Hi Boris, Thank you for the patch! Yet something to improve: [auto build test ERROR on kdave/for-next] [also build test ERROR on v5.8-rc1 next-20200617] [if your patch is applied to the wrong git tree, please drop us a note to help improve the system. BTW, we also suggest to use '--base' option to specify the base tree in git format-patch, please see https://stackoverflow.com/a/37406982] url: https://github.com/0day-ci/linux/commits/Boris-Burkov/btrfs-fix-fatal-ext... base: https://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux.git for-next config: x86_64-allyesconfig (attached as .config) compiler: clang version 11.0.0 (https://github.com/llvm/llvm-project 487ca07fcc75d52755c9fe2ee05bcb3b6eeeec44) reproduce (this is a W=1 build): wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross chmod +x ~/bin/make.cross # install x86_64 cross compiling tool for clang build # apt-get install binutils-x86-64-linux-gnu # save the attached .config to linux build tree COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross ARCH=x86_64 If you fix the issue, kindly add following tag as appropriate Reported-by: kernel test robot <lkp(a)intel.com&gt; All errors (new ones prefixed by >>, old ones prefixed by <<): In file included from fs/btrfs/extent_io.c:19: fs/btrfs/ctree.h:2216:8: warning: 'const' type qualifier on return type has no effect [-Wignored-qualifiers] size_t __const btrfs_get_num_csums(void); ^~~~~~~~ check_buffer_tree_ref(eb); ^ static void check_buffer_tree_ref(struct extent_buffer *eb) ^ fs/btrfs/extent_io.c:3934:2: note: previous implicit declaration is here check_buffer_tree_ref(eb); ^ 1 warning and 2 errors generated. vim +/check_buffer_tree_ref +3934 fs/btrfs/extent_io.c 3915 3916 static noinline_for_stack int write_one_eb(struct extent_buffer *eb, 3917 struct writeback_control *wbc, 3918 struct extent_page_data *epd) 3919 { 3920 u64 offset = eb->start; 3921 u32 nritems; 3922 int i, num_pages; 3923 unsigned long start, end; 3924 unsigned int write_flags = wbc_to_write_flags(wbc) | REQ_META; 3925 int ret = 0; 3926 3927 clear_bit(EXTENT_BUFFER_WRITE_ERR, &eb->bflags); 3928 num_pages = num_extent_pages(eb); 3929 atomic_set(&eb->io_pages, num_pages); 3930 /* 3931 * It is possible for releasepage to clear the TREE_REF bit before we 3932 * set io_pages. See check_buffer_tree_ref for a more detailed comment. 3933 */ 3935 3936 /* set btree blocks beyond nritems with 0 to avoid stale content. */ 3937 nritems = btrfs_header_nritems(eb); 3938 if (btrfs_header_level(eb) > 0) { 3939 end = btrfs_node_key_ptr_offset(nritems); 3940 3941 memzero_extent_buffer(eb, end, eb->len - end); 3942 } else { 3943 /* 3944 * leaf: 3945 * header 0 1 2 .. N ... data_N .. data_2 data_1 data_0 3946 */ 3947 start = btrfs_item_nr_offset(nritems); 3948 end = BTRFS_LEAF_DATA_OFFSET + leaf_data_end(eb); 3949 memzero_extent_buffer(eb, start, end - start); 3950 } 3951 3952 for (i = 0; i < num_pages; i++) { 3953 struct page *p = eb->pages[i]; 3954 3955 clear_page_dirty_for_io(p); 3956 set_page_writeback(p); 3957 ret = submit_extent_page(REQ_OP_WRITE | write_flags, wbc, 3958 p, offset, PAGE_SIZE, 0, 3959 &epd->bio, 3960 end_bio_extent_buffer_writepage, 3961 0, 0, 0, false); 3962 if (ret) { 3963 set_btree_ioerr(p); 3964 if (PageWriteback(p)) 3965 end_page_writeback(p); 3966 if (atomic_sub_and_test(num_pages - i, &eb->io_pages)) 3967 end_extent_buffer_writeback(eb); 3968 ret = -EIO; 3969 break; 3970 } 3971 offset += PAGE_SIZE; 3972 update_nr_written(wbc, 1); 3973 unlock_page(p); 3974 } 3975 3976 if (unlikely(ret)) { 3977 for (; i < num_pages; i++) { 3978 struct page *p = eb->pages[i]; 3979 clear_page_dirty_for_io(p); 3980 unlock_page(p); 3981 } 3982 } 3983 3984 return ret; 3985 } 3986 --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org