NFSv4: Follow a referral From: Manoj Naik Respond to a moved error on NFS lookup by setting up the referral. Note: We don't actually follow the referral during lookup/getattr, but later when we detect fsid mismatch in inode revalidation (similar to the processing done for cloning submounts). Referrals will have fake attributes until they are actually followed or traversed. Signed-off-by: Manoj Naik Signed-off-by: Trond Myklebust --- fs/nfs/inode.c | 5 ++++- fs/nfs/namespace.c | 9 ++++++++- fs/nfs/nfs4proc.c | 46 ++++++++++++++++++++++++++++++++++++++++++++++ include/linux/nfs_fs.h | 1 + include/linux/nfs_xdr.h | 1 + 5 files changed, 60 insertions(+), 2 deletions(-) diff --git a/fs/nfs/inode.c b/fs/nfs/inode.c index 0d8302e..ee13cb0 100644 --- a/fs/nfs/inode.c +++ b/fs/nfs/inode.c @@ -888,7 +888,10 @@ nfs_fhget(struct super_block *sb, struct set_bit(NFS_INO_ADVISE_RDPLUS, &NFS_FLAGS(inode)); /* Deal with crossing mountpoints */ if (!nfs_fsid_equal(&NFS_SB(sb)->fsid, &fattr->fsid)) { - inode->i_op = &nfs_mountpoint_inode_operations; + if (fattr->valid & NFS_ATTR_FATTR_V4_REFERRAL) + inode->i_op = &nfs_referral_inode_operations; + else + inode->i_op = &nfs_mountpoint_inode_operations; inode->i_fop = NULL; } } else if (S_ISLNK(inode->i_mode)) diff --git a/fs/nfs/namespace.c b/fs/nfs/namespace.c index e426516..8ca44b7 100644 --- a/fs/nfs/namespace.c +++ b/fs/nfs/namespace.c @@ -58,7 +58,10 @@ static void * nfs_follow_mountpoint(stru if (err != 0) goto out_err; - mnt = nfs_do_submount(nd->mnt, nd->dentry, &fh, &fattr); + if (fattr.valid & NFS_ATTR_FATTR_V4_REFERRAL) + mnt = nfs_do_refmount(nd->mnt, nd->dentry); + else + mnt = nfs_do_submount(nd->mnt, nd->dentry, &fh, &fattr); err = PTR_ERR(mnt); if (IS_ERR(mnt)) goto out_err; @@ -94,6 +97,10 @@ struct inode_operations nfs_mountpoint_i .getattr = nfs_getattr, }; +struct inode_operations nfs_referral_inode_operations = { + .follow_link = nfs_follow_mountpoint, +}; + static void nfs_expire_automounts(void *data) { struct list_head *list = (struct list_head *)data; diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c index ab5525a..9cddeab 100644 --- a/fs/nfs/nfs4proc.c +++ b/fs/nfs/nfs4proc.c @@ -1462,6 +1462,50 @@ out: return nfs4_map_errors(status); } +/* + * Get locations and (maybe) other attributes of a referral. + * Note that we'll actually follow the referral later when + * we detect fsid mismatch in inode revalidation + */ +static int nfs4_get_referral(struct inode *dir, struct qstr *name, struct nfs_fattr *fattr, struct nfs_fh *fhandle) +{ + int status = -ENOMEM; + struct page *page = NULL; + struct nfs4_fs_locations *locations = NULL; + struct dentry dentry = {}; + + page = alloc_page(GFP_KERNEL); + if (page == NULL) + goto out; + locations = kmalloc(sizeof(struct nfs4_fs_locations), GFP_KERNEL); + if (locations == NULL) + goto out; + + dentry.d_name.name = name->name; + dentry.d_name.len = name->len; + status = nfs4_proc_fs_locations(dir, &dentry, locations, page); + if (status != 0) + goto out; + /* Make sure server returned a different fsid for the referral */ + if (nfs_fsid_equal(&NFS_SERVER(dir)->fsid, &locations->fattr.fsid)) { + dprintk("%s: server did not return a different fsid for a referral at %s\n", __FUNCTION__, name->name); + status = -EIO; + goto out; + } + + memcpy(fattr, &locations->fattr, sizeof(struct nfs_fattr)); + fattr->valid |= NFS_ATTR_FATTR_V4_REFERRAL; + if (!fattr->mode) + fattr->mode = S_IFDIR; + memset(fhandle, 0, sizeof(struct nfs_fh)); +out: + if (page) + __free_page(page); + if (locations) + kfree(locations); + return status; +} + static int _nfs4_proc_getattr(struct nfs_server *server, struct nfs_fh *fhandle, struct nfs_fattr *fattr) { struct nfs4_getattr_arg args = { @@ -1566,6 +1610,8 @@ static int _nfs4_proc_lookup(struct inod dprintk("NFS call lookup %s\n", name->name); status = rpc_call_sync(NFS_CLIENT(dir), &msg, 0); + if (status == -NFS4ERR_MOVED) + status = nfs4_get_referral(dir, name, fattr, fhandle); dprintk("NFS reply lookup: %d\n", status); return status; } diff --git a/include/linux/nfs_fs.h b/include/linux/nfs_fs.h index 09271b1..1527989 100644 --- a/include/linux/nfs_fs.h +++ b/include/linux/nfs_fs.h @@ -409,6 +409,7 @@ #endif */ extern struct list_head nfs_automount_list; extern struct inode_operations nfs_mountpoint_inode_operations; +extern struct inode_operations nfs_referral_inode_operations; extern int nfs_mountpoint_expiry_timeout; extern void nfs_release_automount_timer(void); diff --git a/include/linux/nfs_xdr.h b/include/linux/nfs_xdr.h index d6eea83..7c7320f 100644 --- a/include/linux/nfs_xdr.h +++ b/include/linux/nfs_xdr.h @@ -63,6 +63,7 @@ #define NFS_ATTR_WCC 0x0001 /* pre-op #define NFS_ATTR_FATTR 0x0002 /* post-op attributes */ #define NFS_ATTR_FATTR_V3 0x0004 /* NFSv3 attributes */ #define NFS_ATTR_FATTR_V4 0x0008 /* NFSv4 change attribute */ +#define NFS_ATTR_FATTR_V4_REFERRAL 0x0010 /* NFSv4 referral */ /* * Info on the file system