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Dave Chinner authored
When swalloc is specified as a mount option, allocations are supposed to be aligned to the stripe width rather than the stripe unit of the underlying filesystem. However, it does not do this. What the implementation does is round up the allocation size to a stripe width, hence ensuring that all allocations span a full stripe width. It does not, however, ensure that that allocation is aligned to a stripe width, and hence the allocations can span multiple underlying stripes and so still see RMW cycles for things like direct IO on MD RAID. So, if the swalloc mount option is set, change the allocation alignment in xfs_bmap_btalloc() to use the stripe width rather than the stripe unit. Signed-off-by:
Dave Chinner <dchinner@redhat.com> Reviewed-by:
Christoph Hellwig <hch@lst.de> Reviewed-by:
Ben Myers <bpm@sgi.com> Signed-off-by:
Ben Myers <bpm@sgi.com>
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