libxfs: check all defer ops types

From: Darrick J. Wong <[email protected]>

Make sure we have all the defer ops types loaded before proceeding.

Signed-off-by Darrick J. Wong <[email protected]>

---
 libxfs/init.c      |    5 +++++
 libxfs/xfs_defer.c |   12 ++++++++++++
 libxfs/xfs_defer.h |    1 +
 3 files changed, 18 insertions(+)

libxfs/init.c +5 -0

index 750b8f20..d1fdc3a8 100644
@@ -253,6 +253,11 @@ libxfs_init(libxfs_init_t *a)
 	xfs_rmap_update_init_defer_op();
 	xfs_refcount_update_init_defer_op();
 	xfs_bmap_update_init_defer_op();
+	if (!xfs_defer_check_all_present()) {
+		fprintf(stderr, _("%s: defer ops not all there\n"),
+			progname);
+		goto done;
+	}
 
 	radix_tree_init();
 

libxfs/xfs_defer.c +12 -0

index 5a6da0f3..cd3a8ef3 100644
@@ -545,3 +545,15 @@ xfs_defer_move(
 
 	xfs_defer_reset(stp);
 }
+
+/* Make sure we filled out all the defer_ops types. */
+bool
+xfs_defer_check_all_present(void)
+{
+	int		x;
+
+	for(x = 0; x < XFS_DEFER_OPS_TYPE_MAX; x++)
+		if (defer_op_types[x] == NULL)
+			return false;
+	return true;
+}

libxfs/xfs_defer.h +1 -0

index 2584a5b9..bc7ae7ff 100644
@@ -57,5 +57,6 @@ struct xfs_defer_op_type {
 };
 
 void xfs_defer_init_op_type(const struct xfs_defer_op_type *type);
+bool xfs_defer_check_all_present(void);
 
 #endif /* __XFS_DEFER_H__ */

Quoted 3 lines · Darrick J. Wong

From: Darrick J. Wong <[email protected]>

Make sure we have all the defer ops types loaded before proceeding.

So, the only reason we have this problem is that userspace doesn't exactly share the code which handles all the defer ops.

I think this really needs to be a BUILD_BUG_ON if anything, by the time we get to runtime it's really too late, and a weird thing to run at every invocation.

The only thing I can think of is to make an array containing each of the xfs_defer_op_types, and iterate over it in some sort of xfs_defer_ops_init(), then we can compare the size of that array to XFS_DEFER_OPS_TYPE_MAX with a BUILD_BUG_ON. Worth it?

Quoted 8 lines · Eric Sandeen

Quoted 3 lines · Darrick J. Wong

From: Darrick J. Wong <[email protected]>

Make sure we have all the defer ops types loaded before proceeding.

So, the only reason we have this problem is that userspace doesn't exactly share the code which handles all the defer ops.

Quoted 8 lines

I think this really needs to be a BUILD_BUG_ON if anything, by the time we get to runtime it's really too late, and a weird thing to run at every invocation.

The only thing I can think of is to make an array containing each of the xfs_defer_op_types, and iterate over it in some sort of xfs_defer_ops_init(), then we can compare the size of that array to XFS_DEFER_OPS_TYPE_MAX with a BUILD_BUG_ON. Worth it?

Uh, or just make a statically initialized array?
I guess nothing about this directly enforces that the ->type number is in the right slot of the array.

static const struct
xfs_defer_op_type *defer_op_types[XFS_DEFER_OPS_TYPE_MAX] = {
xfs_bmap_update_defer_type, xfs_refcount_update_defer_type, xfs_rmap_update_defer_type, xfs_extent_free_defer_type, xfs_agfl_free_defer_type,
};

The downside of this is that now we have to declare all those functions somewhere so that the fs/xfs/ and libxfs/defer_item.c can match the prototypes.

static const struct
xfs_defer_op_type *defer_op_types[XFS_DEFER_OPS_TYPE_MAX] = {
xfs_bmap_update_defer_type, xfs_refcount_update_defer_type, xfs_rmap_update_defer_type, xfs_extent_free_defer_type, xfs_agfl_free_defer_type,
};

Quoted 8 lines · Eric Sandeen

static const struct
xfs_defer_op_type *defer_op_types[XFS_DEFER_OPS_TYPE_MAX] = {
xfs_bmap_update_defer_type, xfs_refcount_update_defer_type, xfs_rmap_update_defer_type, xfs_extent_free_defer_type, xfs_agfl_free_defer_type,
};

I think this should be:

static const struct xfs_defer_op_type *defer_op_types[] = {
[XFS_DEFER_OPS_TYPE_BMAP] = &xfs_bmap_update_defer_type,
[XFS_DEFER_OPS_TYPE_REFCOUNT] = &xfs_refcount_update_defer_type,
[XFS_DEFER_OPS_TYPE_RMAP] = &xfs_rmap_update_defer_type,
[XFS_DEFER_OPS_TYPE_FREE] = &xfs_extent_free_defer_type,
[XFS_DEFER_OPS_TYPE_AGFL_FREE] = &xfs_agfl_free_defer_type,
};

somefunc()

{
	BUILD_BUG_ON(ARRAY_SIZE(defer_op_types) != XFS_DEFER_OPS_TYPE_MAX);
}