debugfs: unproxify files created through debugfs_create_bool()

Currently, the struct file_operations fops_bool associated with files
created through the debugfs_create_bool() helpers are not file
lifetime aware.

Thus, a lifetime managing proxy is created around fops_bool each time such
a file is opened which is an unnecessary waste of resources.

Implement file lifetime management for the fops_bool file_operations.
Namely, make debugfs_read_file_bool() and debugfs_write_file_bool() safe
against file removals by means of debugfs_use_file_start() and
debugfs_use_file_finish().

Make debugfs_create_bool() create its files in non-proxying operation mode
through debugfs_create_mode_unsafe().

Finally, purge debugfs_create_mode() as debugfs_create_bool() had been its
last user.

Signed-off-by: Nicolai Stange <nicstange@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 20 insertions, 21 deletions

diff --git a/fs/debugfs/file.c b/fs/debugfs/file.c
index 4b3967e86e97..8a548bee1b3d 100644
--- a/fs/debugfs/file.c
+++ b/fs/debugfs/file.c
@@ -312,22 +312,6 @@ ssize_t debugfs_attr_write(struct file *file, const char __user *buf,
 }
 EXPORT_SYMBOL_GPL(debugfs_attr_write);
 
-static struct dentry *debugfs_create_mode(const char *name, umode_t mode,
-                                          struct dentry *parent, void *value,
-                                          const struct file_operations *fops,
-                                          const struct file_operations *fops_ro,
-                                          const struct file_operations *fops_wo)
-{
-        /* if there are no write bits set, make read only */
-        if (!(mode & S_IWUGO))
-                return debugfs_create_file(name, mode, parent, value, fops_ro);
-        /* if there are no read bits set, make write only */
-        if (!(mode & S_IRUGO))
-                return debugfs_create_file(name, mode, parent, value, fops_wo);
-
-        return debugfs_create_file(name, mode, parent, value, fops);
-}
-
 static struct dentry *debugfs_create_mode_unsafe(const char *name, umode_t mode,
                                         struct dentry *parent, void *value,
                                         const struct file_operations *fops,
@@ -756,9 +740,17 @@ ssize_t debugfs_read_file_bool(struct file *file, char __user *user_buf,
                                size_t count, loff_t *ppos)
 {
         char buf[3];
-        bool *val = file->private_data;
+        bool val;
+        int r, srcu_idx;
+
+        r = debugfs_use_file_start(F_DENTRY(file), &srcu_idx);
+        if (likely(!r))
+                val = *(bool *)file->private_data;
+        debugfs_use_file_finish(srcu_idx);
+        if (r)
+                return r;
 
-        if (*val)
+        if (val)
                 buf[0] = 'Y';
         else
                 buf[0] = 'N';
@@ -774,6 +766,7 @@ ssize_t debugfs_write_file_bool(struct file *file, const char __user *user_buf,
         char buf[32];
         size_t buf_size;
         bool bv;
+        int r, srcu_idx;
         bool *val = file->private_data;
 
         buf_size = min(count, (sizeof(buf)-1));
@@ -781,8 +774,14 @@ ssize_t debugfs_write_file_bool(struct file *file, const char __user *user_buf,
                 return -EFAULT;
 
         buf[buf_size] = '\0';
-        if (strtobool(buf, &bv) == 0)
-                *val = bv;
+        if (strtobool(buf, &bv) == 0) {
+                r = debugfs_use_file_start(F_DENTRY(file), &srcu_idx);
+                if (likely(!r))
+                        *val = bv;
+                debugfs_use_file_finish(srcu_idx);
+                if (r)
+                        return r;
+        }
 
         return count;
 }
@@ -834,7 +833,7 @@ static const struct file_operations fops_bool_wo = {
 struct dentry *debugfs_create_bool(const char *name, umode_t mode,
                                    struct dentry *parent, bool *value)
 {
-        return debugfs_create_mode(name, mode, parent, value, &fops_bool,
+        return debugfs_create_mode_unsafe(name, mode, parent, value, &fops_bool,
                                    &fops_bool_ro, &fops_bool_wo);
 }
 EXPORT_SYMBOL_GPL(debugfs_create_bool);