mm/writeback: Add folio_account_redirty()

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>
Reviewed-by: David Howells <dhowells@redhat.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>

diff --git a/include/linux/writeback.h b/include/linux/writeback.h
index d4f24eba066fd18321bd09aaf11244d4b5ef0b5f..852100bea351efb92ff6d45f8fae421ddccbd978 100644 (file)
--- a/include/linux/writeback.h
+++ b/include/linux/writeback.h
@@ -394,7 +394,11 @@ 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 85c04445de97550a01ddc2808cccd51ee7033461..7ef904363fb7cb99b327182a0cfa472d5a4b5bd8 100644 (file)
--- 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);
@@ -2544,30 +2544,36 @@ 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 = {};
+               long 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