[PATCH] libxfs: remove never-read "offset" assignment in readbufr_map & writebufr

[PATCH] libxfs: remove never-read "offset" assignment in readbufr_map & writebufr

[Eric Sandeen]

libxfs_readbufr_map() & libxfs_writebufr() iterate
over bp->b_map[] and read each chunk.  The loops start
out correctly, getting the offset from bm_bn and the
length from bm_len.  After the IO it correctly
advances the target buffer pointer by len, but then
inexplicably advances "offset" by len as well.  The
whole point of this exercise is to handle discontiguous
ranges - marching offset along by length of IO done
is incorrect.

Thankfully offset is immediately reset to the proper
value again at the top of the loop for the next range,
so this is harmless, other than being confusing.

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
---

diff --git a/libxfs/rdwr.c b/libxfs/rdwr.c
index 9887423..7208a2f 100644
--- a/libxfs/rdwr.c
+++ b/libxfs/rdwr.c
@@ -758,7 +758,6 @@ libxfs_readbufr_map(struct xfs_buftarg *btp, struct xfs_buf *bp, int flags)
 			break;
 		}
 		buf += len;
-		offset += len;
 	}
 
 	if (!error)
@@ -878,7 +877,6 @@ libxfs_writebufr(xfs_buf_t *bp)
 				break;
 			}
 			buf += len;
-			offset += len;
 		}
 	}
 

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Re: [PATCH] libxfs: remove never-read "offset" assignment in readbufr_map & writebufr

[Mark Tinguely]

On 04/09/14 14:20, Eric Sandeen wrote:
> libxfs_readbufr_map()&  libxfs_writebufr() iterate
> over bp->b_map[] and read each chunk.  The loops start
> out correctly, getting the offset from bm_bn and the
> length from bm_len.  After the IO it correctly
> advances the target buffer pointer by len, but then
> inexplicably advances "offset" by len as well.  The
> whole point of this exercise is to handle discontiguous
> ranges - marching offset along by length of IO done
> is incorrect.
>
> Thankfully offset is immediately reset to the proper
> value again at the top of the loop for the next range,
> so this is harmless, other than being confusing.
>
> Signed-off-by: Eric Sandeen<sandeen@redhat.com>

Looks good.

Reviewed-by: Mark Tinguely <tinguely@sgi.com>

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