On Mon, Jan 17, 2011 at 04:18:28PM +1100, Dave Chinner wrote: | On Fri, Jan 14, 2011 at 10:16:29PM -0600, Geoffrey Wehrman wrote: | > On Sat, Jan 15, 2011 at 09:59:07AM +1100, Dave Chinner wrote: | > | On Fri, Jan 14, 2011 at 10:40:16AM -0600, Geoffrey Wehrman wrote: | > | > Also, I'm not saying using XFS_BMAPI_EXACT is feasible. I have a very | > | > minimal understanding of the writepage code path. | > | | > | I think there are situations where this does make sense, but given | > | the potential issues I'm not sure it is a solution that can be | > | extended to the general case. A good discussion point on a different | > | angle, though. ;) | > | > You've convinced me that XFS_BMAPI_EXACT is not the optimal solution. | > | > Upon further consideration, I do like your proposal to make delalloc | > allocation more like an intent/done type operation. The compatibility | > issues aren't all that bad. As long as the filesystem is unmounted | > clean, there is no need for the next mount do log recovery and therefore | > no need to have any knowledge of the new transactions. | | That is a good observation. If there is agreement that this a strong | enough backwards compatibility guarantee (it's good enough for me), | then I think that I will start to prototype this approach. I'm not sure how a version of XFS without the new log recovery code will behave if it encounters a log with the new transactions. I assume it will gracefully abort log recovery and fail the mount with the report of a corrupt log. I have no objection with this compatibility guarantee. | However, this does not solve the extsize allocation issues where we | don't have dirty pages in the page cache covering parts of the | delayed allocation extent so we still need a solution for that. I'm | tending towards zeroing in .aio_write as the simplest solution | because it doesn't cause buffer head/extent tree mapping mismatches, | and it would use the above intent/done operations for crash | resilience so there's no additional, rarely used code path to test | through .writepage. Does that sound reasonable? Zeroing in .aio_write will create zeroed pages covering the entire allocation, correct? This seems like a reasonable and straightforward approach. I wish I had thought of it myself! -- Geoffrey Wehrman 651-683-5496 gwehrman@xxxxxxx _______________________________________________ xfs mailing list xfs@xxxxxxxxxxx http://oss.sgi.com/mailman/listinfo/xfs
