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>

diff --git a/fs/ubifs/debug.c b/fs/ubifs/debug.c
index 24a85073ac6c055b4af720388c776e83c786072e..b98638eb0fcba8a1fe402602c6ccdb87971d5b9e 100644 (file)
--- 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;