Messages in this thread | | | From | Sasha Levin <> | Date | Sat, 31 Mar 2012 10:57:30 +0200 | Subject | Re: [PATCH] kmsg: Use vmalloc instead of kmalloc when writing |
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On Sat, Mar 31, 2012 at 2:02 AM, Kay Sievers <kay@vrfy.org> wrote: > On Sat, Mar 31, 2012 at 01:43, Greg KH <gregkh@linuxfoundation.org> wrote: >> On Sat, Mar 31, 2012 at 12:02:39AM +0200, Sasha Levin wrote: >>> On Fri, Mar 30, 2012 at 11:17 PM, Greg KH <gregkh@linuxfoundation.org> wrote: >>> > On Fri, Mar 30, 2012 at 09:05:52PM +0000, Arnd Bergmann wrote: >>> >> On Friday 30 March 2012, Thomas Gleixner wrote: >>> >> > I think so. This is an interface to inject stuff into dmesg. Limiting >>> >> > that to a reasonable size makes sense. We can probably limit it to >>> >> > something small like 1024, but I don't know about the "ideas" of those >>> >> > folks who think that it's a great idea to do it at all. >>> >> >>> >> I guess a page would be a reasonable size, similar to what we do for >>> >> sysfs. >>> > >>> > Ok. Sasha, as you seem to have noticed this, care to dig in syslog and >>> > systemd to get an idea of the buffer sizes they are expecting to pass >>> > into kmsg, and if they can handle a short write properly? If so, >>> > restricting it to a page is fine with me, otherwise we might want to >>> > make it a bit bigger. >>> >>> systemd seems to use posix LINE_MAX sized buffers, syslog-ng uses >>> dynamic strings, but it chews them one line at the time. >> >> Ok, care to update this patch with a max size? >> >> And again, does systemd and syslog-ng handle short writes properly? > > Printk has a static scratch buffer of 1024, we can not really process > more than that, so we can limit the /dev/kmsg write() to the same > size, I guess.
That's odd. I've tested it by writing 8000 chars into /dev/kmsg, and all of them came out on the printk, and I saw all of them in my dmesg.
This means that while printk may be somehow limited to 1024, it's still possible to dump more than that into dmesg. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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