On 2018/6/21 12:20 AM, Arnd Bergmann wrote: > On Wed, Jun 20, 2018 at 5:51 PM, Coly Li <colyli@xxxxxxx> wrote: >> On 2018/6/20 5:51 PM, Arnd Bergmann wrote: >>> bcache uses get_seconds() to read the current system time and store it in >>> the superblock as well as in uuid_entry structures that are user visible. >>> >>> This changes over from the deprecated function to >>> ktime_get_real_seconds(), which returns a 64-bit timestamp as it >>> should. Unfortunately, the two structures are still limited to 32 bits, >>> so this won't fix any real problems. Let's at least document that >>> properly, in case we get an updated format in the future it can be >>> fixed. Until then, we still have some time, and checking the tools >>> at https://github.com/koverstreet/bcache-tools reveals no access to >>> any of them. >>> >>> Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx> >> >> Hi Arnd, >> >> Firstly thanks to your patch, especially the detailed information in >> patch log, it helps me to understand the problem more easier. >> >> From the information, it seems the problem is current 32bit time stamp >> will be overflow in 2106. So it will be 88 years later, which I have to >> say I don't care. >> >> Also for get_seconds() which works well for current code as many other >> places call it, I would like to keep it. > > I'm currently in the process of removing all instances of get_seconds() > with patches like this. In many cases, we actually want to use > ktime_get_seconds() to return a monotonic time that is immune > to concurrent setttimeofday() calls, in others the code needs to be > changed to avoid the y2038 overflow. For bcache, we don't > really need either of them, but I'd still want to move over everything > to ktime_get_* based interfaces. > Hi Arnd, Oh I see. Now I agree with you, and no more concern. Thanks for your explaining. > Should I clarify that motivation in the changelog text further? > Yes please, that will be great. > I can also do a simple replacement of get_seconds() with > ktime_get_real_seconds() throughout bcache instead of > adding the intermediate helper function. Yes please, it will be better IMHO. Thanks. Coly Li -- To unsubscribe from this list: send the line "unsubscribe linux-bcache" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
