Re: [PATCH btrfs/for-next] btrfs: fix fatal extent_buffer readahead vs releasepage race

[kernel test robot]

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-extent_buffer-readahead-vs-releasepage-race/20200618-002941
base:   https://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux.git for-next
config: x86_64-rhel (attached as .config)
compiler: gcc-9 (Debian 9.3.0-13) 9.3.0
reproduce (this is a W=1 build):
        # save the attached .config to linux build tree
        make W=1 ARCH=x86_64 

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

All error/warnings (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: type qualifiers ignored on function return type [-Wignored-qualifiers]
2216 | size_t __const btrfs_get_num_csums(void);
|        ^~~~~~~
fs/btrfs/extent_io.c: In function 'write_one_eb':
>> fs/btrfs/extent_io.c:3934:2: error: implicit declaration of function 'check_buffer_tree_ref' [-Werror=implicit-function-declaration]
3934 |  check_buffer_tree_ref(eb);
|  ^~~~~~~~~~~~~~~~~~~~~
fs/btrfs/extent_io.c: At top level:
>> fs/btrfs/extent_io.c:5091:13: warning: conflicting types for 'check_buffer_tree_ref'
5091 | static void check_buffer_tree_ref(struct extent_buffer *eb)
|             ^~~~~~~~~~~~~~~~~~~~~
>> fs/btrfs/extent_io.c:5091:13: error: static declaration of 'check_buffer_tree_ref' follows non-static declaration
fs/btrfs/extent_io.c:3934:2: note: previous implicit declaration of 'check_buffer_tree_ref' was here
3934 |  check_buffer_tree_ref(eb);
|  ^~~~~~~~~~~~~~~~~~~~~
cc1: some warnings being treated as errors

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		 */
> 3934		check_buffer_tree_ref(eb);
  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@xxxxxxxxxxxx

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