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Date: Thu, 6 Jun 2024 06:49:06 +0200
From: Christoph Hellwig <hch@lst.de>
To: Kanchan Joshi <joshiiitr@gmail.com>
Cc: Christoph Hellwig <hch@lst.de>, Jens Axboe <axboe@kernel.dk>,
	"Martin K. Petersen" <martin.petersen@oracle.com>,
	Mike Snitzer <snitzer@kernel.org>,
	Mikulas Patocka <mpatocka@redhat.com>, Song Liu <song@kernel.org>,
	Yu Kuai <yukuai3@huawei.com>,
	Dan Williams <dan.j.williams@intel.com>,
	Vishal Verma <vishal.l.verma@intel.com>,
	Dave Jiang <dave.jiang@intel.com>, Ira Weiny <ira.weiny@intel.com>,
	Keith Busch <kbusch@kernel.org>, Sagi Grimberg <sagi@grimberg.me>,
	Chaitanya Kulkarni <kch@nvidia.com>, linux-block@vger.kernel.org,
	dm-devel@lists.linux.dev, linux-raid@vger.kernel.org,
	nvdimm@lists.linux.dev, linux-nvme@lists.infradead.org,
	linux-scsi@vger.kernel.org
Subject: Re: [PATCH 04/12] block: remove the blk_integrity_profile structure
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References: <20240605063031.3286655-1-hch@lst.de> <20240605063031.3286655-5-hch@lst.de> <CA+1E3rJn3uNfkoFtm_am9qwQmwWvhu3nPVMaM63AJ2GBdxZTmQ@mail.gmail.com>
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On Wed, Jun 05, 2024 at 08:05:20PM +0530, Kanchan Joshi wrote:
> On Wed, Jun 5, 2024 at 12:01???PM Christoph Hellwig <hch@lst.de> wrote:
> > @@ -446,13 +446,14 @@ bool bio_integrity_prep(struct bio *bio)
> >         if (bio_integrity(bio))
> >                 return true;
> >
> > +       if (!bi->csum_type)
> > +               return true;
> 
> Changes look mostly good, but trigger a behavior change for non-PI
> metadata format.
> 
> Earlier nop profile was registered for that case. And the block-layer
> continued to attach an appropriately sized meta buffer to incoming IO, even
> though it did not generate/verify. Hence, IOs don't fail.
> 
> Now also we show that the nop profile is set, but the above
> "csum_type" check ensures that
> meta buffer is not attached and REQ_INTEGRITY is not set in the bio.
> NVMe will start failing IOs with BLK_STS_NOTSUPP now [*].

Yes.  I didn't remember that odd case and failed to test it, but I can
trivially reproduce it now.

Which brings up another issue: bio_integrity_prep allocates the metadata
buffer using kmalloc, so we'll leak write random kernel memory to the
devices for this case which is ... not good.  I guess for stable fixes
and backports I'll add a real generate_fn that just zeroes all the
memory for now.