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SubjectRe: [patch] Re: Linux 2.4.5-ac6
On Tue, Jun 05, 2001 at 05:11:01PM +0200, Maciej W. Rozycki wrote:
> Iterating over memory areas twice is ugly.

Hmm, yes. However, your patch isn't pretty, too. You may check
the same area twice, and won't satisfy requested address > TASK_UNMAPPED_BASE.
What do you think about following? Everything is scanned only once, and
returned address matches specified one as close as possible.

Ivan.

--- linux/mm/mmap.c.orig Mon Jun 4 14:19:02 2001
+++ linux/mm/mmap.c Tue Jun 5 21:05:23 2001
@@ -398,22 +398,30 @@ free_vma:
static inline unsigned long arch_get_unmapped_area(struct file *filp, unsigned long addr, unsigned long len, unsigned long pgoff, unsigned long flags)
{
struct vm_area_struct *vma;
+ unsigned long addr_limit = TASK_SIZE - len;

if (len > TASK_SIZE)
return -ENOMEM;

if (addr) {
addr = PAGE_ALIGN(addr);
- vma = find_vma(current->mm, addr);
- if (TASK_SIZE - len >= addr &&
- (!vma || addr + len <= vma->vm_start))
- return addr;
+ if (addr <= TASK_UNMAPPED_BASE)
+ goto scan_low;
+ addr_limit = addr;
+ for (vma = find_vma(current->mm, addr); ; vma = vma->vm_next) {
+ if (TASK_SIZE - len < addr)
+ break;
+ if (!vma || addr + len <= vma->vm_start)
+ return addr;
+ addr = vma->vm_end;
+ }
}
addr = PAGE_ALIGN(TASK_UNMAPPED_BASE);

+scan_low:
for (vma = find_vma(current->mm, addr); ; vma = vma->vm_next) {
/* At this point: (!vma || addr < vma->vm_end). */
- if (TASK_SIZE - len < addr)
+ if (addr_limit < addr)
return -ENOMEM;
if (!vma || addr + len <= vma->vm_start)
return addr;
-
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