[v3,13/15] fcntl: remove FASYNC_MAGIC

  We have largely moved away from this approach, and we have better
debugging instrumentation nowadays: kill it.

Link: https://lore.kernel.org/linux-doc/YyMlovoskUcHLEb7@kroah.com/
Signed-off-by: Ahelenia Ziemiańska <nabijaczleweli@nabijaczleweli.xyz>
---
 Documentation/process/magic-number.rst                    | 1 -
 Documentation/translations/it_IT/process/magic-number.rst | 1 -
 Documentation/translations/zh_CN/process/magic-number.rst | 1 -
 Documentation/translations/zh_TW/process/magic-number.rst | 1 -
 fs/fcntl.c                                                | 6 ------
 include/linux/fs.h                                        | 3 ---
 6 files changed, 13 deletions(-)
  

On Fri, 2022-11-11 at 02:14 +0100, Ahelenia Ziemiańska wrote:
> We have largely moved away from this approach, and we have better
> debugging instrumentation nowadays: kill it.
> 
> Link: https://lore.kernel.org/linux-doc/YyMlovoskUcHLEb7@kroah.com/
> Signed-off-by: Ahelenia Ziemiańska <nabijaczleweli@nabijaczleweli.xyz>
> ---
>  Documentation/process/magic-number.rst                    | 1 -
>  Documentation/translations/it_IT/process/magic-number.rst | 1 -
>  Documentation/translations/zh_CN/process/magic-number.rst | 1 -
>  Documentation/translations/zh_TW/process/magic-number.rst | 1 -
>  fs/fcntl.c                                                | 6 ------
>  include/linux/fs.h                                        | 3 ---
>  6 files changed, 13 deletions(-)
> 
> diff --git a/Documentation/process/magic-number.rst b/Documentation/process/magic-number.rst
> index e59c707ec785..6e432917a5a8 100644
> --- a/Documentation/process/magic-number.rst
> +++ b/Documentation/process/magic-number.rst
> @@ -68,6 +68,5 @@ Changelog::
>  ===================== ================ ======================== ==========================================
>  Magic Name            Number           Structure                File
>  ===================== ================ ======================== ==========================================
> -FASYNC_MAGIC          0x4601           fasync_struct            ``include/linux/fs.h``
>  CCB_MAGIC             0xf2691ad2       ccb                      ``drivers/scsi/ncr53c8xx.c``
>  ===================== ================ ======================== ==========================================
> diff --git a/Documentation/translations/it_IT/process/magic-number.rst b/Documentation/translations/it_IT/process/magic-number.rst
> index 37a539867b6f..7d4c117ac626 100644
> --- a/Documentation/translations/it_IT/process/magic-number.rst
> +++ b/Documentation/translations/it_IT/process/magic-number.rst
> @@ -74,6 +74,5 @@ Registro dei cambiamenti::
>  ===================== ================ ======================== ==========================================
>  Nome magico           Numero           Struttura                File
>  ===================== ================ ======================== ==========================================
> -FASYNC_MAGIC          0x4601           fasync_struct            ``include/linux/fs.h``
>  CCB_MAGIC             0xf2691ad2       ccb                      ``drivers/scsi/ncr53c8xx.c``
>  ===================== ================ ======================== ==========================================
> diff --git a/Documentation/translations/zh_CN/process/magic-number.rst b/Documentation/translations/zh_CN/process/magic-number.rst
> index 8a3a3e872c52..c17e3f20440a 100644
> --- a/Documentation/translations/zh_CN/process/magic-number.rst
> +++ b/Documentation/translations/zh_CN/process/magic-number.rst
> @@ -57,6 +57,5 @@ Linux 魔术数
>  ===================== ================ ======================== ==========================================
>  魔术数名              数字             结构                     文件
>  ===================== ================ ======================== ==========================================
> -FASYNC_MAGIC          0x4601           fasync_struct            ``include/linux/fs.h``
>  CCB_MAGIC             0xf2691ad2       ccb                      ``drivers/scsi/ncr53c8xx.c``
>  ===================== ================ ======================== ==========================================
> diff --git a/Documentation/translations/zh_TW/process/magic-number.rst b/Documentation/translations/zh_TW/process/magic-number.rst
> index 7ace7834f7f9..e2eeb74e7192 100644
> --- a/Documentation/translations/zh_TW/process/magic-number.rst
> +++ b/Documentation/translations/zh_TW/process/magic-number.rst
> @@ -60,6 +60,5 @@ Linux 魔術數
>  ===================== ================ ======================== ==========================================
>  魔術數名              數字             結構                     文件
>  ===================== ================ ======================== ==========================================
> -FASYNC_MAGIC          0x4601           fasync_struct            ``include/linux/fs.h``
>  CCB_MAGIC             0xf2691ad2       ccb                      ``drivers/scsi/ncr53c8xx.c``
>  ===================== ================ ======================== ==========================================
> diff --git a/fs/fcntl.c b/fs/fcntl.c
> index 146c9ab0cd4b..e366a3804108 100644
> --- a/fs/fcntl.c
> +++ b/fs/fcntl.c
> @@ -924,7 +924,6 @@ struct fasync_struct *fasync_insert_entry(int fd, struct file *filp, struct fasy
>  	}
>  
>  	rwlock_init(&new->fa_lock);
> -	new->magic = FASYNC_MAGIC;
>  	new->fa_file = filp;
>  	new->fa_fd = fd;
>  	new->fa_next = *fapp;
> @@ -988,11 +987,6 @@ static void kill_fasync_rcu(struct fasync_struct *fa, int sig, int band)
>  		struct fown_struct *fown;
>  		unsigned long flags;
>  
> -		if (fa->magic != FASYNC_MAGIC) {
> -			printk(KERN_ERR "kill_fasync: bad magic number in "
> -			       "fasync_struct!\n");
> -			return;
> -		}
>  		read_lock_irqsave(&fa->fa_lock, flags);
>  		if (fa->fa_file) {
>  			fown = &fa->fa_file->f_owner;
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index e654435f1651..acfd5db5341a 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -1345,15 +1345,12 @@ static inline int locks_lock_file_wait(struct file *filp, struct file_lock *fl)
>  
>  struct fasync_struct {
>  	rwlock_t		fa_lock;
> -	int			magic;
>  	int			fa_fd;
>  	struct fasync_struct	*fa_next; /* singly linked list */
>  	struct file		*fa_file;
>  	struct rcu_head		fa_rcu;
>  };
>  
> -#define FASYNC_MAGIC 0x4601
> -
>  /* SMP safe fasync helpers: */
>  extern int fasync_helper(int, struct file *, int, struct fasync_struct **);
>  extern struct fasync_struct *fasync_insert_entry(int, struct file *, struct fasync_struct **, struct fasync_struct *);

Reviewed-by: Jeff Layton <jlayton@kernel.org>