From 4bf46a272647d89e780126b52eda04737defd9f4 Mon Sep 17 00:00:00 2001 From: David Howells Date: Thu, 5 Mar 2015 14:09:22 +0000 Subject: VFS: Impose ordering on accesses of d_inode and d_flags Impose ordering on accesses of d_inode and d_flags to avoid the need to do this: if (!dentry->d_inode || d_is_negative(dentry)) { when this: if (d_is_negative(dentry)) { should suffice. This check is especially problematic if a dentry can have its type field set to something other than DENTRY_MISS_TYPE when d_inode is NULL (as in unionmount). What we really need to do is stick a write barrier between setting d_inode and setting d_flags and a read barrier between reading d_flags and reading d_inode. Signed-off-by: David Howells Signed-off-by: Al Viro --- include/linux/dcache.h | 21 +++------------------ 1 file changed, 3 insertions(+), 18 deletions(-) (limited to 'include/linux') diff --git a/include/linux/dcache.h b/include/linux/dcache.h index e83768ee38fc..df334cbacc6d 100644 --- a/include/linux/dcache.h +++ b/include/linux/dcache.h @@ -404,26 +404,11 @@ static inline bool d_mountpoint(const struct dentry *dentry) /* * Directory cache entry type accessor functions. */ -static inline void __d_set_type(struct dentry *dentry, unsigned type) -{ - dentry->d_flags = (dentry->d_flags & ~DCACHE_ENTRY_TYPE) | type; -} - -static inline void __d_clear_type(struct dentry *dentry) -{ - __d_set_type(dentry, DCACHE_MISS_TYPE); -} - -static inline void d_set_type(struct dentry *dentry, unsigned type) -{ - spin_lock(&dentry->d_lock); - __d_set_type(dentry, type); - spin_unlock(&dentry->d_lock); -} - static inline unsigned __d_entry_type(const struct dentry *dentry) { - return dentry->d_flags & DCACHE_ENTRY_TYPE; + unsigned type = READ_ONCE(dentry->d_flags); + smp_rmb(); + return type & DCACHE_ENTRY_TYPE; } static inline bool d_is_miss(const struct dentry *dentry) -- cgit v1.2.3