Re: [PATCH RFC v2 08/12] btrfs: switch buffered read to the new btrfs_read_repair_* based repair routine

[Qu Wenruo <wqu@suse.com>]

#syz test https://github.com/adam900710/linux read_repair

On 2022/4/28 18:08, kernel test robot wrote:
> Hi Qu,
> 
> [FYI, it's a private test report for your RFC patch.]
> [auto build test WARNING on kdave/for-next]
> [also build test WARNING on next-20220428]
> [cannot apply to rostedt-trace/for-next v5.18-rc4]
> [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]
> 
> url:    https://github.com/intel-lab-lkp/linux/commits/Qu-Wenruo/btrfs-introduce-a-pure-data-checksum-checking-helper/20220427-161943
> base:   https://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux.git for-next
> config: arm-randconfig-c002-20220428 (https://download.01.org/0day-ci/archive/20220428/202204281717.jzlTSpQj-lkp@intel.com/config)
> compiler: clang version 15.0.0 (https://github.com/llvm/llvm-project c59473aacce38cd7dd77eebceaf3c98c5707ab3b)
> 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 arm cross compiling tool for clang build
>          # apt-get install binutils-arm-linux-gnueabi
>          # https://github.com/intel-lab-lkp/linux/commit/3f389ea1be2d5c290c4b523743ca200983f45765
>          git remote add linux-review https://github.com/intel-lab-lkp/linux
>          git fetch --no-tags linux-review Qu-Wenruo/btrfs-introduce-a-pure-data-checksum-checking-helper/20220427-161943
>          git checkout 3f389ea1be2d5c290c4b523743ca200983f45765
>          # 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=arm SHELL=/bin/bash fs/btrfs/
> 
> If you fix the issue, kindly add following tag as appropriate
> Reported-by: kernel test robot <lkp@intel.com>
> 
> All warnings (new ones prefixed by >>):
> 
>>> fs/btrfs/extent_io.c:3076:6: warning: variable 'nbits' is used uninitialized whenever 'if' condition is true [-Wsometimes-uninitialized]
>             if (ctrl->error) {
>                 ^~~~~~~~~~~
>     fs/btrfs/extent_io.c:3098:46: note: uninitialized use occurs here
>             for_each_set_bit(bit, ctrl->cur_bad_bitmap, nbits) {
>                                                         ^~~~~
>     include/linux/find.h:284:16: note: expanded from macro 'for_each_set_bit'
>                  (bit) < (size);                                    \
>                           ^~~~
>     fs/btrfs/extent_io.c:3076:2: note: remove the 'if' if its condition is always false
>             if (ctrl->error) {
>             ^~~~~~~~~~~~~~~~~~
>     fs/btrfs/extent_io.c:3064:20: note: initialize the variable 'nbits' to silence this warning
>             unsigned int nbits;
>                               ^
>                                = 0
>     1 warning generated.
> 
> 
> vim +3076 fs/btrfs/extent_io.c
> 
>    3060	
>    3061	static void read_repair_finish(struct btrfs_read_repair_ctrl *ctrl)
>    3062	{
>    3063		struct btrfs_fs_info *fs_info;
>    3064		unsigned int nbits;
>    3065		u32 sectorsize;
>    3066		int bit;
>    3067		int i;
>    3068	
>    3069		if (!ctrl->initialized)
>    3070			return;
>    3071	
>    3072		/*
>    3073		 * Got a critical -ENOMEM error preivously, no repair should have been
>    3074		 * attempted.
>    3075		 */
>> 3076		if (ctrl->error) {
>    3077			ASSERT(bio_list_empty(&ctrl->bios));
>    3078			ASSERT(atomic_read(&ctrl->io_bytes) == 0);
>    3079			goto mark_error;
>    3080		}
>    3081	
>    3082		ASSERT(ctrl->inode);
>    3083		fs_info = btrfs_sb(ctrl->inode->i_sb);
>    3084		nbits = ctrl->bio_size >> fs_info->sectorsize_bits;
>    3085		sectorsize = fs_info->sectorsize;
>    3086	
>    3087		/* Go through each remaining mirrors to do the repair */
>    3088		for (i = get_next_mirror(ctrl->init_mirror, ctrl->num_copies);
>    3089		     i != ctrl->init_mirror; i = get_next_mirror(i, ctrl->num_copies)) {
>    3090			read_repair_from_one_mirror(ctrl, ctrl->inode, i);
>    3091	
>    3092			/* Check the error bitmap to see if no more corrupted sectors */
>    3093			if (bitmap_all_zero(ctrl->cur_bad_bitmap, nbits))
>    3094				break;
>    3095		}
>    3096	mark_error:
>    3097		/* Finish the unrecovered bad sectors */
>    3098		for_each_set_bit(bit, ctrl->cur_bad_bitmap, nbits) {
>    3099			struct page *page;
>    3100			unsigned int pgoff;
>    3101			u64 file_offset = (bit << fs_info->sectorsize_bits) +
>    3102					  ctrl->file_offset;
>    3103	
>    3104			page = read_repair_get_sector(ctrl, bit, &pgoff);
>    3105	
>    3106			end_page_read(page, false, file_offset, sectorsize);
>    3107			unlock_extent_cached_atomic(&BTRFS_I(ctrl->inode)->io_tree,
>    3108					file_offset, file_offset + sectorsize - 1, NULL);
>    3109		}
>    3110		kfree(ctrl->cur_bad_bitmap);
>    3111		kfree(ctrl->prev_bad_bitmap);
>    3112		ctrl->cur_bad_bitmap = NULL;
>    3113		ctrl->prev_bad_bitmap = NULL;
>    3114		ctrl->initialized = false;
>    3115		ctrl->error = false;
>    3116		ctrl->failed_bio = NULL;
>    3117		ASSERT(bio_list_empty(&ctrl->bios));
>    3118		ASSERT(atomic_read(&ctrl->io_bytes) == 0);
>    3119	}
>    3120	
>