Messages in this thread | | | Date | Wed, 8 Jan 2014 06:03:43 -0800 | From | Christoph Hellwig <> | Subject | Re: Terrible performance of sequential O_DIRECT 4k writes in SAN environment. ~3 times slower then Solars 10 with the same HBA/Storage. |
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On Wed, Jan 08, 2014 at 02:17:13AM +0100, Jan Kara wrote: > Well, I was specifically worried about i_mutex locking. In particular: > Before we report appending IO completion we need to update i_size. > To update i_size we need to grab i_mutex. > > Now this is unpleasant because inode_dio_wait() happens under i_mutex so > the above would create lock inversion. And we cannot really do > inode_dio_done() before grabbing i_mutex as that would open interesting > races between truncate decreasing i_size and DIO increasing it.
Yeah, XFS splits this between the ilock and iolock, which just makes life in this area a whole lot easier.
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