1 files changed, 20 insertions, 2 deletions

diff --git a/fs/sysfs/file.c b/fs/sysfs/file.c
index 79b5da2acbe1..b94f93685093 100644
--- 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;