linux-stable/fs/afs/super.c
Linus Torvalds 16df6e07d6 vfs-6.8.netfs
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Merge tag 'vfs-6.8.netfs' of gitolite.kernel.org:pub/scm/linux/kernel/git/vfs/vfs

Pull netfs updates from Christian Brauner:
 "This extends the netfs helper library that network filesystems can use
  to replace their own implementations. Both afs and 9p are ported. cifs
  is ready as well but the patches are way bigger and will be routed
  separately once this is merged. That will remove lots of code as well.

  The overal goal is to get high-level I/O and knowledge of the page
  cache and ouf of the filesystem drivers. This includes knowledge about
  the existence of pages and folios

  The pull request converts afs and 9p. This removes about 800 lines of
  code from afs and 300 from 9p. For 9p it is now possible to do writes
  in larger than a page chunks. Additionally, multipage folio support
  can be turned on for 9p. Separate patches exist for cifs removing
  another 2000+ lines. I've included detailed information in the
  individual pulls I took.

  Summary:

   - Add NFS-style (and Ceph-style) locking around DIO vs buffered I/O
     calls to prevent these from happening at the same time.

   - Support for direct and unbuffered I/O.

   - Support for write-through caching in the page cache.

   - O_*SYNC and RWF_*SYNC writes use write-through rather than writing
     to the page cache and then flushing afterwards.

   - Support for write-streaming.

   - Support for write grouping.

   - Skip reads for which the server could only return zeros or EOF.

   - The fscache module is now part of the netfs library and the
     corresponding maintainer entry is updated.

   - Some helpers from the fscache subsystem are renamed to mark them as
     belonging to the netfs library.

   - Follow-up fixes for the netfs library.

   - Follow-up fixes for the 9p conversion"

* tag 'vfs-6.8.netfs' of gitolite.kernel.org:pub/scm/linux/kernel/git/vfs/vfs: (50 commits)
  netfs: Fix wrong #ifdef hiding wait
  cachefiles: Fix signed/unsigned mixup
  netfs: Fix the loop that unmarks folios after writing to the cache
  netfs: Fix interaction between write-streaming and cachefiles culling
  netfs: Count DIO writes
  netfs: Mark netfs_unbuffered_write_iter_locked() static
  netfs: Fix proc/fs/fscache symlink to point to "netfs" not "../netfs"
  netfs: Rearrange netfs_io_subrequest to put request pointer first
  9p: Use length of data written to the server in preference to error
  9p: Do a couple of cleanups
  9p: Fix initialisation of netfs_inode for 9p
  cachefiles: Fix __cachefiles_prepare_write()
  9p: Use netfslib read/write_iter
  afs: Use the netfs write helpers
  netfs: Export the netfs_sreq tracepoint
  netfs: Optimise away reads above the point at which there can be no data
  netfs: Implement a write-through caching option
  netfs: Provide a launder_folio implementation
  netfs: Provide a writepages implementation
  netfs, cachefiles: Pass upper bound length to allow expansion
  ...
2024-01-19 09:10:23 -08:00

779 lines
18 KiB
C

/* AFS superblock handling
*
* Copyright (c) 2002, 2007, 2018 Red Hat, Inc. All rights reserved.
*
* This software may be freely redistributed under the terms of the
* GNU General Public License.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*
* Authors: David Howells <dhowells@redhat.com>
* David Woodhouse <dwmw2@infradead.org>
*
*/
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/mount.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/fs.h>
#include <linux/pagemap.h>
#include <linux/fs_parser.h>
#include <linux/statfs.h>
#include <linux/sched.h>
#include <linux/nsproxy.h>
#include <linux/magic.h>
#include <net/net_namespace.h>
#include "internal.h"
static void afs_i_init_once(void *foo);
static void afs_kill_super(struct super_block *sb);
static struct inode *afs_alloc_inode(struct super_block *sb);
static void afs_destroy_inode(struct inode *inode);
static void afs_free_inode(struct inode *inode);
static int afs_statfs(struct dentry *dentry, struct kstatfs *buf);
static int afs_show_devname(struct seq_file *m, struct dentry *root);
static int afs_show_options(struct seq_file *m, struct dentry *root);
static int afs_init_fs_context(struct fs_context *fc);
static const struct fs_parameter_spec afs_fs_parameters[];
struct file_system_type afs_fs_type = {
.owner = THIS_MODULE,
.name = "afs",
.init_fs_context = afs_init_fs_context,
.parameters = afs_fs_parameters,
.kill_sb = afs_kill_super,
.fs_flags = FS_RENAME_DOES_D_MOVE,
};
MODULE_ALIAS_FS("afs");
int afs_net_id;
static const struct super_operations afs_super_ops = {
.statfs = afs_statfs,
.alloc_inode = afs_alloc_inode,
.write_inode = netfs_unpin_writeback,
.drop_inode = afs_drop_inode,
.destroy_inode = afs_destroy_inode,
.free_inode = afs_free_inode,
.evict_inode = afs_evict_inode,
.show_devname = afs_show_devname,
.show_options = afs_show_options,
};
static struct kmem_cache *afs_inode_cachep;
static atomic_t afs_count_active_inodes;
enum afs_param {
Opt_autocell,
Opt_dyn,
Opt_flock,
Opt_source,
};
static const struct constant_table afs_param_flock[] = {
{"local", afs_flock_mode_local },
{"openafs", afs_flock_mode_openafs },
{"strict", afs_flock_mode_strict },
{"write", afs_flock_mode_write },
{}
};
static const struct fs_parameter_spec afs_fs_parameters[] = {
fsparam_flag ("autocell", Opt_autocell),
fsparam_flag ("dyn", Opt_dyn),
fsparam_enum ("flock", Opt_flock, afs_param_flock),
fsparam_string("source", Opt_source),
{}
};
/*
* initialise the filesystem
*/
int __init afs_fs_init(void)
{
int ret;
_enter("");
/* create ourselves an inode cache */
atomic_set(&afs_count_active_inodes, 0);
ret = -ENOMEM;
afs_inode_cachep = kmem_cache_create("afs_inode_cache",
sizeof(struct afs_vnode),
0,
SLAB_HWCACHE_ALIGN|SLAB_ACCOUNT,
afs_i_init_once);
if (!afs_inode_cachep) {
printk(KERN_NOTICE "kAFS: Failed to allocate inode cache\n");
return ret;
}
/* now export our filesystem to lesser mortals */
ret = register_filesystem(&afs_fs_type);
if (ret < 0) {
kmem_cache_destroy(afs_inode_cachep);
_leave(" = %d", ret);
return ret;
}
_leave(" = 0");
return 0;
}
/*
* clean up the filesystem
*/
void afs_fs_exit(void)
{
_enter("");
afs_mntpt_kill_timer();
unregister_filesystem(&afs_fs_type);
if (atomic_read(&afs_count_active_inodes) != 0) {
printk("kAFS: %d active inode objects still present\n",
atomic_read(&afs_count_active_inodes));
BUG();
}
/*
* Make sure all delayed rcu free inodes are flushed before we
* destroy cache.
*/
rcu_barrier();
kmem_cache_destroy(afs_inode_cachep);
_leave("");
}
/*
* Display the mount device name in /proc/mounts.
*/
static int afs_show_devname(struct seq_file *m, struct dentry *root)
{
struct afs_super_info *as = AFS_FS_S(root->d_sb);
struct afs_volume *volume = as->volume;
struct afs_cell *cell = as->cell;
const char *suf = "";
char pref = '%';
if (as->dyn_root) {
seq_puts(m, "none");
return 0;
}
switch (volume->type) {
case AFSVL_RWVOL:
break;
case AFSVL_ROVOL:
pref = '#';
if (volume->type_force)
suf = ".readonly";
break;
case AFSVL_BACKVOL:
pref = '#';
suf = ".backup";
break;
}
seq_printf(m, "%c%s:%s%s", pref, cell->name, volume->name, suf);
return 0;
}
/*
* Display the mount options in /proc/mounts.
*/
static int afs_show_options(struct seq_file *m, struct dentry *root)
{
struct afs_super_info *as = AFS_FS_S(root->d_sb);
const char *p = NULL;
if (as->dyn_root)
seq_puts(m, ",dyn");
if (test_bit(AFS_VNODE_AUTOCELL, &AFS_FS_I(d_inode(root))->flags))
seq_puts(m, ",autocell");
switch (as->flock_mode) {
case afs_flock_mode_unset: break;
case afs_flock_mode_local: p = "local"; break;
case afs_flock_mode_openafs: p = "openafs"; break;
case afs_flock_mode_strict: p = "strict"; break;
case afs_flock_mode_write: p = "write"; break;
}
if (p)
seq_printf(m, ",flock=%s", p);
return 0;
}
/*
* Parse the source name to get cell name, volume name, volume type and R/W
* selector.
*
* This can be one of the following:
* "%[cell:]volume[.]" R/W volume
* "#[cell:]volume[.]" R/O or R/W volume (R/O parent),
* or R/W (R/W parent) volume
* "%[cell:]volume.readonly" R/O volume
* "#[cell:]volume.readonly" R/O volume
* "%[cell:]volume.backup" Backup volume
* "#[cell:]volume.backup" Backup volume
*/
static int afs_parse_source(struct fs_context *fc, struct fs_parameter *param)
{
struct afs_fs_context *ctx = fc->fs_private;
struct afs_cell *cell;
const char *cellname, *suffix, *name = param->string;
int cellnamesz;
_enter(",%s", name);
if (fc->source)
return invalf(fc, "kAFS: Multiple sources not supported");
if (!name) {
printk(KERN_ERR "kAFS: no volume name specified\n");
return -EINVAL;
}
if ((name[0] != '%' && name[0] != '#') || !name[1]) {
/* To use dynroot, we don't want to have to provide a source */
if (strcmp(name, "none") == 0) {
ctx->no_cell = true;
return 0;
}
printk(KERN_ERR "kAFS: unparsable volume name\n");
return -EINVAL;
}
/* determine the type of volume we're looking for */
if (name[0] == '%') {
ctx->type = AFSVL_RWVOL;
ctx->force = true;
}
name++;
/* split the cell name out if there is one */
ctx->volname = strchr(name, ':');
if (ctx->volname) {
cellname = name;
cellnamesz = ctx->volname - name;
ctx->volname++;
} else {
ctx->volname = name;
cellname = NULL;
cellnamesz = 0;
}
/* the volume type is further affected by a possible suffix */
suffix = strrchr(ctx->volname, '.');
if (suffix) {
if (strcmp(suffix, ".readonly") == 0) {
ctx->type = AFSVL_ROVOL;
ctx->force = true;
} else if (strcmp(suffix, ".backup") == 0) {
ctx->type = AFSVL_BACKVOL;
ctx->force = true;
} else if (suffix[1] == 0) {
} else {
suffix = NULL;
}
}
ctx->volnamesz = suffix ?
suffix - ctx->volname : strlen(ctx->volname);
_debug("cell %*.*s [%p]",
cellnamesz, cellnamesz, cellname ?: "", ctx->cell);
/* lookup the cell record */
if (cellname) {
cell = afs_lookup_cell(ctx->net, cellname, cellnamesz,
NULL, false);
if (IS_ERR(cell)) {
pr_err("kAFS: unable to lookup cell '%*.*s'\n",
cellnamesz, cellnamesz, cellname ?: "");
return PTR_ERR(cell);
}
afs_unuse_cell(ctx->net, ctx->cell, afs_cell_trace_unuse_parse);
afs_see_cell(cell, afs_cell_trace_see_source);
ctx->cell = cell;
}
_debug("CELL:%s [%p] VOLUME:%*.*s SUFFIX:%s TYPE:%d%s",
ctx->cell->name, ctx->cell,
ctx->volnamesz, ctx->volnamesz, ctx->volname,
suffix ?: "-", ctx->type, ctx->force ? " FORCE" : "");
fc->source = param->string;
param->string = NULL;
return 0;
}
/*
* Parse a single mount parameter.
*/
static int afs_parse_param(struct fs_context *fc, struct fs_parameter *param)
{
struct fs_parse_result result;
struct afs_fs_context *ctx = fc->fs_private;
int opt;
opt = fs_parse(fc, afs_fs_parameters, param, &result);
if (opt < 0)
return opt;
switch (opt) {
case Opt_source:
return afs_parse_source(fc, param);
case Opt_autocell:
ctx->autocell = true;
break;
case Opt_dyn:
ctx->dyn_root = true;
break;
case Opt_flock:
ctx->flock_mode = result.uint_32;
break;
default:
return -EINVAL;
}
_leave(" = 0");
return 0;
}
/*
* Validate the options, get the cell key and look up the volume.
*/
static int afs_validate_fc(struct fs_context *fc)
{
struct afs_fs_context *ctx = fc->fs_private;
struct afs_volume *volume;
struct afs_cell *cell;
struct key *key;
int ret;
if (!ctx->dyn_root) {
if (ctx->no_cell) {
pr_warn("kAFS: Can only specify source 'none' with -o dyn\n");
return -EINVAL;
}
if (!ctx->cell) {
pr_warn("kAFS: No cell specified\n");
return -EDESTADDRREQ;
}
reget_key:
/* We try to do the mount securely. */
key = afs_request_key(ctx->cell);
if (IS_ERR(key))
return PTR_ERR(key);
ctx->key = key;
if (ctx->volume) {
afs_put_volume(ctx->volume, afs_volume_trace_put_validate_fc);
ctx->volume = NULL;
}
if (test_bit(AFS_CELL_FL_CHECK_ALIAS, &ctx->cell->flags)) {
ret = afs_cell_detect_alias(ctx->cell, key);
if (ret < 0)
return ret;
if (ret == 1) {
_debug("switch to alias");
key_put(ctx->key);
ctx->key = NULL;
cell = afs_use_cell(ctx->cell->alias_of,
afs_cell_trace_use_fc_alias);
afs_unuse_cell(ctx->net, ctx->cell, afs_cell_trace_unuse_fc);
ctx->cell = cell;
goto reget_key;
}
}
volume = afs_create_volume(ctx);
if (IS_ERR(volume))
return PTR_ERR(volume);
ctx->volume = volume;
if (volume->type != AFSVL_RWVOL) {
ctx->flock_mode = afs_flock_mode_local;
fc->sb_flags |= SB_RDONLY;
}
}
return 0;
}
/*
* check a superblock to see if it's the one we're looking for
*/
static int afs_test_super(struct super_block *sb, struct fs_context *fc)
{
struct afs_fs_context *ctx = fc->fs_private;
struct afs_super_info *as = AFS_FS_S(sb);
return (as->net_ns == fc->net_ns &&
as->volume &&
as->volume->vid == ctx->volume->vid &&
as->cell == ctx->cell &&
!as->dyn_root);
}
static int afs_dynroot_test_super(struct super_block *sb, struct fs_context *fc)
{
struct afs_super_info *as = AFS_FS_S(sb);
return (as->net_ns == fc->net_ns &&
as->dyn_root);
}
static int afs_set_super(struct super_block *sb, struct fs_context *fc)
{
return set_anon_super(sb, NULL);
}
/*
* fill in the superblock
*/
static int afs_fill_super(struct super_block *sb, struct afs_fs_context *ctx)
{
struct afs_super_info *as = AFS_FS_S(sb);
struct inode *inode = NULL;
int ret;
_enter("");
/* fill in the superblock */
sb->s_blocksize = PAGE_SIZE;
sb->s_blocksize_bits = PAGE_SHIFT;
sb->s_maxbytes = MAX_LFS_FILESIZE;
sb->s_magic = AFS_FS_MAGIC;
sb->s_op = &afs_super_ops;
if (!as->dyn_root)
sb->s_xattr = afs_xattr_handlers;
ret = super_setup_bdi(sb);
if (ret)
return ret;
/* allocate the root inode and dentry */
if (as->dyn_root) {
inode = afs_iget_pseudo_dir(sb, true);
} else {
sprintf(sb->s_id, "%llu", as->volume->vid);
afs_activate_volume(as->volume);
inode = afs_root_iget(sb, ctx->key);
}
if (IS_ERR(inode))
return PTR_ERR(inode);
if (ctx->autocell || as->dyn_root)
set_bit(AFS_VNODE_AUTOCELL, &AFS_FS_I(inode)->flags);
ret = -ENOMEM;
sb->s_root = d_make_root(inode);
if (!sb->s_root)
goto error;
if (as->dyn_root) {
sb->s_d_op = &afs_dynroot_dentry_operations;
ret = afs_dynroot_populate(sb);
if (ret < 0)
goto error;
} else {
sb->s_d_op = &afs_fs_dentry_operations;
rcu_assign_pointer(as->volume->sb, sb);
}
_leave(" = 0");
return 0;
error:
_leave(" = %d", ret);
return ret;
}
static struct afs_super_info *afs_alloc_sbi(struct fs_context *fc)
{
struct afs_fs_context *ctx = fc->fs_private;
struct afs_super_info *as;
as = kzalloc(sizeof(struct afs_super_info), GFP_KERNEL);
if (as) {
as->net_ns = get_net(fc->net_ns);
as->flock_mode = ctx->flock_mode;
if (ctx->dyn_root) {
as->dyn_root = true;
} else {
as->cell = afs_use_cell(ctx->cell, afs_cell_trace_use_sbi);
as->volume = afs_get_volume(ctx->volume,
afs_volume_trace_get_alloc_sbi);
}
}
return as;
}
static void afs_destroy_sbi(struct afs_super_info *as)
{
if (as) {
struct afs_net *net = afs_net(as->net_ns);
afs_put_volume(as->volume, afs_volume_trace_put_destroy_sbi);
afs_unuse_cell(net, as->cell, afs_cell_trace_unuse_sbi);
put_net(as->net_ns);
kfree(as);
}
}
static void afs_kill_super(struct super_block *sb)
{
struct afs_super_info *as = AFS_FS_S(sb);
if (as->dyn_root)
afs_dynroot_depopulate(sb);
/* Clear the callback interests (which will do ilookup5) before
* deactivating the superblock.
*/
if (as->volume)
rcu_assign_pointer(as->volume->sb, NULL);
kill_anon_super(sb);
if (as->volume)
afs_deactivate_volume(as->volume);
afs_destroy_sbi(as);
}
/*
* Get an AFS superblock and root directory.
*/
static int afs_get_tree(struct fs_context *fc)
{
struct afs_fs_context *ctx = fc->fs_private;
struct super_block *sb;
struct afs_super_info *as;
int ret;
ret = afs_validate_fc(fc);
if (ret)
goto error;
_enter("");
/* allocate a superblock info record */
ret = -ENOMEM;
as = afs_alloc_sbi(fc);
if (!as)
goto error;
fc->s_fs_info = as;
/* allocate a deviceless superblock */
sb = sget_fc(fc,
as->dyn_root ? afs_dynroot_test_super : afs_test_super,
afs_set_super);
if (IS_ERR(sb)) {
ret = PTR_ERR(sb);
goto error;
}
if (!sb->s_root) {
/* initial superblock/root creation */
_debug("create");
ret = afs_fill_super(sb, ctx);
if (ret < 0)
goto error_sb;
sb->s_flags |= SB_ACTIVE;
} else {
_debug("reuse");
ASSERTCMP(sb->s_flags, &, SB_ACTIVE);
}
fc->root = dget(sb->s_root);
trace_afs_get_tree(as->cell, as->volume);
_leave(" = 0 [%p]", sb);
return 0;
error_sb:
deactivate_locked_super(sb);
error:
_leave(" = %d", ret);
return ret;
}
static void afs_free_fc(struct fs_context *fc)
{
struct afs_fs_context *ctx = fc->fs_private;
afs_destroy_sbi(fc->s_fs_info);
afs_put_volume(ctx->volume, afs_volume_trace_put_free_fc);
afs_unuse_cell(ctx->net, ctx->cell, afs_cell_trace_unuse_fc);
key_put(ctx->key);
kfree(ctx);
}
static const struct fs_context_operations afs_context_ops = {
.free = afs_free_fc,
.parse_param = afs_parse_param,
.get_tree = afs_get_tree,
};
/*
* Set up the filesystem mount context.
*/
static int afs_init_fs_context(struct fs_context *fc)
{
struct afs_fs_context *ctx;
struct afs_cell *cell;
ctx = kzalloc(sizeof(struct afs_fs_context), GFP_KERNEL);
if (!ctx)
return -ENOMEM;
ctx->type = AFSVL_ROVOL;
ctx->net = afs_net(fc->net_ns);
/* Default to the workstation cell. */
cell = afs_find_cell(ctx->net, NULL, 0, afs_cell_trace_use_fc);
if (IS_ERR(cell))
cell = NULL;
ctx->cell = cell;
fc->fs_private = ctx;
fc->ops = &afs_context_ops;
return 0;
}
/*
* Initialise an inode cache slab element prior to any use. Note that
* afs_alloc_inode() *must* reset anything that could incorrectly leak from one
* inode to another.
*/
static void afs_i_init_once(void *_vnode)
{
struct afs_vnode *vnode = _vnode;
memset(vnode, 0, sizeof(*vnode));
inode_init_once(&vnode->netfs.inode);
mutex_init(&vnode->io_lock);
init_rwsem(&vnode->validate_lock);
spin_lock_init(&vnode->wb_lock);
spin_lock_init(&vnode->lock);
INIT_LIST_HEAD(&vnode->wb_keys);
INIT_LIST_HEAD(&vnode->pending_locks);
INIT_LIST_HEAD(&vnode->granted_locks);
INIT_DELAYED_WORK(&vnode->lock_work, afs_lock_work);
INIT_LIST_HEAD(&vnode->cb_mmap_link);
seqlock_init(&vnode->cb_lock);
}
/*
* allocate an AFS inode struct from our slab cache
*/
static struct inode *afs_alloc_inode(struct super_block *sb)
{
struct afs_vnode *vnode;
vnode = alloc_inode_sb(sb, afs_inode_cachep, GFP_KERNEL);
if (!vnode)
return NULL;
atomic_inc(&afs_count_active_inodes);
/* Reset anything that shouldn't leak from one inode to the next. */
memset(&vnode->fid, 0, sizeof(vnode->fid));
memset(&vnode->status, 0, sizeof(vnode->status));
afs_vnode_set_cache(vnode, NULL);
vnode->volume = NULL;
vnode->lock_key = NULL;
vnode->permit_cache = NULL;
vnode->flags = 1 << AFS_VNODE_UNSET;
vnode->lock_state = AFS_VNODE_LOCK_NONE;
init_rwsem(&vnode->rmdir_lock);
INIT_WORK(&vnode->cb_work, afs_invalidate_mmap_work);
_leave(" = %p", &vnode->netfs.inode);
return &vnode->netfs.inode;
}
static void afs_free_inode(struct inode *inode)
{
kmem_cache_free(afs_inode_cachep, AFS_FS_I(inode));
}
/*
* destroy an AFS inode struct
*/
static void afs_destroy_inode(struct inode *inode)
{
struct afs_vnode *vnode = AFS_FS_I(inode);
_enter("%p{%llx:%llu}", inode, vnode->fid.vid, vnode->fid.vnode);
_debug("DESTROY INODE %p", inode);
atomic_dec(&afs_count_active_inodes);
}
static void afs_get_volume_status_success(struct afs_operation *op)
{
struct afs_volume_status *vs = &op->volstatus.vs;
struct kstatfs *buf = op->volstatus.buf;
if (vs->max_quota == 0)
buf->f_blocks = vs->part_max_blocks;
else
buf->f_blocks = vs->max_quota;
if (buf->f_blocks > vs->blocks_in_use)
buf->f_bavail = buf->f_bfree =
buf->f_blocks - vs->blocks_in_use;
}
static const struct afs_operation_ops afs_get_volume_status_operation = {
.issue_afs_rpc = afs_fs_get_volume_status,
.issue_yfs_rpc = yfs_fs_get_volume_status,
.success = afs_get_volume_status_success,
};
/*
* return information about an AFS volume
*/
static int afs_statfs(struct dentry *dentry, struct kstatfs *buf)
{
struct afs_super_info *as = AFS_FS_S(dentry->d_sb);
struct afs_operation *op;
struct afs_vnode *vnode = AFS_FS_I(d_inode(dentry));
buf->f_type = dentry->d_sb->s_magic;
buf->f_bsize = AFS_BLOCK_SIZE;
buf->f_namelen = AFSNAMEMAX - 1;
if (as->dyn_root) {
buf->f_blocks = 1;
buf->f_bavail = 0;
buf->f_bfree = 0;
return 0;
}
op = afs_alloc_operation(NULL, as->volume);
if (IS_ERR(op))
return PTR_ERR(op);
afs_op_set_vnode(op, 0, vnode);
op->nr_files = 1;
op->volstatus.buf = buf;
op->ops = &afs_get_volume_status_operation;
return afs_do_sync_operation(op);
}