1 files changed, 193 insertions, 61 deletions

diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 2970e35fd03f..dc32dae01e5f 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -69,6 +69,12 @@ static inline long sync_writeback_pages(void)
 int dirty_background_ratio = 5;
 
 /*
+ * dirty_background_bytes starts at 0 (disabled) so that it is a function of
+ * dirty_background_ratio * the amount of dirtyable memory
+ */
+unsigned long dirty_background_bytes;
+
+/*
  * free highmem will not be subtracted from the total free memory
  * for calculating free ratios if vm_highmem_is_dirtyable is true
  */
@@ -80,6 +86,12 @@ int vm_highmem_is_dirtyable;
 int vm_dirty_ratio = 10;
 
 /*
+ * vm_dirty_bytes starts at 0 (disabled) so that it is a function of
+ * vm_dirty_ratio * the amount of dirtyable memory
+ */
+unsigned long vm_dirty_bytes;
+
+/*
  * The interval between `kupdate'-style writebacks, in jiffies
  */
 int dirty_writeback_interval = 5 * HZ;
@@ -135,23 +147,75 @@ static int calc_period_shift(void)
 {
 	unsigned long dirty_total;
 
-	dirty_total = (vm_dirty_ratio * determine_dirtyable_memory()) / 100;
+	if (vm_dirty_bytes)
+		dirty_total = vm_dirty_bytes / PAGE_SIZE;
+	else
+		dirty_total = (vm_dirty_ratio * determine_dirtyable_memory()) /
+				100;
 	return 2 + ilog2(dirty_total - 1);
 }
 
 /*
- * update the period when the dirty ratio changes.
+ * update the period when the dirty threshold changes.
  */
+static void update_completion_period(void)
+{
+	int shift = calc_period_shift();
+	prop_change_shift(&vm_completions, shift);
+	prop_change_shift(&vm_dirties, shift);
+}
+
+int dirty_background_ratio_handler(struct ctl_table *table, int write,
+		struct file *filp, void __user *buffer, size_t *lenp,
+		loff_t *ppos)
+{
+	int ret;
+
+	ret = proc_dointvec_minmax(table, write, filp, buffer, lenp, ppos);
+	if (ret == 0 && write)
+		dirty_background_bytes = 0;
+	return ret;
+}
+
+int dirty_background_bytes_handler(struct ctl_table *table, int write,
+		struct file *filp, void __user *buffer, size_t *lenp,
+		loff_t *ppos)
+{
+	int ret;
+
+	ret = proc_doulongvec_minmax(table, write, filp, buffer, lenp, ppos);
+	if (ret == 0 && write)
+		dirty_background_ratio = 0;
+	return ret;
+}
+
 int dirty_ratio_handler(struct ctl_table *table, int write,
 		struct file *filp, void __user *buffer, size_t *lenp,
 		loff_t *ppos)
 {
 	int old_ratio = vm_dirty_ratio;
-	int ret = proc_dointvec_minmax(table, write, filp, buffer, lenp, ppos);
+	int ret;
+
+	ret = proc_dointvec_minmax(table, write, filp, buffer, lenp, ppos);
 	if (ret == 0 && write && vm_dirty_ratio != old_ratio) {
-		int shift = calc_period_shift();
-		prop_change_shift(&vm_completions, shift);
-		prop_change_shift(&vm_dirties, shift);
+		update_completion_period();
+		vm_dirty_bytes = 0;
+	}
+	return ret;
+}
+
+
+int dirty_bytes_handler(struct ctl_table *table, int write,
+		struct file *filp, void __user *buffer, size_t *lenp,
+		loff_t *ppos)
+{
+	int old_bytes = vm_dirty_bytes;
+	int ret;
+
+	ret = proc_doulongvec_minmax(table, write, filp, buffer, lenp, ppos);
+	if (ret == 0 && write && vm_dirty_bytes != old_bytes) {
+		update_completion_period();
+		vm_dirty_ratio = 0;
 	}
 	return ret;
 }
@@ -362,26 +426,32 @@ unsigned long determine_dirtyable_memory(void)
 }
 
 void
-get_dirty_limits(long *pbackground, long *pdirty, long *pbdi_dirty,
-		 struct backing_dev_info *bdi)
+get_dirty_limits(unsigned long *pbackground, unsigned long *pdirty,
+		 unsigned long *pbdi_dirty, struct backing_dev_info *bdi)
 {
-	int background_ratio;		/* Percentages */
-	int dirty_ratio;
-	long background;
-	long dirty;
+	unsigned long background;
+	unsigned long dirty;
 	unsigned long available_memory = determine_dirtyable_memory();
 	struct task_struct *tsk;
 
-	dirty_ratio = vm_dirty_ratio;
-	if (dirty_ratio < 5)
-		dirty_ratio = 5;
+	if (vm_dirty_bytes)
+		dirty = DIV_ROUND_UP(vm_dirty_bytes, PAGE_SIZE);
+	else {
+		int dirty_ratio;
+
+		dirty_ratio = vm_dirty_ratio;
+		if (dirty_ratio < 5)
+			dirty_ratio = 5;
+		dirty = (dirty_ratio * available_memory) / 100;
+	}
 
-	background_ratio = dirty_background_ratio;
-	if (background_ratio >= dirty_ratio)
-		background_ratio = dirty_ratio / 2;
+	if (dirty_background_bytes)
+		background = DIV_ROUND_UP(dirty_background_bytes, PAGE_SIZE);
+	else
+		background = (dirty_background_ratio * available_memory) / 100;
 
-	background = (background_ratio * available_memory) / 100;
-	dirty = (dirty_ratio * available_memory) / 100;
+	if (background >= dirty)
+		background = dirty / 2;
 	tsk = current;
 	if (tsk->flags & PF_LESS_THROTTLE || rt_task(tsk)) {
 		background += background / 4;
@@ -423,9 +493,9 @@ static void balance_dirty_pages(struct address_space *mapping)
 {
 	long nr_reclaimable, bdi_nr_reclaimable;
 	long nr_writeback, bdi_nr_writeback;
-	long background_thresh;
-	long dirty_thresh;
-	long bdi_thresh;
+	unsigned long background_thresh;
+	unsigned long dirty_thresh;
+	unsigned long bdi_thresh;
 	unsigned long pages_written = 0;
 	unsigned long write_chunk = sync_writeback_pages();
 
@@ -580,8 +650,8 @@ EXPORT_SYMBOL(balance_dirty_pages_ratelimited_nr);
 
 void throttle_vm_writeout(gfp_t gfp_mask)
 {
-	long background_thresh;
-	long dirty_thresh;
+	unsigned long background_thresh;
+	unsigned long dirty_thresh;
 
         for ( ; ; ) {
 		get_dirty_limits(&background_thresh, &dirty_thresh, NULL, NULL);
@@ -624,8 +694,8 @@ static void background_writeout(unsigned long _min_pages)
 	};
 
 	for ( ; ; ) {
-		long background_thresh;
-		long dirty_thresh;
+		unsigned long background_thresh;
+		unsigned long dirty_thresh;
 
 		get_dirty_limits(&background_thresh, &dirty_thresh, NULL, NULL);
 		if (global_page_state(NR_FILE_DIRTY) +
@@ -868,9 +938,11 @@ int write_cache_pages(struct address_space *mapping,
 	int done = 0;
 	struct pagevec pvec;
 	int nr_pages;
+	pgoff_t uninitialized_var(writeback_index);
 	pgoff_t index;
 	pgoff_t end;		/* Inclusive */
-	int scanned = 0;
+	pgoff_t done_index;
+	int cycled;
 	int range_whole = 0;
 	long nr_to_write = wbc->nr_to_write;
 
@@ -881,83 +953,143 @@ int write_cache_pages(struct address_space *mapping,
 
 	pagevec_init(&pvec, 0);
 	if (wbc->range_cyclic) {
-		index = mapping->writeback_index; /* Start from prev offset */
+		writeback_index = mapping->writeback_index; /* prev offset */
+		index = writeback_index;
+		if (index == 0)
+			cycled = 1;
+		else
+			cycled = 0;
 		end = -1;
 	} else {
 		index = wbc->range_start >> PAGE_CACHE_SHIFT;
 		end = wbc->range_end >> PAGE_CACHE_SHIFT;
 		if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX)
 			range_whole = 1;
-		scanned = 1;
+		cycled = 1; /* ignore range_cyclic tests */
 	}
 retry:
-	while (!done && (index <= end) &&
-	       (nr_pages = pagevec_lookup_tag(&pvec, mapping, &index,
-					      PAGECACHE_TAG_DIRTY,
-					      min(end - index, (pgoff_t)PAGEVEC_SIZE-1) + 1))) {
-		unsigned i;
+	done_index = index;
+	while (!done && (index <= end)) {
+		int i;
+
+		nr_pages = pagevec_lookup_tag(&pvec, mapping, &index,
+			      PAGECACHE_TAG_DIRTY,
+			      min(end - index, (pgoff_t)PAGEVEC_SIZE-1) + 1);
+		if (nr_pages == 0)
+			break;
 
-		scanned = 1;
 		for (i = 0; i < nr_pages; i++) {
 			struct page *page = pvec.pages[i];
 
 			/*
-			 * At this point we hold neither mapping->tree_lock nor
-			 * lock on the page itself: the page may be truncated or
-			 * invalidated (changing page->mapping to NULL), or even
-			 * swizzled back from swapper_space to tmpfs file
-			 * mapping
+			 * At this point, the page may be truncated or
+			 * invalidated (changing page->mapping to NULL), or
+			 * even swizzled back from swapper_space to tmpfs file
+			 * mapping. However, page->index will not change
+			 * because we have a reference on the page.
 			 */
+			if (page->index > end) {
+				/*
+				 * can't be range_cyclic (1st pass) because
+				 * end == -1 in that case.
+				 */
+				done = 1;
+				break;
+			}
+
+			done_index = page->index + 1;
+
 			lock_page(page);
 
+			/*
+			 * Page truncated or invalidated. We can freely skip it
+			 * then, even for data integrity operations: the page
+			 * has disappeared concurrently, so there could be no
+			 * real expectation of this data interity operation
+			 * even if there is now a new, dirty page at the same
+			 * pagecache address.
+			 */
 			if (unlikely(page->mapping != mapping)) {
+continue_unlock:
 				unlock_page(page);
 				continue;
 			}
 
-			if (!wbc->range_cyclic && page->index > end) {
-				done = 1;
-				unlock_page(page);
-				continue;
+			if (!PageDirty(page)) {
+				/* someone wrote it for us */
+				goto continue_unlock;
 			}
 
-			if (wbc->sync_mode != WB_SYNC_NONE)
-				wait_on_page_writeback(page);
-
-			if (PageWriteback(page) ||
-			    !clear_page_dirty_for_io(page)) {
-				unlock_page(page);
-				continue;
+			if (PageWriteback(page)) {
+				if (wbc->sync_mode != WB_SYNC_NONE)
+					wait_on_page_writeback(page);
+				else
+					goto continue_unlock;
 			}
 
-			ret = (*writepage)(page, wbc, data);
+			BUG_ON(PageWriteback(page));
+			if (!clear_page_dirty_for_io(page))
+				goto continue_unlock;
 
-			if (unlikely(ret == AOP_WRITEPAGE_ACTIVATE)) {
-				unlock_page(page);
-				ret = 0;
-			}
-			if (ret || (--nr_to_write <= 0))
+			ret = (*writepage)(page, wbc, data);
+			if (unlikely(ret)) {
+				if (ret == AOP_WRITEPAGE_ACTIVATE) {
+					unlock_page(page);
+					ret = 0;
+				} else {
+					/*
+					 * done_index is set past this page,
+					 * so media errors will not choke
+					 * background writeout for the entire
+					 * file. This has consequences for
+					 * range_cyclic semantics (ie. it may
+					 * not be suitable for data integrity
+					 * writeout).
+					 */
+					done = 1;
+					break;
+				}
+ 			}
+
+			if (nr_to_write > 0)
+				nr_to_write--;
+			else if (wbc->sync_mode == WB_SYNC_NONE) {
+				/*
+				 * We stop writing back only if we are not
+				 * doing integrity sync. In case of integrity
+				 * sync we have to keep going because someone
+				 * may be concurrently dirtying pages, and we
+				 * might have synced a lot of newly appeared
+				 * dirty pages, but have not synced all of the
+				 * old dirty pages.
+				 */
 				done = 1;
+				break;
+			}
+
 			if (wbc->nonblocking && bdi_write_congested(bdi)) {
 				wbc->encountered_congestion = 1;
 				done = 1;
+				break;
 			}
 		}
 		pagevec_release(&pvec);
 		cond_resched();
 	}
-	if (!scanned && !done) {
+	if (!cycled) {
 		/*
+		 * range_cyclic:
 		 * We hit the last page and there is more work to be done: wrap
 		 * back to the start of the file
 		 */
-		scanned = 1;
+		cycled = 1;
 		index = 0;
+		end = writeback_index - 1;
 		goto retry;
 	}
 	if (!wbc->no_nrwrite_index_update) {
 		if (wbc->range_cyclic || (range_whole && nr_to_write > 0))
-			mapping->writeback_index = index;
+			mapping->writeback_index = done_index;
 		wbc->nr_to_write = nr_to_write;
 	}