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Subject: Re: [PATCH][next] xfs: Fix fall-through warnings for Clang
To:     "Darrick J. Wong" <djwong@kernel.org>,
        "Gustavo A. R. Silva" <gustavoars@kernel.org>
Cc:     linux-xfs@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-hardening@vger.kernel.org
References: <20210420230652.GA70650@embeddedor>
 <20210420233850.GQ3122264@magnolia>
From:   "Gustavo A. R. Silva" <gustavo@embeddedor.com>
Message-ID: <62895e8c-800d-fa7b-15f6-480179d552be@embeddedor.com>
Date:   Tue, 20 Apr 2021 18:56:32 -0500
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On 4/20/21 18:38, Darrick J. Wong wrote:
> On Tue, Apr 20, 2021 at 06:06:52PM -0500, Gustavo A. R. Silva wrote:
>> In preparation to enable -Wimplicit-fallthrough for Clang, fix
>> the following warnings by replacing /* fall through */ comments,
>> and its variants, with the new pseudo-keyword macro fallthrough:
>>
>> fs/xfs/libxfs/xfs_alloc.c:3167:2: warning: unannotated fall-through between switch labels [-Wimplicit-fallthrough]
>> fs/xfs/libxfs/xfs_da_btree.c:286:3: warning: unannotated fall-through between switch labels [-Wimplicit-fallthrough]
>> fs/xfs/libxfs/xfs_ag_resv.c:346:2: warning: unannotated fall-through between switch labels [-Wimplicit-fallthrough]
>> fs/xfs/libxfs/xfs_ag_resv.c:388:2: warning: unannotated fall-through between switch labels [-Wimplicit-fallthrough]
>> fs/xfs/xfs_bmap_util.c:246:2: warning: unannotated fall-through between switch labels [-Wimplicit-fallthrough]
>> fs/xfs/xfs_export.c:88:2: warning: unannotated fall-through between switch labels [-Wimplicit-fallthrough]
>> fs/xfs/xfs_export.c:96:2: warning: unannotated fall-through between switch labels [-Wimplicit-fallthrough]
>> fs/xfs/xfs_file.c:867:3: warning: unannotated fall-through between switch labels [-Wimplicit-fallthrough]
>> fs/xfs/xfs_ioctl.c:562:2: warning: unannotated fall-through between switch labels [-Wimplicit-fallthrough]
>> fs/xfs/xfs_ioctl.c:1548:2: warning: unannotated fall-through between switch labels [-Wimplicit-fallthrough]
>> fs/xfs/xfs_iomap.c:1040:2: warning: unannotated fall-through between switch labels [-Wimplicit-fallthrough]
>> fs/xfs/xfs_inode.c:852:2: warning: unannotated fall-through between switch labels [-Wimplicit-fallthrough]
>> fs/xfs/xfs_log.c:2627:2: warning: unannotated fall-through between switch labels [-Wimplicit-fallthrough]
>> fs/xfs/xfs_trans_buf.c:298:2: warning: unannotated fall-through between switch labels [-Wimplicit-fallthrough]
>> fs/xfs/scrub/bmap.c:275:2: warning: unannotated fall-through between switch labels [-Wimplicit-fallthrough]
>> fs/xfs/scrub/btree.c:48:2: warning: unannotated fall-through between switch labels [-Wimplicit-fallthrough]
>> fs/xfs/scrub/common.c:85:2: warning: unannotated fall-through between switch labels [-Wimplicit-fallthrough]
>> fs/xfs/scrub/common.c:138:2: warning: unannotated fall-through between switch labels [-Wimplicit-fallthrough]
>> fs/xfs/scrub/common.c:698:2: warning: unannotated fall-through between switch labels [-Wimplicit-fallthrough]
>> fs/xfs/scrub/dabtree.c:51:2: warning: unannotated fall-through between switch labels [-Wimplicit-fallthrough]
>> fs/xfs/scrub/repair.c:951:2: warning: unannotated fall-through between switch labels [-Wimplicit-fallthrough]
>>
>> Notice that Clang doesn't recognize /* fall through */ comments as
>> implicit fall-through markings, so in order to globally enable
>> -Wimplicit-fallthrough for Clang, these comments need to be
>> replaced with fallthrough; in the whole codebase.
>>
>> Link: https://github.com/KSPP/linux/issues/115
>> Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
> 
> I've already NAKd this twice, so I guess I'll NAK it a third time.

Darrick,

The adoption of fallthrough; has been already accepted and in use since Linux v5.7:

https://www.kernel.org/doc/html/v5.7/process/deprecated.html?highlight=fallthrough#implicit-switch-case-fall-through

This change is needed, and I would really prefer if this goes upstream through your tree.

Linus has taken these patches directly for a while, now.

Could you consider taking it this time? :)

Thanks
--
Gustavo

> 
> --D
> 
>> ---
>>  fs/xfs/libxfs/xfs_ag_resv.c  | 4 ++--
>>  fs/xfs/libxfs/xfs_alloc.c    | 2 +-
>>  fs/xfs/libxfs/xfs_da_btree.c | 2 +-
>>  fs/xfs/scrub/bmap.c          | 2 +-
>>  fs/xfs/scrub/btree.c         | 2 +-
>>  fs/xfs/scrub/common.c        | 6 +++---
>>  fs/xfs/scrub/dabtree.c       | 2 +-
>>  fs/xfs/scrub/repair.c        | 2 +-
>>  fs/xfs/xfs_bmap_util.c       | 2 +-
>>  fs/xfs/xfs_export.c          | 4 ++--
>>  fs/xfs/xfs_file.c            | 2 +-
>>  fs/xfs/xfs_inode.c           | 2 +-
>>  fs/xfs/xfs_ioctl.c           | 4 ++--
>>  fs/xfs/xfs_iomap.c           | 2 +-
>>  fs/xfs/xfs_trans_buf.c       | 2 +-
>>  15 files changed, 20 insertions(+), 20 deletions(-)
>>
>> diff --git a/fs/xfs/libxfs/xfs_ag_resv.c b/fs/xfs/libxfs/xfs_ag_resv.c
>> index 6c5f8d10589c..8c3c99a9bf83 100644
>> --- a/fs/xfs/libxfs/xfs_ag_resv.c
>> +++ b/fs/xfs/libxfs/xfs_ag_resv.c
>> @@ -342,7 +342,7 @@ xfs_ag_resv_alloc_extent(
>>  		break;
>>  	default:
>>  		ASSERT(0);
>> -		/* fall through */
>> +		fallthrough;
>>  	case XFS_AG_RESV_NONE:
>>  		field = args->wasdel ? XFS_TRANS_SB_RES_FDBLOCKS :
>>  				       XFS_TRANS_SB_FDBLOCKS;
>> @@ -384,7 +384,7 @@ xfs_ag_resv_free_extent(
>>  		break;
>>  	default:
>>  		ASSERT(0);
>> -		/* fall through */
>> +		fallthrough;
>>  	case XFS_AG_RESV_NONE:
>>  		xfs_trans_mod_sb(tp, XFS_TRANS_SB_FDBLOCKS, (int64_t)len);
>>  		return;
>> diff --git a/fs/xfs/libxfs/xfs_alloc.c b/fs/xfs/libxfs/xfs_alloc.c
>> index aaa19101bb2a..9eabdeeec492 100644
>> --- a/fs/xfs/libxfs/xfs_alloc.c
>> +++ b/fs/xfs/libxfs/xfs_alloc.c
>> @@ -3163,7 +3163,7 @@ xfs_alloc_vextent(
>>  		}
>>  		args->agbno = XFS_FSB_TO_AGBNO(mp, args->fsbno);
>>  		args->type = XFS_ALLOCTYPE_NEAR_BNO;
>> -		/* FALLTHROUGH */
>> +		fallthrough;
>>  	case XFS_ALLOCTYPE_FIRST_AG:
>>  		/*
>>  		 * Rotate through the allocation groups looking for a winner.
>> diff --git a/fs/xfs/libxfs/xfs_da_btree.c b/fs/xfs/libxfs/xfs_da_btree.c
>> index 83ac9771bfb5..747ec77912c3 100644
>> --- a/fs/xfs/libxfs/xfs_da_btree.c
>> +++ b/fs/xfs/libxfs/xfs_da_btree.c
>> @@ -282,7 +282,7 @@ xfs_da3_node_read_verify(
>>  						__this_address);
>>  				break;
>>  			}
>> -			/* fall through */
>> +			fallthrough;
>>  		case XFS_DA_NODE_MAGIC:
>>  			fa = xfs_da3_node_verify(bp);
>>  			if (fa)
>> diff --git a/fs/xfs/scrub/bmap.c b/fs/xfs/scrub/bmap.c
>> index b5ebf1d1b4db..77d5c4a0f09f 100644
>> --- a/fs/xfs/scrub/bmap.c
>> +++ b/fs/xfs/scrub/bmap.c
>> @@ -271,7 +271,7 @@ xchk_bmap_iextent_xref(
>>  	case XFS_DATA_FORK:
>>  		if (xfs_is_reflink_inode(info->sc->ip))
>>  			break;
>> -		/* fall through */
>> +		fallthrough;
>>  	case XFS_ATTR_FORK:
>>  		xchk_xref_is_not_shared(info->sc, agbno,
>>  				irec->br_blockcount);
>> diff --git a/fs/xfs/scrub/btree.c b/fs/xfs/scrub/btree.c
>> index a94bd8122c60..bd1172358964 100644
>> --- a/fs/xfs/scrub/btree.c
>> +++ b/fs/xfs/scrub/btree.c
>> @@ -44,7 +44,7 @@ __xchk_btree_process_error(
>>  		/* Note the badness but don't abort. */
>>  		sc->sm->sm_flags |= errflag;
>>  		*error = 0;
>> -		/* fall through */
>> +		fallthrough;
>>  	default:
>>  		if (cur->bc_flags & XFS_BTREE_ROOT_IN_INODE)
>>  			trace_xchk_ifork_btree_op_error(sc, cur, level,
>> diff --git a/fs/xfs/scrub/common.c b/fs/xfs/scrub/common.c
>> index aa874607618a..ce9a44ea6948 100644
>> --- a/fs/xfs/scrub/common.c
>> +++ b/fs/xfs/scrub/common.c
>> @@ -81,7 +81,7 @@ __xchk_process_error(
>>  		/* Note the badness but don't abort. */
>>  		sc->sm->sm_flags |= errflag;
>>  		*error = 0;
>> -		/* fall through */
>> +		fallthrough;
>>  	default:
>>  		trace_xchk_op_error(sc, agno, bno, *error,
>>  				ret_ip);
>> @@ -134,7 +134,7 @@ __xchk_fblock_process_error(
>>  		/* Note the badness but don't abort. */
>>  		sc->sm->sm_flags |= errflag;
>>  		*error = 0;
>> -		/* fall through */
>> +		fallthrough;
>>  	default:
>>  		trace_xchk_file_op_error(sc, whichfork, offset, *error,
>>  				ret_ip);
>> @@ -694,7 +694,7 @@ xchk_get_inode(
>>  		if (error)
>>  			return -ENOENT;
>>  		error = -EFSCORRUPTED;
>> -		/* fall through */
>> +		fallthrough;
>>  	default:
>>  		trace_xchk_op_error(sc,
>>  				XFS_INO_TO_AGNO(mp, sc->sm->sm_ino),
>> diff --git a/fs/xfs/scrub/dabtree.c b/fs/xfs/scrub/dabtree.c
>> index 653f3280e1c1..9f0dbb47c82c 100644
>> --- a/fs/xfs/scrub/dabtree.c
>> +++ b/fs/xfs/scrub/dabtree.c
>> @@ -47,7 +47,7 @@ xchk_da_process_error(
>>  		/* Note the badness but don't abort. */
>>  		sc->sm->sm_flags |= XFS_SCRUB_OFLAG_CORRUPT;
>>  		*error = 0;
>> -		/* fall through */
>> +		fallthrough;
>>  	default:
>>  		trace_xchk_file_op_error(sc, ds->dargs.whichfork,
>>  				xfs_dir2_da_to_db(ds->dargs.geo,
>> diff --git a/fs/xfs/scrub/repair.c b/fs/xfs/scrub/repair.c
>> index c2857d854c83..b8202dd08939 100644
>> --- a/fs/xfs/scrub/repair.c
>> +++ b/fs/xfs/scrub/repair.c
>> @@ -947,7 +947,7 @@ xrep_ino_dqattach(
>>  			xrep_force_quotacheck(sc, XFS_DQTYPE_GROUP);
>>  		if (XFS_IS_PQUOTA_ON(sc->mp) && !sc->ip->i_pdquot)
>>  			xrep_force_quotacheck(sc, XFS_DQTYPE_PROJ);
>> -		/* fall through */
>> +		fallthrough;
>>  	case -ESRCH:
>>  		error = 0;
>>  		break;
>> diff --git a/fs/xfs/xfs_bmap_util.c b/fs/xfs/xfs_bmap_util.c
>> index a5e9d7d34023..cc628475f9b6 100644
>> --- a/fs/xfs/xfs_bmap_util.c
>> +++ b/fs/xfs/xfs_bmap_util.c
>> @@ -242,7 +242,7 @@ xfs_bmap_count_blocks(
>>  		 */
>>  		*count += btblocks - 1;
>>  
>> -		/* fall through */
>> +		fallthrough;
>>  	case XFS_DINODE_FMT_EXTENTS:
>>  		*nextents = xfs_bmap_count_leaves(ifp, count);
>>  		break;
>> diff --git a/fs/xfs/xfs_export.c b/fs/xfs/xfs_export.c
>> index 465fd9e048d4..1da59bdff245 100644
>> --- a/fs/xfs/xfs_export.c
>> +++ b/fs/xfs/xfs_export.c
>> @@ -84,7 +84,7 @@ xfs_fs_encode_fh(
>>  	case FILEID_INO32_GEN_PARENT:
>>  		fid->i32.parent_ino = XFS_I(parent)->i_ino;
>>  		fid->i32.parent_gen = parent->i_generation;
>> -		/*FALLTHRU*/
>> +		fallthrough;
>>  	case FILEID_INO32_GEN:
>>  		fid->i32.ino = XFS_I(inode)->i_ino;
>>  		fid->i32.gen = inode->i_generation;
>> @@ -92,7 +92,7 @@ xfs_fs_encode_fh(
>>  	case FILEID_INO32_GEN_PARENT | XFS_FILEID_TYPE_64FLAG:
>>  		fid64->parent_ino = XFS_I(parent)->i_ino;
>>  		fid64->parent_gen = parent->i_generation;
>> -		/*FALLTHRU*/
>> +		fallthrough;
>>  	case FILEID_INO32_GEN | XFS_FILEID_TYPE_64FLAG:
>>  		fid64->ino = XFS_I(inode)->i_ino;
>>  		fid64->gen = inode->i_generation;
>> diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
>> index 396ef36dcd0a..3c0749ab9e40 100644
>> --- a/fs/xfs/xfs_file.c
>> +++ b/fs/xfs/xfs_file.c
>> @@ -863,7 +863,7 @@ xfs_break_layouts(
>>  			error = xfs_break_dax_layouts(inode, &retry);
>>  			if (error || retry)
>>  				break;
>> -			/* fall through */
>> +			fallthrough;
>>  		case BREAK_WRITE:
>>  			error = xfs_break_leased_layouts(inode, iolock, &retry);
>>  			break;
>> diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c
>> index 0369eb22c1bb..f2846997c3a8 100644
>> --- a/fs/xfs/xfs_inode.c
>> +++ b/fs/xfs/xfs_inode.c
>> @@ -848,7 +848,7 @@ xfs_init_new_inode(
>>  			xfs_inode_inherit_flags(ip, pip);
>>  		if (pip && (pip->i_diflags2 & XFS_DIFLAG2_ANY))
>>  			xfs_inode_inherit_flags2(ip, pip);
>> -		/* FALLTHROUGH */
>> +		fallthrough;
>>  	case S_IFLNK:
>>  		ip->i_df.if_format = XFS_DINODE_FMT_EXTENTS;
>>  		ip->i_df.if_bytes = 0;
>> diff --git a/fs/xfs/xfs_ioctl.c b/fs/xfs/xfs_ioctl.c
>> index 3925bfcb2365..c4dc6c72ac37 100644
>> --- a/fs/xfs/xfs_ioctl.c
>> +++ b/fs/xfs/xfs_ioctl.c
>> @@ -558,7 +558,7 @@ xfs_ioc_attrmulti_one(
>>  	case ATTR_OP_REMOVE:
>>  		value = NULL;
>>  		*len = 0;
>> -		/* fall through */
>> +		fallthrough;
>>  	case ATTR_OP_SET:
>>  		error = mnt_want_write_file(parfilp);
>>  		if (error)
>> @@ -1544,7 +1544,7 @@ xfs_ioc_getbmap(
>>  	switch (cmd) {
>>  	case XFS_IOC_GETBMAPA:
>>  		bmx.bmv_iflags = BMV_IF_ATTRFORK;
>> -		/*FALLTHRU*/
>> +		fallthrough;
>>  	case XFS_IOC_GETBMAP:
>>  		/* struct getbmap is a strict subset of struct getbmapx. */
>>  		recsize = sizeof(struct getbmap);
>> diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c
>> index d154f42e2dc6..d8cd2583dedb 100644
>> --- a/fs/xfs/xfs_iomap.c
>> +++ b/fs/xfs/xfs_iomap.c
>> @@ -1036,7 +1036,7 @@ xfs_buffered_write_iomap_begin(
>>  			prealloc_blocks = 0;
>>  			goto retry;
>>  		}
>> -		/*FALLTHRU*/
>> +		fallthrough;
>>  	default:
>>  		goto out_unlock;
>>  	}
>> diff --git a/fs/xfs/xfs_trans_buf.c b/fs/xfs/xfs_trans_buf.c
>> index 9aced0a00003..d11d032da0b4 100644
>> --- a/fs/xfs/xfs_trans_buf.c
>> +++ b/fs/xfs/xfs_trans_buf.c
>> @@ -294,7 +294,7 @@ xfs_trans_read_buf_map(
>>  	default:
>>  		if (tp && (tp->t_flags & XFS_TRANS_DIRTY))
>>  			xfs_force_shutdown(tp->t_mountp, SHUTDOWN_META_IO_ERROR);
>> -		/* fall through */
>> +		fallthrough;
>>  	case -ENOMEM:
>>  	case -EAGAIN:
>>  		return error;
>> -- 
>> 2.27.0
>>