On Wednesday 05 January 2011 03:17:16 Shaohua Li wrote: > On Tue, 2011-01-04 at 17:40 +0800, Arnd Bergmann wrote: > > > Have you tried passing just a single metadata_incore_ent > > at the ioctl and looping in user space? I would guess the > > extra overhead of that would be small enough, but that might > > need to be measured. > metadata usually isn't continuous, so this means we have a lot of > metadata_incore_ent entries. And this is called at boot time and I want > to make the overhead as low as possible to not impact boot. Unless there > are certain reasons we can't use indirect pointers, I'd like to make > kernel return a vector of entries. It's not a strict rule, but the indirect data passing is rather ugly and I'd only do that if the difference can be /measured/. If the purpose is to speed up boot time by preloading metadata, the FIMETADATA_INCORE operations should of course not take a significant amount of time compared to the actual preloading, but as long as it's less than one percent of the time you need for the preload, I would just use the simpler interface. > @@ -882,6 +882,7 @@ COMPATIBLE_IOCTL(FIGETBSZ) > /* 'X' - originally XFS but some now in the VFS */ > COMPATIBLE_IOCTL(FIFREEZE) > COMPATIBLE_IOCTL(FITHAW) > +COMPATIBLE_IOCTL(FIMETADATA_INCORE) > COMPATIBLE_IOCTL(KDGETKEYCODE) > COMPATIBLE_IOCTL(KDSETKEYCODE) > COMPATIBLE_IOCTL(KDGKBTYPE) This change can go away as well. Two more general comments: - You probably want to add the ioctls to file_ioctl instead of do_vfs_ioctl, so you don't add another case statement to the common path. - I don't know if there are any rules for what should be an ioctl or an fcntl, we're rather inconsistent about this. If you have found a good reason for making it an ioctl, just put that into the changelog so we can refer to it next time. Arnd -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
