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authorLinus Torvalds <torvalds@linux-foundation.org>2009-06-20 11:29:32 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2009-06-20 11:29:32 -0700
commit12e24f34cb0d55efd08c18b2112507d4bf498008 (patch)
tree83b07be17b8ef45f42360a3b9159b3aaae3fbad4 /arch/x86/mm
parent1eb51c33b21ffa3fceb634d1d6bcd6488c79bc26 (diff)
parenteadc84cc01e04f9f74ec2de0c9355be035c7b396 (diff)
Merge branch 'perfcounters-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip
* 'perfcounters-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip: (49 commits) perfcounter: Handle some IO return values perf_counter: Push perf_sample_data through the swcounter code perf_counter tools: Define and use our own u64, s64 etc. definitions perf_counter: Close race in perf_lock_task_context() perf_counter, x86: Improve interactions with fast-gup perf_counter: Simplify and fix task migration counting perf_counter tools: Add a data file header perf_counter: Update userspace callchain sampling uses perf_counter: Make callchain samples extensible perf report: Filter to parent set by default perf_counter tools: Handle lost events perf_counter: Add event overlow handling fs: Provide empty .set_page_dirty() aop for anon inodes perf_counter: tools: Makefile tweaks for 64-bit powerpc perf_counter: powerpc: Add processor back-end for MPC7450 family perf_counter: powerpc: Make powerpc perf_counter code safe for 32-bit kernels perf_counter: powerpc: Change how processor-specific back-ends get selected perf_counter: powerpc: Use unsigned long for register and constraint values perf_counter: powerpc: Enable use of software counters on 32-bit powerpc perf_counter tools: Add and use isprint() ...
Diffstat (limited to 'arch/x86/mm')
-rw-r--r--arch/x86/mm/gup.c58
1 files changed, 57 insertions, 1 deletions
diff --git a/arch/x86/mm/gup.c b/arch/x86/mm/gup.c
index f9748094126..71da1bca13c 100644
--- a/arch/x86/mm/gup.c
+++ b/arch/x86/mm/gup.c
@@ -14,7 +14,7 @@
static inline pte_t gup_get_pte(pte_t *ptep)
{
#ifndef CONFIG_X86_PAE
- return *ptep;
+ return ACCESS_ONCE(*ptep);
#else
/*
* With get_user_pages_fast, we walk down the pagetables without taking
@@ -219,6 +219,62 @@ static int gup_pud_range(pgd_t pgd, unsigned long addr, unsigned long end,
return 1;
}
+/*
+ * Like get_user_pages_fast() except its IRQ-safe in that it won't fall
+ * back to the regular GUP.
+ */
+int __get_user_pages_fast(unsigned long start, int nr_pages, int write,
+ struct page **pages)
+{
+ struct mm_struct *mm = current->mm;
+ unsigned long addr, len, end;
+ unsigned long next;
+ unsigned long flags;
+ pgd_t *pgdp;
+ int nr = 0;
+
+ start &= PAGE_MASK;
+ addr = start;
+ len = (unsigned long) nr_pages << PAGE_SHIFT;
+ end = start + len;
+ if (unlikely(!access_ok(write ? VERIFY_WRITE : VERIFY_READ,
+ (void __user *)start, len)))
+ return 0;
+
+ /*
+ * XXX: batch / limit 'nr', to avoid large irq off latency
+ * needs some instrumenting to determine the common sizes used by
+ * important workloads (eg. DB2), and whether limiting the batch size
+ * will decrease performance.
+ *
+ * It seems like we're in the clear for the moment. Direct-IO is
+ * the main guy that batches up lots of get_user_pages, and even
+ * they are limited to 64-at-a-time which is not so many.
+ */
+ /*
+ * This doesn't prevent pagetable teardown, but does prevent
+ * the pagetables and pages from being freed on x86.
+ *
+ * So long as we atomically load page table pointers versus teardown
+ * (which we do on x86, with the above PAE exception), we can follow the
+ * address down to the the page and take a ref on it.
+ */
+ local_irq_save(flags);
+ pgdp = pgd_offset(mm, addr);
+ do {
+ pgd_t pgd = *pgdp;
+
+ next = pgd_addr_end(addr, end);
+ if (pgd_none(pgd))
+ break;
+ if (!gup_pud_range(pgd, addr, next, write, pages, &nr))
+ break;
+ } while (pgdp++, addr = next, addr != end);
+ local_irq_restore(flags);
+
+ return nr;
+}
+
/**
* get_user_pages_fast() - pin user pages in memory
* @start: starting user address