[PATCH v3 5/6] xfs: initialise args->total for parent pointer updates

[Javier Tia <javier@peridio.com>]

xfs_parent_da_args_init() builds an xfs_da_args from a zeroed
xfs_parent_args (kmem_cache_zalloc), leaving args->total == 0.
xfs_da_grow_inode_int() treats that field as a running block reservation
and subtracts from it; because it is an xfs_extlen_t (uint32_t), the
first attr-fork growth wraps it to ~0U.  That defeats the free-space
check in xfs_alloc_space_available(), and when it coincides with an AG
that has exactly zero available blocks the allocation is clamped to
maxlen 0 and returns -ENOSPC, which xfs_defer_finish_noroll() escalates
to a filesystem shutdown.

Set args->total the way the log recovery path does
(xfs_attri_recover_work(), xfs_attr_item.c:706), in the add and replace
paths that can grow the fork.  Removals and lookups never grow it, so
they leave the field alone, matching that switch.

Fixes: b7c62d90c12c ("xfs: parent pointer attribute creation")
Cc: <stable@vger.kernel.org> # v6.10
Signed-off-by: Javier Tia <floss@jetm.me>
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
---
 fs/xfs/libxfs/xfs_parent.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/fs/xfs/libxfs/xfs_parent.c b/fs/xfs/libxfs/xfs_parent.c
index 3509cc4b2175..312f33086d53 100644
--- a/fs/xfs/libxfs/xfs_parent.c
+++ b/fs/xfs/libxfs/xfs_parent.c
@@ -194,7 +194,7 @@ xfs_parent_addname(
 	const struct xfs_name	*parent_name,
 	struct xfs_inode	*child)
 {
-	int			error;
+	int			error, local;
 
 	error = xfs_parent_iread_extents(tp, child);
 	if (error)
@@ -204,6 +204,10 @@ xfs_parent_addname(
 	xfs_parent_da_args_init(&ppargs->args, tp, &ppargs->rec, child,
 			child->i_ino, parent_name);
 
+	/* Growing the attr fork needs a real reservation in args->total. */
+	ppargs->args.total = xfs_attr_calc_size(&ppargs->args, &local);
+	ASSERT(local);
+
 	return xfs_attr_setname(&ppargs->args, 0);
 }
 
@@ -240,7 +244,7 @@ xfs_parent_replacename(
 	const struct xfs_name	*new_name,
 	struct xfs_inode	*child)
 {
-	int			error;
+	int			error, local;
 
 	error = xfs_parent_iread_extents(tp, child);
 	if (error)
@@ -250,6 +254,10 @@ xfs_parent_replacename(
 	xfs_parent_da_args_init(&ppargs->args, tp, &ppargs->rec, child,
 			child->i_ino, old_name);
 
+	/* Growing the attr fork needs a real reservation in args->total. */
+	ppargs->args.total = xfs_attr_calc_size(&ppargs->args, &local);
+	ASSERT(local);
+
 	xfs_inode_to_parent_rec(&ppargs->new_rec, new_dp);
 
 	ppargs->args.new_name = new_name->name;
-- 
Javier Tia