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.
Fred
> Benny
>
>> + }
>> + if (overwrite)
>> + memcpy(&old->stateid, &new->stateid, sizeof(new->stateid));
>> write_sequnlock(&lo->seqlock);
>> }
>>
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