On Mar 2, 2012, at 4:58 PM, Boaz Harrosh wrote:
> On 03/02/2012 10:10 AM, Chuck Lever wrote:
>>
>> On Mar 1, 2012, at 5:55 PM, Chuck Lever wrote:
>>
>>>
>>> On Mar 1, 2012, at 5:39 PM, Myklebust, Trond wrote:
>>>
>>>> On Thu, 2012-03-01 at 17:02 -0500, Chuck Lever wrote:
>>>>> Clean up due to code review.
>>>>>
>>>>> sizeof(struct nfs4_deviceid) is the size of the in-core device ID data
>>>>> structure, but NFS4_DEVICEID4_SIZE is the number of octets in an XDR'd
>>>>> device ID. The two are not interchangeable, even if they happen to
>>>>> have the same value. If struct nfs4_deviceid is padded by the
>>>>> compiler, sizeof(struct nfs4_deviceid) may not be the same as the
>>>>> XDR'd size. Not likely, but still.
>>>>>
>>>>> Ensure that the data field is aligned to the largest pointer type that
>>>>> is used to access it: in this case, that's u64. Type-punning among
>>>>> types with different alignment has been discouraged in user space and
>>>>> the kernel, to avoid unneeded pointer aliasing. The use of a union
>>>>> is preferred instead.
>>>>>
>>>>> Ensure that XDR'ing and comparing is done via one of the union's data
>>>>> fields, and not via the whole struct, again in case the compiler pads
>>>>> the struct.
>>>>>
>>>>> As a micro-optimization, this change also ensures that the compiler
>>>>> may perform memcpy() and memcmp() operations on these fields in
>>>>> larger, more efficient, chunks.
>>>>>
>>>>> This patch needs review and testing by pnfs layout specialists.
>>>>>
>>>>> Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
>>>>> ---
>>>>>
>>>>> fs/nfs/blocklayout/blocklayout.c | 2 +-
>>>>> fs/nfs/blocklayout/blocklayoutdev.c | 8 ++++----
>>>>> fs/nfs/blocklayout/extents.c | 5 +++--
>>>>> fs/nfs/callback_xdr.c | 2 +-
>>>>> fs/nfs/nfs4filelayout.c | 3 +--
>>>>> fs/nfs/nfs4xdr.c | 4 ++--
>>>>> fs/nfs/objlayout/pnfs_osd_xdr_cli.c | 8 ++++----
>>>>> fs/nfs/pnfs_dev.c | 7 ++++---
>>>>> include/linux/nfs4.h | 7 ++++++-
>>>>> include/linux/pnfs_osd_xdr.h | 4 ++--
>>>>> 10 files changed, 28 insertions(+), 22 deletions(-)
>>>>>
>>>>> diff --git a/fs/nfs/blocklayout/blocklayout.c b/fs/nfs/blocklayout/blocklayout.c
>>>>> index 783ebd5..3b730bf 100644
>>>>> --- a/fs/nfs/blocklayout/blocklayout.c
>>>>> +++ b/fs/nfs/blocklayout/blocklayout.c
>>>>> @@ -901,7 +901,7 @@ nfs4_blk_get_deviceinfo(struct nfs_server *server, const struct nfs_fh *fh,
>>>>> dev->pglen = PAGE_SIZE * max_pages;
>>>>> dev->mincount = 0;
>>>>>
>>>>> - dprintk("%s: dev_id: %s\n", __func__, dev->dev_id.data);
>>>>> + dprintk("%s: dev_id: %s\n", __func__, dev->dev_id.u.data);
>>>>> rc = nfs4_proc_getdeviceinfo(server, dev);
>>>>> dprintk("%s getdevice info returns %d\n", __func__, rc);
>>>>> if (rc) {
>>>>> diff --git a/fs/nfs/blocklayout/blocklayoutdev.c b/fs/nfs/blocklayout/blocklayoutdev.c
>>>>> index b48f782..2dafca5 100644
>>>>> --- a/fs/nfs/blocklayout/blocklayoutdev.c
>>>>> +++ b/fs/nfs/blocklayout/blocklayoutdev.c
>>>>> @@ -124,8 +124,8 @@ nfs4_blk_decode_device(struct nfs_server *server,
>>>>> struct nfs_net *nn = net_generic(net, nfs_net_id);
>>>>>
>>>>> dprintk("%s CREATING PIPEFS MESSAGE\n", __func__);
>>>>> - dprintk("%s: deviceid: %s, mincount: %d\n", __func__, dev->dev_id.data,
>>>>> - dev->mincount);
>>>>> + dprintk("%s: deviceid: %s, mincount: %d\n", __func__,
>>>>> + dev->dev_id.u.data, dev->mincount);
>>>>>
>>>>> memset(&msg, 0, sizeof(msg));
>>>>> msg.data = kzalloc(sizeof(bl_msg) + dev->mincount, GFP_NOFS);
>>>>> @@ -206,7 +206,7 @@ static struct block_device *translate_devid(struct pnfs_layout_hdr *lo,
>>>>> mid = BLK_ID(lo);
>>>>> spin_lock(&mid->bm_lock);
>>>>> list_for_each_entry(dev, &mid->bm_devlist, bm_node) {
>>>>> - if (memcmp(id->data, dev->bm_mdevid.data,
>>>>> + if (memcmp(id->u.data, dev->bm_mdevid.u.data,
>>>>> NFS4_DEVICEID4_SIZE) == 0) {
>>>>> rv = dev->bm_mdev;
>>>>> goto out;
>>>>> @@ -323,7 +323,7 @@ nfs4_blk_process_layoutget(struct pnfs_layout_hdr *lo,
>>>>> status = -ENOMEM;
>>>>> goto out_err;
>>>>> }
>>>>> - memcpy(&be->be_devid, p, NFS4_DEVICEID4_SIZE);
>>>>> + memcpy(&be->be_devid.u.data, p, NFS4_DEVICEID4_SIZE);
>>>>> p += XDR_QUADLEN(NFS4_DEVICEID4_SIZE);
>>>>> be->be_mdev = translate_devid(lo, &be->be_devid);
>>>>> if (!be->be_mdev)
>>>>> diff --git a/fs/nfs/blocklayout/extents.c b/fs/nfs/blocklayout/extents.c
>>>>> index 1f9a603..52b747c 100644
>>>>> --- a/fs/nfs/blocklayout/extents.c
>>>>> +++ b/fs/nfs/blocklayout/extents.c
>>>>> @@ -675,10 +675,11 @@ encode_pnfs_block_layoutupdate(struct pnfs_block_layout *bl,
>>>>> if (!xdr_start)
>>>>> goto out;
>>>>> list_for_each_entry_safe(lce, save, &bl->bl_commit, bse_node) {
>>>>> - p = xdr_reserve_space(xdr, 7 * 4 + sizeof(lce->bse_devid.data));
>>>>> + p = xdr_reserve_space(xdr, 7 * 4 + NFS4_DEVICEID4_SIZE);
>>>>> if (!p)
>>>>> break;
>>>>> - p = xdr_encode_opaque_fixed(p, lce->bse_devid.data, NFS4_DEVICEID4_SIZE);
>>>>> + p = xdr_encode_opaque_fixed(p, lce->bse_devid.u.data,
>>>>> + NFS4_DEVICEID4_SIZE);
>>>>> p = xdr_encode_hyper(p, lce->bse_f_offset << SECTOR_SHIFT);
>>>>> p = xdr_encode_hyper(p, lce->bse_length << SECTOR_SHIFT);
>>>>> p = xdr_encode_hyper(p, 0LL);
>>>>> diff --git a/fs/nfs/callback_xdr.c b/fs/nfs/callback_xdr.c
>>>>> index 5466829..6061322 100644
>>>>> --- a/fs/nfs/callback_xdr.c
>>>>> +++ b/fs/nfs/callback_xdr.c
>>>>> @@ -347,7 +347,7 @@ __be32 decode_devicenotify_args(struct svc_rqst *rqstp,
>>>>> goto err;
>>>>> }
>>>>> dev->cbd_layout_type = ntohl(*p++);
>>>>> - memcpy(dev->cbd_dev_id.data, p, NFS4_DEVICEID4_SIZE);
>>>>> + memcpy(dev->cbd_dev_id.u.data, p, NFS4_DEVICEID4_SIZE);
>>>>> p += XDR_QUADLEN(NFS4_DEVICEID4_SIZE);
>>>>>
>>>>> if (dev->cbd_layout_type == NOTIFY_DEVICEID4_CHANGE) {
>>>>> diff --git a/fs/nfs/nfs4filelayout.c b/fs/nfs/nfs4filelayout.c
>>>>> index 47e8f34..f0c6ba0 100644
>>>>> --- a/fs/nfs/nfs4filelayout.c
>>>>> +++ b/fs/nfs/nfs4filelayout.c
>>>>> @@ -550,8 +550,7 @@ filelayout_decode_layout(struct pnfs_layout_hdr *flo,
>>>>> if (unlikely(!p))
>>>>> goto out_err;
>>>>>
>>>>> - memcpy(id, p, sizeof(*id));
>>>>> - p += XDR_QUADLEN(NFS4_DEVICEID4_SIZE);
>>>>> + p = xdr_decode_opaque_fixed(p, id->u.data, NFS4_DEVICEID4_SIZE);
>>>>> nfs4_print_deviceid(id);
>>>>>
>>>>> nfl_util = be32_to_cpup(p++);
>>>>> diff --git a/fs/nfs/nfs4xdr.c b/fs/nfs/nfs4xdr.c
>>>>> index 80ba010..91020ea 100644
>>>>> --- a/fs/nfs/nfs4xdr.c
>>>>> +++ b/fs/nfs/nfs4xdr.c
>>>>> @@ -1946,7 +1946,7 @@ encode_getdeviceinfo(struct xdr_stream *xdr,
>>>>>
>>>>> p = reserve_space(xdr, 16 + NFS4_DEVICEID4_SIZE);
>>>>> *p++ = cpu_to_be32(OP_GETDEVICEINFO);
>>>>> - p = xdr_encode_opaque_fixed(p, args->pdev->dev_id.data,
>>>>> + p = xdr_encode_opaque_fixed(p, args->pdev->dev_id.u.data,
>>>>> NFS4_DEVICEID4_SIZE);
>>>>> *p++ = cpu_to_be32(args->pdev->layout_type);
>>>>> *p++ = cpu_to_be32(args->pdev->pglen); /* gdia_maxcount */
>>>>> @@ -5492,7 +5492,7 @@ static int decode_getdevicelist(struct xdr_stream *xdr,
>>>>> if (unlikely(!p))
>>>>> goto out_overflow;
>>>>> for (i = 0; i < res->num_devs; i++)
>>>>> - p = xdr_decode_opaque_fixed(p, res->dev_id[i].data,
>>>>> + p = xdr_decode_opaque_fixed(p, res->dev_id[i].u.data,
>>>>> NFS4_DEVICEID4_SIZE);
>>>>> res->eof = be32_to_cpup(p);
>>>>> return 0;
>>>>> diff --git a/fs/nfs/objlayout/pnfs_osd_xdr_cli.c b/fs/nfs/objlayout/pnfs_osd_xdr_cli.c
>>>>> index b3918f7..99a1e89 100644
>>>>> --- a/fs/nfs/objlayout/pnfs_osd_xdr_cli.c
>>>>> +++ b/fs/nfs/objlayout/pnfs_osd_xdr_cli.c
>>>>> @@ -55,8 +55,8 @@
>>>>> static __be32 *
>>>>> _osd_xdr_decode_objid(__be32 *p, struct pnfs_osd_objid *objid)
>>>>> {
>>>>> - p = xdr_decode_opaque_fixed(p, objid->oid_device_id.data,
>>>>> - sizeof(objid->oid_device_id.data));
>>>>> + p = xdr_decode_opaque_fixed(p, objid->oid_device_id.u.data,
>>>>> + NFS4_DEVICEID4_SIZE);
>>>>>
>>>>> p = xdr_decode_hyper(p, &objid->oid_partition_id);
>>>>> p = xdr_decode_hyper(p, &objid->oid_object_id);
>>>>> @@ -377,8 +377,8 @@ pnfs_osd_xdr_encode_layoutupdate(struct xdr_stream *xdr,
>>>>> static inline __be32 *
>>>>> pnfs_osd_xdr_encode_objid(__be32 *p, struct pnfs_osd_objid *object_id)
>>>>> {
>>>>> - p = xdr_encode_opaque_fixed(p, &object_id->oid_device_id.data,
>>>>> - sizeof(object_id->oid_device_id.data));
>>>>> + p = xdr_encode_opaque_fixed(p, &object_id->oid_device_id.u.data,
>>>>> + NFS4_DEVICEID4_SIZE);
>>>>> p = xdr_encode_hyper(p, object_id->oid_partition_id);
>>>>> p = xdr_encode_hyper(p, object_id->oid_object_id);
>>>>>
>>>>> diff --git a/fs/nfs/pnfs_dev.c b/fs/nfs/pnfs_dev.c
>>>>> index 4f359d2..6c6ab81 100644
>>>>> --- a/fs/nfs/pnfs_dev.c
>>>>> +++ b/fs/nfs/pnfs_dev.c
>>>>> @@ -46,7 +46,7 @@ static DEFINE_SPINLOCK(nfs4_deviceid_lock);
>>>>> void
>>>>> nfs4_print_deviceid(const struct nfs4_deviceid *id)
>>>>> {
>>>>> - u32 *p = (u32 *)id;
>>>>> + const u32 *p = id->u.data32;
>>>>>
>>>>> dprintk("%s: device id= [%x%x%x%x]\n", __func__,
>>>>> p[0], p[1], p[2], p[3]);
>>>>> @@ -56,7 +56,7 @@ EXPORT_SYMBOL_GPL(nfs4_print_deviceid);
>>>>> static inline u32
>>>>> nfs4_deviceid_hash(const struct nfs4_deviceid *id)
>>>>> {
>>>>> - unsigned char *cptr = (unsigned char *)id->data;
>>>>> + const unsigned char *cptr = id->u.data;
>>>>> unsigned int nbytes = NFS4_DEVICEID4_SIZE;
>>>>> u32 x = 0;
>>>>>
>>>>> @@ -77,7 +77,8 @@ _lookup_deviceid(const struct pnfs_layoutdriver_type *ld,
>>>>>
>>>>> hlist_for_each_entry_rcu(d, n, &nfs4_deviceid_cache[hash], node)
>>>>> if (d->ld == ld && d->nfs_client == clp &&
>>>>> - !memcmp(&d->deviceid, id, sizeof(*id))) {
>>>>> + !memcmp(&d->deviceid.u.data, id->u.data,
>>>>> + NFS4_DEVICEID4_SIZE)) {
>>>>> if (atomic_read(&d->ref))
>>>>> return d;
>>>>> else
>>>>> diff --git a/include/linux/nfs4.h b/include/linux/nfs4.h
>>>>> index b1e6b64..979f607 100644
>>>>> --- a/include/linux/nfs4.h
>>>>> +++ b/include/linux/nfs4.h
>>>>> @@ -649,9 +649,14 @@ enum filelayout_hint_care4 {
>>>>> #define NFS4_DEVICEID4_SIZE 16
>>>>>
>>>>> struct nfs4_deviceid {
>>>>> - char data[NFS4_DEVICEID4_SIZE];
>>>>> + union {
>>>>> + unsigned char data[NFS4_DEVICEID4_SIZE];
>>>>> + u32 data32[NFS4_DEVICEID4_SIZE / sizeof(u32)];
>>>>> + u64 data64[NFS4_DEVICEID4_SIZE / sizeof(u64)];
>>>>> + } u;
>>>>> };
>>>>>
>>>>
>>>> Ugh... This just looks worse and worse.... Let's rather just keep these
>>>> as unsigned char. I don't care if OSDs have special secret meanings and
>>>> all that crap. They can cast the damned thing if they need to. The rest
>>>> of us should be considering this to be opaque data.
>>>
>>> One possibility is that OSD and block layout drivers can construct their device ID in a u64 array on the stack, and then memcpy() the array to the nfs4_deviceid.
>>>
>>> But we can't cast pointers to an "unsigned char" field, since it's not guaranteed to be aligned. That's a real bug, one that's hit us before.
>>
>> Accessing a "char x[16]" field by casting x to a (u64 *) is considered harmful. It will work when x happens to be aligned to 64-bits, but otherwise accessing a field that way will cause an oops.
>>
>> It's not clear why the OSD layout driver needs to print device IDs as a pair of unsigned long longs. Why can't nfs4_print_deviceid() be used ?
>>
>
> For the same reason we do debug prints at all, for inconvenience.
>
> If you want I can use the get_unaligned() macro if you prefer. That should be perfectly safe.
> (And will do nothing on x86 ARCs)
Basically we would just use get_unaligned() in the _DEVID_LO and _DEVID_HI macros.
> I agree that it should stay just old plain "char data[NFS4_DEVICEID4_SIZE];"
>
> Thanks
> Boaz
>
>
>
>
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--
Chuck Lever
chuck[dot]lever[at]oracle[dot]com
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