[PATCH] mm: unmap_vmas with inner ptlock
Remove the page_table_lock from around the calls to unmap_vmas, and replace
the pte_offset_map in zap_pte_range by pte_offset_map_lock: all callers are
now safe to descend without page_table_lock.
Don't attempt fancy locking for hugepages, just take page_table_lock in
unmap_hugepage_range. Which makes zap_hugepage_range, and the hugetlb test in
zap_page_range, redundant: unmap_vmas calls unmap_hugepage_range anyway. Nor
does unmap_vmas have much use for its mm arg now.
The tlb_start_vma and tlb_end_vma in unmap_page_range are now called without
page_table_lock: if they're implemented at all, they typically come down to
flush_cache_range (usually done outside page_table_lock) and flush_tlb_range
(which we already audited for the mprotect case).
Signed-off-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/mm/memory.c b/mm/memory.c
index 4ea89a2..622a4ef 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -551,10 +551,11 @@
{
struct mm_struct *mm = tlb->mm;
pte_t *pte;
+ spinlock_t *ptl;
int file_rss = 0;
int anon_rss = 0;
- pte = pte_offset_map(pmd, addr);
+ pte = pte_offset_map_lock(mm, pmd, addr, &ptl);
do {
pte_t ptent = *pte;
if (pte_none(ptent))
@@ -621,7 +622,7 @@
} while (pte++, addr += PAGE_SIZE, addr != end);
add_mm_rss(mm, file_rss, anon_rss);
- pte_unmap(pte - 1);
+ pte_unmap_unlock(pte - 1, ptl);
}
static inline void zap_pmd_range(struct mmu_gather *tlb,
@@ -690,7 +691,6 @@
/**
* unmap_vmas - unmap a range of memory covered by a list of vma's
* @tlbp: address of the caller's struct mmu_gather
- * @mm: the controlling mm_struct
* @vma: the starting vma
* @start_addr: virtual address at which to start unmapping
* @end_addr: virtual address at which to end unmapping
@@ -699,10 +699,10 @@
*
* Returns the end address of the unmapping (restart addr if interrupted).
*
- * Unmap all pages in the vma list. Called under page_table_lock.
+ * Unmap all pages in the vma list.
*
- * We aim to not hold page_table_lock for too long (for scheduling latency
- * reasons). So zap pages in ZAP_BLOCK_SIZE bytecounts. This means we need to
+ * We aim to not hold locks for too long (for scheduling latency reasons).
+ * So zap pages in ZAP_BLOCK_SIZE bytecounts. This means we need to
* return the ending mmu_gather to the caller.
*
* Only addresses between `start' and `end' will be unmapped.
@@ -714,7 +714,7 @@
* ensure that any thus-far unmapped pages are flushed before unmap_vmas()
* drops the lock and schedules.
*/
-unsigned long unmap_vmas(struct mmu_gather **tlbp, struct mm_struct *mm,
+unsigned long unmap_vmas(struct mmu_gather **tlbp,
struct vm_area_struct *vma, unsigned long start_addr,
unsigned long end_addr, unsigned long *nr_accounted,
struct zap_details *details)
@@ -764,19 +764,15 @@
tlb_finish_mmu(*tlbp, tlb_start, start);
if (need_resched() ||
- need_lockbreak(&mm->page_table_lock) ||
(i_mmap_lock && need_lockbreak(i_mmap_lock))) {
if (i_mmap_lock) {
- /* must reset count of rss freed */
- *tlbp = tlb_gather_mmu(mm, fullmm);
+ *tlbp = NULL;
goto out;
}
- spin_unlock(&mm->page_table_lock);
cond_resched();
- spin_lock(&mm->page_table_lock);
}
- *tlbp = tlb_gather_mmu(mm, fullmm);
+ *tlbp = tlb_gather_mmu(vma->vm_mm, fullmm);
tlb_start_valid = 0;
zap_bytes = ZAP_BLOCK_SIZE;
}
@@ -800,18 +796,12 @@
unsigned long end = address + size;
unsigned long nr_accounted = 0;
- if (is_vm_hugetlb_page(vma)) {
- zap_hugepage_range(vma, address, size);
- return end;
- }
-
lru_add_drain();
tlb = tlb_gather_mmu(mm, 0);
update_hiwater_rss(mm);
- spin_lock(&mm->page_table_lock);
- end = unmap_vmas(&tlb, mm, vma, address, end, &nr_accounted, details);
- spin_unlock(&mm->page_table_lock);
- tlb_finish_mmu(tlb, address, end);
+ end = unmap_vmas(&tlb, vma, address, end, &nr_accounted, details);
+ if (tlb)
+ tlb_finish_mmu(tlb, address, end);
return end;
}
@@ -1434,13 +1424,6 @@
restart_addr = zap_page_range(vma, start_addr,
end_addr - start_addr, details);
-
- /*
- * We cannot rely on the break test in unmap_vmas:
- * on the one hand, we don't want to restart our loop
- * just because that broke out for the page_table_lock;
- * on the other hand, it does no test when vma is small.
- */
need_break = need_resched() ||
need_lockbreak(details->i_mmap_lock);