On Mon, Jul 13, 2015 at 05:16:10PM +0200, Jan Kara wrote: > On Fri 03-07-15 11:15:11, Matthew Wilcox wrote: > > From: Matthew Wilcox <willy@xxxxxxxxxxxxxxx> > > > > Currently, if ext4's get_block encounters a hole, it does not modify the > > buffer_head. That's fine for many callers, but for DAX, it's useful to > > know how large the hole is. XFS already returns the length of the hole, > > so this improvement should not confuse any callers. > > > > Signed-off-by: Matthew Wilcox <willy@xxxxxxxxxxxxxxx> > > So I'm somewhat wondering: What is the reason of BH_Uptodate flag being > set? I can see the XFS sets it in some cases as well but the use of the > flag isn't really clear to me... No clue. I'm just following the documentation in buffer.c: * NOTE! All mapped/uptodate combinations are valid: * * Mapped Uptodate Meaning * * No No "unknown" - must do get_block() * No Yes "hole" - zero-filled * Yes No "allocated" - allocated on disk, not read in * Yes Yes "valid" - allocated and up-to-date in memory. -- 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
