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Date: Mon, 17 Jun 2002 11:42:51 -0700
From: Andrew Morton <akpm@zip.com.au>
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To: Andreas Dilger <adilger@clusterfs.com>
CC: Linus Torvalds <torvalds@transmeta.com>,
       lkml <linux-kernel@vger.kernel.org>, Hugh Dickins <hugh@veritas.com>
Subject: Re: [patch 10/19] direct-to-BIO I/O for swapcache pages
References: <3D0D873A.405ED0BB@zip.com.au> <20020617161718.GD22427@clusterfs.com>
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Andreas Dilger wrote:
> 
> On Jun 16, 2002  23:52 -0700, Andrew Morton wrote:
> > This patch changes the swap I/O handling.  The objectives are:
> >
> > At swapon time (for an S_ISBLK swapfile), we install a single swap extent
> > which describes the entire device.
> >
> > +     inode = sis->swap_file->f_dentry->d_inode;
> > +     if (S_ISBLK(inode->i_mode)) {
> > +             ret = add_swap_extent(sis, 0, sis->max, 0);
> > +             goto done;
> > +     }
> 
> I believe it is possible to have blocks marked bad in the swap header,
> even for a block device, so this will try to use those bad blocks.

Well, this establishes the page index -> sector mapping for those
blocks.  But the actual block allocator will not hand out the
SWP_MAP_BAD blocks in the first place.