On 2010-10-07 10:01, Fred Isaman wrote:
> On Thu, Oct 7, 2010 at 9:34 AM, Benny Halevy <bhalevy@xxxxxxxxxxx> wrote:
>> On 2010-10-06 16:35, Fred Isaman wrote:
>>> Right now, when we set the stateid, we blindly overwrite the current
>>> one, allowing the seqid to incorrectly roll backward.
>>>
>>> Signed-off-by: Fred Isaman <iisaman@xxxxxxxxxx>
>>> ---
>>> fs/nfs/pnfs.c | 38 ++++++++++++++++++++++++++++++++------
>>> 1 files changed, 32 insertions(+), 6 deletions(-)
>>>
>>> diff --git a/fs/nfs/pnfs.c b/fs/nfs/pnfs.c
>>> index 39bce9b..555955b 100644
>>> --- a/fs/nfs/pnfs.c
>>> +++ b/fs/nfs/pnfs.c
>>> @@ -459,16 +459,42 @@ pnfs_destroy_all_layouts(struct nfs_client *clp)
>>> }
>>> }
>>>
>>> +/* update lo->stateid with new if is more recent
>>> + *
>>> + * lo->stateid could be the open stateid, in which case we just use what given.
>>> + */
>>> static void
>>> pnfs_set_layout_stateid(struct pnfs_layout_hdr *lo,
>>> - const nfs4_stateid *stateid)
>>> + const nfs4_stateid *new)
>>> {
>>> - /* TODO - should enforce that embedded seqid, in the case
>>> - * that the two stateid.others are equal, only increases.
>>> - * Complicated by wrap-around.
>>> - */
>>> + nfs4_stateid *old = &lo->stateid;
>>> + bool overwrite = false;
>>> +
>>> write_seqlock(&lo->seqlock);
>>> - memcpy(lo->stateid.data, stateid->data, sizeof(lo->stateid.data));
>>> + if (!test_bit(NFS_LAYOUT_STATEID_SET, &lo->state) ||
>>> + memcmp(old->stateid.other, new->stateid.other, sizeof(new->stateid.other)))
>>> + overwrite = true;
>>> + else {
>>> + u32 oldseq, newseq, limit;
>>> +
>>> + oldseq = be32_to_cpu(old->stateid.seqid);
>>> + newseq = be32_to_cpu(new->stateid.seqid);
>>> + /* There are no good bounds on window size, so just
>>> + * use a ridiculously large window of 2^31.
>>> + */
>>> + limit = oldseq + (1 << 31);
>>> + if (oldseq < limit) {
>>> + /* The easy, non-wraparound case */
>>> + if (oldseq < newseq && newseq < limit)
>>> + overwrite = true;
>>> + } else {
>>> + /* Near wraparound edge */
>>> + if (oldseq < newseq || newseq < limit)
>>> + overwrite = true;
>>> + }
>>
>> Wouldn't it be simpler to just look at (int32_t)(newseq - oldseq)?
>>
>
> Why yes it would. I'll send a new version of this patch shortly.
>
No need :)
I'll just change this as follows:
+ else {
+ u32 oldseq, newseq, limit;
+
+ oldseq = be32_to_cpu(old->stateid.seqid);
+ newseq = be32_to_cpu(new->stateid.seqid);
+ if ((int)(newseq - oldseq) > 0)
+ overwrite = true;
+ }
Benny
> Fred
>
>> Benny
>>
>>> + }
>>> + if (overwrite)
>>> + memcpy(&old->stateid, &new->stateid, sizeof(new->stateid));
>>> write_sequnlock(&lo->seqlock);
>>> }
>>>
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