Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs
Pull d_inode/d_flags race fix from Al Viro. I love this fix. Not only does it fix the race in the dentry type handling, it entirely gets rid of the nasty and subtle memory ordering rules for d_type and d_inode, and replaces them with the basic dentry locking rules (sequence numbers under RCU, d_lock elsewhere). * 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: use ->d_seq to get coherency between ->d_inode and ->d_flags
This commit is contained in:
commit
f691b77b1f
20
fs/dcache.c
20
fs/dcache.c
|
@ -269,9 +269,6 @@ static inline int dname_external(const struct dentry *dentry)
|
|||
return dentry->d_name.name != dentry->d_iname;
|
||||
}
|
||||
|
||||
/*
|
||||
* Make sure other CPUs see the inode attached before the type is set.
|
||||
*/
|
||||
static inline void __d_set_inode_and_type(struct dentry *dentry,
|
||||
struct inode *inode,
|
||||
unsigned type_flags)
|
||||
|
@ -279,28 +276,18 @@ static inline void __d_set_inode_and_type(struct dentry *dentry,
|
|||
unsigned flags;
|
||||
|
||||
dentry->d_inode = inode;
|
||||
smp_wmb();
|
||||
flags = READ_ONCE(dentry->d_flags);
|
||||
flags &= ~(DCACHE_ENTRY_TYPE | DCACHE_FALLTHRU);
|
||||
flags |= type_flags;
|
||||
WRITE_ONCE(dentry->d_flags, flags);
|
||||
}
|
||||
|
||||
/*
|
||||
* Ideally, we want to make sure that other CPUs see the flags cleared before
|
||||
* the inode is detached, but this is really a violation of RCU principles
|
||||
* since the ordering suggests we should always set inode before flags.
|
||||
*
|
||||
* We should instead replace or discard the entire dentry - but that sucks
|
||||
* performancewise on mass deletion/rename.
|
||||
*/
|
||||
static inline void __d_clear_type_and_inode(struct dentry *dentry)
|
||||
{
|
||||
unsigned flags = READ_ONCE(dentry->d_flags);
|
||||
|
||||
flags &= ~(DCACHE_ENTRY_TYPE | DCACHE_FALLTHRU);
|
||||
WRITE_ONCE(dentry->d_flags, flags);
|
||||
smp_wmb();
|
||||
dentry->d_inode = NULL;
|
||||
}
|
||||
|
||||
|
@ -370,9 +357,11 @@ static void dentry_unlink_inode(struct dentry * dentry)
|
|||
__releases(dentry->d_inode->i_lock)
|
||||
{
|
||||
struct inode *inode = dentry->d_inode;
|
||||
|
||||
raw_write_seqcount_begin(&dentry->d_seq);
|
||||
__d_clear_type_and_inode(dentry);
|
||||
hlist_del_init(&dentry->d_u.d_alias);
|
||||
dentry_rcuwalk_invalidate(dentry);
|
||||
raw_write_seqcount_end(&dentry->d_seq);
|
||||
spin_unlock(&dentry->d_lock);
|
||||
spin_unlock(&inode->i_lock);
|
||||
if (!inode->i_nlink)
|
||||
|
@ -1758,8 +1747,9 @@ static void __d_instantiate(struct dentry *dentry, struct inode *inode)
|
|||
spin_lock(&dentry->d_lock);
|
||||
if (inode)
|
||||
hlist_add_head(&dentry->d_u.d_alias, &inode->i_dentry);
|
||||
raw_write_seqcount_begin(&dentry->d_seq);
|
||||
__d_set_inode_and_type(dentry, inode, add_flags);
|
||||
dentry_rcuwalk_invalidate(dentry);
|
||||
raw_write_seqcount_end(&dentry->d_seq);
|
||||
spin_unlock(&dentry->d_lock);
|
||||
fsnotify_d_instantiate(dentry, inode);
|
||||
}
|
||||
|
|
|
@ -409,9 +409,7 @@ static inline bool d_mountpoint(const struct dentry *dentry)
|
|||
*/
|
||||
static inline unsigned __d_entry_type(const struct dentry *dentry)
|
||||
{
|
||||
unsigned type = READ_ONCE(dentry->d_flags);
|
||||
smp_rmb();
|
||||
return type & DCACHE_ENTRY_TYPE;
|
||||
return dentry->d_flags & DCACHE_ENTRY_TYPE;
|
||||
}
|
||||
|
||||
static inline bool d_is_miss(const struct dentry *dentry)
|
||||
|
|
Loading…
Reference in a new issue