On Tue, Jan 24, 2017 at 11:17:20AM -0500, Brian Foster wrote: > I thought that while not necessarily guaranteed, generally the entire > extent gets converted from delalloc to real blocks. For buffered I/O that's the case. See the discussion on my recent xfs_bmapi_write patch. > IIRC, that's what > I've seen in the past when looking into the cow fork with bmap. After > all, isn't that the point of the extent size hint? Allocate wider than > the write to accommodate potential subsequent writes into a more > contiguous range. Well, for direct I/O that's not what the current code does. Implementing it might be useful, but I'm not sure how much the front alignment is going to help in usual worksloads - you'd need a backwards write or random writes that happen to look almost backwards for it to make a difference. I suspect most of them time we'd just allocate blocks to reclaim them again a little later. -- To unsubscribe from this list: send the line "unsubscribe linux-xfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
