Messages in this thread | | | Date | Fri, 30 May 2008 01:22:14 -0700 | From | "Paul E. McKenney" <> | Subject | Re: [PATCH 0/9] Scalability requirements for sysv ipc - v3 |
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On Wed, May 07, 2008 at 01:35:53PM +0200, Nadia.Derbey@bull.net wrote: > > After scalability problems have been detected when using the sysV ipcs, I > have proposed to use an RCU based implementation of the IDR api instead (see > threads http://lkml.org/lkml/2008/4/11/212 and > http://lkml.org/lkml/2008/4/29/295). > > This resulted in many people asking to convert the idr API and make it > rcu safe (because most of the code was duplicated and thus unmaintanable > and unreviewable). > > So here is a first attempt. > > The important change wrt to the idr API itself is during idr removes: > idr layers are freed after a grace period, instead of being moved to the > free list. > > The important change wrt to ipcs, is that idr_find() can now be called > locklessly inside a rcu read critical section. > > Here are the results I've got for the pmsg test sent by Manfred: > > 2.6.25-rc3-mm1 2.6.25-rc3-mm1+ 2.6.25-mm1 Patched 2.6.25-mm1 > 1 1168441 1064021 876000 947488 > 2 1094264 921059 1549592 1730685 > 3 2082520 1738165 1694370 2324880 > 4 2079929 1695521 404553 2400408 > 5 2898758 406566 391283 3246580 > 6 2921417 261275 263249 3752148 > 7 3308761 126056 191742 4243142 > 8 3329456 100129 141722 4275780 > > 1st column: stock 2.6.25-rc3-mm1 > 2nd column: 2.6.25-rc3-mm1 + ipc patches (store ipcs into idrs) > 3nd column: stock 2.6.25-mm1 > 4th column: 2.6.25-mm1 + this pacth series. > > I'll send a chart as an answer to this mail: don't know how to do that > with quilt :-( > > > Reviewers are more than ever welcome! > > Patches should be applied on linux-2.6.25-mm1, in the following order: > > [ PATCH 01/09 ] : idr_add_rcu_head.patch > [ PATCH 02/09 ] : idr_rename_routines.patch > [ PATCH 03/09 ] : idr_fix_printk.patch > [ PATCH 04/09 ] : idr_rc_to_errno.patch > [ PATCH 05/09 ] : idr_get_new_rcu_safe.patch > [ PATCH 06/09 ] : idr_find_rcu_safe.patch > [ PATCH 07/09 ] : idr_remove_rcu_safe.patch > [ PATCH 08/09 ] : ipc_fix_ipc_lock.patch > [ PATCH 09/09 ] : remove_ipc_lock_down.patch > > Patches 2, 3 and 4 do not introduce actual changes. > > I won't be available before next Tuesday, so, please, don't be mad at me if > I'm not answering fast enough.
I guess in my case, next Tuesday was not an issue. :-/
Anyway, the idr.c changes look good to me. Not sure why you are using INIT_RCU_HEAD() given that call_rcu() completely initializes the fields. Using INIT_RCU_HEAD() doesn't cause any problems, but does add needless code.
Commentary below, looks good from an RCU viewpoint.
Thanx, Paul
> /* > * 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> > > static struct kmem_cache *idr_layer_cache; > > 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;
OK, this is the freelist which is inaccessible to readers.
> } > 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;
OK, this is the freelist which is inaccessible to readers.
> 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 - reserver resources for idr allocation > * @idp: idr handle > * @gfp_mask: memory allocation flags > * > * This function should be called prior to locking and calling the > * 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, > * 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; > new = kmem_cache_alloc(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;
OK, the caller presumably holds an update-side lock.
> 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 (!(p = pa[l])) { > *starting_id = id; > return IDR_NEED_TO_GROW; > } > > /* 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]) {
OK, we aren't dereferencing. Besides, we should hold the update-side lock at this point.
> new = get_from_free_list(idp); > if (!new) > return -1; > INIT_RCU_HEAD(&new->rcu_head);
Not needed, unless you want this zeroed for debug purposes.
> rcu_assign_pointer(p->ary[m], new); > p->count++; > } > pa[l--] = p; > p = p->ary[m];
Holding update-side lock.
> } > > 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;
OK, the caller presumably holds an update-side lock.
> layers = idp->layers; > if (unlikely(!p)) { > if (!(p = get_from_free_list(idp))) > return -1; > INIT_RCU_HEAD(&p->rcu_head);
Not needed, unless you want this zeroed for debug purposes.
> 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) > 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;
OK, this presumably has not yet been made accessible to readers.
> new->bitmap = new->count = 0; > __move_to_free_list(idp, new); > } > spin_unlock_irqrestore(&idp->lock, flags); > return -1; > } > new->ary[0] = p;
OK, this presumably has not yet been made accessible to readers.
> new->count = 1; > INIT_RCU_HEAD(&new->rcu_head);
Not needed, unless you want this zeroed for debug purposes.
> 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 ide > * @start_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 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 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 ide > * @id: pointer to the allocated handle > * > * This is the allocate id function. 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 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;
OK, the caller presumably holds an update-side lock.
> 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];
OK, the caller presumably holds an update-side lock.
> 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 it's 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]) {
OK, the caller presumably holds the update-side lock.
> /* > * 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];
OK, the caller presumably holds the update-side lock.
> 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; > struct idr_layer *p; > struct idr_layer *pa[MAX_LEVEL]; > struct idr_layer **paa = &pa[0]; > > n = idp->layers * IDR_BITS; > p = idp->top;
OK, the caller presumably holds an update-side lock.
> 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];
OK, the caller presumably holds the update-side lock.
> } > > id += 1 << n; > while (n < fls(id)) { > if (p) > free_layer(p); > n += IDR_BITS; > p = *--paa; > } > } > rcu_assign_pointer(idp->top, NULL); > 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; > > n = idp->layers * IDR_BITS; > p = rcu_dereference(idp->top); > > /* Mask off upper bits we don't use for the search. */ > id &= MAX_ID_MASK; > > if (id >= (1 << n)) > return NULL; > > while (n > 0 && p) { > n -= IDR_BITS; > p = rcu_dereference(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(idp->top); > max = 1 << n; > > id = 0; > while (id < max) { > while (n > 0 && p) { > n -= IDR_BITS; > *paa++ = p; > p = rcu_dereference(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); > > /** > * 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; > > n = idp->layers * IDR_BITS; > p = idp->top;
OK, the caller presumably holds an update-side lock.
> > 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];
OK, the caller presumably holds the update-side lock.
> 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];
OK, the caller presumably holds the update-side lock.
> rcu_assign_pointer(p->ary[n], ptr); > > return old_p; > } > EXPORT_SYMBOL(idr_replace); > > static void idr_cache_ctor(struct kmem_cache *idr_layer_cache, void *idr_layer) > { > memset(idr_layer, 0, sizeof(struct idr_layer)); > } > > void __init idr_init_cache(void) > { > idr_layer_cache = kmem_cache_create("idr_layer_cache", > sizeof(struct idr_layer), 0, SLAB_PANIC, > idr_cache_ctor); > } > > /** > * 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); > > > /* > * 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 > * @staring_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 0 ... 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];
OK, the caller presumably holds the update-side lock.
> 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];
OK, the caller presumably holds the update-side lock.
> shift -= IDR_BITS; > } > > if (p == NULL) > goto err; > > n = idr_id & IDR_MASK; > __clear_bit(n, &p->bitmap); > > bitmap = (void *)p->ary[n];
OK, the caller presumably holds the update-side lock.
> 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_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);
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