This patch changes dma-mapping subsystem to use generic vmalloc areas for all consistent dma allocations. This increases the total size limit of the consistent allocations and removes platform hacks and a lot of duplicated code.
Atomic allocations are served from special pool preallocated on boot, becasue vmalloc areas cannot be reliably created in atomic context.
Signed-off-by: Marek Szyprowski m.szyprowski@samsung.com Reviewed-by: Kyungmin Park kyungmin.park@samsung.com --- Documentation/kernel-parameters.txt | 2 +- arch/arm/include/asm/dma-mapping.h | 2 +- arch/arm/mm/dma-mapping.c | 503 ++++++++++++----------------------- include/linux/vmalloc.h | 1 + mm/vmalloc.c | 10 +- 5 files changed, 189 insertions(+), 329 deletions(-)
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt index a92c5eb..da07f6c 100644 --- a/Documentation/kernel-parameters.txt +++ b/Documentation/kernel-parameters.txt @@ -526,7 +526,7 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
coherent_pool=nn[KMG] [ARM,KNL] Sets the size of memory pool for coherent, atomic dma - allocations if Contiguous Memory Allocator (CMA) is used. + allocations.
code_bytes [X86] How many bytes of object code to print in an oops report. diff --git a/arch/arm/include/asm/dma-mapping.h b/arch/arm/include/asm/dma-mapping.h index bbef15d..80777d87 100644 --- a/arch/arm/include/asm/dma-mapping.h +++ b/arch/arm/include/asm/dma-mapping.h @@ -226,7 +226,7 @@ static inline int dma_mmap_writecombine(struct device *dev, struct vm_area_struc * DMA region above it's default value of 2MB. It must be called before the * memory allocator is initialised, i.e. before any core_initcall. */ -extern void __init init_consistent_dma_size(unsigned long size); +static inline void init_consistent_dma_size(unsigned long size) { }
/* * For SA-1111, IXP425, and ADI systems the dma-mapping functions are "magic" diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c index 106c4c0..b3ffcf9 100644 --- a/arch/arm/mm/dma-mapping.c +++ b/arch/arm/mm/dma-mapping.c @@ -22,6 +22,7 @@ #include <linux/memblock.h> #include <linux/slab.h> #include <linux/iommu.h> +#include <linux/io.h> #include <linux/vmalloc.h>
#include <asm/memory.h> @@ -217,115 +218,66 @@ static void __dma_free_buffer(struct page *page, size_t size) }
#ifdef CONFIG_MMU - -#define CONSISTENT_OFFSET(x) (((unsigned long)(x) - consistent_base) >> PAGE_SHIFT) -#define CONSISTENT_PTE_INDEX(x) (((unsigned long)(x) - consistent_base) >> PMD_SHIFT) - -/* - * These are the page tables (2MB each) covering uncached, DMA consistent allocations - */ -static pte_t **consistent_pte; - -#define DEFAULT_CONSISTENT_DMA_SIZE SZ_2M - -unsigned long consistent_base = CONSISTENT_END - DEFAULT_CONSISTENT_DMA_SIZE; - -void __init init_consistent_dma_size(unsigned long size) -{ - unsigned long base = CONSISTENT_END - ALIGN(size, SZ_2M); - - BUG_ON(consistent_pte); /* Check we're called before DMA region init */ - BUG_ON(base < VMALLOC_END); - - /* Grow region to accommodate specified size */ - if (base < consistent_base) - consistent_base = base; -} - -#include "vmregion.h" - -static struct arm_vmregion_head consistent_head = { - .vm_lock = __SPIN_LOCK_UNLOCKED(&consistent_head.vm_lock), - .vm_list = LIST_HEAD_INIT(consistent_head.vm_list), - .vm_end = CONSISTENT_END, -}; - #ifdef CONFIG_HUGETLB_PAGE #error ARM Coherent DMA allocator does not (yet) support huge TLB #endif
-/* - * Initialise the consistent memory allocation. - */ -static int __init consistent_init(void) -{ - int ret = 0; - pgd_t *pgd; - pud_t *pud; - pmd_t *pmd; - pte_t *pte; - int i = 0; - unsigned long base = consistent_base; - unsigned long num_ptes = (CONSISTENT_END - base) >> PMD_SHIFT; - - if (IS_ENABLED(CONFIG_CMA) && !IS_ENABLED(CONFIG_ARM_DMA_USE_IOMMU)) - return 0; - - consistent_pte = kmalloc(num_ptes * sizeof(pte_t), GFP_KERNEL); - if (!consistent_pte) { - pr_err("%s: no memory\n", __func__); - return -ENOMEM; - } - - pr_debug("DMA memory: 0x%08lx - 0x%08lx:\n", base, CONSISTENT_END); - consistent_head.vm_start = base; - - do { - pgd = pgd_offset(&init_mm, base); - - pud = pud_alloc(&init_mm, pgd, base); - if (!pud) { - pr_err("%s: no pud tables\n", __func__); - ret = -ENOMEM; - break; - } - - pmd = pmd_alloc(&init_mm, pud, base); - if (!pmd) { - pr_err("%s: no pmd tables\n", __func__); - ret = -ENOMEM; - break; - } - WARN_ON(!pmd_none(*pmd)); - - pte = pte_alloc_kernel(pmd, base); - if (!pte) { - pr_err("%s: no pte tables\n", __func__); - ret = -ENOMEM; - break; - } - - consistent_pte[i++] = pte; - base += PMD_SIZE; - } while (base < CONSISTENT_END); - - return ret; -} -core_initcall(consistent_init); - static void *__alloc_from_contiguous(struct device *dev, size_t size, pgprot_t prot, struct page **ret_page);
-static struct arm_vmregion_head coherent_head = { - .vm_lock = __SPIN_LOCK_UNLOCKED(&coherent_head.vm_lock), - .vm_list = LIST_HEAD_INIT(coherent_head.vm_list), +static void *__alloc_remap_buffer(struct device *dev, size_t size, gfp_t gfp, + pgprot_t prot, struct page **ret_page, + const void *caller); + +static void * +__dma_alloc_remap(struct page *page, size_t size, gfp_t gfp, pgprot_t prot, + const void *caller) +{ + struct vm_struct *area; + unsigned long addr; + + area = get_vm_area_caller(size, VM_DMA | VM_USERMAP, caller); + if (!area) + return NULL; + addr = (unsigned long)area->addr; + area->phys_addr = __pfn_to_phys(page_to_pfn(page)); + + if (ioremap_page_range(addr, addr + size, area->phys_addr, prot)) { + vunmap((void *)addr); + return NULL; + } + return (void *)addr; +} + +static void __dma_free_remap(void *cpu_addr, size_t size) +{ + struct vm_struct *area = find_vm_area(cpu_addr); + if (!area || !(area->flags & VM_DMA)) { + pr_err("%s: trying to free invalid coherent area: %p\n", + __func__, cpu_addr); + dump_stack(); + return; + } + unmap_kernel_range((unsigned long)cpu_addr, size); + vunmap(cpu_addr); +} + +struct dma_pool { + size_t size; + spinlock_t lock; + unsigned long *bitmap; + unsigned long nr_pages; + void *vaddr; + struct page *page; };
-size_t coherent_pool_size = DEFAULT_CONSISTENT_DMA_SIZE / 8; +static struct dma_pool atomic_pool = { + .size = SZ_256K, +};
static int __init early_coherent_pool(char *p) { - coherent_pool_size = memparse(p, &p); + atomic_pool.size = memparse(p, &p); return 0; } early_param("coherent_pool", early_coherent_pool); @@ -333,32 +285,45 @@ early_param("coherent_pool", early_coherent_pool); /* * Initialise the coherent pool for atomic allocations. */ -static int __init coherent_init(void) +static int __init atomic_pool_init(void) { + struct dma_pool *pool = &atomic_pool; pgprot_t prot = pgprot_dmacoherent(pgprot_kernel); - size_t size = coherent_pool_size; + unsigned long nr_pages = pool->size >> PAGE_SHIFT; + unsigned long *bitmap; struct page *page; void *ptr; + int bitmap_size = BITS_TO_LONGS(nr_pages) * sizeof(long);
- if (!IS_ENABLED(CONFIG_CMA)) - return 0; + bitmap = kzalloc(bitmap_size, GFP_KERNEL); + if (!bitmap) + goto no_bitmap;
- ptr = __alloc_from_contiguous(NULL, size, prot, &page); + if (IS_ENABLED(CONFIG_CMA)) + ptr = __alloc_from_contiguous(NULL, pool->size, prot, &page); + else + ptr = __alloc_remap_buffer(NULL, pool->size, GFP_KERNEL, prot, + &page, NULL); if (ptr) { - coherent_head.vm_start = (unsigned long) ptr; - coherent_head.vm_end = (unsigned long) ptr + size; - printk(KERN_INFO "DMA: preallocated %u KiB pool for atomic coherent allocations\n", - (unsigned)size / 1024); + spin_lock_init(&pool->lock); + pool->vaddr = ptr; + pool->page = page; + pool->bitmap = bitmap; + pool->nr_pages = nr_pages; + pr_info("DMA: preallocated %u KiB pool for atomic coherent allocations\n", + (unsigned)pool->size / 1024); return 0; } - printk(KERN_ERR "DMA: failed to allocate %u KiB pool for atomic coherent allocation\n", - (unsigned)size / 1024); + kfree(bitmap); +no_bitmap: + pr_err("DMA: failed to allocate %u KiB pool for atomic coherent allocation\n", + (unsigned)pool->size / 1024); return -ENOMEM; } /* * CMA is activated by core_initcall, so we must be called after it. */ -postcore_initcall(coherent_init); +postcore_initcall(atomic_pool_init);
struct dma_contig_early_reserve { phys_addr_t base; @@ -406,112 +371,6 @@ void __init dma_contiguous_remap(void) } }
-static void * -__dma_alloc_remap(struct page *page, size_t size, gfp_t gfp, pgprot_t prot, - const void *caller) -{ - struct arm_vmregion *c; - size_t align; - int bit; - - if (!consistent_pte) { - pr_err("%s: not initialised\n", __func__); - dump_stack(); - return NULL; - } - - /* - * Align the virtual region allocation - maximum alignment is - * a section size, minimum is a page size. This helps reduce - * fragmentation of the DMA space, and also prevents allocations - * smaller than a section from crossing a section boundary. - */ - bit = fls(size - 1); - if (bit > SECTION_SHIFT) - bit = SECTION_SHIFT; - align = 1 << bit; - - /* - * Allocate a virtual address in the consistent mapping region. - */ - c = arm_vmregion_alloc(&consistent_head, align, size, - gfp & ~(__GFP_DMA | __GFP_HIGHMEM), caller); - if (c) { - pte_t *pte; - int idx = CONSISTENT_PTE_INDEX(c->vm_start); - u32 off = CONSISTENT_OFFSET(c->vm_start) & (PTRS_PER_PTE-1); - - pte = consistent_pte[idx] + off; - c->priv = page; - - do { - BUG_ON(!pte_none(*pte)); - - set_pte_ext(pte, mk_pte(page, prot), 0); - page++; - pte++; - off++; - if (off >= PTRS_PER_PTE) { - off = 0; - pte = consistent_pte[++idx]; - } - } while (size -= PAGE_SIZE); - - dsb(); - - return (void *)c->vm_start; - } - return NULL; -} - -static void __dma_free_remap(void *cpu_addr, size_t size) -{ - struct arm_vmregion *c; - unsigned long addr; - pte_t *ptep; - int idx; - u32 off; - - c = arm_vmregion_find_remove(&consistent_head, (unsigned long)cpu_addr); - if (!c) { - pr_err("%s: trying to free invalid coherent area: %p\n", - __func__, cpu_addr); - dump_stack(); - return; - } - - if ((c->vm_end - c->vm_start) != size) { - pr_err("%s: freeing wrong coherent size (%ld != %d)\n", - __func__, c->vm_end - c->vm_start, size); - dump_stack(); - size = c->vm_end - c->vm_start; - } - - idx = CONSISTENT_PTE_INDEX(c->vm_start); - off = CONSISTENT_OFFSET(c->vm_start) & (PTRS_PER_PTE-1); - ptep = consistent_pte[idx] + off; - addr = c->vm_start; - do { - pte_t pte = ptep_get_and_clear(&init_mm, addr, ptep); - - ptep++; - addr += PAGE_SIZE; - off++; - if (off >= PTRS_PER_PTE) { - off = 0; - ptep = consistent_pte[++idx]; - } - - if (pte_none(pte) || !pte_present(pte)) - pr_crit("%s: bad page in kernel page table\n", - __func__); - } while (size -= PAGE_SIZE); - - flush_tlb_kernel_range(c->vm_start, c->vm_end); - - arm_vmregion_free(&consistent_head, c); -} - static int __dma_update_pte(pte_t *pte, pgtable_t token, unsigned long addr, void *data) { @@ -552,15 +411,17 @@ static void *__alloc_remap_buffer(struct device *dev, size_t size, gfp_t gfp, return ptr; }
-static void *__alloc_from_pool(struct device *dev, size_t size, - struct page **ret_page, const void *caller) +static void *__alloc_from_pool(size_t size, struct page **ret_page) { - struct arm_vmregion *c; + struct dma_pool *pool = &atomic_pool; + unsigned int count = size >> PAGE_SHIFT; + unsigned int pageno; + unsigned long flags; + void *ptr = NULL; size_t align;
- if (!coherent_head.vm_start) { - printk(KERN_ERR "%s: coherent pool not initialised!\n", - __func__); + if (!pool->vaddr) { + pr_err("%s: coherent pool not initialised!\n", __func__); dump_stack(); return NULL; } @@ -571,35 +432,42 @@ static void *__alloc_from_pool(struct device *dev, size_t size, * size. This helps reduce fragmentation of the DMA space. */ align = PAGE_SIZE << get_order(size); - c = arm_vmregion_alloc(&coherent_head, align, size, 0, caller); - if (c) { - void *ptr = (void *)c->vm_start; - struct page *page = virt_to_page(ptr); - *ret_page = page; - return ptr; + + spin_lock_irqsave(&pool->lock, flags); + pageno = bitmap_find_next_zero_area(pool->bitmap, pool->nr_pages, + 0, count, (1 << align) - 1); + if (pageno < pool->nr_pages) { + bitmap_set(pool->bitmap, pageno, count); + ptr = pool->vaddr + PAGE_SIZE * pageno; + *ret_page = pool->page + pageno; } - return NULL; + spin_unlock_irqrestore(&pool->lock, flags); + + return ptr; }
-static int __free_from_pool(void *cpu_addr, size_t size) +static int __free_from_pool(void *start, size_t size) { - unsigned long start = (unsigned long)cpu_addr; - unsigned long end = start + size; - struct arm_vmregion *c; + struct dma_pool *pool = &atomic_pool; + unsigned long pageno, count; + unsigned long flags;
- if (start < coherent_head.vm_start || end > coherent_head.vm_end) + if (start < pool->vaddr || start > pool->vaddr + pool->size) return 0;
- c = arm_vmregion_find_remove(&coherent_head, (unsigned long)start); - - if ((c->vm_end - c->vm_start) != size) { - printk(KERN_ERR "%s: freeing wrong coherent size (%ld != %d)\n", - __func__, c->vm_end - c->vm_start, size); + if (start + size > pool->vaddr + pool->size) { + pr_err("%s: freeing wrong coherent size from pool\n", __func__); dump_stack(); - size = c->vm_end - c->vm_start; + return 0; }
- arm_vmregion_free(&coherent_head, c); + pageno = (start - pool->vaddr) >> PAGE_SHIFT; + count = size >> PAGE_SHIFT; + + spin_lock_irqsave(&pool->lock, flags); + bitmap_clear(pool->bitmap, pageno, count); + spin_unlock_irqrestore(&pool->lock, flags); + return 1; }
@@ -702,10 +570,10 @@ static void *__dma_alloc(struct device *dev, size_t size, dma_addr_t *handle,
if (arch_is_coherent() || nommu()) addr = __alloc_simple_buffer(dev, size, gfp, &page); + else if (gfp & GFP_ATOMIC) + addr = __alloc_from_pool(size, &page); else if (!IS_ENABLED(CONFIG_CMA)) addr = __alloc_remap_buffer(dev, size, gfp, prot, &page, caller); - else if (gfp & GFP_ATOMIC) - addr = __alloc_from_pool(dev, size, &page, caller); else addr = __alloc_from_contiguous(dev, size, prot, &page);
@@ -741,16 +609,22 @@ int arm_dma_mmap(struct device *dev, struct vm_area_struct *vma, { int ret = -ENXIO; #ifdef CONFIG_MMU + unsigned long user_count = (vma->vm_end - vma->vm_start) >> PAGE_SHIFT; + unsigned long count = PAGE_ALIGN(size) >> PAGE_SHIFT; unsigned long pfn = dma_to_pfn(dev, dma_addr); + unsigned long off = vma->vm_pgoff; + vma->vm_page_prot = __get_dma_pgprot(attrs, vma->vm_page_prot);
if (dma_mmap_from_coherent(dev, vma, cpu_addr, size, &ret)) return ret;
- ret = remap_pfn_range(vma, vma->vm_start, - pfn + vma->vm_pgoff, - vma->vm_end - vma->vm_start, - vma->vm_page_prot); + if (off < count && user_count <= (count - off)) { + ret = remap_pfn_range(vma, vma->vm_start, + pfn + off, + user_count << PAGE_SHIFT, + vma->vm_page_prot); + } #endif /* CONFIG_MMU */
return ret; @@ -998,9 +872,6 @@ static int arm_dma_set_mask(struct device *dev, u64 dma_mask)
static int __init dma_debug_do_init(void) { -#ifdef CONFIG_MMU - arm_vmregion_create_proc("dma-mappings", &consistent_head); -#endif dma_debug_init(PREALLOC_DMA_DEBUG_ENTRIES); return 0; } @@ -1117,61 +988,31 @@ static int __iommu_free_buffer(struct device *dev, struct page **pages, size_t s * Create a CPU mapping for a specified pages */ static void * -__iommu_alloc_remap(struct page **pages, size_t size, gfp_t gfp, pgprot_t prot) +__iommu_alloc_remap(struct page **pages, size_t size, gfp_t gfp, pgprot_t prot, + const void *caller) { - struct arm_vmregion *c; - size_t align; - size_t count = size >> PAGE_SHIFT; - int bit; + unsigned int i, nr_pages = PAGE_ALIGN(size) >> PAGE_SHIFT; + struct vm_struct *area; + unsigned long p;
- if (!consistent_pte[0]) { - pr_err("%s: not initialised\n", __func__); - dump_stack(); + area = get_vm_area_caller(size, VM_DMA | VM_USERMAP, caller); + if (!area) return NULL; - } - - /* - * Align the virtual region allocation - maximum alignment is - * a section size, minimum is a page size. This helps reduce - * fragmentation of the DMA space, and also prevents allocations - * smaller than a section from crossing a section boundary. - */ - bit = fls(size - 1); - if (bit > SECTION_SHIFT) - bit = SECTION_SHIFT; - align = 1 << bit; - - /* - * Allocate a virtual address in the consistent mapping region. - */ - c = arm_vmregion_alloc(&consistent_head, align, size, - gfp & ~(__GFP_DMA | __GFP_HIGHMEM), NULL); - if (c) { - pte_t *pte; - int idx = CONSISTENT_PTE_INDEX(c->vm_start); - int i = 0; - u32 off = CONSISTENT_OFFSET(c->vm_start) & (PTRS_PER_PTE-1); - - pte = consistent_pte[idx] + off; - c->priv = pages; - - do { - BUG_ON(!pte_none(*pte)); - - set_pte_ext(pte, mk_pte(pages[i], prot), 0); - pte++; - off++; - i++; - if (off >= PTRS_PER_PTE) { - off = 0; - pte = consistent_pte[++idx]; - } - } while (i < count);
- dsb(); + area->pages = pages; + area->nr_pages = nr_pages; + p = (unsigned long)area->addr;
- return (void *)c->vm_start; + for (i = 0; i < nr_pages; i++) { + phys_addr_t phys = __pfn_to_phys(page_to_pfn(pages[i])); + if (ioremap_page_range(p, p + PAGE_SIZE, phys, prot)) + goto err; + p += PAGE_SIZE; } + return area->addr; +err: + unmap_kernel_range((unsigned long)area->addr, size); + vunmap(area->addr); return NULL; }
@@ -1230,6 +1071,16 @@ static int __iommu_remove_mapping(struct device *dev, dma_addr_t iova, size_t si return 0; }
+static struct page **__iommu_get_pages(void *cpu_addr) +{ + struct vm_struct *area; + + area = find_vm_area(cpu_addr); + if (area && (area->flags & VM_DMA)) + return area->pages; + return NULL; +} + static void *arm_iommu_alloc_attrs(struct device *dev, size_t size, dma_addr_t *handle, gfp_t gfp, struct dma_attrs *attrs) { @@ -1248,7 +1099,8 @@ static void *arm_iommu_alloc_attrs(struct device *dev, size_t size, if (*handle == DMA_ERROR_CODE) goto err_buffer;
- addr = __iommu_alloc_remap(pages, size, gfp, prot); + addr = __iommu_alloc_remap(pages, size, gfp, prot, + __builtin_return_address(0)); if (!addr) goto err_mapping;
@@ -1265,31 +1117,25 @@ static int arm_iommu_mmap_attrs(struct device *dev, struct vm_area_struct *vma, void *cpu_addr, dma_addr_t dma_addr, size_t size, struct dma_attrs *attrs) { - struct arm_vmregion *c; + unsigned long uaddr = vma->vm_start; + unsigned long usize = vma->vm_end - vma->vm_start; + struct page **pages = __iommu_get_pages(cpu_addr);
vma->vm_page_prot = __get_dma_pgprot(attrs, vma->vm_page_prot); - c = arm_vmregion_find(&consistent_head, (unsigned long)cpu_addr);
- if (c) { - struct page **pages = c->priv; + if (!pages) + return -ENXIO;
- unsigned long uaddr = vma->vm_start; - unsigned long usize = vma->vm_end - vma->vm_start; - int i = 0; + do { + int ret = vm_insert_page(vma, uaddr, *pages++); + if (ret) { + pr_err("Remapping memory failed: %d\n", ret); + return ret; + } + uaddr += PAGE_SIZE; + usize -= PAGE_SIZE; + } while (usize > 0);
- do { - int ret; - - ret = vm_insert_page(vma, uaddr, pages[i++]); - if (ret) { - pr_err("Remapping memory, error: %d\n", ret); - return ret; - } - - uaddr += PAGE_SIZE; - usize -= PAGE_SIZE; - } while (usize > 0); - } return 0; }
@@ -1300,16 +1146,21 @@ static int arm_iommu_mmap_attrs(struct device *dev, struct vm_area_struct *vma, void arm_iommu_free_attrs(struct device *dev, size_t size, void *cpu_addr, dma_addr_t handle, struct dma_attrs *attrs) { - struct arm_vmregion *c; + struct page **pages = __iommu_get_pages(cpu_addr); size = PAGE_ALIGN(size);
- c = arm_vmregion_find(&consistent_head, (unsigned long)cpu_addr); - if (c) { - struct page **pages = c->priv; - __dma_free_remap(cpu_addr, size); - __iommu_remove_mapping(dev, handle, size); - __iommu_free_buffer(dev, pages, size); + if (!pages) { + pr_err("%s: trying to free invalid coherent area: %p\n", + __func__, cpu_addr); + dump_stack(); + return; } + + unmap_kernel_range((unsigned long)cpu_addr, size); + vunmap(cpu_addr); + + __iommu_remove_mapping(dev, handle, size); + __iommu_free_buffer(dev, pages, size); }
/* diff --git a/include/linux/vmalloc.h b/include/linux/vmalloc.h index e725b7b..8a9555a 100644 --- a/include/linux/vmalloc.h +++ b/include/linux/vmalloc.h @@ -94,6 +94,7 @@ extern struct vm_struct *__get_vm_area_caller(unsigned long size, unsigned long start, unsigned long end, const void *caller); extern struct vm_struct *remove_vm_area(const void *addr); +extern struct vm_struct *find_vm_area(const void *addr);
extern int map_vm_area(struct vm_struct *area, pgprot_t prot, struct page ***pages); diff --git a/mm/vmalloc.c b/mm/vmalloc.c index e04d59b..4ab106c 100644 --- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -1403,7 +1403,15 @@ struct vm_struct *get_vm_area_caller(unsigned long size, unsigned long flags, -1, GFP_KERNEL, caller); }
-static struct vm_struct *find_vm_area(const void *addr) +/** + * find_vm_area - find a continuous kernel virtual area + * @addr: base address + * + * Search for the kernel VM area starting at @addr, and return it. + * It is up to the caller to do all required locking to keep the returned + * pointer valid. + */ +struct vm_struct *find_vm_area(const void *addr) { struct vmap_area *va;