[RFC PATCH v2 14/16] mm,hwpoison: Return 0 if the page is already poisoned in soft-offline

[Oscar Salvador <osalvador@suse.de>]

Currently, there is an inconsistency when calling soft-offline from
different paths on a page that is already poisoned.

1) madvise:

        madvise_inject_error skips any poisoned page and continues
        the loop.
        If that was the only page to madvise, it returns 0.

2) /sys/devices/system/memory/:

        Whe calling soft_offline_page_store()->soft_offline_page(),
        we return -EBUSY in case the page is already poisoned.
        This is inconsistent with a) the above example and b)
        memory_failure, where we return 0 if the page was poisoned.

Fix this by dropping the PageHWPoison() check in madvise_inject_error,
and let soft_offline_page return 0 if it finds the page already poisoned.

Please, note that this represents an user-api change, since now the return
error when calling soft_offline_page_store()->soft_offline_page() will be different.

Signed-off-by: Oscar Salvador <osalvador@suse.de>
---
 mm/madvise.c        | 3 ---
 mm/memory-failure.c | 4 ++--
 2 files changed, 2 insertions(+), 5 deletions(-)

diff --git a/mm/madvise.c b/mm/madvise.c
index 8a0b1f901d72..9ca48345ce45 100644
--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -887,9 +887,6 @@ static int madvise_inject_error(int behavior,
 		 */
 		put_page(page);
 
-		if (PageHWPoison(page))
-			continue;
-
 		if (behavior == MADV_SOFT_OFFLINE) {
 			pr_info("Soft offlining pfn %#lx at process virtual address %#lx\n",
 				 pfn, start);
diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index 3d491c0d3f91..c038896bedf0 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -1767,7 +1767,7 @@ static int __soft_offline_page(struct page *page)
 		unlock_page(page);
 		put_page(page);
 		pr_info("soft offline: %#lx page already poisoned\n", pfn);
-		return -EBUSY;
+		return 0;
 	}
 
 	if (!PageHuge(page))
@@ -1866,7 +1866,7 @@ int soft_offline_page(struct page *page)
 
 	if (PageHWPoison(page)) {
 		pr_info("soft offline: %#lx page already poisoned\n", pfn);
-		return -EBUSY;
+		return 0;
 	}
 
 	get_online_mems();
-- 
2.12.3