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Date:   Tue, 25 Jan 2022 17:27:36 +0800
From:   Ming Lei <ming.lei@redhat.com>
To:     Christoph Hellwig <hch@lst.de>
Cc:     Jens Axboe <axboe@kernel.dk>, linux-block@vger.kernel.org,
        Vivek Goyal <vgoyal@redhat.com>, Pei Zhang <pezhang@redhat.com>
Subject: Re: [PATCH V2] block: loop:use kstatfs.f_bsize of backing file to
 set discard granularity
Message-ID: <Ye/CiFZSHmHQ3Pfu@T590>
References: <20220125044005.211943-1-ming.lei@redhat.com>
 <20220125061057.GA26444@lst.de>
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On Tue, Jan 25, 2022 at 07:10:57AM +0100, Christoph Hellwig wrote:
> On Tue, Jan 25, 2022 at 12:40:05PM +0800, Ming Lei wrote:
> >  	} else {
> > +		struct kstatfs sbuf;
> > +
> >  		max_discard_sectors = UINT_MAX >> 9;
> > -		granularity = inode->i_sb->s_blocksize;
> > +		if (!vfs_statfs(&file->f_path, &sbuf))
> > +			granularity = sbuf.f_bsize;
> > +		else
> > +			granularity = PAGE_SIZE;
> 
> If vfs_statfs fails we're pretty much toast and there isn't really any
> point in continuing here.

But it is configure code path, even though vfs_statfs() fails,
loop_config_discard() still need to keep discard setting consistent.

Setting granularity as PAGE_SIZE is just for making discard granularity
matched with max_discard_sectors. Or you have better/simpler handling?


Thanks,
Ming