Re: [kbuild] [djwong-xfs:djwong-wtf 349/351] fs/xfs/xfs_bmap_util.c:1372 xfs_map_free_extent() warn: missing error code 'error'

From: Darrick J. Wong
Date: Mon Mar 21 2022 - 18:46:22 EST

On Mon, Mar 21, 2022 at 10:33:02AM +0300, Dan Carpenter wrote:
> tree: https://git.kernel.org/pub/scm/linux/kernel/git/djwong/xfs-linux.git djwong-wtf
> head: baa8d54bb35559f0bc36ec9e9933bec9ab23e25f
> commit: b82670045aab66d3d66eca40f277354c3da07f1c [349/351] xfs: fallocate free space into a file
> config: openrisc-randconfig-m031-20220317 (https://download.01.org/0day-ci/archive/20220319/202203190831.AYu7l0vX-lkp@xxxxxxxxx/config )
> compiler: or1k-linux-gcc (GCC) 11.2.0
>
> If you fix the issue, kindly add following tag as appropriate
> Reported-by: kernel test robot <lkp@xxxxxxxxx>
> Reported-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
>
> New smatch warnings:
> fs/xfs/xfs_bmap_util.c:1372 xfs_map_free_extent() warn: missing error code 'error'
>
> Old smatch warnings:
> fs/xfs/xfs_buf.h:430 xfs_buftarg_zeroout() warn: bitwise AND condition is false here
>
> vim +/error +1372 fs/xfs/xfs_bmap_util.c
>
> b82670045aab66 Darrick J. Wong 2022-01-06 1341 /* Find a free extent in this AG and map it into the file. */
> b82670045aab66 Darrick J. Wong 2022-01-06 1342 STATIC int
> b82670045aab66 Darrick J. Wong 2022-01-06 1343 xfs_map_free_extent(
> b82670045aab66 Darrick J. Wong 2022-01-06 1344 struct xfs_inode *ip,
> b82670045aab66 Darrick J. Wong 2022-01-06 1345 struct xfs_perag *pag,
> b82670045aab66 Darrick J. Wong 2022-01-06 1346 xfs_agblock_t *cursor,
> b82670045aab66 Darrick J. Wong 2022-01-06 1347 xfs_agblock_t end_agbno,
> b82670045aab66 Darrick J. Wong 2022-01-06 1348 xfs_agblock_t *last_enospc_agbno)
> b82670045aab66 Darrick J. Wong 2022-01-06 1349 {
> b82670045aab66 Darrick J. Wong 2022-01-06 1350 struct xfs_bmbt_irec irec;
> b82670045aab66 Darrick J. Wong 2022-01-06 1351 struct xfs_mount *mp = ip->i_mount;
> b82670045aab66 Darrick J. Wong 2022-01-06 1352 struct xfs_trans *tp;
> b82670045aab66 Darrick J. Wong 2022-01-06 1353 xfs_off_t endpos;
> b82670045aab66 Darrick J. Wong 2022-01-06 1354 xfs_fsblock_t fsbno;
> b82670045aab66 Darrick J. Wong 2022-01-06 1355 xfs_extlen_t len;
> b82670045aab66 Darrick J. Wong 2022-01-06 1356 int error;
> b82670045aab66 Darrick J. Wong 2022-01-06 1357
> b82670045aab66 Darrick J. Wong 2022-01-06 1358 if (fatal_signal_pending(current))
> b82670045aab66 Darrick J. Wong 2022-01-06 1359 return -EINTR;
> b82670045aab66 Darrick J. Wong 2022-01-06 1360
> b82670045aab66 Darrick J. Wong 2022-01-06 1361 error = xfs_trans_alloc_inode(ip, &M_RES(mp)->tr_write, 0, 0, false,
> b82670045aab66 Darrick J. Wong 2022-01-06 1362 &tp);
> b82670045aab66 Darrick J. Wong 2022-01-06 1363 if (error)
> b82670045aab66 Darrick J. Wong 2022-01-06 1364 return error;
> b82670045aab66 Darrick J. Wong 2022-01-06 1365
> b82670045aab66 Darrick J. Wong 2022-01-06 1366 error = xfs_alloc_find_freesp(tp, pag, cursor, end_agbno, &len);
> b82670045aab66 Darrick J. Wong 2022-01-06 1367 if (error)
> b82670045aab66 Darrick J. Wong 2022-01-06 1368 goto out_cancel;
> b82670045aab66 Darrick J. Wong 2022-01-06 1369
> b82670045aab66 Darrick J. Wong 2022-01-06 1370 /* Bail out if the cursor is beyond what we asked for. */
> b82670045aab66 Darrick J. Wong 2022-01-06 1371 if (*cursor >= end_agbno)
> b82670045aab66 Darrick J. Wong 2022-01-06 @1372 goto out_cancel;
>
> This looks like it should have an error = -EINVAL;

Nope. If xfs_alloc_find_freesp moves @cursor goes beyond end_agbno, we
want to exit early so that the xfs_map_free_extent caller will return to
userspace.

--D

>
> b82670045aab66 Darrick J. Wong 2022-01-06 1373
> b82670045aab66 Darrick J. Wong 2022-01-06 1374 error = xfs_map_free_reserve_more(tp, ip, &len);
> b82670045aab66 Darrick J. Wong 2022-01-06 1375 if (error)
> b82670045aab66 Darrick J. Wong 2022-01-06 1376 goto out_cancel;
> b82670045aab66 Darrick J. Wong 2022-01-06 1377
> b82670045aab66 Darrick J. Wong 2022-01-06 1378 fsbno = XFS_AGB_TO_FSB(mp, pag->pag_agno, *cursor);
> b82670045aab66 Darrick J. Wong 2022-01-06 1379 do {
> b82670045aab66 Darrick J. Wong 2022-01-06 1380 error = xfs_bmapi_freesp(tp, ip, fsbno, len, &irec);
> b82670045aab66 Darrick J. Wong 2022-01-06 1381 if (error == -EAGAIN) {
> b82670045aab66 Darrick J. Wong 2022-01-06 1382 /* Failed to map space but were told to try again. */
> b82670045aab66 Darrick J. Wong 2022-01-06 1383 error = xfs_trans_commit(tp);
> b82670045aab66 Darrick J. Wong 2022-01-06 1384 goto out;
> b82670045aab66 Darrick J. Wong 2022-01-06 1385 }
> b82670045aab66 Darrick J. Wong 2022-01-06 1386 if (error != -ENOSPC)
> b82670045aab66 Darrick J. Wong 2022-01-06 1387 break;
> b82670045aab66 Darrick J. Wong 2022-01-06 1388 /*
> b82670045aab66 Darrick J. Wong 2022-01-06 1389 * If we can't get the space, try asking for successively less
> b82670045aab66 Darrick J. Wong 2022-01-06 1390 * space in case we're bumping up against per-AG metadata
> b82670045aab66 Darrick J. Wong 2022-01-06 1391 * reservation limits...
> b82670045aab66 Darrick J. Wong 2022-01-06 1392 */
> b82670045aab66 Darrick J. Wong 2022-01-06 1393 len >>= 1;
> b82670045aab66 Darrick J. Wong 2022-01-06 1394 } while (len > 0);
> b82670045aab66 Darrick J. Wong 2022-01-06 1395 if (error == -ENOSPC && *last_enospc_agbno != *cursor) {
> b82670045aab66 Darrick J. Wong 2022-01-06 1396 /*
> b82670045aab66 Darrick J. Wong 2022-01-06 1397 * ...but even that might not work if an AGFL fixup allocated
> b82670045aab66 Darrick J. Wong 2022-01-06 1398 * the block at *cursor. The first time this happens, remember
> b82670045aab66 Darrick J. Wong 2022-01-06 1399 * that we ran out of space here, and try again.
> b82670045aab66 Darrick J. Wong 2022-01-06 1400 */
> b82670045aab66 Darrick J. Wong 2022-01-06 1401 *last_enospc_agbno = *cursor;
> b82670045aab66 Darrick J. Wong 2022-01-06 1402 error = 0;
> b82670045aab66 Darrick J. Wong 2022-01-06 1403 goto out_cancel;
> b82670045aab66 Darrick J. Wong 2022-01-06 1404 }
> b82670045aab66 Darrick J. Wong 2022-01-06 1405 if (error)
> b82670045aab66 Darrick J. Wong 2022-01-06 1406 goto out_cancel;
> b82670045aab66 Darrick J. Wong 2022-01-06 1407
> b82670045aab66 Darrick J. Wong 2022-01-06 1408 /* Update isize if needed. */
> b82670045aab66 Darrick J. Wong 2022-01-06 1409 endpos = XFS_FSB_TO_B(mp, irec.br_startoff + irec.br_blockcount);
> b82670045aab66 Darrick J. Wong 2022-01-06 1410 if (endpos > i_size_read(VFS_I(ip))) {
> b82670045aab66 Darrick J. Wong 2022-01-06 1411 i_size_write(VFS_I(ip), endpos);
> b82670045aab66 Darrick J. Wong 2022-01-06 1412 ip->i_disk_size = endpos;
> b82670045aab66 Darrick J. Wong 2022-01-06 1413 xfs_trans_log_inode(tp, ip, XFS_ILOG_CORE);
> b82670045aab66 Darrick J. Wong 2022-01-06 1414 }
> b82670045aab66 Darrick J. Wong 2022-01-06 1415
> b82670045aab66 Darrick J. Wong 2022-01-06 1416 error = xfs_trans_commit(tp);
> b82670045aab66 Darrick J. Wong 2022-01-06 1417 xfs_iunlock(ip, XFS_ILOCK_EXCL);
> b82670045aab66 Darrick J. Wong 2022-01-06 1418 if (error)
> b82670045aab66 Darrick J. Wong 2022-01-06 1419 return error;
> b82670045aab66 Darrick J. Wong 2022-01-06 1420
> b82670045aab66 Darrick J. Wong 2022-01-06 1421 *cursor += irec.br_blockcount;
> b82670045aab66 Darrick J. Wong 2022-01-06 1422 return 0;
> b82670045aab66 Darrick J. Wong 2022-01-06 1423 out_cancel:
> b82670045aab66 Darrick J. Wong 2022-01-06 1424 xfs_trans_cancel(tp);
> b82670045aab66 Darrick J. Wong 2022-01-06 1425 out:
> b82670045aab66 Darrick J. Wong 2022-01-06 1426 xfs_iunlock(ip, XFS_ILOCK_EXCL);
> b82670045aab66 Darrick J. Wong 2022-01-06 1427 return error;
> b82670045aab66 Darrick J. Wong 2022-01-06 1428 }
>
> ---
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