On Tue, Feb 24, 2009 at 4:28 PM, Randy Dunlap <randy.dunlap@xxxxxxxxxx> wrote: > Fred Isaman wrote: >> On Tue, Feb 24, 2009 at 4:03 PM, Sam Ravnborg <sam@xxxxxxxxxxxx> wrote: >>> On Tue, Feb 24, 2009 at 02:05:25PM -0500, Fred Isaman wrote: >>>> The pnfs tree base of of 2.6.29-rc5 uses the new find_last_bit >>>> function (defined in >>>> lib/find_last_bit.c) in a file in the fs/nfs directory. Myself and >>>> another developer (though no one else so far) get the following error >>>> during compile: >>>> >>>> Kernel: arch/x86/boot/bzImage is ready (#5) >>>> Building modules, stage 2. >>>> MODPOST 515 modules >>>> ERROR: "find_last_bit" [fs/nfs/nfs.ko] undefined! >>>> make[2]: *** [__modpost] Error 1 >>>> make[1]: *** [modules] Error 2 >>>> make: *** [sub-make] Error 2 >>>> >>>> >>>> Note that find_last_bit() is not used in any file in the fs directory. >>>> If I add it to any function that is EXPORT_SYMBOL'ed >>>> from the fs directory, suddenly the compile errors go away. (See the >>>> below patch for a more concrete example.) >>>> >>>> I am not sure what is going on, and why it only affects some >>>> developers, but it looks a lot like the kbuild system >>>> is deciding that the library does not need to be included at the fs >>>> directory level, so isn't including it in fs/nfs where >>>> it is needed. >>> kbuild only links in libaries if there is any users of siad library. >>> And your normal config has no users of lib/find_last_bit.c so >>> it is not linked into the kernel. >>> >> >> I don't understand your comment. There *is* a user of the library in the >> (modified) fs/nfs/nfs4proc.c. The problem is that it doesn't compile unless >> there is also a user in some fs/*.c. > > If you build nfs (or pnfs) into the kernel image instead of as a > loadable module, does the build succeed? I expect that it does > (or would). > Yes, you are correct. >>> The general rule is that if any in tree module uses a library >>> then the library is always linked in. >>> And to always link in a library you need to patch the Makefile >>> as Randy suggest in his mail. >>> >>> Sam >>> >> >> Again, I suspect I am misunderstanding. It seems you are suggesting >> that to compile the nfs code I have to alter lib/Makefile. While that is a >> useful workaround, that is certainly not a viable solution. > > Why not? We do that same change for other library options. > I was working under the assumption that, in order to compile nfs, I should only have to adjust the fs/nfs/Makefile. You seem to be saying that when we submit upstream a patch that uses find_last_bit(), if there are no other in-kernel users at that time, we will have to submit a patch to lib/Makefile, similar to commit 5a6dca7... lib: move bitmap.o from lib-y to obj-y. If that is what you mean, I can live with that. Thanks for your help. Fred > > -- > ~Randy > -- To unsubscribe from this list: send the line "unsubscribe linux-kbuild" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
