Re: [PATCH] writeback: Don't wait for completion inwriteback_inodes_sb_nr

From: Christoph Hellwig
Date: Thu Jun 30 2011 - 08:38:16 EST


On Thu, Jun 30, 2011 at 02:15:58PM +0200, Jan Kara wrote:
> Yes. Actually, specifically for filesystems like XFS which update inode
> after IO completion we would need more passes to be efficient and correct:
> for all inodes
> fdatawrite
> for all inodes
> fdatawait
> for all inodes
> write_inode
> for all inodes
> wait for inode IO
>
> But maybe this could be handled by having new WB_SYNC_ mode indicating
> that writeback_single_inode() should not bother waiting (thus we'd really
> end up waiting in sync_inodes_sb()) and then XFS and other filesystems that
> need it would writeout inodes in their sync_fs() implementation (possibly
> using a generic helper)?

We do very little in write_inode these days. Basically just log the
inode size and timestamp sized into the in-memory log. The actual
writeout of the log happens in ->sync_fs already.

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