Hi Namjae, On Fri, Apr 5, 2013 at 11:57 AM, Namjae Jeon <linkinj...@gmail.com> wrote: > Hi. Max. > > I have a question. > Your mmc host driver set to host->max_discard_to by some value instead > of not zero ?
I believe it's zero, because the only place where I can see it initialized (sdhci_add_host in the drivers/mmc/host/sdhci.c) is not built in my configuration. > 2013/4/5, Max Filippov <jcmvb...@gmail.com>: >> On Fri, Apr 5, 2013 at 5:53 AM, Shaohua Li <s...@kernel.org> wrote: >>> On Thu, Apr 04, 2013 at 06:00:18AM +0400, Max Filippov wrote: >> >> [...] >> >>>> the commit 0cfbcafcae8b7364b5fa96c2b26ccde7a3a296a9 'block: add plug >>>> for blkdev_issue_discard' >>>> have added merge opportunity for DISCARD requests. When I do >>>> mkfs.f2fs on a 5G partition (0xad8000 sectors) it submits two bios, >>>> one for 0x7fe000 sectors (0xffc00000 bytes) and another for >>>> 0x2da000 sectors (0x5b400000 bytes). Prior to that commit these >>>> bios weren't merged into one request. Now the second bio gets >>>> merged with the first, but the request's __data_len field is unsigned >>>> int >>>> and it gets wrapped to 0x5b000000 bytes instead of 0x15b000000 >>>> in the bio_attempt_back_merge. Later this reduced size is passed to >>>> the blk_update_request causing KERN_ERR and not completed >>>> request. Reverting this commit fixes mkfs.f2fs for me. >>> >>> A workaround is setting limits.max_discard_sectors to a smaller value. >> >> I'm not sure: >> 1) in my case max_discard_sectors is 0x7fe000 (0xffc00000 bytes, >> which still fits into 32 bits) and >> 2) this parameter will only change size of individual discard requests for >> the discarded range, but as long as these requests are done inside >> the plug they will be merged anyway with an overflow if we try >> to discard more than 4G at once. >> >>> So the question is why __data_len isn't sector based? Since disk is >>> sector >>> based, is there any disk finishing IO in byte granularity? Maybe Jens can >>> answer. -- Thanks. -- Max -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/