[PATCH v2 0/2] xfs: Clear a W=1 warning and some __maybe_unused usage

[PATCH v2 0/2] xfs: Clear a W=1 warning and some __maybe_unused usage

[John Garry]

For configs XFS_DEBUG and XFS_WARN disabled, for a W=1 build
xfs_iwalk_run_callbacks() generates a warning for unused variable. Clean
that up.

Also remove __maybe_unused usage in xfs_alloc.c, which is for protecting
against the same type of warning.

John Garry (2):
  xfs: Clear W=1 warning in xfs_iwalk_run_callbacks()
  xfs: Stop using __maybe_unused in xfs_alloc.c

 fs/xfs/libxfs/xfs_alloc.c | 6 ++----
 fs/xfs/xfs_iwalk.c        | 5 ++---
 2 files changed, 4 insertions(+), 7 deletions(-)

-- 
2.31.1

[PATCH v2 1/2] xfs: Clear W=1 warning in xfs_iwalk_run_callbacks()

[John Garry]

For CONFIG_XFS_DEBUG unset, xfs_iwalk_run_callbacks() generates the
following warning for when building with W=1:

fs/xfs/xfs_iwalk.c: In function ‘xfs_iwalk_run_callbacks’:
fs/xfs/xfs_iwalk.c:354:42: error: variable ‘irec’ set but not used [-Werror=unused-but-set-variable]
  354 |         struct xfs_inobt_rec_incore     *irec;
      |                                          ^~~~
cc1: all warnings being treated as errors

Drop @irec, as it is only an intermediate variable.

Suggested-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: John Garry <john.g.garry@oracle.com>
---
 fs/xfs/xfs_iwalk.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/fs/xfs/xfs_iwalk.c b/fs/xfs/xfs_iwalk.c
index 730c8d48da28..86f14ec7c31f 100644
--- a/fs/xfs/xfs_iwalk.c
+++ b/fs/xfs/xfs_iwalk.c
@@ -351,7 +351,6 @@ xfs_iwalk_run_callbacks(
 	int				*has_more)
 {
 	struct xfs_mount		*mp = iwag->mp;
-	struct xfs_inobt_rec_incore	*irec;
 	xfs_agino_t			next_agino;
 	int				error;
 
@@ -361,8 +360,8 @@ xfs_iwalk_run_callbacks(
 
 	/* Delete cursor but remember the last record we cached... */
 	xfs_iwalk_del_inobt(iwag->tp, curpp, agi_bpp, 0);
-	irec = &iwag->recs[iwag->nr_recs - 1];
-	ASSERT(next_agino >= irec->ir_startino + XFS_INODES_PER_CHUNK);
+	ASSERT(next_agino >= iwag->recs[iwag->nr_recs - 1].ir_startino +
+			XFS_INODES_PER_CHUNK);
 
 	if (iwag->drop_trans) {
 		xfs_trans_cancel(iwag->tp);
-- 
2.31.1

Re: [PATCH v2 1/2] xfs: Clear W=1 warning in xfs_iwalk_run_callbacks()

[Christoph Hellwig]

Looks good:

Reviewed-by: Christoph Hellwig <hch@lst.de>

[PATCH v2 2/2] xfs: Stop using __maybe_unused in xfs_alloc.c

[John Garry]

In both xfs_alloc_cur_finish() and xfs_alloc_ag_vextent_exact(), local
variable @afg is tagged as __maybe_unused. Otherwise an unused variable
warning would be generated for when building with W=1 and CONFIG_XFS_DEBUG
unset. In both cases, the variable is unused as it is only referenced in
an ASSERT() call, which is compiled out (in this config).

It is generally a poor programming style to use __maybe_unused for
variables.

The ASSERT() call is to verify that agbno of the end of the extent is
within bounds for both functions. @afg is used as an intermediate variable
to find the AG length.

However xfs_verify_agbext() already exists to verify a valid extent range.
The arguments for calling xfs_verify_agbext() are already available, so use
that instead.

An advantage of using xfs_verify_agbext() is that it verifies that both the
start and the end of the extent are within the bounds of the AG and
catches overflows.

Suggested-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: John Garry <john.g.garry@oracle.com>
---
 fs/xfs/libxfs/xfs_alloc.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/fs/xfs/libxfs/xfs_alloc.c b/fs/xfs/libxfs/xfs_alloc.c
index 6cb8b2ddc541..6c55a6e88eba 100644
--- a/fs/xfs/libxfs/xfs_alloc.c
+++ b/fs/xfs/libxfs/xfs_alloc.c
@@ -1008,13 +1008,12 @@ xfs_alloc_cur_finish(
 	struct xfs_alloc_arg	*args,
 	struct xfs_alloc_cur	*acur)
 {
-	struct xfs_agf __maybe_unused *agf = args->agbp->b_addr;
 	int			error;
 
 	ASSERT(acur->cnt && acur->bnolt);
 	ASSERT(acur->bno >= acur->rec_bno);
 	ASSERT(acur->bno + acur->len <= acur->rec_bno + acur->rec_len);
-	ASSERT(acur->rec_bno + acur->rec_len <= be32_to_cpu(agf->agf_length));
+	ASSERT(xfs_verify_agbext(args->pag, acur->rec_bno, acur->rec_len));
 
 	error = xfs_alloc_fixup_trees(acur->cnt, acur->bnolt, acur->rec_bno,
 				      acur->rec_len, acur->bno, acur->len, 0);
@@ -1217,7 +1216,6 @@ STATIC int			/* error */
 xfs_alloc_ag_vextent_exact(
 	xfs_alloc_arg_t	*args)	/* allocation argument structure */
 {
-	struct xfs_agf __maybe_unused *agf = args->agbp->b_addr;
 	struct xfs_btree_cur *bno_cur;/* by block-number btree cursor */
 	struct xfs_btree_cur *cnt_cur;/* by count btree cursor */
 	int		error;
@@ -1297,7 +1295,7 @@ xfs_alloc_ag_vextent_exact(
 	 */
 	cnt_cur = xfs_cntbt_init_cursor(args->mp, args->tp, args->agbp,
 					args->pag);
-	ASSERT(args->agbno + args->len <= be32_to_cpu(agf->agf_length));
+	ASSERT(xfs_verify_agbext(args->pag, args->agbno, args->len));
 	error = xfs_alloc_fixup_trees(cnt_cur, bno_cur, fbno, flen, args->agbno,
 				      args->len, XFSA_FIXUP_BNO_OK);
 	if (error) {
-- 
2.31.1

Re: [PATCH v2 2/2] xfs: Stop using __maybe_unused in xfs_alloc.c

[Christoph Hellwig]

Looks good:

Reviewed-by: Christoph Hellwig <hch@lst.de>