Re: 2.6.19 file content corruption on ext3

[Peter Zijlstra]

On Mon, 2006-12-18 at 12:14 -0800, Linus Torvalds wrote:

> OR:
> 
>  - page_mkclean_one() is simply buggy.

GOLD!

it seems to work with all this (full diff against current git).

/me rebuilds full kernel to make sure...
reboot...
test...      pff the tension...
yay, still good!

Andrei; would you please verify.

The magic seems to be in the extra tlb flush after clearing the dirty
bit. Just too bad ptep_clear_flush_dirty() needs ptep not entry.

diff --git a/drivers/connector/connector.c b/drivers/connector/connector.c
index 5e7cd45..2b8893b 100644
--- a/drivers/connector/connector.c
+++ b/drivers/connector/connector.c
@@ -135,8 +135,7 @@ static int cn_call_callback(struct cn_msg *msg, void (*destruct_data)(void *), v
 	spin_lock_bh(&dev->cbdev->queue_lock);
 	list_for_each_entry(__cbq, &dev->cbdev->queue_list, callback_entry) {
 		if (cn_cb_equal(&__cbq->id.id, &msg->id)) {
-			if (likely(!test_bit(WORK_STRUCT_PENDING,
-					     &__cbq->work.work.management) &&
+			if (likely(!delayed_work_pending(&__cbq->work) &&
 					__cbq->data.ddata == NULL)) {
 				__cbq->data.callback_priv = msg;
 
diff --git a/fs/buffer.c b/fs/buffer.c
index d1f1b54..263f88e 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -2834,7 +2834,7 @@ int try_to_free_buffers(struct page *page)
 	int ret = 0;
 
 	BUG_ON(!PageLocked(page));
-	if (PageWriteback(page))
+	if (PageDirty(page) || PageWriteback(page))
 		return 0;
 
 	if (mapping == NULL) {		/* can this still happen? */
@@ -2845,22 +2845,6 @@ int try_to_free_buffers(struct page *page)
 	spin_lock(&mapping->private_lock);
 	ret = drop_buffers(page, &buffers_to_free);
 	spin_unlock(&mapping->private_lock);
-	if (ret) {
-		/*
-		 * If the filesystem writes its buffers by hand (eg ext3)
-		 * then we can have clean buffers against a dirty page.  We
-		 * clean the page here; otherwise later reattachment of buffers
-		 * could encounter a non-uptodate page, which is unresolvable.
-		 * This only applies in the rare case where try_to_free_buffers
-		 * succeeds but the page is not freed.
-		 *
-		 * Also, during truncate, discard_buffer will have marked all
-		 * the page's buffers clean.  We discover that here and clean
-		 * the page also.
-		 */
-		if (test_clear_page_dirty(page))
-			task_io_account_cancelled_write(PAGE_CACHE_SIZE);
-	}
 out:
 	if (buffers_to_free) {
 		struct buffer_head *bh = buffers_to_free;
diff --git a/mm/memory.c b/mm/memory.c
index c00bac6..60e0945 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1842,6 +1842,33 @@ void unmap_mapping_range(struct address_space *mapping,
 }
 EXPORT_SYMBOL(unmap_mapping_range);
 
+static void check_last_page(struct address_space *mapping, loff_t size)
+{
+	pgoff_t index;
+	unsigned int offset;
+	struct page *page;
+
+	if (!mapping)
+		return;
+	offset = size & ~PAGE_MASK;
+	if (!offset)
+		return;
+	index = size >> PAGE_SHIFT;
+	page = find_lock_page(mapping, index);
+	if (page) {
+		unsigned int check = 0;
+		unsigned char *kaddr = kmap_atomic(page, KM_USER0);
+		do {
+			check += kaddr[offset++];
+		} while (offset < PAGE_SIZE);
+		kunmap_atomic(kaddr, KM_USER0);
+		unlock_page(page);
+		page_cache_release(page);
+		if (check)
+			printk(KERN_ERR "%s: BADNESS: truncate check %u\n", current->comm, check);
+	}
+}
+
 /**
  * vmtruncate - unmap mappings "freed" by truncate() syscall
  * @inode: inode of the file used
@@ -1875,6 +1902,7 @@ do_expand:
 		goto out_sig;
 	if (offset > inode->i_sb->s_maxbytes)
 		goto out_big;
+	check_last_page(mapping, inode->i_size);
 	i_size_write(inode, offset);
 
 out_truncate:
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 237107c..f561e72 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -957,7 +957,7 @@ int test_set_page_writeback(struct page *page)
 EXPORT_SYMBOL(test_set_page_writeback);
 
 /*
- * Return true if any of the pages in the mapping are marged with the
+ * Return true if any of the pages in the mapping are marked with the
  * passed tag.
  */
 int mapping_tagged(struct address_space *mapping, int tag)
diff --git a/mm/rmap.c b/mm/rmap.c
index d8a842a..900229a 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -432,7 +432,7 @@ static int page_mkclean_one(struct page *page, struct vm_area_struct *vma)
 {
 	struct mm_struct *mm = vma->vm_mm;
 	unsigned long address;
-	pte_t *pte, entry;
+	pte_t *ptep, entry;
 	spinlock_t *ptl;
 	int ret = 0;
 
@@ -440,22 +440,23 @@ static int page_mkclean_one(struct page *page, struct vm_area_struct *vma)
 	if (address == -EFAULT)
 		goto out;
 
-	pte = page_check_address(page, mm, address, &ptl);
-	if (!pte)
+	ptep = page_check_address(page, mm, address, &ptl);
+	if (!ptep)
 		goto out;
 
-	if (!pte_dirty(*pte) && !pte_write(*pte))
+	if (!pte_dirty(*ptep) && !pte_write(*ptep))
 		goto unlock;
 
-	entry = ptep_get_and_clear(mm, address, pte);
-	entry = pte_mkclean(entry);
+	entry = ptep_get_and_clear(mm, address, ptep);
 	entry = pte_wrprotect(entry);
-	ptep_establish(vma, address, pte, entry);
+	ptep_establish(vma, address, ptep, entry);
+	ret = ptep_clear_flush_dirty(vma, address, ptep) ||
+		page_test_and_clear_dirty(page);
 	lazy_mmu_prot_update(entry);
 	ret = 1;
 
 unlock:
-	pte_unmap_unlock(pte, ptl);
+	pte_unmap_unlock(ptep, ptl);
 out:
 	return ret;
 }


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