vfs: protect i_nlink
Prevent direct modification of i_nlink by making it const and adding a
non-const __i_nlink alias.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Tested-by: Toshiyuki Okajima <toshi.okajima@jp.fujitsu.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
diff --git a/fs/inode.c b/fs/inode.c
index ecbb68d..ee4e66b 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -142,7 +142,7 @@
atomic_set(&inode->i_count, 1);
inode->i_op = &empty_iops;
inode->i_fop = &empty_fops;
- inode->i_nlink = 1;
+ inode->__i_nlink = 1;
inode->i_opflags = 0;
inode->i_uid = 0;
inode->i_gid = 0;
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 48c1f5f..23467d7 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -768,7 +768,17 @@
/* Stat data, not accessed from path walking */
unsigned long i_ino;
- unsigned int i_nlink;
+ /*
+ * Filesystems may only read i_nlink directly. They shall use the
+ * following functions for modification:
+ *
+ * (set|clear|inc|drop)_nlink
+ * inode_(inc|dec)_link_count
+ */
+ union {
+ const unsigned int i_nlink;
+ unsigned int __i_nlink;
+ };
dev_t i_rdev;
loff_t i_size;
struct timespec i_atime;
@@ -1764,7 +1774,7 @@
*/
static inline void set_nlink(struct inode *inode, unsigned int nlink)
{
- inode->i_nlink = nlink;
+ inode->__i_nlink = nlink;
}
/**
@@ -1777,7 +1787,7 @@
*/
static inline void inc_nlink(struct inode *inode)
{
- inode->i_nlink++;
+ inode->__i_nlink++;
}
static inline void inode_inc_link_count(struct inode *inode)
@@ -1799,7 +1809,7 @@
*/
static inline void drop_nlink(struct inode *inode)
{
- inode->i_nlink--;
+ inode->__i_nlink--;
}
/**
@@ -1812,7 +1822,7 @@
*/
static inline void clear_nlink(struct inode *inode)
{
- inode->i_nlink = 0;
+ inode->__i_nlink = 0;
}
static inline void inode_dec_link_count(struct inode *inode)