Re: [PATCH v2 2/3] btrfs: unit tests for pending extent walking functions

[kernel test robot <lkp@intel.com>]

Hi Boris,

kernel test robot noticed the following build warnings:

[auto build test WARNING on kdave/for-next]
[also build test WARNING on linus/master v6.19-rc6 next-20260123]
[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/Boris-Burkov/btrfs-fix-EEXIST-abort-due-to-non-consecutive-gaps-in-chunk-allocation/20260125-054609
base:   https://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux.git for-next
patch link:    https://lore.kernel.org/r/efc4b5a3fbcbc7473afc228badd3e1306298bf33.1769290938.git.boris%40bur.io
patch subject: [PATCH v2 2/3] btrfs: unit tests for pending extent walking functions
config: i386-allnoconfig-bpf (https://download.01.org/0day-ci/archive/20260125/202601251610.dH67mNZI-lkp@intel.com/config)
compiler: clang version 20.1.8 (https://github.com/llvm/llvm-project 87f0227cb60147a26a1eeb4fb06e3b505e9c7261)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260125/202601251610.dH67mNZI-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/202601251610.dH67mNZI-lkp@intel.com/

All warnings (new ones prefixed by >>):

>> fs/btrfs/volumes.c:1529:6: warning: no previous prototype for function 'btrfs_first_pending_extent' [-Wmissing-prototypes]
    1529 | bool btrfs_first_pending_extent(struct btrfs_device *device, u64 start, u64 len,
         |      ^
   fs/btrfs/volumes.c:1529:1: note: declare 'static' if the function is not intended to be used outside of this translation unit
    1529 | bool btrfs_first_pending_extent(struct btrfs_device *device, u64 start, u64 len,
         | ^
         | static 
>> fs/btrfs/volumes.c:1570:6: warning: no previous prototype for function 'btrfs_find_hole_in_pending_extents' [-Wmissing-prototypes]
    1570 | bool btrfs_find_hole_in_pending_extents(struct btrfs_device *device, u64 *start, u64 *len,
         |      ^
   fs/btrfs/volumes.c:1570:1: note: declare 'static' if the function is not intended to be used outside of this translation unit
    1570 | bool btrfs_find_hole_in_pending_extents(struct btrfs_device *device, u64 *start, u64 *len,
         | ^
         | static 
   2 warnings generated.


vim +/btrfs_first_pending_extent +1529 fs/btrfs/volumes.c

  1510	
  1511	/*
  1512	 * Find the first pending extent intersecting a range.
  1513	 *
  1514	 * @device: the device to search
  1515	 * @start: start of the range to check
  1516	 * @len: length of the range to check
  1517	 * @pending_start: output pointer for the start of the found pending extent
  1518	 * @pending_end: output pointer for the end of the found pending extent (inclusive)
  1519	 *
  1520	 * Search for a pending chunk allocation that intersects the half-open range
  1521	 * [start, start + len).
  1522	 *
  1523	 * Return: true if a pending extent was found, false otherwise.
  1524	 * If the return value is true, store the first pending extent in
  1525	 * [*pending_start, *pending_end]. Otherwise, the two output variables
  1526	 * may still be modified, to something outside the range and should not
  1527	 * be used.
  1528	 */
> 1529	bool btrfs_first_pending_extent(struct btrfs_device *device, u64 start, u64 len,
  1530					u64 *pending_start, u64 *pending_end)
  1531	{
  1532		lockdep_assert_held(&device->fs_info->chunk_mutex);
  1533	
  1534		if (btrfs_find_first_extent_bit(&device->alloc_state, start,
  1535						pending_start, pending_end,
  1536						CHUNK_ALLOCATED, NULL)) {
  1537	
  1538			if (in_range(*pending_start, start, len) ||
  1539			    in_range(start, *pending_start,
  1540				     *pending_end + 1 - *pending_start)) {
  1541				return true;
  1542			}
  1543		}
  1544		return false;
  1545	}
  1546	
  1547	/*
  1548	 * Find the first real hole accounting for pending extents.
  1549	 *
  1550	 * @device: the device containing the candidate hole
  1551	 * @start: input/output pointer for the hole start position
  1552	 * @len: input/output pointer for the hole length
  1553	 * @min_hole_size: the size of hole we are looking for
  1554	 *
  1555	 * Given a potential hole specified by [*start, *start + *len), check for pending
  1556	 * chunk allocations within that range. If pending extents are found, the hole is
  1557	 * adjusted to represent the first true free space that is large enough when
  1558	 * accounting for pending chunks.
  1559	 *
  1560	 * Note that this function must handle various cases involving non
  1561	 * consecutive pending extents.
  1562	 *
  1563	 * Returns: true if a suitable hole was found and false otherwise.
  1564	 * If the return value is true, then *start and *len are set to represent the hole.
  1565	 * If the return value is false, then *start is set to the largest hole we
  1566	 * found and *len is set to its length.
  1567	 * If there are no holes at all, then *start is set to the end of the range and
  1568	 * *len is set to 0.
  1569	 */
> 1570	bool btrfs_find_hole_in_pending_extents(struct btrfs_device *device, u64 *start, u64 *len,
  1571						u64 min_hole_size)
  1572	{
  1573		u64 pending_start, pending_end;
  1574		u64 end;
  1575		u64 max_hole_start = 0;
  1576		u64 max_hole_len = 0;
  1577	
  1578		lockdep_assert_held(&device->fs_info->chunk_mutex);
  1579	
  1580		if (*len == 0)
  1581			return false;
  1582	
  1583		end = *start + *len - 1;
  1584	
  1585		/*
  1586		 * Loop until we either see a large enough hole or check every pending
  1587		 * extent overlapping the candidate hole.
  1588		 * At every hole that we observe, record it if it is the new max.
  1589		 * At the end of the iteration, set the output variables to the max hole.
  1590		 */
  1591		while (true) {
  1592			if (btrfs_first_pending_extent(device, *start, *len, &pending_start, &pending_end)) {
  1593				/*
  1594				 * Case 1: the pending extent overlaps the start of
  1595				 * candidate hole. That means the true hole is after the
  1596				 * pending extent, but we need to find the next pending
  1597				 * extent to properly size the hole. In the next loop,
  1598				 * we will reduce to case 2 or 3.
  1599				 * e.g.,
  1600				 *   |----pending A----|    real hole     |----pending B----|
  1601				 *            |           candidate hole        |
  1602				 *         *start                              end
  1603				 */
  1604				if (pending_start <= *start) {
  1605					*start = pending_end + 1;
  1606					goto next;
  1607				}
  1608				/*
  1609				 * Case 2: The pending extent starts after *start (and overlaps
  1610				 * [*start, end), so the first hole just goes up to the start
  1611				 * of the pending extent.
  1612				 * e.g.,
  1613				 *   |    real hole    |----pending A----|
  1614				 *   |       candidate hole     |
  1615				 * *start                      end
  1616				 *
  1617				 */
  1618				*len = pending_start - *start;
  1619				if (*len > max_hole_len) {
  1620					max_hole_start = *start;
  1621					max_hole_len = *len;
  1622				}
  1623				if (*len >= min_hole_size)
  1624					break;
  1625				/*
  1626				 * If the hole wasn't big enough, then we advance past
  1627				 * the pending extent and keep looking.
  1628				 */
  1629				*start = pending_end + 1;
  1630				goto next;
  1631			} else {
  1632				/*
  1633				 * Case 3: There is no pending extent overlapping the
  1634				 * range [*start, *start + *len - 1], so the only remaining
  1635				 * hole is the remaining range.
  1636				 * e.g.,
  1637				 *   |       candidate hole           |
  1638				 *   |          real hole             |
  1639				 * *start                            end
  1640				 */
  1641	
  1642				if (*len > max_hole_len) {
  1643					max_hole_start = *start;
  1644					max_hole_len = *len;
  1645				}
  1646				break;
  1647			}
  1648	next:
  1649			if (*start > end)
  1650				break;
  1651			*len = end - *start + 1;
  1652		}
  1653		if (max_hole_len) {
  1654			*start = max_hole_start;
  1655			*len = max_hole_len;
  1656		} else {
  1657			*start = end + 1;
  1658			*len = 0;
  1659		}
  1660		return max_hole_len >= min_hole_size;
  1661	}
  1662	

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