The flusher works on dirty inodes in batches, and may quit prematurely if the batch of inodes happen to be metadata-only dirtied: in this case wbc->nr_to_write won't be decreased at all, which stands for "no pages written" but also mis-interpreted as "no progress". So introduce writeback_control.inodes_cleaned to count the inodes get cleaned. A non-zero value means there are some progress on writeback, in which case more writeback can be tried. Acked-by: Jan Kara <jack@xxxxxxx> Acked-by: Mel Gorman <mel@xxxxxxxxx> Signed-off-by: Wu Fengguang <fengguang.wu@xxxxxxxxx> --- fs/fs-writeback.c | 4 ++++ include/linux/writeback.h | 1 + 2 files changed, 5 insertions(+) about v1: The initial version was to count successful ->write_inode() calls. However it leads to busy loops for sync() over NFS, because NFS ridiculously returns 0 (success) while at the same time redirties the inode. The NFS case can be trivially fixed, however there may be more hidden bugs in other filesystems.. --- linux-next.orig/fs/fs-writeback.c 2011-05-05 23:30:23.000000000 +0800 +++ linux-next/fs/fs-writeback.c 2011-05-05 23:30:24.000000000 +0800 @@ -464,6 +464,7 @@ writeback_single_inode(struct inode *ino * No need to add it back to the LRU. */ list_del_init(&inode->i_wb_list); + wbc->inodes_cleaned++; } } inode_sync_complete(inode); @@ -725,6 +726,7 @@ static long wb_writeback(struct bdi_writ wbc.more_io = 0; wbc.nr_to_write = write_chunk; wbc.pages_skipped = 0; + wbc.inodes_cleaned = 0; trace_wbc_writeback_start(&wbc, wb->bdi); if (work->sb) @@ -741,6 +743,8 @@ static long wb_writeback(struct bdi_writ */ if (wbc.nr_to_write <= 0) continue; + if (wbc.inodes_cleaned) + continue; /* * Didn't write everything and we don't have more IO, bail */ --- linux-next.orig/include/linux/writeback.h 2011-05-05 23:30:22.000000000 +0800 +++ linux-next/include/linux/writeback.h 2011-05-05 23:30:24.000000000 +0800 @@ -34,6 +34,7 @@ struct writeback_control { long nr_to_write; /* Write this many pages, and decrement this for each page written */ long pages_skipped; /* Pages which were not written */ + long inodes_cleaned; /* # of inodes cleaned */ /* * For a_ops->writepages(): is start or end are non-zero then this is -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html