On Wed, 27 Dec 2017 14:49:46 -0800 Alexei Starovoitov <a...@fb.com> wrote:
> On 12/27/17 12:09 AM, Masami Hiramatsu wrote: > > On Tue, 26 Dec 2017 18:12:56 -0800 > > Alexei Starovoitov <alexei.starovoi...@gmail.com> wrote: > > > >> On Tue, Dec 26, 2017 at 04:48:25PM +0900, Masami Hiramatsu wrote: > >>> Support in-kernel fault-injection framework via debugfs. > >>> This allows you to inject a conditional error to specified > >>> function using debugfs interfaces. > >>> > >>> Signed-off-by: Masami Hiramatsu <mhira...@kernel.org> > >>> --- > >>> Documentation/fault-injection/fault-injection.txt | 5 + > >>> kernel/Makefile | 1 > >>> kernel/fail_function.c | 169 > >>> +++++++++++++++++++++ > >>> lib/Kconfig.debug | 10 + > >>> 4 files changed, 185 insertions(+) > >>> create mode 100644 kernel/fail_function.c > >>> > >>> diff --git a/Documentation/fault-injection/fault-injection.txt > >>> b/Documentation/fault-injection/fault-injection.txt > >>> index 918972babcd8..6243a588dd71 100644 > >>> --- a/Documentation/fault-injection/fault-injection.txt > >>> +++ b/Documentation/fault-injection/fault-injection.txt > >>> @@ -30,6 +30,11 @@ o fail_mmc_request > >>> injects MMC data errors on devices permitted by setting > >>> debugfs entries under /sys/kernel/debug/mmc0/fail_mmc_request > >>> > >>> +o fail_function > >>> + > >>> + injects error return on specific functions by setting debugfs entries > >>> + under /sys/kernel/debug/fail_function. No boot option supported. > >> > >> I like it. > >> Could you document it a bit better? > > > > Yes, I will do in next series. > > > >> In particular retval is configurable, but without an example no one > >> will be able to figure out how to use it. > > > > Ah, right. BTW, as I pointed in the covermail, should we store the > > expected error value range into the injectable list? e.g. > > > > ALLOW_ERROR_INJECTION(open_ctree, -1, -MAX_ERRNO) > > > > And provide APIs to check/get it. > > I'm afraid such check would be too costly. > Right now we have only two functions marked but I expect hundreds more > will be added in the near future as soon as developers realize the > potential of such error injection. > All of ALLOW_ERROR_INJECTION marks add 8 byte overhead each to .data. > Multiple by 1k and we have 8k of data spent on marks. > If we add max/min range marks that doubles it for very little use. > I think marking function only is enough. Sorry, I don't think so. Even if it takes 16 bytes more for each points, I don't think it is any overhead for machines in these days. Even if so, we can provide a kconfig to reduce it. I mean, we are living in GB-order memory are, and it will be bigger in the future. Why we have to worry about hundreds of 16bytes memory pieces? It will take a few KB, and even if we mark thousands of functions, it never reaches 1MB, in GB memory pool. :) Of course, for many small-footprint embedded devices (like having less than 128MB memory), this feature can be a overhead. But they can cut off the table by kconfig. Thank you, -- Masami Hiramatsu <mhira...@kernel.org> -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
