On Mon, Nov 13, 2023 at 09:10:06AM -0800, Andrew Morton wrote: > On Sun, 12 Nov 2023 12:52:00 +0800 kernel test robot <lkp@xxxxxxxxx> wrote: > > > Hi Matthew, > > > > kernel test robot noticed the following build errors: > > > > [auto build test ERROR on akpm-mm/mm-everything] > > [also build test ERROR on linus/master next-20231110] > > [cannot apply to v6.6] > > [If your patch is applied to the wrong git tree, kindly drop us a note. > > And when submitting patch, we suggest to use '--base' as documented in > > https://git-scm.com/docs/git-format-patch#_base_tree_information] > > > > url: https://github.com/intel-lab-lkp/linux/commits/Matthew-Wilcox-Oracle/buffer-Return-bool-from-grow_dev_folio/20231110-051651 > > base: https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-everything > > patch link: https://lore.kernel.org/r/20231109210608.2252323-4-willy%40infradead.org > > patch subject: [PATCH v2 3/7] buffer: Fix grow_buffers() for block size > PAGE_SIZE > > config: hexagon-comet_defconfig (https://download.01.org/0day-ci/archive/20231112/202311121240.AN8GbAbe-lkp@xxxxxxxxx/config) > > compiler: clang version 16.0.4 (https://github.com/llvm/llvm-project.git ae42196bc493ffe877a7e3dff8be32035dea4d07) > > reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20231112/202311121240.AN8GbAbe-lkp@xxxxxxxxx/reproduce) > > > > If you fix the issue in a separate patch/commit (i.e. not just a new version of > > the same patch/commit), kindly add following tags > > | Reported-by: kernel test robot <lkp@xxxxxxxxx> > > | Closes: https://lore.kernel.org/oe-kbuild-all/202311121240.AN8GbAbe-lkp@xxxxxxxxx/ > > > > All errors (new ones prefixed by >>): > > > > >> ld.lld: error: undefined symbol: __muloti4 > > >>> referenced by buffer.c > > >>> fs/buffer.o:(bdev_getblk) in archive vmlinux.a > > >>> referenced by buffer.c > > >>> fs/buffer.o:(bdev_getblk) in archive vmlinux.a > > > > What a peculiar compiler. > > I assume this fixes? > > --- a/fs/buffer.c~buffer-fix-grow_buffers-for-block-size-page_size-fix > +++ a/fs/buffer.c > @@ -1099,7 +1099,7 @@ static bool grow_buffers(struct block_de > } > > /* Create a folio with the proper size buffers */ > - return grow_dev_folio(bdev, block, pos / PAGE_SIZE, size, gfp); > + return grow_dev_folio(bdev, block, pos >> PAGE_SHIFT, size, gfp); > } > > static struct buffer_head * > _ > > No, this is not a division libcall. This seems to be related to the types of the variables used in __builtin_mul_overflow() :/ for some odd reason, clang generates a libcall when passing in an 'unsigned long long' and 'unsigned int', which apparently has not been done before in the kernel? https://github.com/ClangBuiltLinux/linux/issues/1958 https://godbolt.org/z/csfGc6z6c A cast would work around this but that could have other implications I am not aware of (I've done little further investigation due to LPC): diff --git a/fs/buffer.c b/fs/buffer.c index 4eb44ccdc6be..d39934783743 100644 --- a/fs/buffer.c +++ b/fs/buffer.c @@ -1091,7 +1091,7 @@ static bool grow_buffers(struct block_device *bdev, sector_t block, * Check for a block which lies outside our maximum possible * pagecache index. */ - if (check_mul_overflow(block, size, &pos) || pos > MAX_LFS_FILESIZE) { + if (check_mul_overflow(block, (u64)size, &pos) || pos > MAX_LFS_FILESIZE) { printk(KERN_ERR "%s: requested out-of-range block %llu for device %pg\n", __func__, (unsigned long long)block, bdev); Cheers, Nathan
