Re: [PATCH v2 4/5] nilfs-utils: add support for NILFS_IOCTL_SET_SUINFO ioctl

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On Fri, 24 Jan 2014 21:00:03 +0100, Andreas Rohner wrote:
> On 2014-01-24 19:26, Ryusuke Konishi wrote:
>>> +		ret = nilfs_set_suinfo(nilfs, supv, n);
>>> +		free(supv);
>>> +		if (ret >= 0) {
>>> +			/* success, tell caller
>>> +			 * to try another segment/s */
>>> +			ret = -EGCTRYAGAIN;
>>> +			goto out_lock;
>>> +		}

Returning -EGCTRYAGAIN looks confusing, since posix error code Exxxxx
is usually stored in errno variable in userland.  It also looks a bit
hacky.

How about handling this as follows ?

 - Add a new structure to return result of GC, for instance, as
   follows:

struct nilfs_reclaim_status {
	unsigned int	ncleanedsegs; /* number of segments cleaned
					 with nilfs_clean_segments() */
	unsigned int	ndeferredsegs;/* number of segments deferred
					 with nilfs_set_suinfo() */
	unsigned long	nliveblocks;  /* sum of live virtual blocks and live
					 DAT blocks */
	unsigned long	ndeadblocks;  /* number of reclaimable blocks */
	unsigned long	nlivevblocks; /* live virtual blocks */
	unsigned long	nfreevblocks; /* freed virtual block addresses */
	...
};

 - Use the structure as an argument of the "new" API function
   (i.e. variant of nilfs_reclaim_segment() )

 - Rewrite the variant API function so that it returns a success value
   (0) also for the EGCTRYAGAIN case.

 - Store other status information in nilfs_reclaim_status structures.


And, I think adding nilfs_set_suinfo() API should be a separate patch.


Regards,
Ryusuke Konishi
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