On Mon, Mar 18, 2013 at 12:48:16PM +0800, Jeff Liu wrote:
> Hello,
>
> Here is the v2 patch for fixing ASSERTION failed at xfs_vm_write_failed() according
> to Dave's comments, so I added Dave as SOB for credit.
No, please don't add my SOB to a patch you wrote, even if I came up
with the idea of how to do something. A SOB indicates that someone
has verified the origin of the patch (e.g. for copyright reasons),
not who contributed to finding the problem. IOWs, adding someone
else's SOB to a patch you wrote is almost always the wrong thing to
do.
The correct way to acknowledge someone's contribution to the
fix if they didn't write the patch is by a line in the commit
message saying something like "Thanks to .... for helping find and
fix the problem." [Edit: I just noticed you did this bit. ;) ]
If .... agrees with your fix, then they can add a reviewed-by line
to the patch, which has significantly different meaning to a SOB...
....
> Reported-by: Michael L. Semon <mlsemon35@xxxxxxxxx>
> Signed-off-by: Jie Liu <jeff.liu@xxxxxxxxxx>
> Signed-off-by: Dave Chinner <david@xxxxxxxxxxxxx>
> ---
> fs/xfs/xfs_aops.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/fs/xfs/xfs_aops.c b/fs/xfs/xfs_aops.c
> index 5f707e5..a418e17 100644
> --- a/fs/xfs/xfs_aops.c
> +++ b/fs/xfs/xfs_aops.c
> @@ -1494,7 +1494,8 @@ xfs_vm_write_failed(
> loff_t pos,
> unsigned len)
> {
> - loff_t block_offset = pos & PAGE_MASK;
> + loff_t block_offset = (pos >> PAGE_CACHE_SHIFT) <<
> + PAGE_CACHE_SHIFT;
> loff_t block_start;
> loff_t block_end;
> loff_t from = pos & (PAGE_CACHE_SIZE - 1);
This needs a comment explaining why we aren't just masking the value
off with PAGE_MASK. And given that it wraps, something like:
- loff_t block_offset = pos & PAGE_MASK;
+ loff_t block_offset;
.....
+ /*
+ * comment about 32 bit systems, 64 bit variables and masks
+ */
+ block_offset = (pos >> PAGE_CACHE_SHIFT) << PAGE_CACHE_SHIFT;
Cheers,
Dave.
--
Dave Chinner
david@xxxxxxxxxxxxx
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