sync(2) is performed in two stages: the WB_SYNC_NONE sync and the WB_SYNC_ALL sync. Identify the first stage with .tagged_writepages and do livelock prevention for it, too. Note that writeback_inodes_sb() is called by not only sync(), they are treated the same because the other callers also need livelock prevention. Impact: It changes the order in which pages/inodes are synced to disk. Now in the WB_SYNC_NONE stage, it won't proceed to write the next inode until finished with the current inode. Acked-by: Jan Kara CC: Dave Chinner Signed-off-by: Wu Fengguang --- fs/ext4/inode.c | 4 ++-- fs/fs-writeback.c | 17 +++++++++-------- include/linux/writeback.h | 1 + mm/page-writeback.c | 4 ++-- 4 files changed, 14 insertions(+), 12 deletions(-) --- linux-next.orig/fs/fs-writeback.c 2011-06-08 05:20:05.000000000 +0800 +++ linux-next/fs/fs-writeback.c 2011-06-08 05:20:06.000000000 +0800 @@ -36,6 +36,7 @@ struct wb_writeback_work { long nr_pages; struct super_block *sb; enum writeback_sync_modes sync_mode; + unsigned int tagged_writepages:1; unsigned int for_kupdate:1; unsigned int range_cyclic:1; unsigned int for_background:1; @@ -650,6 +651,7 @@ static long wb_writeback(struct bdi_writ { struct writeback_control wbc = { .sync_mode = work->sync_mode, + .tagged_writepages = work->tagged_writepages, .older_than_this = NULL, .for_kupdate = work->for_kupdate, .for_background = work->for_background, @@ -657,7 +659,7 @@ static long wb_writeback(struct bdi_writ }; unsigned long oldest_jif; long wrote = 0; - long write_chunk; + long write_chunk = MAX_WRITEBACK_PAGES; struct inode *inode; if (wbc.for_kupdate) { @@ -683,9 +685,7 @@ static long wb_writeback(struct bdi_writ * (quickly) tag currently dirty pages * (maybe slowly) sync all tagged pages */ - if (wbc.sync_mode == WB_SYNC_NONE) - write_chunk = MAX_WRITEBACK_PAGES; - else + if (wbc.sync_mode == WB_SYNC_ALL || wbc.tagged_writepages) write_chunk = LONG_MAX; wbc.wb_start = jiffies; /* livelock avoidance */ @@ -1188,10 +1188,11 @@ void writeback_inodes_sb_nr(struct super { DECLARE_COMPLETION_ONSTACK(done); struct wb_writeback_work work = { - .sb = sb, - .sync_mode = WB_SYNC_NONE, - .done = &done, - .nr_pages = nr, + .sb = sb, + .sync_mode = WB_SYNC_NONE, + .tagged_writepages = 1, + .done = &done, + .nr_pages = nr, }; WARN_ON(!rwsem_is_locked(&sb->s_umount)); --- linux-next.orig/include/linux/writeback.h 2011-06-08 05:20:05.000000000 +0800 +++ linux-next/include/linux/writeback.h 2011-06-08 05:20:06.000000000 +0800 @@ -47,6 +47,7 @@ struct writeback_control { unsigned encountered_congestion:1; /* An output: a queue is full */ unsigned for_kupdate:1; /* A kupdate writeback */ unsigned for_background:1; /* A background writeback */ + unsigned tagged_writepages:1; /* tag-and-write to avoid livelock */ unsigned for_reclaim:1; /* Invoked from the page allocator */ unsigned range_cyclic:1; /* range_start is cyclic */ unsigned more_io:1; /* more io to be dispatched */ --- linux-next.orig/mm/page-writeback.c 2011-06-08 05:20:05.000000000 +0800 +++ linux-next/mm/page-writeback.c 2011-06-08 05:20:06.000000000 +0800 @@ -892,12 +892,12 @@ int write_cache_pages(struct address_spa range_whole = 1; cycled = 1; /* ignore range_cyclic tests */ } - if (wbc->sync_mode == WB_SYNC_ALL) + if (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages) tag = PAGECACHE_TAG_TOWRITE; else tag = PAGECACHE_TAG_DIRTY; retry: - if (wbc->sync_mode == WB_SYNC_ALL) + if (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages) tag_pages_for_writeback(mapping, index, end); done_index = index; while (!done && (index <= end)) { --- linux-next.orig/fs/ext4/inode.c 2011-06-08 05:20:05.000000000 +0800 +++ linux-next/fs/ext4/inode.c 2011-06-08 05:20:06.000000000 +0800 @@ -2741,7 +2741,7 @@ static int write_cache_pages_da(struct a index = wbc->range_start >> PAGE_CACHE_SHIFT; end = wbc->range_end >> PAGE_CACHE_SHIFT; - if (wbc->sync_mode == WB_SYNC_ALL) + if (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages) tag = PAGECACHE_TAG_TOWRITE; else tag = PAGECACHE_TAG_DIRTY; @@ -2973,7 +2973,7 @@ static int ext4_da_writepages(struct add } retry: - if (wbc->sync_mode == WB_SYNC_ALL) + if (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages) tag_pages_for_writeback(mapping, index, end); while (!ret && wbc->nr_to_write > 0) { -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/