From 90db4d4441f58d433ecf74f7e3bd17e0a553c20c Mon Sep 17 00:00:00 2001 From: Christoph Hellwig Date: Fri, 17 Oct 2025 05:45:48 +0200 Subject: writeback: allow the file system to override MIN_WRITEBACK_PAGES The relatively low minimal writeback size of 4MiB means that written back inodes on rotational media are switched a lot. Besides introducing additional seeks, this also can lead to extreme file fragmentation on zoned devices when a lot of files are cached relative to the available writeback bandwidth. Add a superblock field that allows the file system to override the default size. Signed-off-by: Christoph Hellwig Link: https://patch.msgid.link/20251017034611.651385-3-hch@lst.de Reviewed-by: Jan Kara Reviewed-by: Darrick J. Wong Signed-off-by: Christian Brauner --- fs/fs-writeback.c | 14 +++++--------- 1 file changed, 5 insertions(+), 9 deletions(-) (limited to 'fs/fs-writeback.c') diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c index 30de37865fa1..52763fa499d6 100644 --- a/fs/fs-writeback.c +++ b/fs/fs-writeback.c @@ -32,11 +32,6 @@ #include #include "internal.h" -/* - * 4MB minimal write chunk size - */ -#define MIN_WRITEBACK_PAGES (4096UL >> (PAGE_SHIFT - 10)) - /* * Passed into wb_writeback(), essentially a subset of writeback_control */ @@ -1889,8 +1884,8 @@ out: return ret; } -static long writeback_chunk_size(struct bdi_writeback *wb, - struct wb_writeback_work *work) +static long writeback_chunk_size(struct super_block *sb, + struct bdi_writeback *wb, struct wb_writeback_work *work) { long pages; @@ -1913,7 +1908,8 @@ static long writeback_chunk_size(struct bdi_writeback *wb, pages = min(wb->avg_write_bandwidth / 2, global_wb_domain.dirty_limit / DIRTY_SCOPE); pages = min(pages, work->nr_pages); - return round_down(pages + MIN_WRITEBACK_PAGES, MIN_WRITEBACK_PAGES); + return round_down(pages + sb->s_min_writeback_pages, + sb->s_min_writeback_pages); } /* @@ -2015,7 +2011,7 @@ static long writeback_sb_inodes(struct super_block *sb, inode->i_state |= I_SYNC; wbc_attach_and_unlock_inode(&wbc, inode); - write_chunk = writeback_chunk_size(wb, work); + write_chunk = writeback_chunk_size(inode->i_sb, wb, work); wbc.nr_to_write = write_chunk; wbc.pages_skipped = 0; -- cgit