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On Fri, Dec 20, 2002 at 09:44:47AM +0000, Joe Thornber wrote: > On Fri, Dec 20, 2002 at 12:31:50AM -0800, Greg KH wrote: > > Look reasonable? > Yes, it looks promising. Some worries: > > i) The 'status' and 'table' files do not contain a single value. > Splitting it up into single values would be ungainly to say the least, > eg. > > dm > |-- table > |-- target1 > | |-- sector_start > | |-- sector_len > | |-- target_type > | `-- target args > | > |-- target2 > |-- sector_start > > hmm ... maybe that's not too bad. Yeah, it's not that bad, I'll look into it when I get to those files :) > ii) If the table files are not split up then we have the problem that > they can be larger than a single page, which sysfs can't handle > (is this still true ?). Yes, I think this is still true. And it's also a good way to enforce the "one value per file" rule :) > iii) We need to be able to poll on the status file so that people can > block until there is a change of status. eg, a snapshot uses up > another 5% of its COW storage, a mirror completes its initial > build, a path fails in the multipath target. I saw that logic. I don't think sysfs can handle poll right now, but we could modify the last access/modify/change time when the status changes so stat(2) can be used on the file. This is how usbfs currently notifies userspace of changes to their files. Would this be acceptable? > > Ok. I can place all of the sysfs specific functions in dm.c, just like > > drivers/block/genhd.c has, or if we place struct mapped_device into > > dm.h, they can live in their own file. Doesn't bother me either way. > > Either put it in dm.c, or define some extra access functions (like > dm_suspended() and dm_kdev()) to get the information you need. I > would prefer the latter, but we can always move things later. Ok, will do. thanks for your comments, greg k-h - 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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