linux/fs/afs/callback.c
David Howells f642404a04 afs: Make vnode->cb_interest RCU safe
Use RCU-based freeing for afs_cb_interest struct objects and use RCU on
vnode->cb_interest.  Use that change to allow afs_check_validity() to use
read_seqbegin_or_lock() instead of read_seqlock_excl().

This also requires the caller of afs_check_validity() to hold the RCU read
lock across the call.

Signed-off-by: David Howells <dhowells@redhat.com>
2019-05-16 22:23:21 +01:00

335 lines
8.0 KiB
C

/*
* Copyright (c) 2002, 2007 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 Woodhouse <dwmw2@infradead.org>
* David Howells <dhowells@redhat.com>
*
*/
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/circ_buf.h>
#include <linux/sched.h>
#include "internal.h"
/*
* Create volume and callback interests on a server.
*/
static struct afs_cb_interest *afs_create_interest(struct afs_server *server,
struct afs_vnode *vnode)
{
struct afs_vol_interest *new_vi, *vi;
struct afs_cb_interest *new;
struct hlist_node **pp;
new_vi = kzalloc(sizeof(struct afs_vol_interest), GFP_KERNEL);
if (!new_vi)
return NULL;
new = kzalloc(sizeof(struct afs_cb_interest), GFP_KERNEL);
if (!new) {
kfree(new_vi);
return NULL;
}
new_vi->usage = 1;
new_vi->vid = vnode->volume->vid;
INIT_HLIST_NODE(&new_vi->srv_link);
INIT_HLIST_HEAD(&new_vi->cb_interests);
refcount_set(&new->usage, 1);
new->sb = vnode->vfs_inode.i_sb;
new->vid = vnode->volume->vid;
new->server = afs_get_server(server);
INIT_HLIST_NODE(&new->cb_vlink);
write_lock(&server->cb_break_lock);
for (pp = &server->cb_volumes.first; *pp; pp = &(*pp)->next) {
vi = hlist_entry(*pp, struct afs_vol_interest, srv_link);
if (vi->vid < new_vi->vid)
continue;
if (vi->vid > new_vi->vid)
break;
vi->usage++;
goto found_vi;
}
new_vi->srv_link.pprev = pp;
new_vi->srv_link.next = *pp;
if (*pp)
(*pp)->pprev = &new_vi->srv_link.next;
*pp = &new_vi->srv_link;
vi = new_vi;
new_vi = NULL;
found_vi:
new->vol_interest = vi;
hlist_add_head(&new->cb_vlink, &vi->cb_interests);
write_unlock(&server->cb_break_lock);
kfree(new_vi);
return new;
}
/*
* Set up an interest-in-callbacks record for a volume on a server and
* register it with the server.
* - Called with vnode->io_lock held.
*/
int afs_register_server_cb_interest(struct afs_vnode *vnode,
struct afs_server_list *slist,
unsigned int index)
{
struct afs_server_entry *entry = &slist->servers[index];
struct afs_cb_interest *cbi, *vcbi, *new, *old;
struct afs_server *server = entry->server;
again:
vcbi = rcu_dereference_protected(vnode->cb_interest,
lockdep_is_held(&vnode->io_lock));
if (vcbi && likely(vcbi == entry->cb_interest))
return 0;
read_lock(&slist->lock);
cbi = afs_get_cb_interest(entry->cb_interest);
read_unlock(&slist->lock);
if (vcbi) {
if (vcbi == cbi) {
afs_put_cb_interest(afs_v2net(vnode), cbi);
return 0;
}
/* Use a new interest in the server list for the same server
* rather than an old one that's still attached to a vnode.
*/
if (cbi && vcbi->server == cbi->server) {
write_seqlock(&vnode->cb_lock);
old = rcu_dereference_protected(vnode->cb_interest,
lockdep_is_held(&vnode->cb_lock.lock));
rcu_assign_pointer(vnode->cb_interest, cbi);
write_sequnlock(&vnode->cb_lock);
afs_put_cb_interest(afs_v2net(vnode), old);
return 0;
}
/* Re-use the one attached to the vnode. */
if (!cbi && vcbi->server == server) {
write_lock(&slist->lock);
if (entry->cb_interest) {
write_unlock(&slist->lock);
afs_put_cb_interest(afs_v2net(vnode), cbi);
goto again;
}
entry->cb_interest = cbi;
write_unlock(&slist->lock);
return 0;
}
}
if (!cbi) {
new = afs_create_interest(server, vnode);
if (!new)
return -ENOMEM;
write_lock(&slist->lock);
if (!entry->cb_interest) {
entry->cb_interest = afs_get_cb_interest(new);
cbi = new;
new = NULL;
} else {
cbi = afs_get_cb_interest(entry->cb_interest);
}
write_unlock(&slist->lock);
afs_put_cb_interest(afs_v2net(vnode), new);
}
ASSERT(cbi);
/* Change the server the vnode is using. This entails scrubbing any
* interest the vnode had in the previous server it was using.
*/
write_seqlock(&vnode->cb_lock);
old = rcu_dereference_protected(vnode->cb_interest,
lockdep_is_held(&vnode->cb_lock.lock));
rcu_assign_pointer(vnode->cb_interest, cbi);
vnode->cb_s_break = cbi->server->cb_s_break;
vnode->cb_v_break = vnode->volume->cb_v_break;
clear_bit(AFS_VNODE_CB_PROMISED, &vnode->flags);
write_sequnlock(&vnode->cb_lock);
afs_put_cb_interest(afs_v2net(vnode), old);
return 0;
}
/*
* Remove an interest on a server.
*/
void afs_put_cb_interest(struct afs_net *net, struct afs_cb_interest *cbi)
{
struct afs_vol_interest *vi;
if (cbi && refcount_dec_and_test(&cbi->usage)) {
if (!hlist_unhashed(&cbi->cb_vlink)) {
write_lock(&cbi->server->cb_break_lock);
hlist_del_init(&cbi->cb_vlink);
vi = cbi->vol_interest;
cbi->vol_interest = NULL;
if (--vi->usage == 0)
hlist_del(&vi->srv_link);
else
vi = NULL;
write_unlock(&cbi->server->cb_break_lock);
if (vi)
kfree_rcu(vi, rcu);
afs_put_server(net, cbi->server);
}
kfree_rcu(cbi, rcu);
}
}
/*
* allow the fileserver to request callback state (re-)initialisation
*/
void afs_init_callback_state(struct afs_server *server)
{
server->cb_s_break++;
}
/*
* actually break a callback
*/
void __afs_break_callback(struct afs_vnode *vnode)
{
_enter("");
clear_bit(AFS_VNODE_NEW_CONTENT, &vnode->flags);
if (test_and_clear_bit(AFS_VNODE_CB_PROMISED, &vnode->flags)) {
vnode->cb_break++;
afs_clear_permits(vnode);
if (vnode->lock_state == AFS_VNODE_LOCK_WAITING_FOR_CB)
afs_lock_may_be_available(vnode);
}
}
void afs_break_callback(struct afs_vnode *vnode)
{
write_seqlock(&vnode->cb_lock);
__afs_break_callback(vnode);
write_sequnlock(&vnode->cb_lock);
}
/*
* allow the fileserver to explicitly break one callback
* - happens when
* - the backing file is changed
* - a lock is released
*/
static void afs_break_one_callback(struct afs_server *server,
struct afs_fid *fid)
{
struct afs_vol_interest *vi;
struct afs_cb_interest *cbi;
struct afs_iget_data data;
struct afs_vnode *vnode;
struct inode *inode;
read_lock(&server->cb_break_lock);
hlist_for_each_entry(vi, &server->cb_volumes, srv_link) {
if (vi->vid < fid->vid)
continue;
if (vi->vid > fid->vid) {
vi = NULL;
break;
}
//atomic_inc(&vi->usage);
break;
}
/* TODO: Find all matching volumes if we couldn't match the server and
* break them anyway.
*/
if (!vi)
goto out;
/* Step through all interested superblocks. There may be more than one
* because of cell aliasing.
*/
hlist_for_each_entry(cbi, &vi->cb_interests, cb_vlink) {
if (fid->vnode == 0 && fid->unique == 0) {
/* The callback break applies to an entire volume. */
struct afs_super_info *as = AFS_FS_S(cbi->sb);
struct afs_volume *volume = as->volume;
write_lock(&volume->cb_break_lock);
volume->cb_v_break++;
write_unlock(&volume->cb_break_lock);
} else {
data.volume = NULL;
data.fid = *fid;
inode = ilookup5_nowait(cbi->sb, fid->vnode,
afs_iget5_test, &data);
if (inode) {
vnode = AFS_FS_I(inode);
afs_break_callback(vnode);
iput(inode);
}
}
}
out:
read_unlock(&server->cb_break_lock);
}
/*
* allow the fileserver to break callback promises
*/
void afs_break_callbacks(struct afs_server *server, size_t count,
struct afs_callback_break *callbacks)
{
_enter("%p,%zu,", server, count);
ASSERT(server != NULL);
ASSERTCMP(count, <=, AFSCBMAX);
/* TODO: Sort the callback break list by volume ID */
for (; count > 0; callbacks++, count--) {
_debug("- Fid { vl=%08llx n=%llu u=%u }",
callbacks->fid.vid,
callbacks->fid.vnode,
callbacks->fid.unique);
afs_break_one_callback(server, &callbacks->fid);
}
_leave("");
return;
}
/*
* Clear the callback interests in a server list.
*/
void afs_clear_callback_interests(struct afs_net *net, struct afs_server_list *slist)
{
int i;
for (i = 0; i < slist->nr_servers; i++) {
afs_put_cb_interest(net, slist->servers[i].cb_interest);
slist->servers[i].cb_interest = NULL;
}
}