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percpu: make pcpu_alloc_area() capable of allocating only from populated areas

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Update pcpu_alloc_area() so that it can skip unpopulated areas if the
new parameter @pop_only is true.  This is implemented by a new
function, pcpu_fit_in_area(), which determines the amount of head
padding considering the alignment and populated state.

@pop_only is currently always false but this will be used to implement
atomic allocation.

Signed-off-by: Tejun Heo <tj@kernel.org>
This commit is contained in:
Tejun Heo 2014-09-02 14:46:02 -04:00
parent b38d08f318
commit a16037c8df
1 changed files with 58 additions and 7 deletions
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65
mm/percpu.c
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@ -399,11 +399,61 @@ out_unlock:
return 0;
}
/**
* pcpu_fit_in_area - try to fit the requested allocation in a candidate area
* @chunk: chunk the candidate area belongs to
* @off: the offset to the start of the candidate area
* @this_size: the size of the candidate area
* @size: the size of the target allocation
* @align: the alignment of the target allocation
* @pop_only: only allocate from already populated region
*
* We're trying to allocate @size bytes aligned at @align. @chunk's area
* at @off sized @this_size is a candidate. This function determines
* whether the target allocation fits in the candidate area and returns the
* number of bytes to pad after @off. If the target area doesn't fit, -1
* is returned.
*
* If @pop_only is %true, this function only considers the already
* populated part of the candidate area.
*/
static int pcpu_fit_in_area(struct pcpu_chunk *chunk, int off, int this_size,
int size, int align, bool pop_only)
{
int cand_off = off;
while (true) {
int head = ALIGN(cand_off, align) - off;
int page_start, page_end, rs, re;
if (this_size < head + size)
return -1;
if (!pop_only)
return head;
/*
* If the first unpopulated page is beyond the end of the
* allocation, the whole allocation is populated;
* otherwise, retry from the end of the unpopulated area.
*/
page_start = PFN_DOWN(head + off);
page_end = PFN_UP(head + off + size);
rs = page_start;
pcpu_next_unpop(chunk, &rs, &re, PFN_UP(off + this_size));
if (rs >= page_end)
return head;
cand_off = re * PAGE_SIZE;
}
}
/**
* pcpu_alloc_area - allocate area from a pcpu_chunk
* @chunk: chunk of interest
* @size: wanted size in bytes
* @align: wanted align
* @pop_only: allocate only from the populated area
*
* Try to allocate @size bytes area aligned at @align from @chunk.
* Note that this function only allocates the offset. It doesn't
@ -418,7 +468,8 @@ out_unlock:
* Allocated offset in @chunk on success, -1 if no matching area is
* found.
*/
static int pcpu_alloc_area(struct pcpu_chunk *chunk, int size, int align)
static int pcpu_alloc_area(struct pcpu_chunk *chunk, int size, int align,
bool pop_only)
{
int oslot = pcpu_chunk_slot(chunk);
int max_contig = 0;
@ -434,11 +485,11 @@ static int pcpu_alloc_area(struct pcpu_chunk *chunk, int size, int align)
if (off & 1)
continue;
/* extra for alignment requirement */
head = ALIGN(off, align) - off;
this_size = (p[1] & ~1) - off;
if (this_size < head + size) {
head = pcpu_fit_in_area(chunk, off, this_size, size, align,
pop_only);
if (head < 0) {
if (!seen_free) {
chunk->first_free = i;
seen_free = true;
@ -730,7 +781,7 @@ static void __percpu *pcpu_alloc(size_t size, size_t align, bool reserved)
spin_lock_irqsave(&pcpu_lock, flags);
}
off = pcpu_alloc_area(chunk, size, align);
off = pcpu_alloc_area(chunk, size, align, false);
if (off >= 0)
goto area_found;
@ -761,7 +812,7 @@ restart:
goto restart;
}
off = pcpu_alloc_area(chunk, size, align);
off = pcpu_alloc_area(chunk, size, align, false);
if (off >= 0)
goto area_found;
}