Return-Path: linux-nfs-owner@vger.kernel.org Received: from natasha.panasas.com ([67.152.220.90]:49454 "EHLO natasha.panasas.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758615Ab2CBV7W (ORCPT ); Fri, 2 Mar 2012 16:59:22 -0500 Message-ID: <4F51429B.1040106@panasas.com> Date: Fri, 2 Mar 2012 13:58:51 -0800 From: Boaz Harrosh MIME-Version: 1.0 To: Chuck Lever CC: Benny Halevy , Linux NFS Mailing List , Trond Myklebust Subject: Re: [PATCH 15/15] NFS: Fix some minor problems with nfs4_deviceids References: <20120301215755.2138.73488.stgit@degas.1015granger.net> <20120301220222.2138.65095.stgit@degas.1015granger.net> <1330641595.15828.16.camel@lade.trondhjem.org> <4D0F430A-73F2-4AAE-A087-302EE08D29C0@oracle.com> In-Reply-To: Content-Type: text/plain; charset="UTF-8" Sender: linux-nfs-owner@vger.kernel.org List-ID: 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 >>>> --- >>>> >>>> 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) I agree that it should stay just old plain "char data[NFS4_DEVICEID4_SIZE];" Thanks Boaz