[PATCH v14 075/138] mm/writeback: Add folio_account_redirty()

Matthew Wilcox (Oracle)
2021-07-15T04:38:03Z

Account the number of pages in the folio that we're redirtying.
Turn account_page_dirty() into a wrapper around it. Also turn
the comment on folio_account_redirty() into kernel-doc and
edit it slightly so it makes sense to its potential callers.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
---
include/linux/writeback.h | 6 +++++-
mm/page-writeback.c | 32 +++++++++++++++++++-------------
2 files changed, 24 insertions(+), 14 deletions(-)

diff --git a/include/linux/writeback.h b/include/linux/writeback.h
index eda9cc778ef6..50cb6e25ab9e 100644
--- a/include/linux/writeback.h
+++ b/include/linux/writeback.h
@@ -399,7 +399,11 @@ void tag_pages_for_writeback(struct address_space *mapping,
pgoff_t start, pgoff_t end);

bool filemap_dirty_folio(struct address_space *mapping, struct folio *folio);
-void account_page_redirty(struct page *page);
+void folio_account_redirty(struct folio *folio);
+static inline void account_page_redirty(struct page *page)
+{
+ folio_account_redirty(page_folio(page));
+}

void sb_mark_inode_writeback(struct inode *inode);
void sb_clear_inode_writeback(struct inode *inode);
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 66060bbf6aad..d7bd5580c91e 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -1084,7 +1084,7 @@ static void wb_update_write_bandwidth(struct bdi_writeback *wb,
* write_bandwidth = ---------------------------------------------------
* period
*
- * @written may have decreased due to account_page_redirty().
+ * @written may have decreased due to folio_account_redirty().
* Avoid underflowing @bw calculation.
*/
bw = written - min(written, wb->written_stamp);
@@ -2527,30 +2527,36 @@ bool filemap_dirty_folio(struct address_space *mapping, struct folio *folio)
}
EXPORT_SYMBOL(filemap_dirty_folio);

-/*
- * Call this whenever redirtying a page, to de-account the dirty counters
- * (NR_DIRTIED, WB_DIRTIED, tsk->nr_dirtied), so that they match the written
- * counters (NR_WRITTEN, WB_WRITTEN) in long term. The mismatches will lead to
- * systematic errors in balanced_dirty_ratelimit and the dirty pages position
- * control.
+/**
+ * folio_account_redirty - Manually account for redirtying a page.
+ * @folio: The folio which is being redirtied.
+ *
+ * Most filesystems should call folio_redirty_for_writepage() instead
+ * of this fuction. If your filesystem is doing writeback outside the
+ * context of a writeback_control(), it can call this when redirtying
+ * a folio, to de-account the dirty counters (NR_DIRTIED, WB_DIRTIED,
+ * tsk->nr_dirtied), so that they match the written counters (NR_WRITTEN,
+ * WB_WRITTEN) in long term. The mismatches will lead to systematic errors
+ * in balanced_dirty_ratelimit and the dirty pages position control.
*/
-void account_page_redirty(struct page *page)
+void folio_account_redirty(struct folio *folio)
{
- struct address_space *mapping = page->mapping;
+ struct address_space *mapping = folio->mapping;

if (mapping && mapping_can_writeback(mapping)) {
struct inode *inode = mapping->host;
struct bdi_writeback *wb;
struct wb_lock_cookie cookie = {};
+ unsigned nr = folio_nr_pages(folio);

wb = unlocked_inode_to_wb_begin(inode, &cookie);
- current->nr_dirtied--;
- dec_node_page_state(page, NR_DIRTIED);
- dec_wb_stat(wb, WB_DIRTIED);
+ current->nr_dirtied -= nr;
+ node_stat_mod_folio(folio, NR_DIRTIED, -nr);
+ wb_stat_mod(wb, WB_DIRTIED, -nr);
unlocked_inode_to_wb_end(inode, &cookie);
}
}
-EXPORT_SYMBOL(account_page_redirty);
+EXPORT_SYMBOL(folio_account_redirty);

/*
* When a writepage implementation decides that it doesn't want to write this
--
2.30.2