[Linux-ha-dev] SFEX resource agent for heartbeat

[Lars Marowsky-Bree]

On 2008-10-17T01:03:07, Xinwei Hu <hxinwei at gmail.com> wrote:

> > This is incorrect. O_DIRECT needs to be page-aligned. valign()
> > provides the proper guarantees w/o needing to know the pagesize.
> According to "man 2 open", "Under Linux 2.6, alignment to 512-byte
> boundaries suffices." em.

That's true for sector_size == 512, I think, but it could be larger.

> And I also can't find where's valign from.
> Will that be OK if I fallback to posix_memalign(ptr,
> sysconf(_SC_PAGESIZE), ...) ?

My mistake; the call is valloc(), not valign().

And, well, I now see it is just a convenient wrapper around
posix_memalign(), so this part seems to be right - I stand corrected,
even though valloc() is easier to read ;-)

> >> +typedef struct sfex_controldata_ondisk {
> >> +  uint8_t magic[4];
> >> +  uint8_t version[4];
> >> +  uint8_t revision[4];
> >> +  uint8_t blocksize[8];
> >> +  uint8_t numlocks[4];
> >> +  uint8_t padding[SFEX_ODIRECT_ALIGNMENT - 24 ];
> >> +} sfex_controldata_ondisk;
> >
> > Why have both? uint32_t etc exist, and the read/write IO functions can
> > convert as needed. That saves double definitions.
> 
> I think the double definitions help to make it clear that on disk meta
> data contains strings only, while the in-memory meta data contains
> integers. :)

Well, it still needs to be sector-aligned.

> > This simply needs to call valloc() and all is well.
> valloc is obsoleted by posix_memalign, as far as I remember :)

Ah, well, who can keep track of all this modern stuff ;-)

> >> +  if (uname(&u)) {
> >> +    SFEX_LOG_ERR("%s: ERROR: %s\n", progname, strerror(errno));
> >> +    exit(3);
> >> +  }
> >
> > I'm surprised this worked. Are you sure it shouldn't read "uname() < 0"?
> 
> uname returns 0 on success and -1 on failure.
> I don't see difference of if(uname() < 0) and if(uname()) ?

It's clearer, I think - apparently it managed to confuse me briefly ;-)
I'd write != 0 or < 0.


Regards,
    Lars

-- 
Teamlead Kernel, SuSE Labs, Research and Development
SUSE LINUX Products GmbH, GF: Markus Rex, HRB 16746 (AG Nürnberg)
"Experience is the name everyone gives to their mistakes." -- Oscar Wilde