From: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx> [ Upstream commit 8344a3d44be3d18671e18c4ba23bb03dd21e14ad ] nr_to_write is a count of pages, so we need to decrease it by the number of pages in the folio we just wrote, not by 1. Most callers specify either LONG_MAX or 1, so are unaffected, but writeback_sb_inodes() might end up writing 512x as many pages as it asked for. Dave added: : XFS is the only filesystem this would affect, right? AFAIA, nothing : else enables large folios and uses writeback through : write_cache_pages() at this point... : : In which case, I'd be surprised if much difference, if any, gets : noticed by anyone. Link: https://lkml.kernel.org/r/20230628185548.981888-1-willy@xxxxxxxxxxxxx Fixes: 793917d997df ("mm/readahead: Add large folio readahead") Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx> Reviewed-by: Christoph Hellwig <hch@xxxxxx> Cc: Jan Kara <jack@xxxxxxx> Cc: Dave Chinner <david@xxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> --- mm/page-writeback.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/mm/page-writeback.c b/mm/page-writeback.c index db79439990073..6faa09f1783b3 100644 --- a/mm/page-writeback.c +++ b/mm/page-writeback.c @@ -2434,6 +2434,7 @@ int write_cache_pages(struct address_space *mapping, for (i = 0; i < nr_folios; i++) { struct folio *folio = fbatch.folios[i]; + unsigned long nr; done_index = folio->index; @@ -2471,6 +2472,7 @@ int write_cache_pages(struct address_space *mapping, trace_wbc_writepage(wbc, inode_to_bdi(mapping->host)); error = writepage(folio, wbc, data); + nr = folio_nr_pages(folio); if (unlikely(error)) { /* * Handle errors according to the type of @@ -2489,8 +2491,7 @@ int write_cache_pages(struct address_space *mapping, error = 0; } else if (wbc->sync_mode != WB_SYNC_ALL) { ret = error; - done_index = folio->index + - folio_nr_pages(folio); + done_index = folio->index + nr; done = 1; break; } @@ -2504,7 +2505,8 @@ int write_cache_pages(struct address_space *mapping, * keep going until we have written all the pages * we tagged for writeback prior to entering this loop. */ - if (--wbc->nr_to_write <= 0 && + wbc->nr_to_write -= nr; + if (wbc->nr_to_write <= 0 && wbc->sync_mode == WB_SYNC_NONE) { done = 1; break; -- 2.39.2
