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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>
This commit is contained in:
Nadia Derbey 2008-07-25 01:48:02 -07:00 committed by Linus Torvalds
parent f9c46d6ea5
commit cf481c20c4
1 changed files with 43 additions and 14 deletions
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57
lib/idr.c
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@ -52,6 +52,19 @@ static struct idr_layer *get_from_free_list(struct idr *idp)
return(p);
}
static void idr_layer_rcu_free(struct rcu_head *head)
{
struct idr_layer *layer;
layer = container_of(head, struct idr_layer, rcu_head);
kmem_cache_free(idr_layer_cache, layer);
}
static inline void free_layer(struct idr_layer *p)
{
call_rcu(&p->rcu_head, idr_layer_rcu_free);
}
/* only called when idp->lock is held */
static void __move_to_free_list(struct idr *idp, struct idr_layer *p)
{
@ -331,6 +344,7 @@ static void sub_remove(struct idr *idp, int shift, int id)
struct idr_layer *p = idp->top;
struct idr_layer **pa[MAX_LEVEL];
struct idr_layer ***paa = &pa[0];
struct idr_layer *to_free;
int n;
*paa = NULL;
@ -346,13 +360,18 @@ static void sub_remove(struct idr *idp, int shift, int id)
n = id & IDR_MASK;
if (likely(p != NULL && test_bit(n, &p->bitmap))){
__clear_bit(n, &p->bitmap);
p->ary[n] = NULL;
rcu_assign_pointer(p->ary[n], NULL);
to_free = NULL;
while(*paa && ! --((**paa)->count)){
move_to_free_list(idp, **paa);
if (to_free)
free_layer(to_free);
to_free = **paa;
**paa-- = NULL;
}
if (!*paa)
idp->layers = 0;
if (to_free)
free_layer(to_free);
} else
idr_remove_warning(id);
}
@ -365,22 +384,34 @@ static void sub_remove(struct idr *idp, int shift, int id)
void idr_remove(struct idr *idp, int id)
{
struct idr_layer *p;
struct idr_layer *to_free;
/* Mask off upper bits we don't use for the search. */
id &= MAX_ID_MASK;
sub_remove(idp, (idp->layers - 1) * IDR_BITS, id);
if (idp->top && idp->top->count == 1 && (idp->layers > 1) &&
idp->top->ary[0]) { // We can drop a layer
idp->top->ary[0]) {
/*
* Single child at leftmost slot: we can shrink the tree.
* This level is not needed anymore since when layers are
* inserted, they are inserted at the top of the existing
* tree.
*/
to_free = idp->top;
p = idp->top->ary[0];
idp->top->bitmap = idp->top->count = 0;
move_to_free_list(idp, idp->top);
idp->top = p;
rcu_assign_pointer(idp->top, p);
--idp->layers;
to_free->bitmap = to_free->count = 0;
free_layer(to_free);
}
while (idp->id_free_cnt >= IDR_FREE_MAX) {
p = get_from_free_list(idp);
/*
* Note: we don't call the rcu callback here, since the only
* layers that fall into the freelist are those that have been
* preallocated.
*/
kmem_cache_free(idr_layer_cache, p);
}
return;
@ -421,15 +452,13 @@ void idr_remove_all(struct idr *idp)
id += 1 << n;
while (n < fls(id)) {
if (p) {
memset(p, 0, sizeof *p);
move_to_free_list(idp, p);
}
if (p)
free_layer(p);
n += IDR_BITS;
p = *--paa;
}
}
idp->top = NULL;
rcu_assign_pointer(idp->top, NULL);
idp->layers = 0;
}
EXPORT_SYMBOL(idr_remove_all);
@ -546,7 +575,7 @@ EXPORT_SYMBOL(idr_for_each);
* A -ENOENT return indicates that @id was not found.
* A -EINVAL return indicates that @id was not within valid constraints.
*
* The caller must serialize vs idr_find(), idr_get_new(), and idr_remove().
* The caller must serialize with writers.
*/
void *idr_replace(struct idr *idp, void *ptr, int id)
{
@ -572,7 +601,7 @@ void *idr_replace(struct idr *idp, void *ptr, int id)
return ERR_PTR(-ENOENT);
old_p = p->ary[n];
p->ary[n] = ptr;
rcu_assign_pointer(p->ary[n], ptr);
return old_p;
}