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Date: Wed, 21 Nov 2018 17:11:45 +0100
From: Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH V11 14/19] block: handle non-cluster bio out of
 blk_bio_segment_split
Message-ID: <20181121161145.GC4977@lst.de>
References: <20181121032327.8434-1-ming.lei@redhat.com> <20181121032327.8434-15-ming.lei@redhat.com> <20181121143355.GB2594@lst.de> <20181121153726.GC19111@ming.t460p>
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To: Ming Lei <ming.lei@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>, Jens Axboe <axboe@kernel.dk>, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Theodore Ts'o <tytso@mit.edu>, Omar Sandoval <osandov@fb.com>, Sagi Grimberg <sagi@grimberg.me>, Dave Chinner <dchinner@redhat.com>, Kent Overstreet <kent.overstreet@gmail.com>, Mike Snitzer <snitzer@redhat.com>, dm-devel@redhat.com, Alexander Viro <viro@zeniv.linux.org.uk>, linux-fsdevel@vger.kernel.org, Shaohua Li <shli@kernel.org>, linux-raid@vger.kernel.org, David Sterba <dsterba@suse.com>, linux-btrfs@vger.kernel.org, "Darrick J . Wong" <darrick.wong@oracle.com>, linux-xfs@vger.kernel.org, Gao Xiang <gaoxiang25@huawei.com>, linux-ext4@vger.kernel.org, Coly Li <colyli@suse.de>, linux-bcache@vger.kernel.org, Boaz Harrosh <ooo@electrozaur.com>, Bob Peterson <rpeterso@redhat.com>, cluster-devel@redhat.com

On Wed, Nov 21, 2018 at 11:37:27PM +0800, Ming Lei wrote:
> > +	bio = bio_alloc_bioset(GFP_NOIO, bio_segments(*bio_orig),
> > +			&non_cluster_bio_set);
> 
> bio_segments(*bio_orig) may be > 256, so bio_alloc_bioset() may fail.

Nothing a little min with BIO_MAX_PAGES couldn't fix.  This patch
was just intended as an idea how I think this code could work.