores @val boolean value in the user
+ * buffer when the user reads one of UBIFS debugfs files. Returns amount of
+ * bytes written to @u in case of success and a negative error code in case of
+ * failure.
+ */
+static int provide_user_output(int val, char __user *u, size_t count,
+                               loff_t *ppos)
+{
+        char buf[3];
+
+        if (val)
+                buf[0] = '1';
+        else
+                buf[0] = '0';
+        buf[1] = '\n';
+        buf[2] = 0x00;
+
+        return simple_read_from_buffer(u, count, ppos, buf, 2);
+}
+
 static ssize_t dfs_file_read(struct file *file, char __user *u, size_t count,
                              loff_t *ppos)
 {
         struct dentry *dent = file->f_path.dentry;
         struct ubifs_info *c = file->private_data;
         struct ubifs_debug_info *d = c->dbg;
-        char buf[3];
         int val;
 
         if (dent == d->dfs_chk_gen)
@@ -2844,14 +2870,33 @@ static ssize_t dfs_file_read(struct file *file, char __user *u, size_t count,
         else
                 return -EINVAL;
 
-        if (val)
-                buf[0] = '1';
-        else
-                buf[0] = '0';
-        buf[1] = '\n';
-        buf[2] = 0x00;
+        return provide_user_output(val, u, count, ppos);
+}
 
-        return simple_read_from_buffer(u, count, ppos, buf, 2);
+/**
+ * interpret_user_input - interpret user debugfs file input.
+ * @u: user-provided buffer with the input
+ * @count: buffer size
+ *
+ * This is a helper function which interpret user input to a boolean UBIFS
+ * debugfs file. Returns %0 or %1 in case of success and a negative error code
+ * in case of failure.
+ */
+static int interpret_user_input(const char __user *u, size_t count)
+{
+        size_t buf_size;
+        char buf[8];
+
+        buf_size = min_t(size_t, count, (sizeof(buf) - 1));
+        if (copy_from_user(buf, u, buf_size))
+                return -EFAULT;
+
+        if (buf[0] == '1')
+                return 1;
+        else if (buf[0] == '0')
+                return 0;
+
+        return -EINVAL;
 }
 
 static ssize_t dfs_file_write(struct file *file, const char __user *u,
@@ -2860,8 +2905,6 @@ static ssize_t dfs_file_write(struct file *file, const char __user *u,
         struct ubifs_info *c = file->private_data;
         struct ubifs_debug_info *d = c->dbg;
         struct dentry *dent = file->f_path.dentry;
-        size_t buf_size;
-        char buf[8];
         int val;
 
         /*
@@ -2891,16 +2934,9 @@ static ssize_t dfs_file_write(struct file *file, const char __user *u,
                 return count;
         }
 
-        buf_size = min_t(size_t, count, (sizeof(buf) - 1));
-        if (copy_from_user(buf, u, buf_size))
-                return -EFAULT;
-
-        if (buf[0] == '1')
-                val = 1;
-        else if (buf[0] == '0')
-                val = 0;
-        else
-                return -EINVAL;
+        val = interpret_user_input(u, count);
+        if (val < 0)
+                return val;
 
         if (dent == d->dfs_chk_gen)
                 d->chk_gen = val;