Re: git: 099a81a4173b - main - linprocfs: Add support for proc/sysvipc/{msg,sem,shm}

On Sat, May 11, 2024 at 07:39:18PM +0000, Warner Losh wrote:
> The branch main has been updated by imp:
> 
> URL: https://cgit.FreeBSD.org/src/commit/?id=099a81a4173bc5b121e50d4e27ea5fafdda8475b
> 
> commit 099a81a4173bc5b121e50d4e27ea5fafdda8475b
> Author:     Ricardo Branco <rbranco@suse.de>
> AuthorDate: 2024-05-04 13:38:20 +0000
> Commit:     Warner Losh <imp@FreeBSD.org>
> CommitDate: 2024-05-11 19:37:47 +0000
> 
>     linprocfs: Add support for proc/sysvipc/{msg,sem,shm}
>     
>     Signed-off-by: Ricardo Branco <rbranco@suse.de>
>     Reviewed by: imp
>     Pull Request: https://github.com/freebsd/freebsd-src/pull/1218
> ---
>  sys/compat/linprocfs/linprocfs.c | 182 +++++++++++++++++++++++++++++++++++++++
>  1 file changed, 182 insertions(+)
> 
> diff --git a/sys/compat/linprocfs/linprocfs.c b/sys/compat/linprocfs/linprocfs.c
> index 391d5f679ee5..a877d4065c18 100644
> --- a/sys/compat/linprocfs/linprocfs.c
> +++ b/sys/compat/linprocfs/linprocfs.c
> @@ -126,6 +126,9 @@
>  #define P2K(x) ((x) << (PAGE_SHIFT - 10))		/* pages to kbytes */
>  #define TV2J(x)	((x)->tv_sec * 100UL + (x)->tv_usec / 10000)
>  
> +/* Value defined in sys/kern/sysv_shm.c */
> +#define SHMSEG_ALLOCATED	0x0800
> +
>  /**
>   * @brief Mapping of ki_stat in struct kinfo_proc to the linux state
>   *
> @@ -2092,6 +2095,176 @@ linprocfs_domax_map_cnt(PFS_FILL_ARGS)
>  	return (0);
>  }
>  
> +/*
> + * Filler function for proc/sysvipc/msg
> + */
> +static int
> +linprocfs_dosysvipc_msg(PFS_FILL_ARGS)
> +{
> +	struct msqid_kernel *msqids;
> +	u_long id, msgmni;
> +	size_t sz;
> +	int error;
> +
> +	sbuf_printf(sb,
> +	    "%10s %10s %4s  %10s %10s %5s %5s %5s %5s %5s %5s %10s %10s %10s\n",
> +	    "key", "msqid", "perms", "cbytes", "qnum", "lspid", "lrpid",
> +	    "uid", "gid", "cuid", "cgid", "stime", "rtime", "ctime");
> +
> +again:
> +	msgmni = msginfo.msgmni;
> +	sz = sizeof(struct msqid_kernel) * msgmni;
> +	msqids = malloc(sz, M_TEMP, M_NOWAIT);
Why M_NOWAIT?  What does prevent us from waiting there?

> +	if (msqids == NULL)
> +		return (ENOMEM);
> +	if (msgmni != msginfo.msgmni) {
What prevents msginfo.msgmni from changing again?  Otherwise, why this check
is needed?

(Same questions for other two similar places trimmed below).