Re: [PATCH 05/36] xfs: pass perag to xfs_alloc_read_agf()

kernel test robot
2021-12-03T07:20:04Z

Hi Dave,

Thank you for the patch! Perhaps something to improve:

[auto build test WARNING on xfs-linux/for-next]
[also build test WARNING on v5.16-rc3 next-20211202]
[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/0day-ci/linux/commits/Dave-Chinner/xfs-more-work-towards-shrinking/20211203-080331
base: https://git.kernel.org/pub/scm/fs/xfs/xfs-linux.git for-next
config: hexagon-randconfig-r036-20211203 (https://download.01.org/0day-ci/archive/20211203/202112031527.dpUjvB8h-lkp@intel.com/config)
compiler: clang version 14.0.0 (https://github.com/llvm/llvm-project 1e328b06c15273edf4a40a27ca24931b5efb3a87)
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/0day-ci/linux/commit/bf14ac7fff281f5586699613ea95b4671aa8a811
git remote add linux-review https://github.com/0day-ci/linux
git fetch --no-tags linux-review Dave-Chinner/xfs-more-work-towards-shrinking/20211203-080331
git checkout bf14ac7fff281f5586699613ea95b4671aa8a811
# save the config file to linux build tree
mkdir build_dir
COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=hexagon SHELL=/bin/bash fs/xfs/

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/xfs/xfs_reflink.c:129:1: warning: no previous prototype for function 'xfs_reflink_find_shared' [-Wmissing-prototypes]
xfs_reflink_find_shared(
^
fs/xfs/xfs_reflink.c:128:1: note: declare 'static' if the function is not intended to be used outside of this translation unit
int
^
static
fs/xfs/xfs_reflink.c:996:12: warning: variable 'qdelta' set but not used [-Wunused-but-set-variable]
int64_t qdelta = 0;
^
2 warnings generated.

vim +/xfs_reflink_find_shared +129 fs/xfs/xfs_reflink.c

3993baeb3c52f4 Darrick J. Wong 2016-10-03 32
3993baeb3c52f4 Darrick J. Wong 2016-10-03 33 /*
3993baeb3c52f4 Darrick J. Wong 2016-10-03 34 * Copy on Write of Shared Blocks
3993baeb3c52f4 Darrick J. Wong 2016-10-03 35 *
3993baeb3c52f4 Darrick J. Wong 2016-10-03 36 * XFS must preserve "the usual" file semantics even when two files share
3993baeb3c52f4 Darrick J. Wong 2016-10-03 37 * the same physical blocks. This means that a write to one file must not
3993baeb3c52f4 Darrick J. Wong 2016-10-03 38 * alter the blocks in a different file; the way that we'll do that is
3993baeb3c52f4 Darrick J. Wong 2016-10-03 39 * through the use of a copy-on-write mechanism. At a high level, that
3993baeb3c52f4 Darrick J. Wong 2016-10-03 40 * means that when we want to write to a shared block, we allocate a new
3993baeb3c52f4 Darrick J. Wong 2016-10-03 41 * block, write the data to the new block, and if that succeeds we map the
3993baeb3c52f4 Darrick J. Wong 2016-10-03 42 * new block into the file.
3993baeb3c52f4 Darrick J. Wong 2016-10-03 43 *
3993baeb3c52f4 Darrick J. Wong 2016-10-03 44 * XFS provides a "delayed allocation" mechanism that defers the allocation
3993baeb3c52f4 Darrick J. Wong 2016-10-03 45 * of disk blocks to dirty-but-not-yet-mapped file blocks as long as
3993baeb3c52f4 Darrick J. Wong 2016-10-03 46 * possible. This reduces fragmentation by enabling the filesystem to ask
3993baeb3c52f4 Darrick J. Wong 2016-10-03 47 * for bigger chunks less often, which is exactly what we want for CoW.
3993baeb3c52f4 Darrick J. Wong 2016-10-03 48 *
3993baeb3c52f4 Darrick J. Wong 2016-10-03 49 * The delalloc mechanism begins when the kernel wants to make a block
3993baeb3c52f4 Darrick J. Wong 2016-10-03 50 * writable (write_begin or page_mkwrite). If the offset is not mapped, we
3993baeb3c52f4 Darrick J. Wong 2016-10-03 51 * create a delalloc mapping, which is a regular in-core extent, but without
3993baeb3c52f4 Darrick J. Wong 2016-10-03 52 * a real startblock. (For delalloc mappings, the startblock encodes both
3993baeb3c52f4 Darrick J. Wong 2016-10-03 53 * a flag that this is a delalloc mapping, and a worst-case estimate of how
3993baeb3c52f4 Darrick J. Wong 2016-10-03 54 * many blocks might be required to put the mapping into the BMBT.) delalloc
3993baeb3c52f4 Darrick J. Wong 2016-10-03 55 * mappings are a reservation against the free space in the filesystem;
3993baeb3c52f4 Darrick J. Wong 2016-10-03 56 * adjacent mappings can also be combined into fewer larger mappings.
3993baeb3c52f4 Darrick J. Wong 2016-10-03 57 *
5eda43000064a6 Darrick J. Wong 2017-02-02 58 * As an optimization, the CoW extent size hint (cowextsz) creates
5eda43000064a6 Darrick J. Wong 2017-02-02 59 * outsized aligned delalloc reservations in the hope of landing out of
5eda43000064a6 Darrick J. Wong 2017-02-02 60 * order nearby CoW writes in a single extent on disk, thereby reducing
5eda43000064a6 Darrick J. Wong 2017-02-02 61 * fragmentation and improving future performance.
5eda43000064a6 Darrick J. Wong 2017-02-02 62 *
5eda43000064a6 Darrick J. Wong 2017-02-02 63 * D: --RRRRRRSSSRRRRRRRR--- (data fork)
5eda43000064a6 Darrick J. Wong 2017-02-02 64 * C: ------DDDDDDD--------- (CoW fork)
5eda43000064a6 Darrick J. Wong 2017-02-02 65 *
3993baeb3c52f4 Darrick J. Wong 2016-10-03 66 * When dirty pages are being written out (typically in writepage), the
5eda43000064a6 Darrick J. Wong 2017-02-02 67 * delalloc reservations are converted into unwritten mappings by
5eda43000064a6 Darrick J. Wong 2017-02-02 68 * allocating blocks and replacing the delalloc mapping with real ones.
5eda43000064a6 Darrick J. Wong 2017-02-02 69 * A delalloc mapping can be replaced by several unwritten ones if the
5eda43000064a6 Darrick J. Wong 2017-02-02 70 * free space is fragmented.
5eda43000064a6 Darrick J. Wong 2017-02-02 71 *
5eda43000064a6 Darrick J. Wong 2017-02-02 72 * D: --RRRRRRSSSRRRRRRRR---
5eda43000064a6 Darrick J. Wong 2017-02-02 73 * C: ------UUUUUUU---------
3993baeb3c52f4 Darrick J. Wong 2016-10-03 74 *
3993baeb3c52f4 Darrick J. Wong 2016-10-03 75 * We want to adapt the delalloc mechanism for copy-on-write, since the
3993baeb3c52f4 Darrick J. Wong 2016-10-03 76 * write paths are similar. The first two steps (creating the reservation
3993baeb3c52f4 Darrick J. Wong 2016-10-03 77 * and allocating the blocks) are exactly the same as delalloc except that
3993baeb3c52f4 Darrick J. Wong 2016-10-03 78 * the mappings must be stored in a separate CoW fork because we do not want
3993baeb3c52f4 Darrick J. Wong 2016-10-03 79 * to disturb the mapping in the data fork until we're sure that the write
3993baeb3c52f4 Darrick J. Wong 2016-10-03 80 * succeeded. IO completion in this case is the process of removing the old
3993baeb3c52f4 Darrick J. Wong 2016-10-03 81 * mapping from the data fork and moving the new mapping from the CoW fork to
3993baeb3c52f4 Darrick J. Wong 2016-10-03 82 * the data fork. This will be discussed shortly.
3993baeb3c52f4 Darrick J. Wong 2016-10-03 83 *
3993baeb3c52f4 Darrick J. Wong 2016-10-03 84 * For now, unaligned directio writes will be bounced back to the page cache.
3993baeb3c52f4 Darrick J. Wong 2016-10-03 85 * Block-aligned directio writes will use the same mechanism as buffered
3993baeb3c52f4 Darrick J. Wong 2016-10-03 86 * writes.
3993baeb3c52f4 Darrick J. Wong 2016-10-03 87 *
5eda43000064a6 Darrick J. Wong 2017-02-02 88 * Just prior to submitting the actual disk write requests, we convert
5eda43000064a6 Darrick J. Wong 2017-02-02 89 * the extents representing the range of the file actually being written
5eda43000064a6 Darrick J. Wong 2017-02-02 90 * (as opposed to extra pieces created for the cowextsize hint) to real
5eda43000064a6 Darrick J. Wong 2017-02-02 91 * extents. This will become important in the next step:
5eda43000064a6 Darrick J. Wong 2017-02-02 92 *
5eda43000064a6 Darrick J. Wong 2017-02-02 93 * D: --RRRRRRSSSRRRRRRRR---
5eda43000064a6 Darrick J. Wong 2017-02-02 94 * C: ------UUrrUUU---------
5eda43000064a6 Darrick J. Wong 2017-02-02 95 *
3993baeb3c52f4 Darrick J. Wong 2016-10-03 96 * CoW remapping must be done after the data block write completes,
3993baeb3c52f4 Darrick J. Wong 2016-10-03 97 * because we don't want to destroy the old data fork map until we're sure
3993baeb3c52f4 Darrick J. Wong 2016-10-03 98 * the new block has been written. Since the new mappings are kept in a
3993baeb3c52f4 Darrick J. Wong 2016-10-03 99 * separate fork, we can simply iterate these mappings to find the ones
3993baeb3c52f4 Darrick J. Wong 2016-10-03 100 * that cover the file blocks that we just CoW'd. For each extent, simply
3993baeb3c52f4 Darrick J. Wong 2016-10-03 101 * unmap the corresponding range in the data fork, map the new range into
5eda43000064a6 Darrick J. Wong 2017-02-02 102 * the data fork, and remove the extent from the CoW fork. Because of
5eda43000064a6 Darrick J. Wong 2017-02-02 103 * the presence of the cowextsize hint, however, we must be careful
5eda43000064a6 Darrick J. Wong 2017-02-02 104 * only to remap the blocks that we've actually written out -- we must
5eda43000064a6 Darrick J. Wong 2017-02-02 105 * never remap delalloc reservations nor CoW staging blocks that have
5eda43000064a6 Darrick J. Wong 2017-02-02 106 * yet to be written. This corresponds exactly to the real extents in
5eda43000064a6 Darrick J. Wong 2017-02-02 107 * the CoW fork:
5eda43000064a6 Darrick J. Wong 2017-02-02 108 *
5eda43000064a6 Darrick J. Wong 2017-02-02 109 * D: --RRRRRRrrSRRRRRRRR---
5eda43000064a6 Darrick J. Wong 2017-02-02 110 * C: ------UU--UUU---------
3993baeb3c52f4 Darrick J. Wong 2016-10-03 111 *
3993baeb3c52f4 Darrick J. Wong 2016-10-03 112 * Since the remapping operation can be applied to an arbitrary file
3993baeb3c52f4 Darrick J. Wong 2016-10-03 113 * range, we record the need for the remap step as a flag in the ioend
3993baeb3c52f4 Darrick J. Wong 2016-10-03 114 * instead of declaring a new IO type. This is required for direct io
3993baeb3c52f4 Darrick J. Wong 2016-10-03 115 * because we only have ioend for the whole dio, and we have to be able to
3993baeb3c52f4 Darrick J. Wong 2016-10-03 116 * remember the presence of unwritten blocks and CoW blocks with a single
3993baeb3c52f4 Darrick J. Wong 2016-10-03 117 * ioend structure. Better yet, the more ground we can cover with one
3993baeb3c52f4 Darrick J. Wong 2016-10-03 118 * ioend, the better.
3993baeb3c52f4 Darrick J. Wong 2016-10-03 119 */
2a06705cd59540 Darrick J. Wong 2016-10-03 120
2a06705cd59540 Darrick J. Wong 2016-10-03 121 /*
2a06705cd59540 Darrick J. Wong 2016-10-03 122 * Given an AG extent, find the lowest-numbered run of shared blocks
2a06705cd59540 Darrick J. Wong 2016-10-03 123 * within that range and return the range in fbno/flen. If
2a06705cd59540 Darrick J. Wong 2016-10-03 124 * find_end_of_shared is true, return the longest contiguous extent of
2a06705cd59540 Darrick J. Wong 2016-10-03 125 * shared blocks. If there are no shared extents, fbno and flen will
2a06705cd59540 Darrick J. Wong 2016-10-03 126 * be set to NULLAGBLOCK and 0, respectively.
2a06705cd59540 Darrick J. Wong 2016-10-03 127 */
2a06705cd59540 Darrick J. Wong 2016-10-03 128 int
2a06705cd59540 Darrick J. Wong 2016-10-03 @129 xfs_reflink_find_shared(
bf14ac7fff281f Dave Chinner 2021-12-03 130 struct xfs_perag *pag,
92ff7285f1df55 Darrick J. Wong 2017-06-16 131 struct xfs_trans *tp,
2a06705cd59540 Darrick J. Wong 2016-10-03 132 xfs_agblock_t agbno,
2a06705cd59540 Darrick J. Wong 2016-10-03 133 xfs_extlen_t aglen,
2a06705cd59540 Darrick J. Wong 2016-10-03 134 xfs_agblock_t *fbno,
2a06705cd59540 Darrick J. Wong 2016-10-03 135 xfs_extlen_t *flen,
2a06705cd59540 Darrick J. Wong 2016-10-03 136 bool find_end_of_shared)
2a06705cd59540 Darrick J. Wong 2016-10-03 137 {
2a06705cd59540 Darrick J. Wong 2016-10-03 138 struct xfs_buf *agbp;
2a06705cd59540 Darrick J. Wong 2016-10-03 139 struct xfs_btree_cur *cur;
2a06705cd59540 Darrick J. Wong 2016-10-03 140 int error;
2a06705cd59540 Darrick J. Wong 2016-10-03 141
bf14ac7fff281f Dave Chinner 2021-12-03 142 error = xfs_alloc_read_agf(pag, tp, 0, &agbp);
2a06705cd59540 Darrick J. Wong 2016-10-03 143 if (error)
2a06705cd59540 Darrick J. Wong 2016-10-03 144 return error;
2a06705cd59540 Darrick J. Wong 2016-10-03 145
bf14ac7fff281f Dave Chinner 2021-12-03 146 cur = xfs_refcountbt_init_cursor(pag->pag_mount, tp, agbp, pag);
2a06705cd59540 Darrick J. Wong 2016-10-03 147
2a06705cd59540 Darrick J. Wong 2016-10-03 148 error = xfs_refcount_find_shared(cur, agbno, aglen, fbno, flen,
2a06705cd59540 Darrick J. Wong 2016-10-03 149 find_end_of_shared);
2a06705cd59540 Darrick J. Wong 2016-10-03 150
0b04b6b875b32f Darrick J. Wong 2018-07-19 151 xfs_btree_del_cursor(cur, error);
2a06705cd59540 Darrick J. Wong 2016-10-03 152
92ff7285f1df55 Darrick J. Wong 2017-06-16 153 xfs_trans_brelse(tp, agbp);
2a06705cd59540 Darrick J. Wong 2016-10-03 154 return error;
2a06705cd59540 Darrick J. Wong 2016-10-03 155 }
2a06705cd59540 Darrick J. Wong 2016-10-03 156

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