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Driver core: fix race in sysfs between sysfs_remove_file() and read()/write()

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This patch prevents a race between IO and removing a file from sysfs.
It introduces a list of sysfs_buffers associated with a file at the inode.
Upon removal of a file the list is walked and the buffers marked orphaned.
IO to orphaned buffers fails with -ENODEV. The driver can safely free
associated data structures or be unloaded.

Signed-off-by: Oliver Neukum <oliver@neukum.name>
Acked-by: Maneesh Soni <maneesh@in.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
This commit is contained in:
Oliver Neukum
2006-12-20 10:52:44 +01:00
committed by Greg Kroah-Hartman
parent cb986b749c
commit 94bebf4d1b
8 changed files with 103 additions and 17 deletions
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24
fs/sysfs/inode.c
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@@ -13,6 +13,7 @@
#include <linux/backing-dev.h>
#include <linux/capability.h>
#include <linux/errno.h>
#include <asm/semaphore.h>
#include "sysfs.h"
extern struct super_block * sysfs_sb;
@@ -209,6 +210,22 @@ const unsigned char * sysfs_get_name(struct sysfs_dirent *sd)
return NULL;
}
static inline void orphan_all_buffers(struct inode *node)
{
struct sysfs_buffer_collection *set = node->i_private;
struct sysfs_buffer *buf;
mutex_lock(&node->i_mutex);
if (node->i_private) {
list_for_each_entry(buf, &set->associates, associates) {
down(&buf->sem);
buf->orphaned = 1;
up(&buf->sem);
}
}
mutex_unlock(&node->i_mutex);
}
/*
* Unhashes the dentry corresponding to given sysfs_dirent
@@ -217,16 +234,23 @@ const unsigned char * sysfs_get_name(struct sysfs_dirent *sd)
void sysfs_drop_dentry(struct sysfs_dirent * sd, struct dentry * parent)
{
struct dentry * dentry = sd->s_dentry;
struct inode *inode;
if (dentry) {
spin_lock(&dcache_lock);
spin_lock(&dentry->d_lock);
if (!(d_unhashed(dentry) && dentry->d_inode)) {
inode = dentry->d_inode;
spin_lock(&inode->i_lock);
__iget(inode);
spin_unlock(&inode->i_lock);
dget_locked(dentry);
__d_drop(dentry);
spin_unlock(&dentry->d_lock);
spin_unlock(&dcache_lock);
simple_unlink(parent->d_inode, dentry);
orphan_all_buffers(inode);
iput(inode);
} else {
spin_unlock(&dentry->d_lock);
spin_unlock(&dcache_lock);