simple_xattr: change interface to pass struct simple_xattrs **

Change the simple_xattr API to accept pointer-to-pointer (struct
simple_xattrs **) instead of pointer.  This allows the functions to handle
lazy allocation internally without requiring callers to use
simple_xattrs_lazy_alloc().

The simple_xattr_set(), simple_xattr_set_limited() and simple_xattr_add()
functions now handle allocation when xattrs is NULL.  simple_xattrs_free()
now also frees the xattrs structure itself and sets the pointer to NULL.

This simplifies callers and removes the need for most callers to explicitly
manage xattrs allocation and lifetime.

In shmem_initxattrs(), the total required space for all initial xattrs
(ispace) is pre-calculated and deducted from sbinfo->free_ispace.

Since this patch modifies the function to add new xattrs directly to the
inode's &info->xattrs list rather than using a local temporary variable, a
failure means that the partially populated info->xattrs list remains
attached to the inode.

When the VFS caller handles the -ENOMEM error, it drops the newly created
inode via iput(), shmem_free_inode() adds freed to sbinfo->free_ispace a
second time, permanently inflating the tmpfs free space quota.

Fix by substracting already added xattrs from ispace.

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Link: https://patch.msgid.link/20260605135322.2632068-4-mszeredi@redhat.com
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>

1 files changed, 6 insertions, 15 deletions

diff --git a/include/linux/xattr.h b/include/linux/xattr.h
index 8b6601367eae..ded446c1ef81 100644
--- a/include/linux/xattr.h
+++ b/include/linux/xattr.h
@@ -133,26 +133,23 @@ static inline void simple_xattr_limits_init(struct simple_xattr_limits *limits)
 }
 
 int simple_xattrs_init(struct simple_xattrs *xattrs);
-struct simple_xattrs *simple_xattrs_alloc(void);
-struct simple_xattrs *simple_xattrs_lazy_alloc(struct simple_xattrs **xattrsp,
-					       const void *value, int flags);
-void simple_xattrs_free(struct simple_xattrs *xattrs, size_t *freed_space);
+void simple_xattrs_free(struct simple_xattrs **xattrs, size_t *freed_space);
 size_t simple_xattr_space(const char *name, size_t size);
 struct simple_xattr *simple_xattr_alloc(const void *value, size_t size);
 void simple_xattr_free(struct simple_xattr *xattr);
 void simple_xattr_free_rcu(struct simple_xattr *xattr);
-int simple_xattr_get(struct simple_xattrs *xattrs, const char *name,
+int simple_xattr_get(struct simple_xattrs **xattrs, const char *name,
 		     void *buffer, size_t size);
-struct simple_xattr *simple_xattr_set(struct simple_xattrs *xattrs,
+struct simple_xattr *simple_xattr_set(struct simple_xattrs **xattrs,
 				      const char *name, const void *value,
 				      size_t size, int flags);
-int simple_xattr_set_limited(struct simple_xattrs *xattrs,
+int simple_xattr_set_limited(struct simple_xattrs **xattrs,
 			     struct simple_xattr_limits *limits,
 			     const char *name, const void *value,
 			     size_t size, int flags);
-ssize_t simple_xattr_list(struct inode *inode, struct simple_xattrs *xattrs,
+ssize_t simple_xattr_list(struct inode *inode, struct simple_xattrs **xattrs,
 			  char *buffer, size_t size);
-int simple_xattr_add(struct simple_xattrs *xattrs,
+int simple_xattr_add(struct simple_xattrs **xattrs,
 		     struct simple_xattr *new_xattr);
 int xattr_list_one(char **buffer, ssize_t *remaining_size, const char *name);
 
@@ -162,10 +159,4 @@ DEFINE_CLASS(simple_xattr,
 	     simple_xattr_alloc(value, size),
 	     const void *value, size_t size)
 
-DEFINE_CLASS(simple_xattrs,
-            struct simple_xattrs *,
-            if (!IS_ERR_OR_NULL(_T)) { simple_xattrs_free(_T, NULL); kfree(_T); },
-            simple_xattrs_alloc(),
-            void)
-
 #endif	/* _LINUX_XATTR_H */