From a8b14744429f90763f258ad0f69601cdcad610aa Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Wed, 4 Dec 2013 09:20:40 -0500 Subject: [PATCH] sysfs: give different locking key to regular and bin files 027a485d12e0 ("sysfs: use a separate locking class for open files depending on mmap") assigned different lockdep key to sysfs_open_file->mutex depending on whether the file implements mmap or not in an attempt to avoid spurious lockdep warning caused by merging of regular and bin file paths. While this restored some of the original behavior of using different locks (at least lockdep is concerned) for the different clases of files. The restoration wasn't full because now the lockdep key assignment depends on whether the file has mmap or not instead of whether it's a regular file or not. This means that bin files which don't implement mmap will get assigned the same lockdep class as regular files. This is problematic because file_operations for bin files still implements the mmap file operation and checking whether the sysfs file actually implements mmap happens in the file operation after grabbing @sysfs_open_file->mutex. We still end up adding locking dependency from mmap locking to sysfs_open_file->mutex to the regular file mutex which triggers spurious circular locking warning. Fix it by restoring the original behavior fully by differentiating lockdep key by whether the file is regular or bin, instead of the existence of mmap. Signed-off-by: Tejun Heo Reported-by: Dave Jones Link: http://lkml.kernel.org/g/20131203184324.GA11320@redhat.com Signed-off-by: Greg Kroah-Hartman --- fs/sysfs/file.c | 8 +++----- 1 file changed, 3 insertions(+), 5 deletions(-) diff --git a/fs/sysfs/file.c b/fs/sysfs/file.c index b94f93685093..35e7d08fe629 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, has_mmap; + bool has_read, has_write; int error = -EACCES; /* need attr_sd for attr and ops, its parent for kobj */ @@ -621,7 +621,6 @@ 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); @@ -633,7 +632,6 @@ 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 */ @@ -661,9 +659,9 @@ static int sysfs_open_file(struct inode *inode, struct file *file) * 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. + * whether the file is bin or not for now. */ - if (has_mmap) + if (sysfs_is_bin(attr_sd)) mutex_init(&of->mutex); else mutex_init(&of->mutex); -- 2.39.5