From: "Darrick J. Wong" <darrick.wong@oracle.com>
To: Eric Sandeen <sandeen@redhat.com>
Cc: linux-xfs <linux-xfs@vger.kernel.org>,
fsdevel <linux-fsdevel@vger.kernel.org>,
Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH] fs: fix iomap_bmap position calculation
Date: Thu, 2 Aug 2018 14:02:40 -0700 [thread overview]
Message-ID: <20180802210240.GV30972@magnolia> (raw)
In-Reply-To: <78937e83-5665-11bf-14a6-7815221bf4d8@redhat.com>
On Thu, Aug 02, 2018 at 03:03:51PM -0500, Eric Sandeen wrote:
> The position calculation in iomap_bmap() shifts bno the wrong way,
> so we don't progress properly and end up re-mapping block zero
> over and over, yielding an unchanging physical block range as the
> logical block advances:
>
> # filefrag -Be file
> ext: logical_offset: physical_offset: length: expected: flags:
> 0: 0.. 0: 21.. 21: 1: merged
> 1: 1.. 1: 21.. 21: 1: 22: merged
> Discontinuity: Block 1 is at 21 (was 22)
> 2: 2.. 2: 21.. 21: 1: 22: merged
> Discontinuity: Block 2 is at 21 (was 22)
> 3: 3.. 3: 21.. 21: 1: 22: merged
>
> This breaks the FIBMAP interface for anyone using it (XFS), which
> in turn breaks LILO, zipl, etc.
>
> Bug-actually-spotted-by: Darrick J. Wong <darrick.wong@oracle.com>
> Fixes: 89eb1906a953 ("iomap: add an iomap-based bmap implementation")
> Cc: stable@vger.kernel.org
> Signed-off-by: Eric Sandeen <sandeen@redhat.com>
I coulda sworn I already RVBd this, but perhaps not?
Will test it out, anyway...
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
--D
> ---
>
> diff --git a/fs/iomap.c b/fs/iomap.c
> index 77397b5a96ef..0d0bd8845586 100644
> --- a/fs/iomap.c
> +++ b/fs/iomap.c
> @@ -1443,7 +1443,7 @@ iomap_bmap(struct address_space *mapping, sector_t bno,
> const struct iomap_ops *ops)
> {
> struct inode *inode = mapping->host;
> - loff_t pos = bno >> inode->i_blkbits;
> + loff_t pos = bno << inode->i_blkbits;
> unsigned blocksize = i_blocksize(inode);
>
> if (filemap_write_and_wait(mapping))
>
> --
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next prev parent reply other threads:[~2018-08-02 22:55 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-08-02 20:03 [PATCH] fs: fix iomap_bmap position calculation Eric Sandeen
2018-08-02 20:08 ` Darrick J. Wong
2018-08-02 21:02 ` Darrick J. Wong [this message]
2018-08-03 15:24 ` Christoph Hellwig
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