On 09/23/2013 08:24 AM, Dave Chinner wrote:
> On Sat, Sep 21, 2013 at 10:38:31PM +0800, Jeff Liu wrote:
>> From: Jie Liu <jeff.liu@xxxxxxxxxx>
>>
>> At xfs_iext_add(), if extent(s) are being appended to the last
>> page in the indirection array and the new extent(s) don't fit
>> in the page, the number of extents(erp->er_extcount) in a new
>> allocated entry should be the minimum value between count and
>> XFS_LINEAR_EXTS, instead of count.
>
> Definitely looks like a bug, but what are the symptoms of it and how
> did you find the problem? Is there any test case that demonstrates a
> problem with the er_extcount being set incorrectly here?
Sorry for the too late response, I found this problem while reading the code.
However, I can not figure out a test case to break the kernel until now. :(
>
>> Signed-off-by: Jie Liu <jeff.liu@xxxxxxxxxx>
>> ---
>> fs/xfs/xfs_inode_fork.c | 8 ++++----
>> 1 file changed, 4 insertions(+), 4 deletions(-)
>>
>> diff --git a/fs/xfs/xfs_inode_fork.c b/fs/xfs/xfs_inode_fork.c
>> index 02f1083..dfb4226 100644
>> --- a/fs/xfs/xfs_inode_fork.c
>> +++ b/fs/xfs/xfs_inode_fork.c
>> @@ -1035,11 +1035,11 @@ xfs_iext_add(
>>
>> while (count) {
>> erp = xfs_iext_irec_new(ifp, erp_idx);
>> - erp->er_extcount = count;
>> - count -= MIN(count, (int)XFS_LINEAR_EXTS);
>> - if (count) {
>> + erp->er_extcount = MIN(count,
>> + (int)XFS_LINEAR_EXTS);
>> + count -= erp->er_extcount;
>
> count is declared as an int, whereas XFS_LINEAR_EXTS probably ends
> up with a type of uint because of a cast in the macro. because we
> are decrementing to zero, the count can be declared as a uint, too,
> and the cast in the MIN() can go away. Indeed, MIN() should be
> converted to min() seeing as we are touching the code here, and if
> you want to retain the current types, the min_t() is appropriate,
> not min(x, (some cast)y)....
Ok, will fix it.
Thanks,
-Jeff
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