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Date: Thu, 23 Sep 2021 08:47:28 +0200 From: Greg Kroah-Hartman <gregkh@...uxfoundation.org> To: Coly Li <colyli@...e.de> Cc: linux-kernel@...r.kernel.org, linux-block@...r.kernel.org, linux-raid@...r.kernel.org, nvdimm@...ts.linux.dev, antlists@...ngman.org.uk, Dan Williams <dan.j.williams@...el.com>, Hannes Reinecke <hare@...e.de>, Jens Axboe <axboe@...nel.dk>, NeilBrown <neilb@...e.de>, Richard Fan <richard.fan@...e.com>, Vishal L Verma <vishal.l.verma@...el.com>, rafael@...nel.org Subject: Re: Too large badblocks sysfs file (was: [PATCH v3 0/7] badblocks improvement for multiple bad block ranges) On Thu, Sep 23, 2021 at 02:14:12PM +0800, Coly Li wrote: > On 9/23/21 2:08 PM, Greg Kroah-Hartman wrote: > > On Thu, Sep 23, 2021 at 01:59:28PM +0800, Coly Li wrote: > > > Hi all the kernel gurus, and folks in mailing lists, > > > > > > This is a question about exporting 4KB+ text information via sysfs > > > interface. I need advice on how to handle the problem. > > Hi Greg, > > This is the code in mainline kernel for quite long time. {sigh} What tools rely on this? If none, just don't add new stuff to the file and work to create a new api instead. > > Please do not do that. Seriously, that is not what sysfs is for, and is > > an abuse of it. > > > > sysfs is for "one value per file" and should never even get close to a > > 4kb limit. If it does, you are doing something really really wrong and > > should just remove that sysfs file from the system and redesign your > > api. > > I understand this. And what I addressed is the problem I need to fix. > > The code is there for almost 10 years, I just find it during my work on bad > blocks API fixing. > > > > > Recently I work on the bad blocks API (block/badblocks.c) improvement, there > > > is a sysfs file to export the bad block ranges for me raid. E.g for a md > > > raid1 device, file > > > /sys/block/md0/md/rd0/bad_blocks > > > may contain the following text content, > > > 64 32 > > > 128 8 > > Ick, again, that's not ok at all. sysfs files should never have to be > > parsed like this. > > I cannot agree more with you. What I am asking for was ---- how to fix it ? Best solution, come up with a new api. Worst solution, you are stuck with the existing file and I can show you the "way out" of dealing with files larger than 4kb in sysfs that a number of other apis are being forced to do as they grow over time. But ideally, just drop ths api and make a new one please. thanks, greg k-h
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