Messages in this thread | | | Date | Fri, 7 Jan 2011 02:29:34 -0500 | From | Christoph Hellwig <> | Subject | Re: [patch 8/8] fs: add i_op->sync_inode |
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On Fri, Jan 07, 2011 at 02:24:30AM -0500, Christoph Hellwig wrote: > On Fri, Jan 07, 2011 at 03:47:34PM +1100, Nick Piggin wrote: > > No, you misunderstand 1. I am saying they should be treated as > > WB_SYNC_NONE. > > > > In fact 2 would cause much more IO, because dirty writeout would > > never clean them so it will just keep writing them out. I don't > > know how 2 could be feasible. > > WB_SYNC_NONE means ->write_inode behaves non-blocking. That is > we do not block on memory allocations, and we do not take locks > blocking. Most journaling filesystems currently take the easy > way out an make it a no-op due to that, but take a look at XFS > how complicated it is to avoid the blocking if you want a non-noop > implementation.
Btw, there's an easy way how we could get this right, in fact the write_inode in XFS is already trying to do it, it's just the caller not copying with it:
- if we can't get locks for a non-blocking ->write_inode we return EAGAIN, and the callers sets the dirty bits again.
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