diff options
Diffstat (limited to 'kernel')
-rw-r--r-- | kernel/resource.c | 151 |
1 files changed, 135 insertions, 16 deletions
diff --git a/kernel/resource.c b/kernel/resource.c index 9c9841cb690..9fad33efd0d 100644 --- a/kernel/resource.c +++ b/kernel/resource.c @@ -40,6 +40,23 @@ EXPORT_SYMBOL(iomem_resource); static DEFINE_RWLOCK(resource_lock); +/* + * By default, we allocate free space bottom-up. The architecture can request + * top-down by clearing this flag. The user can override the architecture's + * choice with the "resource_alloc_from_bottom" kernel boot option, but that + * should only be a debugging tool. + */ +int resource_alloc_from_bottom = 1; + +static __init int setup_alloc_from_bottom(char *s) +{ + printk(KERN_INFO + "resource: allocating from bottom-up; please report a bug\n"); + resource_alloc_from_bottom = 1; + return 0; +} +early_param("resource_alloc_from_bottom", setup_alloc_from_bottom); + static void *r_next(struct seq_file *m, void *v, loff_t *pos) { struct resource *p = v; @@ -357,8 +374,97 @@ int __weak page_is_ram(unsigned long pfn) return walk_system_ram_range(pfn, 1, NULL, __is_ram) == 1; } +static resource_size_t simple_align_resource(void *data, + const struct resource *avail, + resource_size_t size, + resource_size_t align) +{ + return avail->start; +} + +static void resource_clip(struct resource *res, resource_size_t min, + resource_size_t max) +{ + if (res->start < min) + res->start = min; + if (res->end > max) + res->end = max; +} + +static bool resource_contains(struct resource *res1, struct resource *res2) +{ + return res1->start <= res2->start && res1->end >= res2->end; +} + +/* + * Find the resource before "child" in the sibling list of "root" children. + */ +static struct resource *find_sibling_prev(struct resource *root, struct resource *child) +{ + struct resource *this; + + for (this = root->child; this; this = this->sibling) + if (this->sibling == child) + return this; + + return NULL; +} + /* * Find empty slot in the resource tree given range and alignment. + * This version allocates from the end of the root resource first. + */ +static int find_resource_from_top(struct resource *root, struct resource *new, + resource_size_t size, resource_size_t min, + resource_size_t max, resource_size_t align, + resource_size_t (*alignf)(void *, + const struct resource *, + resource_size_t, + resource_size_t), + void *alignf_data) +{ + struct resource *this; + struct resource tmp, avail, alloc; + + tmp.start = root->end; + tmp.end = root->end; + + this = find_sibling_prev(root, NULL); + for (;;) { + if (this) { + if (this->end < root->end) + tmp.start = this->end + 1; + } else + tmp.start = root->start; + + resource_clip(&tmp, min, max); + + /* Check for overflow after ALIGN() */ + avail = *new; + avail.start = ALIGN(tmp.start, align); + avail.end = tmp.end; + if (avail.start >= tmp.start) { + alloc.start = alignf(alignf_data, &avail, size, align); + alloc.end = alloc.start + size - 1; + if (resource_contains(&avail, &alloc)) { + new->start = alloc.start; + new->end = alloc.end; + return 0; + } + } + + if (!this || this->start == root->start) + break; + + tmp.end = this->start - 1; + this = find_sibling_prev(root, this); + } + return -EBUSY; +} + +/* + * Find empty slot in the resource tree given range and alignment. + * This version allocates from the beginning of the root resource first. */ static int find_resource(struct resource *root, struct resource *new, resource_size_t size, resource_size_t min, @@ -370,36 +476,43 @@ static int find_resource(struct resource *root, struct resource *new, void *alignf_data) { struct resource *this = root->child; - struct resource tmp = *new; + struct resource tmp = *new, avail, alloc; tmp.start = root->start; /* - * Skip past an allocated resource that starts at 0, since the assignment - * of this->start - 1 to tmp->end below would cause an underflow. + * Skip past an allocated resource that starts at 0, since the + * assignment of this->start - 1 to tmp->end below would cause an + * underflow. */ if (this && this->start == 0) { tmp.start = this->end + 1; this = this->sibling; } - for(;;) { + for (;;) { if (this) tmp.end = this->start - 1; else tmp.end = root->end; - if (tmp.start < min) - tmp.start = min; - if (tmp.end > max) - tmp.end = max; - tmp.start = ALIGN(tmp.start, align); - if (alignf) - tmp.start = alignf(alignf_data, &tmp, size, align); - if (tmp.start < tmp.end && tmp.end - tmp.start >= size - 1) { - new->start = tmp.start; - new->end = tmp.start + size - 1; - return 0; + + resource_clip(&tmp, min, max); + + /* Check for overflow after ALIGN() */ + avail = *new; + avail.start = ALIGN(tmp.start, align); + avail.end = tmp.end; + if (avail.start >= tmp.start) { + alloc.start = alignf(alignf_data, &avail, size, align); + alloc.end = alloc.start + size - 1; + if (resource_contains(&avail, &alloc)) { + new->start = alloc.start; + new->end = alloc.end; + return 0; + } } + if (!this) break; + tmp.start = this->end + 1; this = this->sibling; } @@ -428,8 +541,14 @@ int allocate_resource(struct resource *root, struct resource *new, { int err; + if (!alignf) + alignf = simple_align_resource; + write_lock(&resource_lock); - err = find_resource(root, new, size, min, max, align, alignf, alignf_data); + if (resource_alloc_from_bottom) + err = find_resource(root, new, size, min, max, align, alignf, alignf_data); + else + err = find_resource_from_top(root, new, size, min, max, align, alignf, alignf_data); if (err >= 0 && __request_resource(root, new)) err = -EBUSY; write_unlock(&resource_lock); |