On Tue, Jan 21, 2014 at 04:46:23PM -0600, Eric Sandeen wrote: > Some time ago, mkfs.xfs started picking the storage physical > sector size as the default filesystem "sector size" in order > to avoid RMW costs incurred by doing IOs at logical sector > size alignments. > > However, this means that for a filesystem made with i.e. > a 4k sector size on an "advanced format" 4k/512 disk, > 512-byte direct IOs are no longer allowed. This means > that XFS has essentially turned this AF drive into a hard > 4K device, from the filesystem on up. > > XFS's mkfs-specified "sector size" is really just controlling > the minimum size & alignment of filesystem metadata. > > There is no real need to tightly couple XFS's minimal > metadata size to the minimum allowed direct IO size; > XFS can continue doing metadata in optimal sizes, but > still allow smaller DIOs for apps which issue them, > for whatever reason. > > This patch adds a new field to the xfs_buftarg, so that > we now track 2 sizes: > > 1) The metadata sector size, which is the minimum unit and > alignment of IO which will be performed by metadata operations. > 2) The device logical sector size > > The first is used internally by the file system for metadata > alignment and IOs. > The second is used for the minimum allowed direct IO alignment. > > This has passed xfstests on filesystems made with 4k sectors, > including when run under the patch I sent to ignore > XFS_IOC_DIOINFO, and issue 512 DIOs anyway. I also directly > tested end of block behavior on preallocated, sparse, and > existing files when we do a 512 IO into a 4k file on a > 4k-sector filesystem, to be sure there were no unexpected > behaviors. > > Signed-off-by: Eric Sandeen <sandeen@xxxxxxxxxx> Looks good. Nice work with the comments. Reviewed-by: Dave Chinner <dchinner@xxxxxxxxxx> -- Dave Chinner david@xxxxxxxxxxxxx _______________________________________________ xfs mailing list xfs@xxxxxxxxxxx http://oss.sgi.com/mailman/listinfo/xfs
