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SubjectRe: simplify procfs code for seq_file instances V2
On Sun, May 06, 2018 at 06:45:31PM +0100, Al Viro wrote:
> On Sun, May 06, 2018 at 08:19:49PM +0300, Alexey Dobriyan wrote:

> > @@ -62,9 +62,9 @@ struct proc_dir_entry {
> > umode_t mode;
> > u8 namelen;
> > #ifdef CONFIG_64BIT
> > -#define SIZEOF_PDE_INLINE_NAME (192-139)
> > +#define SIZEOF_PDE_INLINE_NAME (192-155)
> > #else
> > -#define SIZEOF_PDE_INLINE_NAME (128-87)
> > +#define SIZEOF_PDE_INLINE_NAME (128-95)
>
> > #endif
> > char inline_name[SIZEOF_PDE_INLINE_NAME];
> > } __randomize_layout;
>
> *UGH*

I agree. Maintaining these numbers is a pain point.
Who knew people were going to start adding fields right away.

> Both to the original state and that kind of "adjustments".
> Incidentally, with __bugger_layout in there these expressions
> are simply wrong.

Struct randomization is exempt from maintaining sizeof as they are already
screwing cachelines and everything. But if patch works with lockdep and
randomization -- even better.

> If nothing else, I would suggest turning the last one into
> char inline_name[];
> in hope that layout won't get... randomized that much and
> used
>
> #ifdef CONFIG_64BIT
> #define PDE_SIZE 192
> #else
> #define PDE_SIZE 128
> #endif
>
> union __proc_dir_entry {
> char pad[PDE_SIZE];
> struct proc_dir_entry real;
> };
>
> #define SIZEOF_PDE_INLINE_NAME (PDE_SIZE - offsetof(struct proc_dir_entry, inline_name))
>
> for constants, adjusted sizeof and sizeof_field when creating
> proc_dir_entry_cache and turned proc_root into
>
> union __proc_dir_entry __proc_root = { .real = {
> .low_ino = PROC_ROOT_INO,
> .namelen = 5,
> .mode = S_IFDIR | S_IRUGO | S_IXUGO,
> .nlink = 2,
> .refcnt = REFCOUNT_INIT(1),
> .proc_iops = &proc_root_inode_operations,
> .proc_fops = &proc_root_operations,
> .parent = &__proc_root.real,
> .subdir = RB_ROOT,
> .name = __proc_root.real.inline_name,
> .inline_name = "/proc",
> }};
>
> #define proc_root __proc_root.real
> (or actually used __proc_root.real in all of a 6 places where it remains).
>
> > - size_t state_size = PDE(inode)->state_size;
> > + unsigned int state_size = PDE(inode)->state_size;
>
> <shakes head>
> You and your "size_t is evil" crusade...

[nods]

unsigned long flags; /* error bits */
unsigned long i_state;
unsigned long s_blocksize;
unsigned long s_flags;
unsigned long s_iflags; /* internal SB_I_* flags */

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