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-rw-r--r--lib/idr.c140
1 files changed, 82 insertions, 58 deletions
diff --git a/lib/idr.c b/lib/idr.c
index 7a02e173f02..3476f8203e9 100644
--- a/lib/idr.c
+++ b/lib/idr.c
@@ -6,6 +6,8 @@
* Modified by George Anzinger to reuse immediately and to use
* find bit instructions. Also removed _irq on spinlocks.
*
+ * Modified by Nadia Derbey to make it RCU safe.
+ *
* Small id to pointer translation service.
*
* It uses a radix tree like structure as a sparse array indexed
@@ -35,7 +37,7 @@
static struct kmem_cache *idr_layer_cache;
-static struct idr_layer *alloc_layer(struct idr *idp)
+static struct idr_layer *get_from_free_list(struct idr *idp)
{
struct idr_layer *p;
unsigned long flags;
@@ -50,15 +52,28 @@ static struct idr_layer *alloc_layer(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 __free_layer(struct idr *idp, struct idr_layer *p)
+static void __move_to_free_list(struct idr *idp, struct idr_layer *p)
{
p->ary[0] = idp->id_free;
idp->id_free = p;
idp->id_free_cnt++;
}
-static void free_layer(struct idr *idp, struct idr_layer *p)
+static void move_to_free_list(struct idr *idp, struct idr_layer *p)
{
unsigned long flags;
@@ -66,7 +81,7 @@ static void free_layer(struct idr *idp, struct idr_layer *p)
* Depends on the return element being zeroed.
*/
spin_lock_irqsave(&idp->lock, flags);
- __free_layer(idp, p);
+ __move_to_free_list(idp, p);
spin_unlock_irqrestore(&idp->lock, flags);
}
@@ -96,7 +111,7 @@ static void idr_mark_full(struct idr_layer **pa, int id)
* @gfp_mask: memory allocation flags
*
* This function should be called prior to locking and calling the
- * following function. It preallocates enough memory to satisfy
+ * idr_get_new* functions. It preallocates enough memory to satisfy
* the worst possible allocation.
*
* If the system is REALLY out of memory this function returns 0,
@@ -109,7 +124,7 @@ int idr_pre_get(struct idr *idp, gfp_t gfp_mask)
new = kmem_cache_alloc(idr_layer_cache, gfp_mask);
if (new == NULL)
return (0);
- free_layer(idp, new);
+ move_to_free_list(idp, new);
}
return 1;
}
@@ -143,7 +158,7 @@ static int sub_alloc(struct idr *idp, int *starting_id, struct idr_layer **pa)
/* if already at the top layer, we need to grow */
if (!(p = pa[l])) {
*starting_id = id;
- return -2;
+ return IDR_NEED_TO_GROW;
}
/* If we need to go up one layer, continue the
@@ -160,16 +175,17 @@ static int sub_alloc(struct idr *idp, int *starting_id, struct idr_layer **pa)
id = ((id >> sh) ^ n ^ m) << sh;
}
if ((id >= MAX_ID_BIT) || (id < 0))
- return -3;
+ return IDR_NOMORE_SPACE;
if (l == 0)
break;
/*
* Create the layer below if it is missing.
*/
if (!p->ary[m]) {
- if (!(new = alloc_layer(idp)))
+ new = get_from_free_list(idp);
+ if (!new)
return -1;
- p->ary[m] = new;
+ rcu_assign_pointer(p->ary[m], new);
p->count++;
}
pa[l--] = p;
@@ -192,7 +208,7 @@ build_up:
p = idp->top;
layers = idp->layers;
if (unlikely(!p)) {
- if (!(p = alloc_layer(idp)))
+ if (!(p = get_from_free_list(idp)))
return -1;
layers = 1;
}
@@ -204,7 +220,7 @@ build_up:
layers++;
if (!p->count)
continue;
- if (!(new = alloc_layer(idp))) {
+ if (!(new = get_from_free_list(idp))) {
/*
* The allocation failed. If we built part of
* the structure tear it down.
@@ -214,7 +230,7 @@ build_up:
p = p->ary[0];
new->ary[0] = NULL;
new->bitmap = new->count = 0;
- __free_layer(idp, new);
+ __move_to_free_list(idp, new);
}
spin_unlock_irqrestore(&idp->lock, flags);
return -1;
@@ -225,10 +241,10 @@ build_up:
__set_bit(0, &new->bitmap);
p = new;
}
- idp->top = p;
+ rcu_assign_pointer(idp->top, p);
idp->layers = layers;
v = sub_alloc(idp, &id, pa);
- if (v == -2)
+ if (v == IDR_NEED_TO_GROW)
goto build_up;
return(v);
}
@@ -244,7 +260,8 @@ static int idr_get_new_above_int(struct idr *idp, void *ptr, int starting_id)
* Successfully found an empty slot. Install the user
* pointer and mark the slot full.
*/
- pa[0]->ary[id & IDR_MASK] = (struct idr_layer *)ptr;
+ rcu_assign_pointer(pa[0]->ary[id & IDR_MASK],
+ (struct idr_layer *)ptr);
pa[0]->count++;
idr_mark_full(pa, id);
}
@@ -277,12 +294,8 @@ int idr_get_new_above(struct idr *idp, void *ptr, int starting_id, int *id)
* This is a cheap hack until the IDR code can be fixed to
* return proper error values.
*/
- if (rv < 0) {
- if (rv == -1)
- return -EAGAIN;
- else /* Will be -3 */
- return -ENOSPC;
- }
+ if (rv < 0)
+ return _idr_rc_to_errno(rv);
*id = rv;
return 0;
}
@@ -312,12 +325,8 @@ int idr_get_new(struct idr *idp, void *ptr, int *id)
* This is a cheap hack until the IDR code can be fixed to
* return proper error values.
*/
- if (rv < 0) {
- if (rv == -1)
- return -EAGAIN;
- else /* Will be -3 */
- return -ENOSPC;
- }
+ if (rv < 0)
+ return _idr_rc_to_errno(rv);
*id = rv;
return 0;
}
@@ -325,7 +334,8 @@ EXPORT_SYMBOL(idr_get_new);
static void idr_remove_warning(int id)
{
- printk("idr_remove called for id=%d which is not allocated.\n", id);
+ printk(KERN_WARNING
+ "idr_remove called for id=%d which is not allocated.\n", id);
dump_stack();
}
@@ -334,6 +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;
@@ -349,13 +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)){
- free_layer(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);
}
@@ -368,22 +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;
- free_layer(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 = alloc_layer(idp);
+ 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;
@@ -424,15 +452,13 @@ void idr_remove_all(struct idr *idp)
id += 1 << n;
while (n < fls(id)) {
- if (p) {
- memset(p, 0, sizeof *p);
- free_layer(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);
@@ -444,7 +470,7 @@ EXPORT_SYMBOL(idr_remove_all);
void idr_destroy(struct idr *idp)
{
while (idp->id_free_cnt) {
- struct idr_layer *p = alloc_layer(idp);
+ struct idr_layer *p = get_from_free_list(idp);
kmem_cache_free(idr_layer_cache, p);
}
}
@@ -459,7 +485,8 @@ EXPORT_SYMBOL(idr_destroy);
* return indicates that @id is not valid or you passed %NULL in
* idr_get_new().
*
- * The caller must serialize idr_find() vs idr_get_new() and idr_remove().
+ * This function can be called under rcu_read_lock(), given that the leaf
+ * pointers lifetimes are correctly managed.
*/
void *idr_find(struct idr *idp, int id)
{
@@ -467,7 +494,7 @@ void *idr_find(struct idr *idp, int id)
struct idr_layer *p;
n = idp->layers * IDR_BITS;
- p = idp->top;
+ p = rcu_dereference(idp->top);
/* Mask off upper bits we don't use for the search. */
id &= MAX_ID_MASK;
@@ -477,7 +504,7 @@ void *idr_find(struct idr *idp, int id)
while (n > 0 && p) {
n -= IDR_BITS;
- p = p->ary[(id >> n) & IDR_MASK];
+ p = rcu_dereference(p->ary[(id >> n) & IDR_MASK]);
}
return((void *)p);
}
@@ -510,7 +537,7 @@ int idr_for_each(struct idr *idp,
struct idr_layer **paa = &pa[0];
n = idp->layers * IDR_BITS;
- p = idp->top;
+ p = rcu_dereference(idp->top);
max = 1 << n;
id = 0;
@@ -518,7 +545,7 @@ int idr_for_each(struct idr *idp,
while (n > 0 && p) {
n -= IDR_BITS;
*paa++ = p;
- p = p->ary[(id >> n) & IDR_MASK];
+ p = rcu_dereference(p->ary[(id >> n) & IDR_MASK]);
}
if (p) {
@@ -548,7 +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)
{
@@ -574,7 +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;
}
@@ -694,12 +721,8 @@ int ida_get_new_above(struct ida *ida, int starting_id, int *p_id)
restart:
/* get vacant slot */
t = idr_get_empty_slot(&ida->idr, idr_id, pa);
- if (t < 0) {
- if (t == -1)
- return -EAGAIN;
- else /* will be -3 */
- return -ENOSPC;
- }
+ if (t < 0)
+ return _idr_rc_to_errno(t);
if (t * IDA_BITMAP_BITS >= MAX_ID_BIT)
return -ENOSPC;
@@ -720,7 +743,8 @@ int ida_get_new_above(struct ida *ida, int starting_id, int *p_id)
return -EAGAIN;
memset(bitmap, 0, sizeof(struct ida_bitmap));
- pa[0]->ary[idr_id & IDR_MASK] = (void *)bitmap;
+ rcu_assign_pointer(pa[0]->ary[idr_id & IDR_MASK],
+ (void *)bitmap);
pa[0]->count++;
}
@@ -749,7 +773,7 @@ int ida_get_new_above(struct ida *ida, int starting_id, int *p_id)
* allocation.
*/
if (ida->idr.id_free_cnt || ida->free_bitmap) {
- struct idr_layer *p = alloc_layer(&ida->idr);
+ struct idr_layer *p = get_from_free_list(&ida->idr);
if (p)
kmem_cache_free(idr_layer_cache, p);
}
generated by cgit v1.2.3 (git 2.25.1) at 2024-11-04 08:35:12 +0000