From: Peter Zijlstra Count per BDI writeback pages. Signed-off-by: Peter Zijlstra Signed-off-by: Andrew Morton --- include/linux/backing-dev.h | 1 + mm/page-writeback.c | 12 ++++++++++-- 2 files changed, 11 insertions(+), 2 deletions(-) diff -puN include/linux/backing-dev.h~mm-count-writeback-pages-per-bdi include/linux/backing-dev.h --- a/include/linux/backing-dev.h~mm-count-writeback-pages-per-bdi +++ a/include/linux/backing-dev.h @@ -28,6 +28,7 @@ typedef int (congested_fn)(void *, int); enum bdi_stat_item { BDI_RECLAIMABLE, + BDI_WRITEBACK, NR_BDI_STAT_ITEMS }; diff -puN mm/page-writeback.c~mm-count-writeback-pages-per-bdi mm/page-writeback.c --- a/mm/page-writeback.c~mm-count-writeback-pages-per-bdi +++ a/mm/page-writeback.c @@ -978,14 +978,18 @@ int test_clear_page_writeback(struct pag int ret; if (mapping) { + struct backing_dev_info *bdi = mapping->backing_dev_info; unsigned long flags; write_lock_irqsave(&mapping->tree_lock, flags); ret = TestClearPageWriteback(page); - if (ret) + if (ret) { radix_tree_tag_clear(&mapping->page_tree, page_index(page), PAGECACHE_TAG_WRITEBACK); + if (bdi_cap_writeback_dirty(bdi)) + __dec_bdi_stat(bdi, BDI_WRITEBACK); + } write_unlock_irqrestore(&mapping->tree_lock, flags); } else { ret = TestClearPageWriteback(page); @@ -1001,14 +1005,18 @@ int test_set_page_writeback(struct page int ret; if (mapping) { + struct backing_dev_info *bdi = mapping->backing_dev_info; unsigned long flags; write_lock_irqsave(&mapping->tree_lock, flags); ret = TestSetPageWriteback(page); - if (!ret) + if (!ret) { radix_tree_tag_set(&mapping->page_tree, page_index(page), PAGECACHE_TAG_WRITEBACK); + if (bdi_cap_writeback_dirty(bdi)) + __inc_bdi_stat(bdi, BDI_WRITEBACK); + } if (!PageDirty(page)) radix_tree_tag_clear(&mapping->page_tree, page_index(page), _