On 07/12/2010 11:15 AM, Lukas Czerner wrote: > On Mon, 12 Jul 2010, Lukas Czerner wrote: > >> On Mon, 12 Jul 2010, Ric Wheeler wrote: >> >>> On 07/12/2010 11:19 AM, Jan Kara wrote: >>>>> Those mount option has the same meaning as in ext4 file system. It >>>>> provide a way to enable/disable file system's trim support. The trim >>>>> support is off by default, thus nodiscard option is not actually >>>>> necessary. >>>> I kind of miss why ext3 should have a 'discard' mount option. When >>>> user calls DISCARD ioctl on the filesystem, then he probably wants >>>> discard to be performed. >>>> >>>> Honza >>>> >>> >>> Sorry I misunderstood your original question. >>> >>> One reason that you might want to have a "discard" option is to allow a system >>> admin to mount without barriers to protect flaky hardware (we have had some >>> mixed results for example). As you say, the user probably wants to have the >>> ioctl do the discard and should be reasonable for doing it only on solid >>> devices, >> >> The question is what in does on device other than SSD. I know it does >> not harm the deivce, but is there some kernel logic preventing the trim >> command to be send to device that does not support it ? I hope so. >> > > Yes, there is a check whether device support trim in blkdev_issue_discard > code. I also sent an ext4 patch so that a failed discard clears the flag so we don't keep attempting more. However, the LVM guys aren't too happy with that because they point to cases like: a) pvmove off of, and back onto, a trim-capable device b) composite devices of trim-capable and -incapable devices I don't care much either way, I don't think we do much harm in continuing to send discards after a failure; the original motivation for the patch was so that if a user asked for discard and the (simple) device didn't support it, they'd get a message, and we'd stop trying. -Eric > -Lukas -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
