On Sun, May 01, 2011 at 06:36:06AM +0800, Wu Fengguang wrote:
> sync(2) is performed in two stages: the WB_SYNC_NONE sync and the
> WB_SYNC_ALL sync. Tag both stages with wbc.for_sync for livelock
> prevention.
>
> Note that writeback_inodes_sb() is called by not only sync(), they
> are treated the same because the other callers need also need livelock
> prevention.
>
> Impacts:
>
> - 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.
>
> - this adds a new field to the writeback trace events and may possibly
> break some scripts.
.....
> --- linux-next.orig/mm/page-writeback.c 2011-05-01 06:35:16.000000000 +0800
> +++ linux-next/mm/page-writeback.c 2011-05-01 06:35:17.000000000 +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->for_sync)
> tag = PAGECACHE_TAG_TOWRITE;
> else
> tag = PAGECACHE_TAG_DIRTY;
> retry:
> - if (wbc->sync_mode == WB_SYNC_ALL)
> + if (wbc->for_sync)
> tag_pages_for_writeback(mapping, index, end);
> done_index = index;
> while (!done && (index <= end)) {
Doesn't that break anything that uses
filemap_write_and_wait{_range}() or filemap_fdatawrite{_range}()?
e.g. fsync, sync buffered writes, etc? i.e. everything that
currently relies on WB_SYNC_ALL for data integrity writeback is now
b0rken except for sync(1)?
Cheers,
Dave.
--
Dave Chinner
david@xxxxxxxxxxxxx
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