Return-Path: linux-nfs-owner@vger.kernel.org Received: from acsinet15.oracle.com ([141.146.126.227]:35365 "EHLO acsinet15.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751828Ab2CBSLI convert rfc822-to-8bit (ORCPT ); Fri, 2 Mar 2012 13:11:08 -0500 Subject: Re: [PATCH 15/15] NFS: Fix some minor problems with nfs4_deviceids Mime-Version: 1.0 (Apple Message framework v1257) Content-Type: text/plain; charset=us-ascii From: Chuck Lever In-Reply-To: <4D0F430A-73F2-4AAE-A087-302EE08D29C0@oracle.com> Date: Fri, 2 Mar 2012 13:10:59 -0500 Cc: Linux NFS Mailing List , Trond Myklebust Message-Id: 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> To: Benny Halevy , Boaz Harrosh Sender: linux-nfs-owner@vger.kernel.org List-ID: 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 ? -- Chuck Lever chuck[dot]lever[at]oracle[dot]com