On Wed, Dec 18, 2013 at 07:27:49AM -0700, Matthew Wilcox wrote: > > I think there is a callback in xip_file_write(), and it's get_xip_mem(). > From what you're saying, it sounds like it's just not doing enough. The problem is that git_xip_mem() is called before we write to the memory, right? We need to convert the uninit extents to be marked as initialized in *after* the write has been sent to the storage medium. > Could you take pity on me and tell me what flags I need to check in the > buffer_head to determine this state of affairs? The buffer head flag is BH_Unwritten, but note that how BH_Delay and BH_Boundary are handled is very file system specific. There is no guarantee that all file systems will use these flags, nor will use them in the same way. (I've been considering changing ext4 to not attach buffer heads to the pages at all -- except for DIO, which requires them today -- because iterating over all of the buffer heads attached to the pages is a pain in the tuckus, and ext4 now has an extent status tree which we could use to get this information without needing to lock the pages.) It's much better to give a way for the file system to attach a callback to the XIP request object. Cheers, - Ted -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
