Re: [linux-next:master 7512/8919] fs/xfs/libxfs/xfs_alloc_btree.c:302:40: sparse: warning: incorrect type in argument 2 (different base types)

["Darrick J. Wong" <darrick.wong@oracle.com>]

On Sat, Feb 16, 2019 at 07:05:28AM -0500, Brian Foster wrote:
> On Fri, Feb 15, 2019 at 02:55:24PM -0800, Darrick J. Wong wrote:
> > [rip all the cc off]
> > 
> 
> cc linux-xfs
> 
> > On Sat, Feb 16, 2019 at 04:02:13AM +0800, kbuild test robot wrote:
> > > tree:   https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master
> > > head:   7a92eb7cc1dc4c63e3a2fa9ab8e3c1049f199249
> > > commit: b8f89801664f8413a88cf2c7539d1aeae07dd3c5 [7512/8919] xfs: distinguish between bnobt and cntbt magic values
> > > reproduce:
> > >         # apt-get install sparse
> > >         git checkout b8f89801664f8413a88cf2c7539d1aeae07dd3c5
> > >         make ARCH=x86_64 allmodconfig
> > >         make C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__'
> > > 
> > > All warnings (new ones prefixed by >>):
> > > 
> > > >> fs/xfs/libxfs/xfs_alloc_btree.c:302:40: sparse: warning: incorrect type in argument 2 (different base types)
> > >    fs/xfs/libxfs/xfs_alloc_btree.c:302:40: sparse:    expected unsigned int [usertype] dmagic
> > >    fs/xfs/libxfs/xfs_alloc_btree.c:302:40: sparse:    got restricted __be32 [usertype] bb_magic
> > 
> > Hmmmm, I suspected this was going to happen, though when I built with
> > those parameters the endian checking didn't trigger so I decided not to
> > press any further.  Oh well...
> > 
> 
> Argh. Sorry, I wasn't aware this would result in noise.

Heh.  It turned out that I forgot that my computer was configured to use
smatch instead of sparse, and only sparse does the endian checking.
(Gee, I thought smatch was supposed to be a superset of sparse!)

So with the addition of /even more/ wrapper scripts I can now run
/both/.

> > Can we get a fix going for this ASAP, please?
> > 
> 
> FYI it probably won't be Monday until I can spin a proper patch. In the
> meantime, what's the preferred solution?
> 
> I thought we might be able to address the callers fairly cleanly by
> creating a couple xfs_verify_magic[16|32]() wrappers and cast to the
> underlying format, but then sparse just generates warnings for the
> casts. So AFAICT, the options are to create separate wrappers and
> xfs_buf_ops fields (magic16/magic32) for each magic type and use them
> appropriately in each verifier or go back to how this patch was written
> originally and use the in-core values.

Hmm.  It would be sort of ugly to have to re-add the endian conversions
back into the verifier code now; I think I lean towards having a magic16
array and a xfs_verify_magic16.

(Though I cheat and use anonymous unions :P)

> The former seems silly to me. My preference is the latter. Thoughts or
> other ideas? Is there some other way to safely cast a "restricted" type?

None that I know of, sparse complains about any cast between restricted
types.  I shut up sparse with the following mostly untested patch:

--D

xfs: fix xfs_buf magic number endian checks

Create a separate magic16 check function so that we don't run afoul of
static checkers.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
---
 fs/xfs/libxfs/xfs_attr_leaf.c |    4 ++--
 fs/xfs/libxfs/xfs_da_btree.c  |    8 ++++----
 fs/xfs/libxfs/xfs_dir2_leaf.c |    8 ++++----
 fs/xfs/libxfs/xfs_dquot_buf.c |    8 ++++----
 fs/xfs/libxfs/xfs_inode_buf.c |   10 +++++-----
 fs/xfs/xfs_buf.c              |   20 +++++++++++++++++++-
 fs/xfs/xfs_buf.h              |    8 ++++++--
 fs/xfs/xfs_log_recover.c      |    2 +-
 8 files changed, 45 insertions(+), 23 deletions(-)

diff --git a/fs/xfs/libxfs/xfs_attr_leaf.c b/fs/xfs/libxfs/xfs_attr_leaf.c
index 0c92987f57fc..1f6e3965ff74 100644
--- a/fs/xfs/libxfs/xfs_attr_leaf.c
+++ b/fs/xfs/libxfs/xfs_attr_leaf.c
@@ -358,8 +358,8 @@ xfs_attr3_leaf_read_verify(
 
 const struct xfs_buf_ops xfs_attr3_leaf_buf_ops = {
 	.name = "xfs_attr3_leaf",
-	.magic = { cpu_to_be16(XFS_ATTR_LEAF_MAGIC),
-		   cpu_to_be16(XFS_ATTR3_LEAF_MAGIC) },
+	.magic16 = { cpu_to_be16(XFS_ATTR_LEAF_MAGIC),
+		     cpu_to_be16(XFS_ATTR3_LEAF_MAGIC) },
 	.verify_read = xfs_attr3_leaf_read_verify,
 	.verify_write = xfs_attr3_leaf_write_verify,
 	.verify_struct = xfs_attr3_leaf_verify,
diff --git a/fs/xfs/libxfs/xfs_da_btree.c b/fs/xfs/libxfs/xfs_da_btree.c
index eb2cee428f26..e2737e2ac2ae 100644
--- a/fs/xfs/libxfs/xfs_da_btree.c
+++ b/fs/xfs/libxfs/xfs_da_btree.c
@@ -129,7 +129,7 @@ xfs_da3_blkinfo_verify(
 	struct xfs_mount	*mp = bp->b_target->bt_mount;
 	struct xfs_da_blkinfo	*hdr = &hdr3->hdr;
 
-	if (!xfs_verify_magic(bp, hdr->magic))
+	if (!xfs_verify_magic16(bp, hdr->magic))
 		return __this_address;
 
 	if (xfs_sb_version_hascrc(&mp->m_sb)) {
@@ -141,7 +141,7 @@ xfs_da3_blkinfo_verify(
 			return __this_address;
 	}
 
-	return 0;
+	return NULL;
 }
 
 static xfs_failaddr_t
@@ -274,8 +274,8 @@ xfs_da3_node_verify_struct(
 
 const struct xfs_buf_ops xfs_da3_node_buf_ops = {
 	.name = "xfs_da3_node",
-	.magic = { cpu_to_be16(XFS_DA_NODE_MAGIC),
-		   cpu_to_be16(XFS_DA3_NODE_MAGIC) },
+	.magic16 = { cpu_to_be16(XFS_DA_NODE_MAGIC),
+		     cpu_to_be16(XFS_DA3_NODE_MAGIC) },
 	.verify_read = xfs_da3_node_read_verify,
 	.verify_write = xfs_da3_node_write_verify,
 	.verify_struct = xfs_da3_node_verify_struct,
diff --git a/fs/xfs/libxfs/xfs_dir2_leaf.c b/fs/xfs/libxfs/xfs_dir2_leaf.c
index 094028b7b162..9a3767818c50 100644
--- a/fs/xfs/libxfs/xfs_dir2_leaf.c
+++ b/fs/xfs/libxfs/xfs_dir2_leaf.c
@@ -198,8 +198,8 @@ xfs_dir3_leaf_write_verify(
 
 const struct xfs_buf_ops xfs_dir3_leaf1_buf_ops = {
 	.name = "xfs_dir3_leaf1",
-	.magic = { cpu_to_be16(XFS_DIR2_LEAF1_MAGIC),
-		   cpu_to_be16(XFS_DIR3_LEAF1_MAGIC) },
+	.magic16 = { cpu_to_be16(XFS_DIR2_LEAF1_MAGIC),
+		     cpu_to_be16(XFS_DIR3_LEAF1_MAGIC) },
 	.verify_read = xfs_dir3_leaf_read_verify,
 	.verify_write = xfs_dir3_leaf_write_verify,
 	.verify_struct = xfs_dir3_leaf_verify,
@@ -207,8 +207,8 @@ const struct xfs_buf_ops xfs_dir3_leaf1_buf_ops = {
 
 const struct xfs_buf_ops xfs_dir3_leafn_buf_ops = {
 	.name = "xfs_dir3_leafn",
-	.magic = { cpu_to_be16(XFS_DIR2_LEAFN_MAGIC),
-		   cpu_to_be16(XFS_DIR3_LEAFN_MAGIC) },
+	.magic16 = { cpu_to_be16(XFS_DIR2_LEAFN_MAGIC),
+		     cpu_to_be16(XFS_DIR3_LEAFN_MAGIC) },
 	.verify_read = xfs_dir3_leaf_read_verify,
 	.verify_write = xfs_dir3_leaf_write_verify,
 	.verify_struct = xfs_dir3_leaf_verify,
diff --git a/fs/xfs/libxfs/xfs_dquot_buf.c b/fs/xfs/libxfs/xfs_dquot_buf.c
index b956638a3532..fb5bd9a804f6 100644
--- a/fs/xfs/libxfs/xfs_dquot_buf.c
+++ b/fs/xfs/libxfs/xfs_dquot_buf.c
@@ -277,8 +277,8 @@ xfs_dquot_buf_write_verify(
 
 const struct xfs_buf_ops xfs_dquot_buf_ops = {
 	.name = "xfs_dquot",
-	.magic = { cpu_to_be16(XFS_DQUOT_MAGIC),
-		   cpu_to_be16(XFS_DQUOT_MAGIC) },
+	.magic16 = { cpu_to_be16(XFS_DQUOT_MAGIC),
+		     cpu_to_be16(XFS_DQUOT_MAGIC) },
 	.verify_read = xfs_dquot_buf_read_verify,
 	.verify_write = xfs_dquot_buf_write_verify,
 	.verify_struct = xfs_dquot_buf_verify_struct,
@@ -286,8 +286,8 @@ const struct xfs_buf_ops xfs_dquot_buf_ops = {
 
 const struct xfs_buf_ops xfs_dquot_buf_ra_ops = {
 	.name = "xfs_dquot_ra",
-	.magic = { cpu_to_be16(XFS_DQUOT_MAGIC),
-		   cpu_to_be16(XFS_DQUOT_MAGIC) },
+	.magic16 = { cpu_to_be16(XFS_DQUOT_MAGIC),
+		     cpu_to_be16(XFS_DQUOT_MAGIC) },
 	.verify_read = xfs_dquot_buf_readahead_verify,
 	.verify_write = xfs_dquot_buf_write_verify,
 };
diff --git a/fs/xfs/libxfs/xfs_inode_buf.c b/fs/xfs/libxfs/xfs_inode_buf.c
index f92f14e93ad3..e021d5133ccb 100644
--- a/fs/xfs/libxfs/xfs_inode_buf.c
+++ b/fs/xfs/libxfs/xfs_inode_buf.c
@@ -97,7 +97,7 @@ xfs_inode_buf_verify(
 
 		dip = xfs_buf_offset(bp, (i << mp->m_sb.sb_inodelog));
 		unlinked_ino = be32_to_cpu(dip->di_next_unlinked);
-		di_ok = xfs_verify_magic(bp, dip->di_magic) &&
+		di_ok = xfs_verify_magic16(bp, dip->di_magic) &&
 			xfs_dinode_good_version(mp, dip->di_version) &&
 			xfs_verify_agino_or_null(mp, agno, unlinked_ino);
 		if (unlikely(XFS_TEST_ERROR(!di_ok, mp,
@@ -146,16 +146,16 @@ xfs_inode_buf_write_verify(
 
 const struct xfs_buf_ops xfs_inode_buf_ops = {
 	.name = "xfs_inode",
-	.magic = { cpu_to_be16(XFS_DINODE_MAGIC),
-		   cpu_to_be16(XFS_DINODE_MAGIC) },
+	.magic16 = { cpu_to_be16(XFS_DINODE_MAGIC),
+		     cpu_to_be16(XFS_DINODE_MAGIC) },
 	.verify_read = xfs_inode_buf_read_verify,
 	.verify_write = xfs_inode_buf_write_verify,
 };
 
 const struct xfs_buf_ops xfs_inode_buf_ra_ops = {
 	.name = "xfs_inode_ra",
-	.magic = { cpu_to_be16(XFS_DINODE_MAGIC),
-		   cpu_to_be16(XFS_DINODE_MAGIC) },
+	.magic16 = { cpu_to_be16(XFS_DINODE_MAGIC),
+		     cpu_to_be16(XFS_DINODE_MAGIC) },
 	.verify_read = xfs_inode_buf_readahead_verify,
 	.verify_write = xfs_inode_buf_write_verify,
 };
diff --git a/fs/xfs/xfs_buf.c b/fs/xfs/xfs_buf.c
index 52a382b8cbce..548344e25128 100644
--- a/fs/xfs/xfs_buf.c
+++ b/fs/xfs/xfs_buf.c
@@ -2213,7 +2213,7 @@ void xfs_buf_set_ref(struct xfs_buf *bp, int lru_ref)
 bool
 xfs_verify_magic(
 	struct xfs_buf		*bp,
-	uint32_t		dmagic)
+	__be32			dmagic)
 {
 	struct xfs_mount	*mp = bp->b_target->bt_mount;
 	int			idx;
@@ -2223,3 +2223,21 @@ xfs_verify_magic(
 		return false;
 	return dmagic == bp->b_ops->magic[idx];
 }
+/*
+ * Verify an on-disk magic value against the magic value specified in the
+ * verifier structure. The verifier magic is in disk byte order so the caller is
+ * expected to pass the value directly from disk.
+ */
+bool
+xfs_verify_magic16(
+	struct xfs_buf		*bp,
+	__be16			dmagic)
+{
+	struct xfs_mount	*mp = bp->b_target->bt_mount;
+	int			idx;
+
+	idx = xfs_sb_version_hascrc(&mp->m_sb);
+	if (unlikely(WARN_ON(!bp->b_ops || !bp->b_ops->magic16[idx])))
+		return false;
+	return dmagic == bp->b_ops->magic16[idx];
+}
diff --git a/fs/xfs/xfs_buf.h b/fs/xfs/xfs_buf.h
index 44f9423a1861..d0b96e071cec 100644
--- a/fs/xfs/xfs_buf.h
+++ b/fs/xfs/xfs_buf.h
@@ -125,7 +125,10 @@ struct xfs_buf_map {
 
 struct xfs_buf_ops {
 	char *name;
-	uint32_t magic[2];		/* v4 and v5 on disk magic values */
+	union {
+		__be32 magic[2];	/* v4 and v5 on disk magic values */
+		__be16 magic16[2];	/* v4 and v5 on disk magic values */
+	};
 	void (*verify_read)(struct xfs_buf *);
 	void (*verify_write)(struct xfs_buf *);
 	xfs_failaddr_t (*verify_struct)(struct xfs_buf *bp);
@@ -387,6 +390,7 @@ extern int xfs_setsize_buftarg(xfs_buftarg_t *, unsigned int);
 #define xfs_readonly_buftarg(buftarg)	bdev_read_only((buftarg)->bt_bdev)
 
 int xfs_buf_reverify(struct xfs_buf *bp, const struct xfs_buf_ops *ops);
-bool xfs_verify_magic(struct xfs_buf *bp, uint32_t dmagic);
+bool xfs_verify_magic(struct xfs_buf *bp, __be32 dmagic);
+bool xfs_verify_magic16(struct xfs_buf *bp, __be16 dmagic);
 
 #endif	/* __XFS_BUF_H__ */
diff --git a/fs/xfs/xfs_log_recover.c b/fs/xfs/xfs_log_recover.c
index f5948d16015b..3371d1ff27c4 100644
--- a/fs/xfs/xfs_log_recover.c
+++ b/fs/xfs/xfs_log_recover.c
@@ -3049,7 +3049,7 @@ xlog_recover_inode_pass2(
 	 * Make sure the place we're flushing out to really looks
 	 * like an inode!
 	 */
-	if (unlikely(!xfs_verify_magic(bp, dip->di_magic))) {
+	if (unlikely(!xfs_verify_magic16(bp, dip->di_magic))) {
 		xfs_alert(mp,
 	"%s: Bad inode magic number, dip = "PTR_FMT", dino bp = "PTR_FMT", ino = %Ld",
 			__func__, dip, bp, in_f->ilf_ino);