From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christoph Hellwig Subject: Re: why is i_ino unsigned long, anyway? Date: Sun, 29 Sep 2013 04:54:54 -0700 Message-ID: <20130929115454.GA3953@infradead.org> References: <20130912160324.GE1462@fieldses.org> <20130912193328.GP13318@ZenIV.linux.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: "J. Bruce Fields" , linux-fsdevel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-nfs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, sandeen-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org To: Al Viro Return-path: Content-Disposition: inline In-Reply-To: <20130912193328.GP13318-3bDd1+5oDREiFSDQTTA3OLVCufUGDwFn@public.gmane.org> Sender: linux-nfs-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: linux-fsdevel.vger.kernel.org On Thu, Sep 12, 2013 at 08:33:28PM +0100, Al Viro wrote: > i_ino use is entirely up to filesystem; it may be used by library helpers, > provided that the choice of using or not using those is, again, up to > filesystem in question. With more and more filesystems using large inode numbers I'm starting to wonder if this still makes sense. But given that it's been this way for a long time we should have more documentation of it for sure. > NFSD has no damn business looking at it; library > helpers in fs/exportfs might, but that makes them not suitable for use > by filesystems without inode numbers or with 64bit ones. > > The reason why it's there at all is that it serves as convenient icache > search key for many filesystems. IOW, it's used by iget_locked() and > avoiding the overhead of 64bit comparisons on 32bit hosts is the main > reason to avoid making it u64. > > Again, no fs-independent code has any business looking at it, 64bit or > not. From the VFS point of view there is no such thing as inode number. > And get_name() is just a library helper. For many fs types it works > as suitable ->s_export_op->get_name() instance, but decision to use it > or not belongs to filesystem in question and frankly, it's probably better > to provide an instance of your own anyway. Given that these days most exportable filesystems use 64-bit inode numbers I think we should put the patch from Bruce in. Nevermind that it's in a slow path, so the overhead of vfs_getattr really doesn't hurt. -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html