* Re: [PATCH 2/2] btrfs: fix memory barrier order in reloc_root_is_dead()
2026-06-12 19:13 ` [PATCH 2/2] btrfs: fix memory barrier order in reloc_root_is_dead() kernel test robot
@ 2026-06-12 19:24 ` Filipe Manana
0 siblings, 0 replies; 2+ messages in thread
From: Filipe Manana @ 2026-06-12 19:24 UTC (permalink / raw)
To: kernel test robot; +Cc: linux-btrfs, llvm, oe-kbuild-all
On Fri, Jun 12, 2026 at 8:13 PM kernel test robot <lkp@intel.com> wrote:
>
> Hi Filipe,
>
> kernel test robot noticed the following build errors:
>
> [auto build test ERROR on kdave/for-next]
> [also build test ERROR on linus/master v7.1-rc7 next-20260611]
> [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/fdmanana-kernel-org/btrfs-fix-reloc-root-cleanup-in-merge_reloc_roots/20260612-202603
> base: https://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux.git for-next
> patch link: https://lore.kernel.org/r/62602395bf1488aa81645ea59e22405d6c06d3f7.1781263239.git.fdmanana%40suse.com
> patch subject: [PATCH 2/2] btrfs: fix memory barrier order in reloc_root_is_dead()
> config: x86_64-kexec (https://download.01.org/0day-ci/archive/20260612/202606122155.6ncF2GHC-lkp@intel.com/config)
> compiler: clang version 22.0.0git (https://github.com/llvm/llvm-project f43d6834093b19baf79beda8c0337ab020ac5f17)
> reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260612/202606122155.6ncF2GHC-lkp@intel.com/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@intel.com>
> | Closes: https://lore.kernel.org/oe-kbuild-all/202606122155.6ncF2GHC-lkp@intel.com/
>
> All errors (new ones prefixed by >>):
>
> >> fs/btrfs/relocation.c:1928:6: error: call to undeclared function 'clear_reloc_root'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
> 1928 | clear_reloc_root(root);
> | ^
> fs/btrfs/relocation.c:1928:6: note: did you mean 'create_reloc_root'?
> fs/btrfs/relocation.c:631:27: note: 'create_reloc_root' declared here
> 631 | static struct btrfs_root *create_reloc_root(struct btrfs_trans_handle *trans,
> | ^
> 1 error generated.
This is because it depends on a patch that is in the giithub for-next
branch but not yet in Linus' tree or linux-next:
https://lore.kernel.org/linux-btrfs/cf84f1a217c719e25b6b69e4298dd7afd36c9427.1781194426.git.fdmanana@suse.com/
https://github.com/btrfs/linux/commits/for-next/
>
>
> vim +/clear_reloc_root +1928 fs/btrfs/relocation.c
>
> 1867
> 1868 static noinline_for_stack
> 1869 void merge_reloc_roots(struct reloc_control *rc)
> 1870 {
> 1871 struct btrfs_fs_info *fs_info = rc->extent_root->fs_info;
> 1872 struct btrfs_root *root;
> 1873 struct btrfs_root *reloc_root;
> 1874 LIST_HEAD(reloc_roots);
> 1875 bool found = false;
> 1876 int ret = 0;
> 1877 again:
> 1878 root = rc->extent_root;
> 1879
> 1880 /*
> 1881 * this serializes us with btrfs_record_root_in_transaction,
> 1882 * we have to make sure nobody is in the middle of
> 1883 * adding their roots to the list while we are
> 1884 * doing this splice
> 1885 */
> 1886 mutex_lock(&fs_info->reloc_mutex);
> 1887 list_splice_init(&rc->reloc_roots, &reloc_roots);
> 1888 mutex_unlock(&fs_info->reloc_mutex);
> 1889
> 1890 while (!list_empty(&reloc_roots)) {
> 1891 found = true;
> 1892 reloc_root = list_first_entry(&reloc_roots, struct btrfs_root, root_list);
> 1893
> 1894 root = btrfs_get_fs_root(fs_info, reloc_root->root_key.offset,
> 1895 false);
> 1896 if (btrfs_root_refs(&reloc_root->root_item) > 0) {
> 1897 if (WARN_ON(IS_ERR(root))) {
> 1898 /*
> 1899 * For recovery we read the fs roots on mount,
> 1900 * and if we didn't find the root then we marked
> 1901 * the reloc root as a garbage root. For normal
> 1902 * relocation obviously the root should exist in
> 1903 * memory. However there's no reason we can't
> 1904 * handle the error properly here just in case.
> 1905 */
> 1906 ret = PTR_ERR(root);
> 1907 goto out;
> 1908 }
> 1909 if (WARN_ON(root->reloc_root != reloc_root)) {
> 1910 /*
> 1911 * This can happen if on-disk metadata has some
> 1912 * corruption, e.g. bad reloc tree key offset.
> 1913 */
> 1914 ret = -EINVAL;
> 1915 goto out;
> 1916 }
> 1917 ret = merge_reloc_root(rc, root);
> 1918 btrfs_put_root(root);
> 1919 if (ret) {
> 1920 if (list_empty(&reloc_root->root_list))
> 1921 list_add_tail(&reloc_root->root_list,
> 1922 &reloc_roots);
> 1923 goto out;
> 1924 }
> 1925 } else {
> 1926 if (!IS_ERR(root)) {
> 1927 if (root->reloc_root == reloc_root) {
> > 1928 clear_reloc_root(root);
> 1929 /* Drop the ref for root->reloc_root. */
> 1930 btrfs_put_root(reloc_root);
> 1931 }
> 1932 btrfs_put_root(root);
> 1933 }
> 1934
> 1935 list_del_init(&reloc_root->root_list);
> 1936 /* Don't forget to queue this reloc root for cleanup */
> 1937 list_add_tail(&reloc_root->reloc_dirty_list,
> 1938 &rc->dirty_subvol_roots);
> 1939 }
> 1940 }
> 1941
> 1942 if (found) {
> 1943 found = false;
> 1944 goto again;
> 1945 }
> 1946 out:
> 1947 if (ret) {
> 1948 btrfs_handle_fs_error(fs_info, ret, NULL);
> 1949 free_reloc_roots(&reloc_roots);
> 1950
> 1951 /* new reloc root may be added */
> 1952 mutex_lock(&fs_info->reloc_mutex);
> 1953 list_splice_init(&rc->reloc_roots, &reloc_roots);
> 1954 mutex_unlock(&fs_info->reloc_mutex);
> 1955 free_reloc_roots(&reloc_roots);
> 1956 }
> 1957
> 1958 /*
> 1959 * We used to have
> 1960 *
> 1961 * BUG_ON(!RB_EMPTY_ROOT(&rc->reloc_root_tree.rb_root));
> 1962 *
> 1963 * here, but it's wrong. If we fail to start the transaction in
> 1964 * prepare_to_merge() we will have only 0 ref reloc roots, none of which
> 1965 * have actually been removed from the reloc_root_tree rb tree. This is
> 1966 * fine because we're bailing here, and we hold a reference on the root
> 1967 * for the list that holds it, so these roots will be cleaned up when we
> 1968 * do the reloc_dirty_list afterwards. Meanwhile the root->reloc_root
> 1969 * will be cleaned up on unmount.
> 1970 *
> 1971 * The remaining nodes will be cleaned up by put_reloc_control().
> 1972 */
> 1973 }
> 1974
>
> --
> 0-DAY CI Kernel Test Service
> https://github.com/intel/lkp-tests/wiki
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