From df9c7d8d8f3ed0785ed83e7fd0c7ddc92cbfbe15 Mon Sep 17 00:00:00 2001
From: "Gustavo A. R. Silva" <gustavoars@kernel.org>
Date: Fri, 1 Oct 2021 16:03:54 -0400
Subject: [PATCH] xfs: Fix fall-through warnings for Clang

Source kernel commit: 53004ee78d6273c994534ccf79d993098ac89769

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]
fs/xfs/scrub/agheader.c:89:2: 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>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Eric Sandeen <sandeen@sandeen.net>
---
 include/linux.h       | 21 +++++++++++++++++++++
 libxfs/xfs_ag_resv.c  |  4 ++--
 libxfs/xfs_alloc.c    |  2 +-
 libxfs/xfs_da_btree.c |  2 +-
 4 files changed, 25 insertions(+), 4 deletions(-)

diff --git a/include/linux.h b/include/linux.h
index a22f78121..246502285 100644
--- a/include/linux.h
+++ b/include/linux.h
@@ -359,4 +359,25 @@ fsmap_advance(
 #include <asm-generic/mman-common.h>
 #endif /* HAVE_MAP_SYNC */
 
+/*
+ * Add the pseudo keyword 'fallthrough' so case statement blocks
+ * must end with any of these keywords:
+ *   break;
+ *   fallthrough;
+ *   continue;
+ *   goto <label>;
+ *   return [expression];
+ *
+ *  gcc: https://gcc.gnu.org/onlinedocs/gcc/Statement-Attributes.html#Statement-Attributes
+ */
+#if defined __has_attribute
+#  if __has_attribute(__fallthrough__)
+#    define fallthrough                    __attribute__((__fallthrough__))
+#  else
+#    define fallthrough                    do {} while (0)  /* fallthrough */
+#  endif
+#else
+#    define fallthrough                    do {} while (0)  /* fallthrough */
+#endif
+
 #endif	/* __XFS_LINUX_H__ */
diff --git a/libxfs/xfs_ag_resv.c b/libxfs/xfs_ag_resv.c
index 1aac33732..7d426d08f 100644
--- a/libxfs/xfs_ag_resv.c
+++ b/libxfs/xfs_ag_resv.c
@@ -365,7 +365,7 @@ 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;
@@ -407,7 +407,7 @@ 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/libxfs/xfs_alloc.c b/libxfs/xfs_alloc.c
index d99622a68..300a91f85 100644
--- a/libxfs/xfs_alloc.c
+++ b/libxfs/xfs_alloc.c
@@ -3170,7 +3170,7 @@ 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/libxfs/xfs_da_btree.c b/libxfs/xfs_da_btree.c
index 43f090c51..f4e1fe80d 100644
--- a/libxfs/xfs_da_btree.c
+++ b/libxfs/xfs_da_btree.c
@@ -279,7 +279,7 @@ xfs_da3_node_read_verify(
 						__this_address);
 				break;
 			}
-			/* fall through */
+			fallthrough;
 		case XFS_DA_NODE_MAGIC:
 			fa = xfs_da3_node_verify(bp);
 			if (fa)
-- 
2.47.2