Merge tag 'char-misc-3.13-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/gregk...

[linux-2.6-microblaze.git] / fs / sysfs / file.c

diff --git a/fs/sysfs/file.c b/fs/sysfs/file.c
index 79b5da2..b94f936 100644 (file)
--- a/fs/sysfs/file.c
+++ b/fs/sysfs/file.c
@@ -609,7 +609,7 @@ static int sysfs_open_file(struct inode *inode, struct file *file)
        struct sysfs_dirent *attr_sd = file->f_path.dentry->d_fsdata;
        struct kobject *kobj = attr_sd->s_parent->s_dir.kobj;
        struct sysfs_open_file *of;
-       bool has_read, has_write;
+       bool has_read, has_write, has_mmap;
        int error = -EACCES;
 
        /* need attr_sd for attr and ops, its parent for kobj */
@@ -621,6 +621,7 @@ static int sysfs_open_file(struct inode *inode, struct file *file)
 
                has_read = battr->read || battr->mmap;
                has_write = battr->write || battr->mmap;
+               has_mmap = battr->mmap;
        } else {
                const struct sysfs_ops *ops = sysfs_file_ops(attr_sd);
 
@@ -632,6 +633,7 @@ static int sysfs_open_file(struct inode *inode, struct file *file)
 
                has_read = ops->show;
                has_write = ops->store;
+               has_mmap = false;
        }
 
        /* check perms and supported operations */
@@ -649,7 +651,23 @@ static int sysfs_open_file(struct inode *inode, struct file *file)
        if (!of)
                goto err_out;
 
-       mutex_init(&of->mutex);
+       /*
+        * The following is done to give a different lockdep key to
+        * @of->mutex for files which implement mmap.  This is a rather
+        * crude way to avoid false positive lockdep warning around
+        * mm->mmap_sem - mmap nests @of->mutex under mm->mmap_sem and
+        * reading /sys/block/sda/trace/act_mask grabs sr_mutex, under
+        * which mm->mmap_sem nests, while holding @of->mutex.  As each
+        * open file has a separate mutex, it's okay as long as those don't
+        * happen on the same file.  At this point, we can't easily give
+        * each file a separate locking class.  Let's differentiate on
+        * whether the file has mmap or not for now.
+        */
+       if (has_mmap)
+               mutex_init(&of->mutex);
+       else
+               mutex_init(&of->mutex);
+
        of->sd = attr_sd;
        of->file = file;