Change dmapool free block management
Use a list of free blocks within a page instead of using a bitmap. Update documentation to reflect this. As well as being a slight reduction in memory allocation, locked ops and lines of code, it speeds up a transaction processing benchmark by 0.4%. Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
This commit is contained in:
Matthew Wilcox
Родитель
6182a0943a
Коммит
a35a345514
119
mm/dmapool.c
119
mm/dmapool.c
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@ -17,7 +17,9 @@
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* The current design of this allocator is fairly simple. The pool is
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* represented by the 'struct dma_pool' which keeps a doubly-linked list of
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* allocated pages. Each page in the page_list is split into blocks of at
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* least 'size' bytes.
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* least 'size' bytes. Free blocks are tracked in an unsorted singly-linked
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* list of free blocks within the page. Used blocks aren't tracked, but we
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* keep a count of how many are currently allocated from each page.
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*/
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#include <linux/device.h>
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@ -38,7 +40,6 @@
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struct dma_pool { /* the pool */
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struct list_head page_list;
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spinlock_t lock;
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size_t blocks_per_page;
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size_t size;
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struct device *dev;
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size_t allocation;
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@ -51,8 +52,8 @@ struct dma_page { /* cacheable header for 'allocation' bytes */
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struct list_head page_list;
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void *vaddr;
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dma_addr_t dma;
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unsigned in_use;
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unsigned long bitmap[0];
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unsigned int in_use;
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unsigned int offset;
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};
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#define POOL_TIMEOUT_JIFFIES ((100 /* msec */ * HZ) / 1000)
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@ -87,8 +88,8 @@ show_pools(struct device *dev, struct device_attribute *attr, char *buf)
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/* per-pool info, no real statistics yet */
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temp = scnprintf(next, size, "%-16s %4u %4Zu %4Zu %2u\n",
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pool->name,
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blocks, pages * pool->blocks_per_page,
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pool->name, blocks,
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pages * (pool->allocation / pool->size),
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pool->size, pages);
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size -= temp;
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next += temp;
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@ -132,8 +133,11 @@ struct dma_pool *dma_pool_create(const char *name, struct device *dev,
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return NULL;
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}
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if (size == 0)
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if (size == 0) {
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return NULL;
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} else if (size < 4) {
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size = 4;
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}
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if ((size % align) != 0)
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size = ALIGN(size, align);
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@ -160,7 +164,6 @@ struct dma_pool *dma_pool_create(const char *name, struct device *dev,
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spin_lock_init(&retval->lock);
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retval->size = size;
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retval->allocation = allocation;
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retval->blocks_per_page = allocation / size;
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init_waitqueue_head(&retval->waitq);
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if (dev) {
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@ -186,28 +189,36 @@ struct dma_pool *dma_pool_create(const char *name, struct device *dev,
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}
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EXPORT_SYMBOL(dma_pool_create);
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static void pool_initialise_page(struct dma_pool *pool, struct dma_page *page)
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{
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unsigned int offset = 0;
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do {
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unsigned int next = offset + pool->size;
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if (unlikely((next + pool->size) >= pool->allocation))
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next = pool->allocation;
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*(int *)(page->vaddr + offset) = next;
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offset = next;
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} while (offset < pool->allocation);
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}
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static struct dma_page *pool_alloc_page(struct dma_pool *pool, gfp_t mem_flags)
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{
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struct dma_page *page;
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int mapsize;
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mapsize = pool->blocks_per_page;
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mapsize = (mapsize + BITS_PER_LONG - 1) / BITS_PER_LONG;
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mapsize *= sizeof(long);
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page = kmalloc(mapsize + sizeof *page, mem_flags);
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page = kmalloc(sizeof(*page), mem_flags);
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if (!page)
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return NULL;
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page->vaddr = dma_alloc_coherent(pool->dev,
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pool->allocation,
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page->vaddr = dma_alloc_coherent(pool->dev, pool->allocation,
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&page->dma, mem_flags);
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if (page->vaddr) {
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memset(page->bitmap, 0xff, mapsize); /* bit set == free */
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#ifdef CONFIG_DEBUG_SLAB
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memset(page->vaddr, POOL_POISON_FREED, pool->allocation);
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#endif
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pool_initialise_page(pool, page);
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list_add(&page->page_list, &pool->page_list);
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page->in_use = 0;
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page->offset = 0;
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} else {
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kfree(page);
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page = NULL;
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@ -215,14 +226,9 @@ static struct dma_page *pool_alloc_page(struct dma_pool *pool, gfp_t mem_flags)
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return page;
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}
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static inline int is_page_busy(int blocks, unsigned long *bitmap)
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static inline int is_page_busy(struct dma_page *page)
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{
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while (blocks > 0) {
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if (*bitmap++ != ~0UL)
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return 1;
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blocks -= BITS_PER_LONG;
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}
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return 0;
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return page->in_use != 0;
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}
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static void pool_free_page(struct dma_pool *pool, struct dma_page *page)
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@ -257,7 +263,7 @@ void dma_pool_destroy(struct dma_pool *pool)
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struct dma_page *page;
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page = list_entry(pool->page_list.next,
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struct dma_page, page_list);
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if (is_page_busy(pool->blocks_per_page, page->bitmap)) {
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if (is_page_busy(page)) {
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if (pool->dev)
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dev_err(pool->dev,
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"dma_pool_destroy %s, %p busy\n",
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@ -292,27 +298,14 @@ void *dma_pool_alloc(struct dma_pool *pool, gfp_t mem_flags,
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{
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unsigned long flags;
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struct dma_page *page;
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int map, block;
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size_t offset;
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void *retval;
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spin_lock_irqsave(&pool->lock, flags);
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restart:
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list_for_each_entry(page, &pool->page_list, page_list) {
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int i;
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/* only cachable accesses here ... */
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for (map = 0, i = 0;
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i < pool->blocks_per_page; i += BITS_PER_LONG, map++) {
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if (page->bitmap[map] == 0)
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continue;
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block = ffz(~page->bitmap[map]);
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if ((i + block) < pool->blocks_per_page) {
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clear_bit(block, &page->bitmap[map]);
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offset = (BITS_PER_LONG * map) + block;
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offset *= pool->size;
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goto ready;
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}
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}
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if (page->offset < pool->allocation)
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goto ready;
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}
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page = pool_alloc_page(pool, GFP_ATOMIC);
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if (!page) {
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@ -333,10 +326,10 @@ void *dma_pool_alloc(struct dma_pool *pool, gfp_t mem_flags,
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goto done;
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}
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clear_bit(0, &page->bitmap[0]);
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offset = 0;
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ready:
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page->in_use++;
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offset = page->offset;
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page->offset = *(int *)(page->vaddr + offset);
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retval = offset + page->vaddr;
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*handle = offset + page->dma;
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#ifdef CONFIG_DEBUG_SLAB
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@ -379,7 +372,7 @@ void dma_pool_free(struct dma_pool *pool, void *vaddr, dma_addr_t dma)
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{
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struct dma_page *page;
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unsigned long flags;
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int map, block;
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unsigned int offset;
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page = pool_find_page(pool, dma);
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if (!page) {
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@ -393,13 +386,9 @@ void dma_pool_free(struct dma_pool *pool, void *vaddr, dma_addr_t dma)
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return;
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}
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block = dma - page->dma;
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block /= pool->size;
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map = block / BITS_PER_LONG;
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block %= BITS_PER_LONG;
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offset = vaddr - page->vaddr;
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#ifdef CONFIG_DEBUG_SLAB
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if (((dma - page->dma) + (void *)page->vaddr) != vaddr) {
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if ((dma - page->dma) != offset) {
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if (pool->dev)
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dev_err(pool->dev,
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"dma_pool_free %s, %p (bad vaddr)/%Lx\n",
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@ -410,28 +399,36 @@ void dma_pool_free(struct dma_pool *pool, void *vaddr, dma_addr_t dma)
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pool->name, vaddr, (unsigned long long)dma);
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return;
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}
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if (page->bitmap[map] & (1UL << block)) {
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if (pool->dev)
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dev_err(pool->dev,
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"dma_pool_free %s, dma %Lx already free\n",
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pool->name, (unsigned long long)dma);
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else
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printk(KERN_ERR
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"dma_pool_free %s, dma %Lx already free\n",
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pool->name, (unsigned long long)dma);
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return;
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{
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unsigned int chain = page->offset;
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while (chain < pool->allocation) {
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if (chain != offset) {
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chain = *(int *)(page->vaddr + chain);
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continue;
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}
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if (pool->dev)
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dev_err(pool->dev, "dma_pool_free %s, dma %Lx "
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"already free\n", pool->name,
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(unsigned long long)dma);
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else
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printk(KERN_ERR "dma_pool_free %s, dma %Lx "
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"already free\n", pool->name,
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(unsigned long long)dma);
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return;
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}
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}
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memset(vaddr, POOL_POISON_FREED, pool->size);
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#endif
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spin_lock_irqsave(&pool->lock, flags);
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page->in_use--;
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set_bit(block, &page->bitmap[map]);
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*(int *)vaddr = page->offset;
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page->offset = offset;
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if (waitqueue_active(&pool->waitq))
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wake_up_locked(&pool->waitq);
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/*
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* Resist a temptation to do
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* if (!is_page_busy(bpp, page->bitmap)) pool_free_page(pool, page);
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* if (!is_page_busy(page)) pool_free_page(pool, page);
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* Better have a few empty pages hang around.
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*/
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spin_unlock_irqrestore(&pool->lock, flags);
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