idr: make idr_remove rcu-safe
Introduce the free_layer() routine: it is the one that actually frees memory after a grace period has elapsed. Signed-off-by: Nadia Derbey <Nadia.Derbey@bull.net> Reviewed-by: "Paul E. McKenney" <paulmck@us.ibm.com> Cc: Manfred Spraul <manfred@colorfullife.com> Cc: Jim Houston <jim.houston@comcast.net> Cc: Pierre Peiffer <peifferp@gmail.com> Acked-by: Rik van Riel <riel@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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parent
f9c46d6ea5
commit
cf481c20c4
57
lib/idr.c
57
lib/idr.c
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@ -52,6 +52,19 @@ static struct idr_layer *get_from_free_list(struct idr *idp)
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return(p);
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}
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static void idr_layer_rcu_free(struct rcu_head *head)
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{
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struct idr_layer *layer;
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layer = container_of(head, struct idr_layer, rcu_head);
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kmem_cache_free(idr_layer_cache, layer);
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}
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static inline void free_layer(struct idr_layer *p)
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{
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call_rcu(&p->rcu_head, idr_layer_rcu_free);
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}
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/* only called when idp->lock is held */
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static void __move_to_free_list(struct idr *idp, struct idr_layer *p)
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{
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@ -331,6 +344,7 @@ static void sub_remove(struct idr *idp, int shift, int id)
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struct idr_layer *p = idp->top;
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struct idr_layer **pa[MAX_LEVEL];
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struct idr_layer ***paa = &pa[0];
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struct idr_layer *to_free;
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int n;
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*paa = NULL;
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@ -346,13 +360,18 @@ static void sub_remove(struct idr *idp, int shift, int id)
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n = id & IDR_MASK;
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if (likely(p != NULL && test_bit(n, &p->bitmap))){
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__clear_bit(n, &p->bitmap);
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p->ary[n] = NULL;
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rcu_assign_pointer(p->ary[n], NULL);
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to_free = NULL;
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while(*paa && ! --((**paa)->count)){
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move_to_free_list(idp, **paa);
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if (to_free)
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free_layer(to_free);
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to_free = **paa;
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**paa-- = NULL;
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}
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if (!*paa)
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idp->layers = 0;
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if (to_free)
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free_layer(to_free);
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} else
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idr_remove_warning(id);
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}
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@ -365,22 +384,34 @@ static void sub_remove(struct idr *idp, int shift, int id)
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void idr_remove(struct idr *idp, int id)
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{
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struct idr_layer *p;
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struct idr_layer *to_free;
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/* Mask off upper bits we don't use for the search. */
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id &= MAX_ID_MASK;
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sub_remove(idp, (idp->layers - 1) * IDR_BITS, id);
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if (idp->top && idp->top->count == 1 && (idp->layers > 1) &&
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idp->top->ary[0]) { // We can drop a layer
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idp->top->ary[0]) {
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/*
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* Single child at leftmost slot: we can shrink the tree.
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* This level is not needed anymore since when layers are
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* inserted, they are inserted at the top of the existing
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* tree.
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*/
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to_free = idp->top;
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p = idp->top->ary[0];
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idp->top->bitmap = idp->top->count = 0;
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move_to_free_list(idp, idp->top);
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idp->top = p;
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rcu_assign_pointer(idp->top, p);
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--idp->layers;
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to_free->bitmap = to_free->count = 0;
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free_layer(to_free);
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}
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while (idp->id_free_cnt >= IDR_FREE_MAX) {
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p = get_from_free_list(idp);
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/*
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* Note: we don't call the rcu callback here, since the only
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* layers that fall into the freelist are those that have been
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* preallocated.
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*/
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kmem_cache_free(idr_layer_cache, p);
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}
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return;
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@ -421,15 +452,13 @@ void idr_remove_all(struct idr *idp)
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id += 1 << n;
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while (n < fls(id)) {
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if (p) {
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memset(p, 0, sizeof *p);
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move_to_free_list(idp, p);
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}
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if (p)
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free_layer(p);
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n += IDR_BITS;
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p = *--paa;
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}
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}
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idp->top = NULL;
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rcu_assign_pointer(idp->top, NULL);
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idp->layers = 0;
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}
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EXPORT_SYMBOL(idr_remove_all);
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@ -546,7 +575,7 @@ EXPORT_SYMBOL(idr_for_each);
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* A -ENOENT return indicates that @id was not found.
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* A -EINVAL return indicates that @id was not within valid constraints.
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*
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* The caller must serialize vs idr_find(), idr_get_new(), and idr_remove().
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* The caller must serialize with writers.
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*/
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void *idr_replace(struct idr *idp, void *ptr, int id)
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{
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@ -572,7 +601,7 @@ void *idr_replace(struct idr *idp, void *ptr, int id)
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return ERR_PTR(-ENOENT);
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old_p = p->ary[n];
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p->ary[n] = ptr;
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rcu_assign_pointer(p->ary[n], ptr);
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return old_p;
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}
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