On Tue, Oct 27, 2009 at 05:46:21PM -0500, Serge Hallyn wrote:
> From: Serge E. Hallyn <serue@xxxxxxxxxx>
>
> Error messages are both sent to an optional user-provided logfile,
> and, if CONFIG_CHECKPOINT_DEBUG=y, sent to syslog.
>
> Changelog:
> Oct 27: add %(C) for ctx->total.
> Oct 26: Per Oren suggestion, return -EBADF for bad
> logfile in ckpt_ctx_alloc().
>
> Signed-off-by: Serge E. Hallyn <serue@xxxxxxxxxx>
Reviewed-by: Matt Helsley <matthltc@xxxxxxxxxx>
> ---
> checkpoint/objhash.c | 2 +
> checkpoint/sys.c | 67 +++++++++++++++++++++++++++++++++++---
> include/linux/checkpoint.h | 5 +++
> include/linux/checkpoint_types.h | 1 +
> include/linux/syscalls.h | 5 ++-
> 5 files changed, 73 insertions(+), 7 deletions(-)
>
> diff --git a/checkpoint/objhash.c b/checkpoint/objhash.c
> index a152e69..25b9c10 100644
> --- a/checkpoint/objhash.c
> +++ b/checkpoint/objhash.c
> @@ -858,6 +858,8 @@ int ckpt_obj_contained(struct ckpt_ctx *ctx)
>
> /* account for ctx->file reference (if in the table already) */
> ckpt_obj_users_inc(ctx, ctx->file, 1);
> + if (ctx->logfile)
> + ckpt_obj_users_inc(ctx, ctx->logfile, 1);
> /* account for ctx->root_nsproxy reference (if in the table already) */
> ckpt_obj_users_inc(ctx, ctx->root_nsproxy, 1);
>
> diff --git a/checkpoint/sys.c b/checkpoint/sys.c
> index 38e65e4..ab0f294 100644
> --- a/checkpoint/sys.c
> +++ b/checkpoint/sys.c
> @@ -204,6 +204,8 @@ static void ckpt_ctx_free(struct ckpt_ctx *ctx)
>
> if (ctx->file)
> fput(ctx->file);
> + if (ctx->logfile)
> + fput(ctx->logfile);
>
> ckpt_obj_hash_free(ctx);
> path_put(&ctx->fs_mnt);
> @@ -225,7 +227,7 @@ static void ckpt_ctx_free(struct ckpt_ctx *ctx)
> }
>
> static struct ckpt_ctx *ckpt_ctx_alloc(int fd, unsigned long uflags,
> - unsigned long kflags)
> + unsigned long kflags, int logfd)
> {
> struct ckpt_ctx *ctx;
> int err;
> @@ -254,6 +256,12 @@ static struct ckpt_ctx *ckpt_ctx_alloc(int fd, unsigned long uflags,
> if (!ctx->file)
> goto err;
>
> + if (logfd != -1) {
> + ctx->logfile = fget(logfd);
> + if (!ctx->logfile)
> + goto err;
> + }
> +
> err = -ENOMEM;
> if (ckpt_obj_hash_alloc(ctx) < 0)
> goto err;
> @@ -401,6 +409,9 @@ char *ckpt_generate_fmt(struct ckpt_ctx *ctx, char *fmt)
> case 'E':
> len += sprintf(format+len, "[%s]", "err %d");
> break;
> + case 'C': /* count of bytes read/written to checkpoint image */
> + len += sprintf(format+len, "[%s]", "pos %d");
> + break;
Instead we could always output ckpt->total and then we wouldn't need %(C). I
suspect it's such a useful piece of information that it'll be repeated
in many/all format strings eventually.
> case 'O':
> len += sprintf(format+len, "[%s]", "obj %d");
> break;
> @@ -435,6 +446,51 @@ char *ckpt_generate_fmt(struct ckpt_ctx *ctx, char *fmt)
> return format;
> }
>
> +void ckpt_log_error(struct ckpt_ctx *ctx, char *fmt, ...)
> +{
> + mm_segment_t fs;
> + struct file *file;
> + int count;
> + va_list ap, aq, az;
> + char *format;
> + char buf[200], *bufp = buf;
I believe this buffer is too big for a kernel stack -- especially
for ckpt_log_error() which might be invoked "deep" in
the kernel stack.
> +
> + if (!ctx || !ctx->logfile)
> + return;
> + file = ctx->logfile;
> +
> + va_start(ap, fmt);
> + format = ckpt_generate_fmt(ctx, fmt);
> + va_copy(aq, ap);
> + va_copy(az, ap);
> + /* I'm not clear here - can I re-use aq, or do i need
> + * a third copy? */
I'm no varargs expert but I have re-read the man page and
seen a purported snippet of the standard. :)
I think you need a third copy operation but you may only need
two va_lists so long as you do a va_end before the next va_copy:
va_copy(aq, ap);
... <use aq> ...
va_end(aq);
va_copy(aq, ap);
... <use aq> ...
va_end(aq);
...
va_end(ap);
Based on my reading it sounded like some arch/ABIs require space
proportional to the number of arguments for each un-va_end-ed copy.
> + count = vsnprintf(bufp, 200, format ? : fmt, aq);
BTW -- I think you can use snprintf() without the buffer and length
arguments if you just need the length calculated. Perhaps the same
is possible with vsnprintf():
count = vsnprintf(NULL, 0, format ? : fmt, aq);
If that works with vsnprintf() too then you could get rid of the
stack buf and always kmalloc the space..
Cheers,
-Matt Helsley
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