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SubjectRe: [PATCH V4 1/3] MCE: fix an error of mce_bad_pages statistics
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On Wed, Dec 12, 2012 at 11:35:25AM +0800, Xishi Qiu wrote:
> Move poisoned page check at the beginning of the function in order to
> fix the error.

Thanks for the fix.
It works fine both on normal pages and hugepages in my testing.

Tested-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>

Just nitpick below ...

> Signed-off-by: Xishi Qiu <qiuxishi@huawei.com>
> Signed-off-by: Jiang Liu <jiang.liu@huawei.com>
> ---
> mm/memory-failure.c | 38 +++++++++++++++++---------------------
> 1 files changed, 17 insertions(+), 21 deletions(-)
>
> diff --git a/mm/memory-failure.c b/mm/memory-failure.c
> index 8b20278..3a8b4b2 100644
> --- a/mm/memory-failure.c
> +++ b/mm/memory-failure.c
> @@ -1419,18 +1419,17 @@ static int soft_offline_huge_page(struct page *page, int flags)
> unsigned long pfn = page_to_pfn(page);
> struct page *hpage = compound_head(page);
>
> + if (PageHWPoison(hpage)) {
> + pr_info("soft offline: %#lx hugepage already poisoned\n", pfn);
> + return -EBUSY;
> + }
> +
> ret = get_any_page(page, pfn, flags);
> if (ret < 0)
> return ret;
> if (ret == 0)
> goto done;
>
> - if (PageHWPoison(hpage)) {
> - put_page(hpage);
> - pr_info("soft offline: %#lx hugepage already poisoned\n", pfn);
> - return -EBUSY;
> - }
> -
> /* Keep page count to indicate a given hugepage is isolated. */
> ret = migrate_huge_page(hpage, new_page, MPOL_MF_MOVE_ALL, false,
> MIGRATE_SYNC);
> @@ -1441,12 +1440,11 @@ static int soft_offline_huge_page(struct page *page, int flags)
> return ret;
> }
> done:
> - if (!PageHWPoison(hpage))
> - atomic_long_add(1 << compound_trans_order(hpage),
> - &mce_bad_pages);
> + /* keep elevated page count for bad page */
> + atomic_long_add(1 << compound_trans_order(hpage), &mce_bad_pages);
> set_page_hwpoison_huge_page(hpage);
> dequeue_hwpoisoned_huge_page(hpage);
> - /* keep elevated page count for bad page */
> +

I think this comment refers to "returning without decrementing page refcount",
and it's not about mce_bad_pages, so keeping the comment as it is seems good
for me.

> return ret;
> }
>
> @@ -1488,6 +1486,11 @@ int soft_offline_page(struct page *page, int flags)
> }
> }
>
> + if (PageHWPoison(page)) {
> + pr_info("soft offline: %#lx page already poisoned\n", pfn);
> + return -EBUSY;
> + }
> +
> ret = get_any_page(page, pfn, flags);
> if (ret < 0)
> return ret;
> @@ -1519,19 +1522,11 @@ int soft_offline_page(struct page *page, int flags)
> return -EIO;
> }
>
> - lock_page(page);
> - wait_on_page_writeback(page);
> -
> /*
> * Synchronized using the page lock with memory_failure()
> */
> - if (PageHWPoison(page)) {
> - unlock_page(page);
> - put_page(page);
> - pr_info("soft offline: %#lx page already poisoned\n", pfn);
> - return -EBUSY;
> - }
> -
> + lock_page(page);
> + wait_on_page_writeback(page);
> /*
> * Try to invalidate first. This should work for
> * non dirty unmapped page cache pages.
> @@ -1582,8 +1577,9 @@ int soft_offline_page(struct page *page, int flags)
> return ret;
>
> done:
> + /* keep elevated page count for bad page */
> atomic_long_add(1, &mce_bad_pages);
> SetPageHWPoison(page);
> - /* keep elevated page count for bad page */
> +
> return ret;
> }

Ditto here.

Thanks,
Naoya


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