linux/lib/idr.c

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/*
* 2002-10-18 written by Jim Houston jim.houston@ccur.com
* Copyright (C) 2002 by Concurrent Computer Corporation
* Distributed under the GNU GPL license version 2.
*
* 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
* by the id to obtain the pointer. The bitmap makes allocating
* a new id quick.
*
* You call it to allocate an id (an int) an associate with that id a
* pointer or what ever, we treat it as a (void *). You can pass this
* id to a user for him to pass back at a later time. You then pass
* that id to this code and it returns your pointer.
* You can release ids at any time. When all ids are released, most of
* the memory is returned (we keep IDR_FREE_MAX) in a local pool so we
* don't need to go to the memory "store" during an id allocate, just
* so you don't need to be too concerned about locking and conflicts
* with the slab allocator.
*/
#ifndef TEST // to test in user space...
#include <linux/slab.h>
#include <linux/init.h>
#include <linux/module.h>
#endif
#include <linux/err.h>
#include <linux/string.h>
#include <linux/idr.h>
#include <linux/spinlock.h>
static struct kmem_cache *idr_layer_cache;
static DEFINE_SPINLOCK(simple_ida_lock);
static struct idr_layer *get_from_free_list(struct idr *idp)
{
struct idr_layer *p;
unsigned long flags;
spin_lock_irqsave(&idp->lock, flags);
if ((p = idp->id_free)) {
idp->id_free = p->ary[0];
idp->id_free_cnt--;
p->ary[0] = NULL;
}
spin_unlock_irqrestore(&idp->lock, flags);
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)
{
p->ary[0] = idp->id_free;
idp->id_free = p;
idp->id_free_cnt++;
}
static void move_to_free_list(struct idr *idp, struct idr_layer *p)
{
unsigned long flags;
/*
* Depends on the return element being zeroed.
*/
spin_lock_irqsave(&idp->lock, flags);
__move_to_free_list(idp, p);
spin_unlock_irqrestore(&idp->lock, flags);
}
static void idr_mark_full(struct idr_layer **pa, int id)
{
struct idr_layer *p = pa[0];
int l = 0;
__set_bit(id & IDR_MASK, &p->bitmap);
/*
* If this layer is full mark the bit in the layer above to
* show that this part of the radix tree is full. This may
* complete the layer above and require walking up the radix
* tree.
*/
while (p->bitmap == IDR_FULL) {
if (!(p = pa[++l]))
break;
id = id >> IDR_BITS;
__set_bit((id & IDR_MASK), &p->bitmap);
}
}
/**
* idr_pre_get - reserve resources for idr allocation
* @idp: idr handle
* @gfp_mask: memory allocation flags
*
* This function should be called prior to calling the idr_get_new* functions.
* It preallocates enough memory to satisfy the worst possible allocation. The
* caller should pass in GFP_KERNEL if possible. This of course requires that
* no spinning locks be held.
*
* If the system is REALLY out of memory this function returns %0,
* otherwise %1.
*/
int idr_pre_get(struct idr *idp, gfp_t gfp_mask)
{
while (idp->id_free_cnt < IDR_FREE_MAX) {
struct idr_layer *new;
lib/idr.c: use kmem_cache_zalloc() for the idr_layer cache David points out that the idr_remove_all() function returns unused slabs to the kmem cache, but needs to zero them first or else they will be uninitialized upon next use. This causes crashes which have been observed in the firewire subsystem. He fixed this by zeroing the object before freeing it in idr_remove_all(). But we agree that simply removing the constructor and zeroing the object at allocation time is simpler than relying upon slab constructor machinery and might even be faster. This problem was introduced by "idr: make idr_remove rcu-safe" (commit cf481c20c476ad2c0febdace9ce23f5a4db19582), which was first released in 2.6.27. There are no known codesites which trigger this bug in 2.6.27 or 2.6.28. The post-2.6.28 firewire changes are the only known triggerer. There might of course be not-yet-discovered triggerers in 2.6.27 and 2.6.28, and there might be out-of-tree triggerers which are added to those kernel versions. I'll let the -stable guys decide whether they want to backport this fix. Reported-by: David Moore <dcm@acm.org> Cc: Stefan Richter <stefanr@s5r6.in-berlin.de> Cc: Nadia Derbey <Nadia.Derbey@bull.net> Cc: Paul E. McKenney <paulmck@us.ibm.com> Cc: Manfred Spraul <manfred@colorfullife.com> Cc: Kristian Hgsberg <krh@redhat.com> Acked-by: Pekka Enberg <penberg@cs.helsinki.fi> Cc: <stable@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2009-01-16 05:51:21 +08:00
new = kmem_cache_zalloc(idr_layer_cache, gfp_mask);
if (new == NULL)
return (0);
move_to_free_list(idp, new);
}
return 1;
}
EXPORT_SYMBOL(idr_pre_get);
static int sub_alloc(struct idr *idp, int *starting_id, struct idr_layer **pa)
{
int n, m, sh;
struct idr_layer *p, *new;
int l, id, oid;
unsigned long bm;
id = *starting_id;
restart:
p = idp->top;
l = idp->layers;
pa[l--] = NULL;
while (1) {
/*
* We run around this while until we reach the leaf node...
*/
n = (id >> (IDR_BITS*l)) & IDR_MASK;
bm = ~p->bitmap;
m = find_next_bit(&bm, IDR_SIZE, n);
if (m == IDR_SIZE) {
/* no space available go back to previous layer. */
l++;
oid = id;
id = (id | ((1 << (IDR_BITS * l)) - 1)) + 1;
/* if already at the top layer, we need to grow */
if (id >= 1 << (idp->layers * IDR_BITS)) {
*starting_id = id;
return IDR_NEED_TO_GROW;
}
p = pa[l];
BUG_ON(!p);
/* If we need to go up one layer, continue the
* loop; otherwise, restart from the top.
*/
sh = IDR_BITS * (l + 1);
if (oid >> sh == id >> sh)
continue;
else
goto restart;
}
if (m != n) {
sh = IDR_BITS*l;
id = ((id >> sh) ^ n ^ m) << sh;
}
if ((id >= MAX_ID_BIT) || (id < 0))
return IDR_NOMORE_SPACE;
if (l == 0)
break;
/*
* Create the layer below if it is missing.
*/
if (!p->ary[m]) {
new = get_from_free_list(idp);
if (!new)
return -1;
new->layer = l-1;
rcu_assign_pointer(p->ary[m], new);
p->count++;
}
pa[l--] = p;
p = p->ary[m];
}
pa[l] = p;
return id;
}
static int idr_get_empty_slot(struct idr *idp, int starting_id,
struct idr_layer **pa)
{
struct idr_layer *p, *new;
int layers, v, id;
unsigned long flags;
id = starting_id;
build_up:
p = idp->top;
layers = idp->layers;
if (unlikely(!p)) {
if (!(p = get_from_free_list(idp)))
return -1;
p->layer = 0;
layers = 1;
}
/*
* Add a new layer to the top of the tree if the requested
* id is larger than the currently allocated space.
*/
while ((layers < (MAX_LEVEL - 1)) && (id >= (1 << (layers*IDR_BITS)))) {
layers++;
if (!p->count) {
/* special case: if the tree is currently empty,
* then we grow the tree by moving the top node
* upwards.
*/
p->layer++;
continue;
}
if (!(new = get_from_free_list(idp))) {
/*
* The allocation failed. If we built part of
* the structure tear it down.
*/
spin_lock_irqsave(&idp->lock, flags);
for (new = p; p && p != idp->top; new = p) {
p = p->ary[0];
new->ary[0] = NULL;
new->bitmap = new->count = 0;
__move_to_free_list(idp, new);
}
spin_unlock_irqrestore(&idp->lock, flags);
return -1;
}
new->ary[0] = p;
new->count = 1;
new->layer = layers-1;
if (p->bitmap == IDR_FULL)
__set_bit(0, &new->bitmap);
p = new;
}
rcu_assign_pointer(idp->top, p);
idp->layers = layers;
v = sub_alloc(idp, &id, pa);
if (v == IDR_NEED_TO_GROW)
goto build_up;
return(v);
}
static int idr_get_new_above_int(struct idr *idp, void *ptr, int starting_id)
{
struct idr_layer *pa[MAX_LEVEL];
int id;
id = idr_get_empty_slot(idp, starting_id, pa);
if (id >= 0) {
/*
* Successfully found an empty slot. Install the user
* pointer and mark the slot full.
*/
rcu_assign_pointer(pa[0]->ary[id & IDR_MASK],
(struct idr_layer *)ptr);
pa[0]->count++;
idr_mark_full(pa, id);
}
return id;
}
/**
* idr_get_new_above - allocate new idr entry above or equal to a start id
* @idp: idr handle
* @ptr: pointer you want associated with the id
* @starting_id: id to start search at
* @id: pointer to the allocated handle
*
* This is the allocate id function. It should be called with any
* required locks.
*
* If allocation from IDR's private freelist fails, idr_get_new_above() will
* return %-EAGAIN. The caller should retry the idr_pre_get() call to refill
* IDR's preallocation and then retry the idr_get_new_above() call.
*
* If the idr is full idr_get_new_above() will return %-ENOSPC.
*
* @id returns a value in the range @starting_id ... %0x7fffffff
*/
int idr_get_new_above(struct idr *idp, void *ptr, int starting_id, int *id)
{
int rv;
rv = idr_get_new_above_int(idp, ptr, starting_id);
/*
* This is a cheap hack until the IDR code can be fixed to
* return proper error values.
*/
if (rv < 0)
return _idr_rc_to_errno(rv);
*id = rv;
return 0;
}
EXPORT_SYMBOL(idr_get_new_above);
/**
* idr_get_new - allocate new idr entry
* @idp: idr handle
* @ptr: pointer you want associated with the id
* @id: pointer to the allocated handle
*
* If allocation from IDR's private freelist fails, idr_get_new_above() will
* return %-EAGAIN. The caller should retry the idr_pre_get() call to refill
* IDR's preallocation and then retry the idr_get_new_above() call.
*
* If the idr is full idr_get_new_above() will return %-ENOSPC.
*
* @id returns a value in the range %0 ... %0x7fffffff
*/
int idr_get_new(struct idr *idp, void *ptr, int *id)
{
int rv;
rv = idr_get_new_above_int(idp, ptr, 0);
/*
* This is a cheap hack until the IDR code can be fixed to
* return proper error values.
*/
if (rv < 0)
return _idr_rc_to_errno(rv);
*id = rv;
return 0;
}
EXPORT_SYMBOL(idr_get_new);
static void idr_remove_warning(int id)
{
printk(KERN_WARNING
"idr_remove called for id=%d which is not allocated.\n", id);
dump_stack();
}
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;
*++paa = &idp->top;
while ((shift > 0) && p) {
n = (id >> shift) & IDR_MASK;
__clear_bit(n, &p->bitmap);
*++paa = &p->ary[n];
p = p->ary[n];
shift -= IDR_BITS;
}
n = id & IDR_MASK;
if (likely(p != NULL && test_bit(n, &p->bitmap))){
__clear_bit(n, &p->bitmap);
rcu_assign_pointer(p->ary[n], NULL);
to_free = NULL;
while(*paa && ! --((**paa)->count)){
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);
}
/**
* idr_remove - remove the given id and free its slot
* @idp: idr handle
* @id: unique key
*/
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]) {
/*
* 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];
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;
}
EXPORT_SYMBOL(idr_remove);
/**
* idr_remove_all - remove all ids from the given idr tree
* @idp: idr handle
*
* idr_destroy() only frees up unused, cached idp_layers, but this
* function will remove all id mappings and leave all idp_layers
* unused.
*
* A typical clean-up sequence for objects stored in an idr tree will
* use idr_for_each() to free all objects, if necessay, then
* idr_remove_all() to remove all ids, and idr_destroy() to free
* up the cached idr_layers.
*/
void idr_remove_all(struct idr *idp)
{
int n, id, max;
idr: fix backtrack logic in idr_remove_all Currently idr_remove_all will fail with a use after free error if idr::layers is bigger than 2, which on 32 bit systems corresponds to items more than 1024. This is due to stepping back too many levels during backtracking. For simplicity let's assume that IDR_BITS=1 -> we have 2 nodes at each level below the root node and each leaf node stores two IDs. (In reality for 32 bit systems IDR_BITS=5, with 32 nodes at each sub-root level and 32 IDs in each leaf node). The sequence of freeing the nodes at the moment is as follows: layer 1 -> a(7) 2 -> b(3) c(5) 3 -> d(1) e(2) f(4) g(6) Until step 4 things go fine, but then node c is freed, whereas node g should be freed first. Since node c contains the pointer to node g we'll have a use after free error at step 6. How many levels we step back after visiting the leaf nodes is currently determined by the msb of the id we are currently visiting: Step 1. node d with IDs 0,1 is freed, current ID is advanced to 2. msb of the current ID bit 1. This means we need to step back 1 level to node b and take the next sibling, node e. 2-3. node e with IDs 2,3 is freed, current ID is 4, msb is bit 2. This means we need to step back 2 levels to node a, freeing node b on the way. 4-5. node f with IDs 4,5 is freed, current ID is 6, msb is still bit 2. This means we again need to step back 2 levels to node a and free c on the way. 6. We should visit node g, but its pointer is not available as node c was freed. The fix changes how we determine the number of levels to step back. Instead of deducting this merely from the msb of the current ID, we should really check if advancing the ID causes an overflow to a bit position corresponding to a given layer. In the above example overflow from bit 0 to bit 1 should mean stepping back 1 level. Overflow from bit 1 to bit 2 should mean stepping back 2 levels and so on. The fix was tested with IDs up to 1 << 20, which corresponds to 4 layers on 32 bit systems. Signed-off-by: Imre Deak <imre.deak@nokia.com> Reviewed-by: Tejun Heo <tj@kernel.org> Cc: Eric Paris <eparis@redhat.com> Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> Cc: <stable@kernel.org> [2.6.34.1] Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2010-05-27 05:43:38 +08:00
int bt_mask;
struct idr_layer *p;
struct idr_layer *pa[MAX_LEVEL];
struct idr_layer **paa = &pa[0];
n = idp->layers * IDR_BITS;
p = idp->top;
rcu_assign_pointer(idp->top, NULL);
max = 1 << n;
id = 0;
while (id < max) {
while (n > IDR_BITS && p) {
n -= IDR_BITS;
*paa++ = p;
p = p->ary[(id >> n) & IDR_MASK];
}
idr: fix backtrack logic in idr_remove_all Currently idr_remove_all will fail with a use after free error if idr::layers is bigger than 2, which on 32 bit systems corresponds to items more than 1024. This is due to stepping back too many levels during backtracking. For simplicity let's assume that IDR_BITS=1 -> we have 2 nodes at each level below the root node and each leaf node stores two IDs. (In reality for 32 bit systems IDR_BITS=5, with 32 nodes at each sub-root level and 32 IDs in each leaf node). The sequence of freeing the nodes at the moment is as follows: layer 1 -> a(7) 2 -> b(3) c(5) 3 -> d(1) e(2) f(4) g(6) Until step 4 things go fine, but then node c is freed, whereas node g should be freed first. Since node c contains the pointer to node g we'll have a use after free error at step 6. How many levels we step back after visiting the leaf nodes is currently determined by the msb of the id we are currently visiting: Step 1. node d with IDs 0,1 is freed, current ID is advanced to 2. msb of the current ID bit 1. This means we need to step back 1 level to node b and take the next sibling, node e. 2-3. node e with IDs 2,3 is freed, current ID is 4, msb is bit 2. This means we need to step back 2 levels to node a, freeing node b on the way. 4-5. node f with IDs 4,5 is freed, current ID is 6, msb is still bit 2. This means we again need to step back 2 levels to node a and free c on the way. 6. We should visit node g, but its pointer is not available as node c was freed. The fix changes how we determine the number of levels to step back. Instead of deducting this merely from the msb of the current ID, we should really check if advancing the ID causes an overflow to a bit position corresponding to a given layer. In the above example overflow from bit 0 to bit 1 should mean stepping back 1 level. Overflow from bit 1 to bit 2 should mean stepping back 2 levels and so on. The fix was tested with IDs up to 1 << 20, which corresponds to 4 layers on 32 bit systems. Signed-off-by: Imre Deak <imre.deak@nokia.com> Reviewed-by: Tejun Heo <tj@kernel.org> Cc: Eric Paris <eparis@redhat.com> Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> Cc: <stable@kernel.org> [2.6.34.1] Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2010-05-27 05:43:38 +08:00
bt_mask = id;
id += 1 << n;
idr: fix backtrack logic in idr_remove_all Currently idr_remove_all will fail with a use after free error if idr::layers is bigger than 2, which on 32 bit systems corresponds to items more than 1024. This is due to stepping back too many levels during backtracking. For simplicity let's assume that IDR_BITS=1 -> we have 2 nodes at each level below the root node and each leaf node stores two IDs. (In reality for 32 bit systems IDR_BITS=5, with 32 nodes at each sub-root level and 32 IDs in each leaf node). The sequence of freeing the nodes at the moment is as follows: layer 1 -> a(7) 2 -> b(3) c(5) 3 -> d(1) e(2) f(4) g(6) Until step 4 things go fine, but then node c is freed, whereas node g should be freed first. Since node c contains the pointer to node g we'll have a use after free error at step 6. How many levels we step back after visiting the leaf nodes is currently determined by the msb of the id we are currently visiting: Step 1. node d with IDs 0,1 is freed, current ID is advanced to 2. msb of the current ID bit 1. This means we need to step back 1 level to node b and take the next sibling, node e. 2-3. node e with IDs 2,3 is freed, current ID is 4, msb is bit 2. This means we need to step back 2 levels to node a, freeing node b on the way. 4-5. node f with IDs 4,5 is freed, current ID is 6, msb is still bit 2. This means we again need to step back 2 levels to node a and free c on the way. 6. We should visit node g, but its pointer is not available as node c was freed. The fix changes how we determine the number of levels to step back. Instead of deducting this merely from the msb of the current ID, we should really check if advancing the ID causes an overflow to a bit position corresponding to a given layer. In the above example overflow from bit 0 to bit 1 should mean stepping back 1 level. Overflow from bit 1 to bit 2 should mean stepping back 2 levels and so on. The fix was tested with IDs up to 1 << 20, which corresponds to 4 layers on 32 bit systems. Signed-off-by: Imre Deak <imre.deak@nokia.com> Reviewed-by: Tejun Heo <tj@kernel.org> Cc: Eric Paris <eparis@redhat.com> Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> Cc: <stable@kernel.org> [2.6.34.1] Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2010-05-27 05:43:38 +08:00
/* Get the highest bit that the above add changed from 0->1. */
while (n < fls(id ^ bt_mask)) {
if (p)
free_layer(p);
n += IDR_BITS;
p = *--paa;
}
}
idp->layers = 0;
}
EXPORT_SYMBOL(idr_remove_all);
/**
* idr_destroy - release all cached layers within an idr tree
* @idp: idr handle
*/
void idr_destroy(struct idr *idp)
{
while (idp->id_free_cnt) {
struct idr_layer *p = get_from_free_list(idp);
kmem_cache_free(idr_layer_cache, p);
}
}
EXPORT_SYMBOL(idr_destroy);
/**
* idr_find - return pointer for given id
* @idp: idr handle
* @id: lookup key
*
* Return the pointer given the id it has been registered with. A %NULL
* return indicates that @id is not valid or you passed %NULL in
* idr_get_new().
*
* 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)
{
int n;
struct idr_layer *p;
p = rcu_dereference_raw(idp->top);
if (!p)
return NULL;
n = (p->layer+1) * IDR_BITS;
/* Mask off upper bits we don't use for the search. */
id &= MAX_ID_MASK;
if (id >= (1 << n))
return NULL;
BUG_ON(n == 0);
while (n > 0 && p) {
n -= IDR_BITS;
BUG_ON(n != p->layer*IDR_BITS);
p = rcu_dereference_raw(p->ary[(id >> n) & IDR_MASK]);
}
return((void *)p);
}
EXPORT_SYMBOL(idr_find);
/**
* idr_for_each - iterate through all stored pointers
* @idp: idr handle
* @fn: function to be called for each pointer
* @data: data passed back to callback function
*
* Iterate over the pointers registered with the given idr. The
* callback function will be called for each pointer currently
* registered, passing the id, the pointer and the data pointer passed
* to this function. It is not safe to modify the idr tree while in
* the callback, so functions such as idr_get_new and idr_remove are
* not allowed.
*
* We check the return of @fn each time. If it returns anything other
* than %0, we break out and return that value.
*
* The caller must serialize idr_for_each() vs idr_get_new() and idr_remove().
*/
int idr_for_each(struct idr *idp,
int (*fn)(int id, void *p, void *data), void *data)
{
int n, id, max, error = 0;
struct idr_layer *p;
struct idr_layer *pa[MAX_LEVEL];
struct idr_layer **paa = &pa[0];
n = idp->layers * IDR_BITS;
p = rcu_dereference_raw(idp->top);
max = 1 << n;
id = 0;
while (id < max) {
while (n > 0 && p) {
n -= IDR_BITS;
*paa++ = p;
p = rcu_dereference_raw(p->ary[(id >> n) & IDR_MASK]);
}
if (p) {
error = fn(id, (void *)p, data);
if (error)
break;
}
id += 1 << n;
while (n < fls(id)) {
n += IDR_BITS;
p = *--paa;
}
}
return error;
}
EXPORT_SYMBOL(idr_for_each);
cgroup: CSS ID support Patch for Per-CSS(Cgroup Subsys State) ID and private hierarchy code. This patch attaches unique ID to each css and provides following. - css_lookup(subsys, id) returns pointer to struct cgroup_subysys_state of id. - css_get_next(subsys, id, rootid, depth, foundid) returns the next css under "root" by scanning When cgroup_subsys->use_id is set, an id for css is maintained. The cgroup framework only parepares - css_id of root css for subsys - id is automatically attached at creation of css. - id is *not* freed automatically. Because the cgroup framework don't know lifetime of cgroup_subsys_state. free_css_id() function is provided. This must be called by subsys. There are several reasons to develop this. - Saving space .... For example, memcg's swap_cgroup is array of pointers to cgroup. But it is not necessary to be very fast. By replacing pointers(8bytes per ent) to ID (2byes per ent), we can reduce much amount of memory usage. - Scanning without lock. CSS_ID provides "scan id under this ROOT" function. By this, scanning css under root can be written without locks. ex) do { rcu_read_lock(); next = cgroup_get_next(subsys, id, root, &found); /* check sanity of next here */ css_tryget(); rcu_read_unlock(); id = found + 1 } while(...) Characteristics: - Each css has unique ID under subsys. - Lifetime of ID is controlled by subsys. - css ID contains "ID" and "Depth in hierarchy" and stack of hierarchy - Allowed ID is 1-65535, ID 0 is UNUSED ID. Design Choices: - scan-by-ID v.s. scan-by-tree-walk. As /proc's pid scan does, scan-by-ID is robust when scanning is done by following kind of routine. scan -> rest a while(release a lock) -> conitunue from interrupted memcg's hierarchical reclaim does this. - When subsys->use_id is set, # of css in the system is limited to 65535. [bharata@linux.vnet.ibm.com: remove rcu_read_lock() from css_get_next()] Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Acked-by: Paul Menage <menage@google.com> Cc: Li Zefan <lizf@cn.fujitsu.com> Cc: Balbir Singh <balbir@in.ibm.com> Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> Signed-off-by: Bharata B Rao <bharata@linux.vnet.ibm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2009-04-03 07:57:25 +08:00
/**
* idr_get_next - lookup next object of id to given id.
* @idp: idr handle
* @nextidp: pointer to lookup key
cgroup: CSS ID support Patch for Per-CSS(Cgroup Subsys State) ID and private hierarchy code. This patch attaches unique ID to each css and provides following. - css_lookup(subsys, id) returns pointer to struct cgroup_subysys_state of id. - css_get_next(subsys, id, rootid, depth, foundid) returns the next css under "root" by scanning When cgroup_subsys->use_id is set, an id for css is maintained. The cgroup framework only parepares - css_id of root css for subsys - id is automatically attached at creation of css. - id is *not* freed automatically. Because the cgroup framework don't know lifetime of cgroup_subsys_state. free_css_id() function is provided. This must be called by subsys. There are several reasons to develop this. - Saving space .... For example, memcg's swap_cgroup is array of pointers to cgroup. But it is not necessary to be very fast. By replacing pointers(8bytes per ent) to ID (2byes per ent), we can reduce much amount of memory usage. - Scanning without lock. CSS_ID provides "scan id under this ROOT" function. By this, scanning css under root can be written without locks. ex) do { rcu_read_lock(); next = cgroup_get_next(subsys, id, root, &found); /* check sanity of next here */ css_tryget(); rcu_read_unlock(); id = found + 1 } while(...) Characteristics: - Each css has unique ID under subsys. - Lifetime of ID is controlled by subsys. - css ID contains "ID" and "Depth in hierarchy" and stack of hierarchy - Allowed ID is 1-65535, ID 0 is UNUSED ID. Design Choices: - scan-by-ID v.s. scan-by-tree-walk. As /proc's pid scan does, scan-by-ID is robust when scanning is done by following kind of routine. scan -> rest a while(release a lock) -> conitunue from interrupted memcg's hierarchical reclaim does this. - When subsys->use_id is set, # of css in the system is limited to 65535. [bharata@linux.vnet.ibm.com: remove rcu_read_lock() from css_get_next()] Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Acked-by: Paul Menage <menage@google.com> Cc: Li Zefan <lizf@cn.fujitsu.com> Cc: Balbir Singh <balbir@in.ibm.com> Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> Signed-off-by: Bharata B Rao <bharata@linux.vnet.ibm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2009-04-03 07:57:25 +08:00
*
* Returns pointer to registered object with id, which is next number to
* given id. After being looked up, *@nextidp will be updated for the next
* iteration.
cgroup: CSS ID support Patch for Per-CSS(Cgroup Subsys State) ID and private hierarchy code. This patch attaches unique ID to each css and provides following. - css_lookup(subsys, id) returns pointer to struct cgroup_subysys_state of id. - css_get_next(subsys, id, rootid, depth, foundid) returns the next css under "root" by scanning When cgroup_subsys->use_id is set, an id for css is maintained. The cgroup framework only parepares - css_id of root css for subsys - id is automatically attached at creation of css. - id is *not* freed automatically. Because the cgroup framework don't know lifetime of cgroup_subsys_state. free_css_id() function is provided. This must be called by subsys. There are several reasons to develop this. - Saving space .... For example, memcg's swap_cgroup is array of pointers to cgroup. But it is not necessary to be very fast. By replacing pointers(8bytes per ent) to ID (2byes per ent), we can reduce much amount of memory usage. - Scanning without lock. CSS_ID provides "scan id under this ROOT" function. By this, scanning css under root can be written without locks. ex) do { rcu_read_lock(); next = cgroup_get_next(subsys, id, root, &found); /* check sanity of next here */ css_tryget(); rcu_read_unlock(); id = found + 1 } while(...) Characteristics: - Each css has unique ID under subsys. - Lifetime of ID is controlled by subsys. - css ID contains "ID" and "Depth in hierarchy" and stack of hierarchy - Allowed ID is 1-65535, ID 0 is UNUSED ID. Design Choices: - scan-by-ID v.s. scan-by-tree-walk. As /proc's pid scan does, scan-by-ID is robust when scanning is done by following kind of routine. scan -> rest a while(release a lock) -> conitunue from interrupted memcg's hierarchical reclaim does this. - When subsys->use_id is set, # of css in the system is limited to 65535. [bharata@linux.vnet.ibm.com: remove rcu_read_lock() from css_get_next()] Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Acked-by: Paul Menage <menage@google.com> Cc: Li Zefan <lizf@cn.fujitsu.com> Cc: Balbir Singh <balbir@in.ibm.com> Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> Signed-off-by: Bharata B Rao <bharata@linux.vnet.ibm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2009-04-03 07:57:25 +08:00
*/
void *idr_get_next(struct idr *idp, int *nextidp)
{
struct idr_layer *p, *pa[MAX_LEVEL];
struct idr_layer **paa = &pa[0];
int id = *nextidp;
int n, max;
/* find first ent */
n = idp->layers * IDR_BITS;
max = 1 << n;
p = rcu_dereference_raw(idp->top);
cgroup: CSS ID support Patch for Per-CSS(Cgroup Subsys State) ID and private hierarchy code. This patch attaches unique ID to each css and provides following. - css_lookup(subsys, id) returns pointer to struct cgroup_subysys_state of id. - css_get_next(subsys, id, rootid, depth, foundid) returns the next css under "root" by scanning When cgroup_subsys->use_id is set, an id for css is maintained. The cgroup framework only parepares - css_id of root css for subsys - id is automatically attached at creation of css. - id is *not* freed automatically. Because the cgroup framework don't know lifetime of cgroup_subsys_state. free_css_id() function is provided. This must be called by subsys. There are several reasons to develop this. - Saving space .... For example, memcg's swap_cgroup is array of pointers to cgroup. But it is not necessary to be very fast. By replacing pointers(8bytes per ent) to ID (2byes per ent), we can reduce much amount of memory usage. - Scanning without lock. CSS_ID provides "scan id under this ROOT" function. By this, scanning css under root can be written without locks. ex) do { rcu_read_lock(); next = cgroup_get_next(subsys, id, root, &found); /* check sanity of next here */ css_tryget(); rcu_read_unlock(); id = found + 1 } while(...) Characteristics: - Each css has unique ID under subsys. - Lifetime of ID is controlled by subsys. - css ID contains "ID" and "Depth in hierarchy" and stack of hierarchy - Allowed ID is 1-65535, ID 0 is UNUSED ID. Design Choices: - scan-by-ID v.s. scan-by-tree-walk. As /proc's pid scan does, scan-by-ID is robust when scanning is done by following kind of routine. scan -> rest a while(release a lock) -> conitunue from interrupted memcg's hierarchical reclaim does this. - When subsys->use_id is set, # of css in the system is limited to 65535. [bharata@linux.vnet.ibm.com: remove rcu_read_lock() from css_get_next()] Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Acked-by: Paul Menage <menage@google.com> Cc: Li Zefan <lizf@cn.fujitsu.com> Cc: Balbir Singh <balbir@in.ibm.com> Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> Signed-off-by: Bharata B Rao <bharata@linux.vnet.ibm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2009-04-03 07:57:25 +08:00
if (!p)
return NULL;
while (id < max) {
while (n > 0 && p) {
n -= IDR_BITS;
*paa++ = p;
p = rcu_dereference_raw(p->ary[(id >> n) & IDR_MASK]);
cgroup: CSS ID support Patch for Per-CSS(Cgroup Subsys State) ID and private hierarchy code. This patch attaches unique ID to each css and provides following. - css_lookup(subsys, id) returns pointer to struct cgroup_subysys_state of id. - css_get_next(subsys, id, rootid, depth, foundid) returns the next css under "root" by scanning When cgroup_subsys->use_id is set, an id for css is maintained. The cgroup framework only parepares - css_id of root css for subsys - id is automatically attached at creation of css. - id is *not* freed automatically. Because the cgroup framework don't know lifetime of cgroup_subsys_state. free_css_id() function is provided. This must be called by subsys. There are several reasons to develop this. - Saving space .... For example, memcg's swap_cgroup is array of pointers to cgroup. But it is not necessary to be very fast. By replacing pointers(8bytes per ent) to ID (2byes per ent), we can reduce much amount of memory usage. - Scanning without lock. CSS_ID provides "scan id under this ROOT" function. By this, scanning css under root can be written without locks. ex) do { rcu_read_lock(); next = cgroup_get_next(subsys, id, root, &found); /* check sanity of next here */ css_tryget(); rcu_read_unlock(); id = found + 1 } while(...) Characteristics: - Each css has unique ID under subsys. - Lifetime of ID is controlled by subsys. - css ID contains "ID" and "Depth in hierarchy" and stack of hierarchy - Allowed ID is 1-65535, ID 0 is UNUSED ID. Design Choices: - scan-by-ID v.s. scan-by-tree-walk. As /proc's pid scan does, scan-by-ID is robust when scanning is done by following kind of routine. scan -> rest a while(release a lock) -> conitunue from interrupted memcg's hierarchical reclaim does this. - When subsys->use_id is set, # of css in the system is limited to 65535. [bharata@linux.vnet.ibm.com: remove rcu_read_lock() from css_get_next()] Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Acked-by: Paul Menage <menage@google.com> Cc: Li Zefan <lizf@cn.fujitsu.com> Cc: Balbir Singh <balbir@in.ibm.com> Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> Signed-off-by: Bharata B Rao <bharata@linux.vnet.ibm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2009-04-03 07:57:25 +08:00
}
if (p) {
*nextidp = id;
return p;
}
id += 1 << n;
while (n < fls(id)) {
n += IDR_BITS;
p = *--paa;
}
}
return NULL;
}
EXPORT_SYMBOL(idr_get_next);
cgroup: CSS ID support Patch for Per-CSS(Cgroup Subsys State) ID and private hierarchy code. This patch attaches unique ID to each css and provides following. - css_lookup(subsys, id) returns pointer to struct cgroup_subysys_state of id. - css_get_next(subsys, id, rootid, depth, foundid) returns the next css under "root" by scanning When cgroup_subsys->use_id is set, an id for css is maintained. The cgroup framework only parepares - css_id of root css for subsys - id is automatically attached at creation of css. - id is *not* freed automatically. Because the cgroup framework don't know lifetime of cgroup_subsys_state. free_css_id() function is provided. This must be called by subsys. There are several reasons to develop this. - Saving space .... For example, memcg's swap_cgroup is array of pointers to cgroup. But it is not necessary to be very fast. By replacing pointers(8bytes per ent) to ID (2byes per ent), we can reduce much amount of memory usage. - Scanning without lock. CSS_ID provides "scan id under this ROOT" function. By this, scanning css under root can be written without locks. ex) do { rcu_read_lock(); next = cgroup_get_next(subsys, id, root, &found); /* check sanity of next here */ css_tryget(); rcu_read_unlock(); id = found + 1 } while(...) Characteristics: - Each css has unique ID under subsys. - Lifetime of ID is controlled by subsys. - css ID contains "ID" and "Depth in hierarchy" and stack of hierarchy - Allowed ID is 1-65535, ID 0 is UNUSED ID. Design Choices: - scan-by-ID v.s. scan-by-tree-walk. As /proc's pid scan does, scan-by-ID is robust when scanning is done by following kind of routine. scan -> rest a while(release a lock) -> conitunue from interrupted memcg's hierarchical reclaim does this. - When subsys->use_id is set, # of css in the system is limited to 65535. [bharata@linux.vnet.ibm.com: remove rcu_read_lock() from css_get_next()] Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Acked-by: Paul Menage <menage@google.com> Cc: Li Zefan <lizf@cn.fujitsu.com> Cc: Balbir Singh <balbir@in.ibm.com> Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> Signed-off-by: Bharata B Rao <bharata@linux.vnet.ibm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2009-04-03 07:57:25 +08:00
/**
* idr_replace - replace pointer for given id
* @idp: idr handle
* @ptr: pointer you want associated with the id
* @id: lookup key
*
* Replace the pointer registered with an id and return the old value.
* A %-ENOENT return indicates that @id was not found.
* A %-EINVAL return indicates that @id was not within valid constraints.
*
* The caller must serialize with writers.
*/
void *idr_replace(struct idr *idp, void *ptr, int id)
{
int n;
struct idr_layer *p, *old_p;
p = idp->top;
if (!p)
return ERR_PTR(-EINVAL);
n = (p->layer+1) * IDR_BITS;
id &= MAX_ID_MASK;
if (id >= (1 << n))
return ERR_PTR(-EINVAL);
n -= IDR_BITS;
while ((n > 0) && p) {
p = p->ary[(id >> n) & IDR_MASK];
n -= IDR_BITS;
}
n = id & IDR_MASK;
if (unlikely(p == NULL || !test_bit(n, &p->bitmap)))
return ERR_PTR(-ENOENT);
old_p = p->ary[n];
rcu_assign_pointer(p->ary[n], ptr);
return old_p;
}
EXPORT_SYMBOL(idr_replace);
void __init idr_init_cache(void)
{
idr_layer_cache = kmem_cache_create("idr_layer_cache",
lib/idr.c: use kmem_cache_zalloc() for the idr_layer cache David points out that the idr_remove_all() function returns unused slabs to the kmem cache, but needs to zero them first or else they will be uninitialized upon next use. This causes crashes which have been observed in the firewire subsystem. He fixed this by zeroing the object before freeing it in idr_remove_all(). But we agree that simply removing the constructor and zeroing the object at allocation time is simpler than relying upon slab constructor machinery and might even be faster. This problem was introduced by "idr: make idr_remove rcu-safe" (commit cf481c20c476ad2c0febdace9ce23f5a4db19582), which was first released in 2.6.27. There are no known codesites which trigger this bug in 2.6.27 or 2.6.28. The post-2.6.28 firewire changes are the only known triggerer. There might of course be not-yet-discovered triggerers in 2.6.27 and 2.6.28, and there might be out-of-tree triggerers which are added to those kernel versions. I'll let the -stable guys decide whether they want to backport this fix. Reported-by: David Moore <dcm@acm.org> Cc: Stefan Richter <stefanr@s5r6.in-berlin.de> Cc: Nadia Derbey <Nadia.Derbey@bull.net> Cc: Paul E. McKenney <paulmck@us.ibm.com> Cc: Manfred Spraul <manfred@colorfullife.com> Cc: Kristian Hgsberg <krh@redhat.com> Acked-by: Pekka Enberg <penberg@cs.helsinki.fi> Cc: <stable@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2009-01-16 05:51:21 +08:00
sizeof(struct idr_layer), 0, SLAB_PANIC, NULL);
}
/**
* idr_init - initialize idr handle
* @idp: idr handle
*
* This function is use to set up the handle (@idp) that you will pass
* to the rest of the functions.
*/
void idr_init(struct idr *idp)
{
memset(idp, 0, sizeof(struct idr));
spin_lock_init(&idp->lock);
}
EXPORT_SYMBOL(idr_init);
/**
* DOC: IDA description
* IDA - IDR based ID allocator
*
* This is id allocator without id -> pointer translation. Memory
* usage is much lower than full blown idr because each id only
* occupies a bit. ida uses a custom leaf node which contains
* IDA_BITMAP_BITS slots.
*
* 2007-04-25 written by Tejun Heo <htejun@gmail.com>
*/
static void free_bitmap(struct ida *ida, struct ida_bitmap *bitmap)
{
unsigned long flags;
if (!ida->free_bitmap) {
spin_lock_irqsave(&ida->idr.lock, flags);
if (!ida->free_bitmap) {
ida->free_bitmap = bitmap;
bitmap = NULL;
}
spin_unlock_irqrestore(&ida->idr.lock, flags);
}
kfree(bitmap);
}
/**
* ida_pre_get - reserve resources for ida allocation
* @ida: ida handle
* @gfp_mask: memory allocation flag
*
* This function should be called prior to locking and calling the
* following function. It preallocates enough memory to satisfy the
* worst possible allocation.
*
* If the system is REALLY out of memory this function returns %0,
* otherwise %1.
*/
int ida_pre_get(struct ida *ida, gfp_t gfp_mask)
{
/* allocate idr_layers */
if (!idr_pre_get(&ida->idr, gfp_mask))
return 0;
/* allocate free_bitmap */
if (!ida->free_bitmap) {
struct ida_bitmap *bitmap;
bitmap = kmalloc(sizeof(struct ida_bitmap), gfp_mask);
if (!bitmap)
return 0;
free_bitmap(ida, bitmap);
}
return 1;
}
EXPORT_SYMBOL(ida_pre_get);
/**
* ida_get_new_above - allocate new ID above or equal to a start id
* @ida: ida handle
* @starting_id: id to start search at
* @p_id: pointer to the allocated handle
*
* Allocate new ID above or equal to @ida. It should be called with
* any required locks.
*
* If memory is required, it will return %-EAGAIN, you should unlock
* and go back to the ida_pre_get() call. If the ida is full, it will
* return %-ENOSPC.
*
* @p_id returns a value in the range @starting_id ... %0x7fffffff.
*/
int ida_get_new_above(struct ida *ida, int starting_id, int *p_id)
{
struct idr_layer *pa[MAX_LEVEL];
struct ida_bitmap *bitmap;
unsigned long flags;
int idr_id = starting_id / IDA_BITMAP_BITS;
int offset = starting_id % IDA_BITMAP_BITS;
int t, id;
restart:
/* get vacant slot */
t = idr_get_empty_slot(&ida->idr, idr_id, pa);
if (t < 0)
return _idr_rc_to_errno(t);
if (t * IDA_BITMAP_BITS >= MAX_ID_BIT)
return -ENOSPC;
if (t != idr_id)
offset = 0;
idr_id = t;
/* if bitmap isn't there, create a new one */
bitmap = (void *)pa[0]->ary[idr_id & IDR_MASK];
if (!bitmap) {
spin_lock_irqsave(&ida->idr.lock, flags);
bitmap = ida->free_bitmap;
ida->free_bitmap = NULL;
spin_unlock_irqrestore(&ida->idr.lock, flags);
if (!bitmap)
return -EAGAIN;
memset(bitmap, 0, sizeof(struct ida_bitmap));
rcu_assign_pointer(pa[0]->ary[idr_id & IDR_MASK],
(void *)bitmap);
pa[0]->count++;
}
/* lookup for empty slot */
t = find_next_zero_bit(bitmap->bitmap, IDA_BITMAP_BITS, offset);
if (t == IDA_BITMAP_BITS) {
/* no empty slot after offset, continue to the next chunk */
idr_id++;
offset = 0;
goto restart;
}
id = idr_id * IDA_BITMAP_BITS + t;
if (id >= MAX_ID_BIT)
return -ENOSPC;
__set_bit(t, bitmap->bitmap);
if (++bitmap->nr_busy == IDA_BITMAP_BITS)
idr_mark_full(pa, idr_id);
*p_id = id;
/* Each leaf node can handle nearly a thousand slots and the
* whole idea of ida is to have small memory foot print.
* Throw away extra resources one by one after each successful
* allocation.
*/
if (ida->idr.id_free_cnt || ida->free_bitmap) {
struct idr_layer *p = get_from_free_list(&ida->idr);
if (p)
kmem_cache_free(idr_layer_cache, p);
}
return 0;
}
EXPORT_SYMBOL(ida_get_new_above);
/**
* ida_get_new - allocate new ID
* @ida: idr handle
* @p_id: pointer to the allocated handle
*
* Allocate new ID. It should be called with any required locks.
*
* If memory is required, it will return %-EAGAIN, you should unlock
* and go back to the idr_pre_get() call. If the idr is full, it will
* return %-ENOSPC.
*
* @id returns a value in the range %0 ... %0x7fffffff.
*/
int ida_get_new(struct ida *ida, int *p_id)
{
return ida_get_new_above(ida, 0, p_id);
}
EXPORT_SYMBOL(ida_get_new);
/**
* ida_remove - remove the given ID
* @ida: ida handle
* @id: ID to free
*/
void ida_remove(struct ida *ida, int id)
{
struct idr_layer *p = ida->idr.top;
int shift = (ida->idr.layers - 1) * IDR_BITS;
int idr_id = id / IDA_BITMAP_BITS;
int offset = id % IDA_BITMAP_BITS;
int n;
struct ida_bitmap *bitmap;
/* clear full bits while looking up the leaf idr_layer */
while ((shift > 0) && p) {
n = (idr_id >> shift) & IDR_MASK;
__clear_bit(n, &p->bitmap);
p = p->ary[n];
shift -= IDR_BITS;
}
if (p == NULL)
goto err;
n = idr_id & IDR_MASK;
__clear_bit(n, &p->bitmap);
bitmap = (void *)p->ary[n];
if (!test_bit(offset, bitmap->bitmap))
goto err;
/* update bitmap and remove it if empty */
__clear_bit(offset, bitmap->bitmap);
if (--bitmap->nr_busy == 0) {
__set_bit(n, &p->bitmap); /* to please idr_remove() */
idr_remove(&ida->idr, idr_id);
free_bitmap(ida, bitmap);
}
return;
err:
printk(KERN_WARNING
"ida_remove called for id=%d which is not allocated.\n", id);
}
EXPORT_SYMBOL(ida_remove);
/**
* ida_destroy - release all cached layers within an ida tree
* @ida: ida handle
*/
void ida_destroy(struct ida *ida)
{
idr_destroy(&ida->idr);
kfree(ida->free_bitmap);
}
EXPORT_SYMBOL(ida_destroy);
/**
* ida_simple_get - get a new id.
* @ida: the (initialized) ida.
* @start: the minimum id (inclusive, < 0x8000000)
* @end: the maximum id (exclusive, < 0x8000000 or 0)
* @gfp_mask: memory allocation flags
*
* Allocates an id in the range start <= id < end, or returns -ENOSPC.
* On memory allocation failure, returns -ENOMEM.
*
* Use ida_simple_remove() to get rid of an id.
*/
int ida_simple_get(struct ida *ida, unsigned int start, unsigned int end,
gfp_t gfp_mask)
{
int ret, id;
unsigned int max;
BUG_ON((int)start < 0);
BUG_ON((int)end < 0);
if (end == 0)
max = 0x80000000;
else {
BUG_ON(end < start);
max = end - 1;
}
again:
if (!ida_pre_get(ida, gfp_mask))
return -ENOMEM;
spin_lock(&simple_ida_lock);
ret = ida_get_new_above(ida, start, &id);
if (!ret) {
if (id > max) {
ida_remove(ida, id);
ret = -ENOSPC;
} else {
ret = id;
}
}
spin_unlock(&simple_ida_lock);
if (unlikely(ret == -EAGAIN))
goto again;
return ret;
}
EXPORT_SYMBOL(ida_simple_get);
/**
* ida_simple_remove - remove an allocated id.
* @ida: the (initialized) ida.
* @id: the id returned by ida_simple_get.
*/
void ida_simple_remove(struct ida *ida, unsigned int id)
{
BUG_ON((int)id < 0);
spin_lock(&simple_ida_lock);
ida_remove(ida, id);
spin_unlock(&simple_ida_lock);
}
EXPORT_SYMBOL(ida_simple_remove);
/**
* ida_init - initialize ida handle
* @ida: ida handle
*
* This function is use to set up the handle (@ida) that you will pass
* to the rest of the functions.
*/
void ida_init(struct ida *ida)
{
memset(ida, 0, sizeof(struct ida));
idr_init(&ida->idr);
}
EXPORT_SYMBOL(ida_init);