Re: [PATCH 01/15] writeback: introduce .tagged_writepages for theWB_SYNC_NONE sync stage

[Andrew Morton]

On Wed, 08 Jun 2011 05:32:37 +0800
Wu Fengguang <fengguang.wu@xxxxxxxxx> wrote:

> 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.

What problem is this patch actually fixing?  It sounds like there's
some livelock scenario in the WB_SYNC_NONE phase.  otoh the final
paragraph implies that the WB_SYNC_NONE phase is failing to write some
pages under some situations.

Suggest that the changelog be fleshed out to cover all of this.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/