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Subject[PATCH -vfs] proc: don't maintain sizeof(struct proc_dir_entry)
Automatically cap sizeof(struct proc_dir_entry) at 192/128 bytes or
256/192 bytes if spinlock debugging/lockdep is enabled.

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
---

fs/proc/generic.c | 2 +-
fs/proc/inode.c | 5 +++--
fs/proc/internal.h | 10 ++++++----
3 files changed, 10 insertions(+), 7 deletions(-)

--- a/fs/proc/generic.c
+++ b/fs/proc/generic.c
@@ -410,7 +410,7 @@ static struct proc_dir_entry *__proc_create(struct proc_dir_entry **parent,
if (!ent)
goto out;

- if (qstr.len + 1 <= sizeof(ent->inline_name)) {
+ if (qstr.len + 1 <= SIZEOF_PDE_INLINE_NAME) {
ent->name = ent->inline_name;
} else {
ent->name = kmalloc(qstr.len + 1, GFP_KERNEL);
--- a/fs/proc/inode.c
+++ b/fs/proc/inode.c
@@ -105,9 +105,10 @@ void __init proc_init_kmemcache(void)
kmem_cache_create("pde_opener", sizeof(struct pde_opener), 0,
SLAB_ACCOUNT|SLAB_PANIC, NULL);
proc_dir_entry_cache = kmem_cache_create_usercopy(
- "proc_dir_entry", sizeof(struct proc_dir_entry), 0, SLAB_PANIC,
+ "proc_dir_entry", SIZEOF_PDE, 0, SLAB_PANIC,
offsetof(struct proc_dir_entry, inline_name),
- sizeof_field(struct proc_dir_entry, inline_name), NULL);
+ SIZEOF_PDE_INLINE_NAME, NULL);
+ BUILD_BUG_ON(sizeof(struct proc_dir_entry) >= SIZEOF_PDE);
}

static int proc_show_options(struct seq_file *seq, struct dentry *root)
--- a/fs/proc/internal.h
+++ b/fs/proc/internal.h
@@ -61,13 +61,15 @@ struct proc_dir_entry {
char *name;
umode_t mode;
u8 namelen;
+ char inline_name[];
+} __randomize_layout;
+
#ifdef CONFIG_64BIT
-#define SIZEOF_PDE_INLINE_NAME (192-155)
+#define SIZEOF_PDE (sizeof(spinlock_t) == 4 ? 192 : 256)
#else
-#define SIZEOF_PDE_INLINE_NAME (128-95)
+#define SIZEOF_PDE (sizeof(spinlock_t) == 4 ? 128 : 192)
#endif
- char inline_name[SIZEOF_PDE_INLINE_NAME];
-} __randomize_layout;
+#define SIZEOF_PDE_INLINE_NAME (SIZEOF_PDE - sizeof(struct proc_dir_entry))

extern struct kmem_cache *proc_dir_entry_cache;
void pde_free(struct proc_dir_entry *pde);
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