On Tue, 2009-07-21 at 15:54 -0600, Andreas Dilger wrote: > On Jul 21, 2009 14:29 -0700, Frank Mayhar wrote: > > I've spent a little while today digging into this. My guess (only a > > guess at this point until I have a chance to prove it) is that > > i_disksize should be updated by fallocate() even when KEEP_SIZE is > > specified. It's currently not updated in that case. > > No, that isn't correct. The intent of KEEP_SIZE is to allow fallocate > to preallocate blocks beyond the EOF, so that it doesn't affect the > file data visible to userspace, but can avoid fragmentation from e.g. > log files or mbox files. > > The i_disksize variable is just to handle the lag in updating the on-disk > file size during truncate, because the VFS updates i_size to indicate a > truncate, but in order to handle the truncation of files within finite > transaction sizes the on-disk file size needs to be shrunk incrementally. Okay, thanks, this makes this much more clear. It does sound like there needs to be a flag somewhere (probably in the on-disk inode) that indicates that there are allocated blocks beyond EOF, as you say. Then use that in ftruncate(). We would really like to avoid your workaround for performance reasons. -- Frank Mayhar <fmayhar@xxxxxxxxxx> Google, Inc. -- 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
