linux-kernel - Re: [PATCH] clean_bdev_aliases: Prevent cleaning blocks that are not in block range

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Date:   Tue, 3 Jan 2017 00:21:45 +0800
From:   Eryu Guan <guaneryu@...il.com>
To:     Jan Kara <jack@...e.cz>
Cc:     Chandan Rajendra <chandan@...ux.vnet.ibm.com>, axboe@...nel.dk,
        linux-block@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] clean_bdev_aliases: Prevent cleaning blocks that are not
 in block range

On Mon, Jan 02, 2017 at 04:58:03PM +0100, Jan Kara wrote:
> On Sun 25-12-16 19:01:03, Chandan Rajendra wrote:
> > The first block to be cleaned may start at a non-zero page offset. In
> > such a scenario clean_bdev_aliases() will end up cleaning blocks that
> > do not fall in the range of blocks to be cleaned. This commit fixes the
> > issue by skipping blocks that do not fall in valid block range.
> > 
> > Signed-off-by: Chandan Rajendra <chandan@...ux.vnet.ibm.com>
> 
> Ah, very good catch! How did you spot this?

I failed to notice this patch, and I came up with a same patch today
myself, and I'm still testing it.

I found this by xfstests, many tests (tens of tests) failed fsck after
test when testing extN if blocksize < pagesize. E.g. generic/013 could
reproduce the fs corruption quite reliablely for me.

Reviewed-by: Eryu Guan <eguan@...hat.com>

> 
> The patch looks good. You can add:
> 
> Reviewed-by: Jan Kara <jack@...e.cz>
> 
> Jens, please merge this fix quickly as we may end up discarding changes to
> innocent metadata blocks due to this... Thanks!
> 
> 								Honza
> > ---
> >  fs/buffer.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/fs/buffer.c b/fs/buffer.c
> > index 1df2bd5..28484b3 100644
> > --- a/fs/buffer.c
> > +++ b/fs/buffer.c
> > @@ -1660,7 +1660,7 @@ void clean_bdev_aliases(struct block_device *bdev, sector_t block, sector_t len)
> >  			head = page_buffers(page);
> >  			bh = head;
> >  			do {
> > -				if (!buffer_mapped(bh))
> > +				if (!buffer_mapped(bh) || (bh->b_blocknr < block))
> >  					goto next;
> >  				if (bh->b_blocknr >= block + len)
> >  					break;
> > -- 
> > 2.5.5
> > 
> -- 
> Jan Kara <jack@...e.com>
> SUSE Labs, CR
> --
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