Merge branch 'hwpoison-cleanups' into hwpoison

mm/memory-failure.c

@@ -7,21 +7,26 @@
  * Free Software Foundation.
  *
  * High level machine check handler. Handles pages reported by the
- * hardware as being corrupted usually due to a 2bit ECC memory or cache
+ * hardware as being corrupted usually due to a multi-bit ECC memory or cache
  * failure.
+ * 
+ * In addition there is a "soft offline" entry point that allows stop using
+ * not-yet-corrupted-by-suspicious pages without killing anything.
  *
  * Handles page cache pages in various states.	The tricky part
- * here is that we can access any page asynchronous to other VM
- * users, because memory failures could happen anytime and anywhere,
- * possibly violating some of their assumptions. This is why this code
- * has to be extremely careful. Generally it tries to use normal locking
- * rules, as in get the standard locks, even if that means the
- * error handling takes potentially a long time.
- *
- * The operation to map back from RMAP chains to processes has to walk
- * the complete process list and has non linear complexity with the number
- * mappings. In short it can be quite slow. But since memory corruptions
- * are rare we hope to get away with this.
+ * here is that we can access any page asynchronously in respect to 
+ * other VM users, because memory failures could happen anytime and 
+ * anywhere. This could violate some of their assumptions. This is why 
+ * this code has to be extremely careful. Generally it tries to use 
+ * normal locking rules, as in get the standard locks, even if that means 
+ * the error handling takes potentially a long time.
+ * 
+ * There are several operations here with exponential complexity because
+ * of unsuitable VM data structures. For example the operation to map back 
+ * from RMAP chains to processes has to walk the complete process list and 
+ * has non linear complexity with the number. But since memory corruptions
+ * are rare we hope to get away with this. This avoids impacting the core 
+ * VM.
  */
 
 /*
@@ -30,7 +35,6 @@
  * - kcore/oldmem/vmcore/mem/kmem check for hwpoison pages
  * - pass bad pages to kdump next kernel
  */
-#define DEBUG 1		/* remove me in 2.6.34 */
 #include <linux/kernel.h>
 #include <linux/mm.h>
 #include <linux/page-flags.h>
@@ -78,7 +82,7 @@ static int hwpoison_filter_dev(struct page *p)
 		return 0;
 
 	/*
-	 * page_mapping() does not accept slab page
+	 * page_mapping() does not accept slab pages.
 	 */
 	if (PageSlab(p))
 		return -EINVAL;
@@ -268,7 +272,7 @@ struct to_kill {
 	struct list_head nd;
 	struct task_struct *tsk;
 	unsigned long addr;
-	unsigned addr_valid:1;
+	char addr_valid;
 };
 
 /*
@@ -309,7 +313,7 @@ static void add_to_kill(struct task_struct *tsk, struct page *p,
 	 * a SIGKILL because the error is not contained anymore.
 	 */
 	if (tk->addr == -EFAULT) {
-		pr_debug("MCE: Unable to find user space address %lx in %s\n",
+		pr_info("MCE: Unable to find user space address %lx in %s\n",
 			page_to_pfn(p), tsk->comm);
 		tk->addr_valid = 0;
 	}
@@ -577,7 +581,7 @@ static int me_pagecache_clean(struct page *p, unsigned long pfn)
 					pfn, err);
 		} else if (page_has_private(p) &&
 				!try_to_release_page(p, GFP_NOIO)) {
-			pr_debug("MCE %#lx: failed to release buffers\n", pfn);
+			pr_info("MCE %#lx: failed to release buffers\n", pfn);
 		} else {
 			ret = RECOVERED;
 		}
@@ -836,8 +840,6 @@ static int page_action(struct page_state *ps, struct page *p,
 	return (result == RECOVERED || result == DELAYED) ? 0 : -EBUSY;
 }
 
-#define N_UNMAP_TRIES 5
-
 /*
  * Do all that is necessary to remove user space mappings. Unmap
  * the pages and send SIGBUS to the processes if the data was dirty.
@@ -849,7 +851,6 @@ static int hwpoison_user_mappings(struct page *p, unsigned long pfn,
 	struct address_space *mapping;
 	LIST_HEAD(tokill);
 	int ret;
-	int i;
 	int kill = 1;
 	struct page *hpage = compound_head(p);
 
@@ -903,17 +904,7 @@ static int hwpoison_user_mappings(struct page *p, unsigned long pfn,
 	if (kill)
 		collect_procs(hpage, &tokill);
 
-	/*
-	 * try_to_unmap can fail temporarily due to races.
-	 * Try a few times (RED-PEN better strategy?)
-	 */
-	for (i = 0; i < N_UNMAP_TRIES; i++) {
-		ret = try_to_unmap(hpage, ttu);
-		if (ret == SWAP_SUCCESS)
-			break;
-		pr_debug("MCE %#lx: try_to_unmap retry needed %d\n", pfn,  ret);
-	}
-
+	ret = try_to_unmap(hpage, ttu);
 	if (ret != SWAP_SUCCESS)
 		printk(KERN_ERR "MCE %#lx: failed to unmap page (mapcount=%d)\n",
 				pfn, page_mapcount(hpage));
@@ -1147,7 +1138,7 @@ int unpoison_memory(unsigned long pfn)
 	page = compound_head(p);
 
 	if (!PageHWPoison(p)) {
-		pr_debug("MCE: Page was already unpoisoned %#lx\n", pfn);
+		pr_info("MCE: Page was already unpoisoned %#lx\n", pfn);
 		return 0;
 	}
 
@@ -1156,7 +1147,7 @@ int unpoison_memory(unsigned long pfn)
 	if (!get_page_unless_zero(page)) {
 		if (TestClearPageHWPoison(p))
 			atomic_long_sub(nr_pages, &mce_bad_pages);
-		pr_debug("MCE: Software-unpoisoned free page %#lx\n", pfn);
+		pr_info("MCE: Software-unpoisoned free page %#lx\n", pfn);
 		return 0;
 	}
 
@@ -1168,7 +1159,7 @@ int unpoison_memory(unsigned long pfn)
 	 * the free buddy page pool.
 	 */
 	if (TestClearPageHWPoison(page)) {
-		pr_debug("MCE: Software-unpoisoned page %#lx\n", pfn);
+		pr_info("MCE: Software-unpoisoned page %#lx\n", pfn);
 		atomic_long_sub(nr_pages, &mce_bad_pages);
 		freeit = 1;
 	}
@@ -1217,12 +1208,12 @@ static int get_any_page(struct page *p, unsigned long pfn, int flags)
 	set_migratetype_isolate(p);
 	if (!get_page_unless_zero(compound_head(p))) {
 		if (is_free_buddy_page(p)) {
-			pr_debug("get_any_page: %#lx free buddy page\n", pfn);
+			pr_info("get_any_page: %#lx free buddy page\n", pfn);
 			/* Set hwpoison bit while page is still isolated */
 			SetPageHWPoison(p);
 			ret = 0;
 		} else {
-			pr_debug("get_any_page: %#lx: unknown zero refcount page type %lx\n",
+			pr_info("get_any_page: %#lx: unknown zero refcount page type %lx\n",
 				pfn, p->flags);
 			ret = -EIO;
 		}
@@ -1288,7 +1279,7 @@ int soft_offline_page(struct page *page, int flags)
 			goto done;
 	}
 	if (!PageLRU(page)) {
-		pr_debug("soft_offline: %#lx: unknown non LRU page type %lx\n",
+		pr_info("soft_offline: %#lx: unknown non LRU page type %lx\n",
 				pfn, page->flags);
 		return -EIO;
 	}
@@ -1302,7 +1293,7 @@ int soft_offline_page(struct page *page, int flags)
 	if (PageHWPoison(page)) {
 		unlock_page(page);
 		put_page(page);
-		pr_debug("soft offline: %#lx page already poisoned\n", pfn);
+		pr_info("soft offline: %#lx page already poisoned\n", pfn);
 		return -EBUSY;
 	}
 
@@ -1323,7 +1314,7 @@ int soft_offline_page(struct page *page, int flags)
 	put_page(page);
 	if (ret == 1) {
 		ret = 0;
-		pr_debug("soft_offline: %#lx: invalidated\n", pfn);
+		pr_info("soft_offline: %#lx: invalidated\n", pfn);
 		goto done;
 	}
 
@@ -1339,13 +1330,13 @@ int soft_offline_page(struct page *page, int flags)
 		list_add(&page->lru, &pagelist);
 		ret = migrate_pages(&pagelist, new_page, MPOL_MF_MOVE_ALL, 0);
 		if (ret) {
-			pr_debug("soft offline: %#lx: migration failed %d, type %lx\n",
+			pr_info("soft offline: %#lx: migration failed %d, type %lx\n",
 				pfn, ret, page->flags);
 			if (ret > 0)
 				ret = -EIO;
 		}
 	} else {
-		pr_debug("soft offline: %#lx: isolation failed: %d, page count %d, type %lx\n",
+		pr_info("soft offline: %#lx: isolation failed: %d, page count %d, type %lx\n",
 				pfn, ret, page_count(page), page->flags);
 	}
 	if (ret)