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Date:   Mon, 21 Mar 2022 14:59:08 -0700
From:   "Darrick J. Wong" <djwong@...nel.org>
To:     Dan Carpenter <dan.carpenter@...cle.com>
Cc:     kbuild@...ts.01.org, lkp@...el.com, kbuild-all@...ts.01.org,
        "Darrick J. Wong" <darrick.wong@...cle.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [kbuild] [djwong-xfs:djwong-wtf 349/351]
 fs/xfs/xfs_bmap_util.c:1372 xfs_map_free_extent() warn: missing error code
 'error'

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@intel.com/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@...el.com>
> Reported-by: Dan Carpenter <dan.carpenter@...cle.com>
> 
> 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  }
> 
> ---
> 0-DAY CI Kernel Test Service
> https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org 
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