On Tue, Nov 16, 2010 at 6:09 AM, Nick Piggin <npiggin@xxxxxxxxx> wrote:
> Index: linux-2.6/fs/dcache.c
> ===================================================================
> --- linux-2.6.orig/fs/dcache.c 2010-11-17 00:52:37.000000000 +1100
> +++ linux-2.6/fs/dcache.c 2010-11-17 01:05:44.000000000 +1100
> @@ -217,24 +219,22 @@ static void dentry_lru_move_tail(struct
> *
> * If this is the root of the dentry tree, return NULL.
> *
> - * dcache_lock and d_lock must be held by caller, are dropped by d_kill.
> + * dcache_lock and d_lock and d_parent->d_lock must be held by caller, and
> + * are dropped by d_kill.
> */
> -static struct dentry *d_kill(struct dentry *dentry)
> +static struct dentry *d_kill(struct dentry *dentry, struct dentry *parent)
> __releases(dentry->d_lock)
> + __releases(parent->d_lock)
> __releases(dcache_lock)
> {
> - struct dentry *parent;
> -
> list_del(&dentry->d_u.d_child);
> + if (parent)
> + spin_unlock(&parent->d_lock);
> dentry_iput(dentry);
> /*
> * dentry_iput drops the locks, at which point nobody (except
> * transient RCU lookups) can reach this dentry.
> */
> - if (IS_ROOT(dentry))
> - parent = NULL;
> - else
> - parent = dentry->d_parent;
> d_free(dentry);
> return parent;
> }
> @@ -270,6 +270,7 @@ static struct dentry *d_kill(struct dent
>
> void dput(struct dentry *dentry)
> {
> + struct dentry *parent;
> if (!dentry)
> return;
>
> @@ -277,6 +278,10 @@ void dput(struct dentry *dentry)
> if (dentry->d_count == 1)
> might_sleep();
> spin_lock(&dentry->d_lock);
> + if (IS_ROOT(dentry))
> + parent = NULL;
> + else
> + parent = dentry->d_parent;
> if (dentry->d_count == 1) {
> if (!spin_trylock(&dcache_lock)) {
> /*
Removed one and added three of the IS_ROOT() checks I think...Maybe
add a macro for setting the local parent pointer? Ah never mind. In
patch 28 they collapse back into a single instance.
In this patch the nested locking starts to feel a little more natural
to me. The last number of patches in the series end up re-simplifying
a lot of intermediate complexity.
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