On Wed, May 04, 2011 at 05:42:21PM +0800, Christoph Hellwig wrote: > On Wed, May 04, 2011 at 05:17:10PM +0800, Wu Fengguang wrote: > > This ensures large dirty files can be written in the full 4MB writeback > > chunk size, rather than whatever remained quota in wbc->nr_to_write. > > I like the high-level idea, but the implementation of overriding > nr_to_write and then copying it back seems rather ugly. > > The basic problem seems to be that struct writeback_control is > designed to control writeback of a single file, but we keep abuse it > for writing multiple files in writeback_sb_inodes and its callers. > > It seems like we should only build the struct writeback_control from > struct wb_writeback_work down in writeback_sb_inodes, even if that > means passing some more information to it either in struct > wb_writeback_work or on the stack. Yes it's very reasonable and possible according to your notes in another email. > Then writeback_sb_inodes can do something like > > if (wbc.sync_mode == WB_SYNC_NONE) > wbc.nr_to_write = min(MAX_WRITEBACK_PAGES, work->nr_pages); I like the min() idea. However it have the side effect of (very possible) smallish IO from balance_dirty_pages(), which may call us with small ->nr_pages. We may explicitly do "write_chunk = max(MAX_WRITEBACK_PAGES, write_chunk)" in balance_dirty_pages() to retain the old behavior. > else > wbc.nr_to_write = LONG_MAX; > > for each inode it writes. Thanks, Fengguang -- 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
