linux-kernel - [ammarfaizi2-block:dhowells/linux-fs/netfs-maple 37/44] fs/netfs/buffered_write.c:757:6: warning: variable 'spare_region' is used uninitialized whenever 'if' condition is true

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Date:   Sat, 23 Apr 2022 07:53:00 +0800
From:   kernel test robot <lkp@...el.com>
To:     David Howells <dhowells@...hat.com>
Cc:     llvm@...ts.linux.dev, kbuild-all@...ts.01.org,
        GNU/Weeb Mailing List <gwml@...r.gnuweeb.org>,
        linux-kernel@...r.kernel.org
Subject: [ammarfaizi2-block:dhowells/linux-fs/netfs-maple 37/44]
 fs/netfs/buffered_write.c:757:6: warning: variable 'spare_region' is used
 uninitialized whenever 'if' condition is true

tree:   https://github.com/ammarfaizi2/linux-block dhowells/linux-fs/netfs-maple
head:   931e50676c6598d0eda1954ead465519ff91874d
commit: 289cadcc7f9a897a36b3cba0e12083ce36182827 [37/44] netfs: Allow buffered shared-writeable mmap through netfs_page_mkwrite()
config: x86_64-randconfig-a016 (https://download.01.org/0day-ci/archive/20220423/202204230756.Ep4wbrdW-lkp@intel.com/config)
compiler: clang version 15.0.0 (https://github.com/llvm/llvm-project 5bd87350a5ae429baf8f373cb226a57b62f87280)
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
        # https://github.com/ammarfaizi2/linux-block/commit/289cadcc7f9a897a36b3cba0e12083ce36182827
        git remote add ammarfaizi2-block https://github.com/ammarfaizi2/linux-block
        git fetch --no-tags ammarfaizi2-block dhowells/linux-fs/netfs-maple
        git checkout 289cadcc7f9a897a36b3cba0e12083ce36182827
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=x86_64 SHELL=/bin/bash fs/netfs/

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@...el.com>

All warnings (new ones prefixed by >>):

>> fs/netfs/buffered_write.c:757:6: warning: variable 'spare_region' is used uninitialized whenever 'if' condition is true [-Wsometimes-uninitialized]
           if (mas_expected_entries(&mas, 2) < 0) {
               ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   fs/netfs/buffered_write.c:793:30: note: uninitialized use occurs here
           netfs_put_dirty_region(ctx, spare_region, netfs_region_trace_put_discard);
                                       ^~~~~~~~~~~~
   fs/netfs/buffered_write.c:757:2: note: remove the 'if' if its condition is always false
           if (mas_expected_entries(&mas, 2) < 0) {
           ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   fs/netfs/buffered_write.c:754:6: warning: variable 'spare_region' is used uninitialized whenever 'if' condition is true [-Wsometimes-uninitialized]
           if (folio_lock_killable(folio) < 0)
               ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   fs/netfs/buffered_write.c:793:30: note: uninitialized use occurs here
           netfs_put_dirty_region(ctx, spare_region, netfs_region_trace_put_discard);
                                       ^~~~~~~~~~~~
   fs/netfs/buffered_write.c:754:2: note: remove the 'if' if its condition is always false
           if (folio_lock_killable(folio) < 0)
           ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   fs/netfs/buffered_write.c:751:6: warning: variable 'spare_region' is used uninitialized whenever 'if' condition is true [-Wsometimes-uninitialized]
           if (folio_wait_writeback_killable(folio))
               ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   fs/netfs/buffered_write.c:793:30: note: uninitialized use occurs here
           netfs_put_dirty_region(ctx, spare_region, netfs_region_trace_put_discard);
                                       ^~~~~~~~~~~~
   fs/netfs/buffered_write.c:751:2: note: remove the 'if' if its condition is always false
           if (folio_wait_writeback_killable(folio))
           ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   fs/netfs/buffered_write.c:734:41: note: initialize the variable 'spare_region' to silence this warning
           struct netfs_dirty_region *spare_region;
                                                  ^
                                                   = NULL
   3 warnings generated.


vim +757 fs/netfs/buffered_write.c

   727	
   728	/*
   729	 * Notification that a previously read-only page is about to become writable.
   730	 * Note that the caller indicates a single page of a multipage folio.
   731	 */
   732	vm_fault_t netfs_page_mkwrite(struct vm_fault *vmf)
   733	{
   734		struct netfs_dirty_region *spare_region;
   735		struct folio *folio = page_folio(vmf->page);
   736		struct file *file = vmf->vma->vm_file;
   737		struct inode *inode = file_inode(file);
   738		struct netfs_i_context *ctx = netfs_i_context(inode);
   739		vm_fault_t ret = VM_FAULT_RETRY;
   740		int err;
   741	
   742		MA_STATE(mas, &ctx->dirty_regions, vmf->page->index, PAGE_SIZE);
   743	
   744		_enter("%lx", folio->index);
   745	
   746		if (ctx->ops->validate_for_write(inode, file) < 0)
   747			return VM_FAULT_SIGBUS;
   748	
   749		sb_start_pagefault(inode->i_sb);
   750	
   751		if (folio_wait_writeback_killable(folio))
   752			goto out;
   753	
   754		if (folio_lock_killable(folio) < 0)
   755			goto out;
   756	
 > 757		if (mas_expected_entries(&mas, 2) < 0) {

-- 
0-DAY CI Kernel Test Service
https://01.org/lkp