Clang's version of -Wunused-but-set-variable recently gained support for unary operations, which reveals two unused variables:

fs/btrfs/block-group.c:2949:6: error: variable 'num_started' set but not used [-Werror,-Wunused-but-set-variable] int num_started = 0; ^ fs/btrfs/block-group.c:3116:6: error: variable 'num_started' set but not used [-Werror,-Wunused-but-set-variable] int num_started = 0; ^ 2 errors generated.

These variables appear to be unused from their introduction, so just remove them to silence the warnings.

Cc: stable@vger.kernel.org Fixes: c9dc4c657850 ("Btrfs: two stage dirty block group writeout") Fixes: 1bbc621ef284 ("Btrfs: allow block group cache writeout outside critical section in commit") Link: https://github.com/ClangBuiltLinux/linux/issues/1614 Signed-off-by: Nathan Chancellor nathan@kernel.org ---

I am requesting a stable backport because this is visible with allmodconfig, which enables CONFIG_WERROR, breaking the build.

To quote Linus:

"EVERYBODY should have CONFIG_WERROR=y on at least x86-64 and other serious architectures, unless you have some completely random experimental (and broken) compiler."

https://lore.kernel.org/r/CAHk-=wifoM9VOp-55OZCRcO9MnqQ109UTuCiXeZ-eyX_JcNVG...

fs/btrfs/block-group.c | 4 ---- 1 file changed, 4 deletions(-)

diff --git a/fs/btrfs/block-group.c b/fs/btrfs/block-group.c index c22d287e020b..9ad265066225 100644 --- a/fs/btrfs/block-group.c +++ b/fs/btrfs/block-group.c @@ -2946,7 +2946,6 @@ int btrfs_start_dirty_block_groups(struct btrfs_trans_handle *trans) struct btrfs_path *path = NULL; LIST_HEAD(dirty); struct list_head *io = &cur_trans->io_bgs; - int num_started = 0; int loops = 0;

spin_lock(&cur_trans->dirty_bgs_lock); @@ -3012,7 +3011,6 @@ int btrfs_start_dirty_block_groups(struct btrfs_trans_handle *trans) cache->io_ctl.inode = NULL; ret = btrfs_write_out_cache(trans, cache, path); if (ret == 0 && cache->io_ctl.inode) { - num_started++; should_put = 0;

/* @@ -3113,7 +3111,6 @@ int btrfs_write_dirty_block_groups(struct btrfs_trans_handle *trans) int should_put; struct btrfs_path *path; struct list_head *io = &cur_trans->io_bgs; - int num_started = 0;

path = btrfs_alloc_path(); if (!path) @@ -3171,7 +3168,6 @@ int btrfs_write_dirty_block_groups(struct btrfs_trans_handle *trans) cache->io_ctl.inode = NULL; ret = btrfs_write_out_cache(trans, cache, path); if (ret == 0 && cache->io_ctl.inode) { - num_started++; should_put = 0; list_add_tail(&cache->io_list, io); } else {

base-commit: d3e29967079c522ce1c5cab0e9fab2c280b977eb