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>
diff --git a/fs/afs/inode.c b/fs/afs/inode.c
index 5c95da7..ba35b48 100644
--- a/fs/afs/inode.c
+++ b/fs/afs/inode.c
@@ -139,9 +139,10 @@ static int afs_inode_init_from_status(struct afs_vnode *vnode, struct key *key,
vnode->cb_expires_at = ktime_get_real_seconds();
} else {
vnode->cb_expires_at = scb->callback.expires_at;
- old_cbi = vnode->cb_interest;
+ old_cbi = rcu_dereference_protected(vnode->cb_interest,
+ lockdep_is_held(&vnode->cb_lock.lock));
if (cbi != old_cbi)
- vnode->cb_interest = afs_get_cb_interest(cbi);
+ rcu_assign_pointer(vnode->cb_interest, afs_get_cb_interest(cbi));
else
old_cbi = NULL;
set_bit(AFS_VNODE_CB_PROMISED, &vnode->flags);
@@ -245,9 +246,10 @@ static void afs_apply_callback(struct afs_fs_cursor *fc,
if (!afs_cb_is_broken(cb_break, vnode, fc->cbi)) {
vnode->cb_expires_at = cb->expires_at;
- old = vnode->cb_interest;
+ old = rcu_dereference_protected(vnode->cb_interest,
+ lockdep_is_held(&vnode->cb_lock.lock));
if (old != fc->cbi) {
- vnode->cb_interest = afs_get_cb_interest(fc->cbi);
+ rcu_assign_pointer(vnode->cb_interest, afs_get_cb_interest(fc->cbi));
afs_put_cb_interest(afs_v2net(vnode), old);
}
set_bit(AFS_VNODE_CB_PROMISED, &vnode->flags);
@@ -565,36 +567,46 @@ void afs_zap_data(struct afs_vnode *vnode)
*/
bool afs_check_validity(struct afs_vnode *vnode)
{
+ struct afs_cb_interest *cbi;
+ struct afs_server *server;
+ struct afs_volume *volume = vnode->volume;
time64_t now = ktime_get_real_seconds();
bool valid;
+ unsigned int cb_break, cb_s_break, cb_v_break;
+ int seq = 0;
- /* Quickly check the callback state. Ideally, we'd use read_seqbegin
- * here, but we have no way to pass the net namespace to the RCU
- * cleanup for the server record.
- */
- read_seqlock_excl(&vnode->cb_lock);
+ do {
+ read_seqbegin_or_lock(&vnode->cb_lock, &seq);
+ cb_v_break = READ_ONCE(volume->cb_v_break);
+ cb_break = vnode->cb_break;
- if (test_bit(AFS_VNODE_CB_PROMISED, &vnode->flags)) {
- if (vnode->cb_s_break != vnode->cb_interest->server->cb_s_break ||
- vnode->cb_v_break != vnode->volume->cb_v_break) {
- vnode->cb_s_break = vnode->cb_interest->server->cb_s_break;
- vnode->cb_v_break = vnode->volume->cb_v_break;
- valid = false;
- } else if (test_bit(AFS_VNODE_ZAP_DATA, &vnode->flags)) {
- valid = false;
- } else if (vnode->cb_expires_at - 10 <= now) {
- valid = false;
- } else {
+ if (test_bit(AFS_VNODE_CB_PROMISED, &vnode->flags)) {
+ cbi = rcu_dereference(vnode->cb_interest);
+ server = rcu_dereference(cbi->server);
+ cb_s_break = READ_ONCE(server->cb_s_break);
+
+ if (vnode->cb_s_break != cb_s_break ||
+ vnode->cb_v_break != cb_v_break) {
+ vnode->cb_s_break = cb_s_break;
+ vnode->cb_v_break = cb_v_break;
+ valid = false;
+ } else if (test_bit(AFS_VNODE_ZAP_DATA, &vnode->flags)) {
+ valid = false;
+ } else if (vnode->cb_expires_at - 10 <= now) {
+ valid = false;
+ } else {
+ valid = true;
+ }
+ } else if (test_bit(AFS_VNODE_DELETED, &vnode->flags)) {
valid = true;
+ } else {
+ vnode->cb_v_break = cb_v_break;
+ valid = false;
}
- } else if (test_bit(AFS_VNODE_DELETED, &vnode->flags)) {
- valid = true;
- } else {
- vnode->cb_v_break = vnode->volume->cb_v_break;
- valid = false;
- }
- read_sequnlock_excl(&vnode->cb_lock);
+ } while (need_seqretry(&vnode->cb_lock, seq));
+
+ done_seqretry(&vnode->cb_lock, seq);
return valid;
}
@@ -616,7 +628,9 @@ int afs_validate(struct afs_vnode *vnode, struct key *key)
vnode->fid.vid, vnode->fid.vnode, vnode->flags,
key_serial(key));
+ rcu_read_lock();
valid = afs_check_validity(vnode);
+ rcu_read_unlock();
if (test_bit(AFS_VNODE_DELETED, &vnode->flags))
clear_nlink(&vnode->vfs_inode);
@@ -703,6 +717,7 @@ int afs_drop_inode(struct inode *inode)
*/
void afs_evict_inode(struct inode *inode)
{
+ struct afs_cb_interest *cbi;
struct afs_vnode *vnode;
vnode = AFS_FS_I(inode);
@@ -719,10 +734,14 @@ void afs_evict_inode(struct inode *inode)
truncate_inode_pages_final(&inode->i_data);
clear_inode(inode);
- if (vnode->cb_interest) {
- afs_put_cb_interest(afs_i2net(inode), vnode->cb_interest);
- vnode->cb_interest = NULL;
+ write_seqlock(&vnode->cb_lock);
+ cbi = rcu_dereference_protected(vnode->cb_interest,
+ lockdep_is_held(&vnode->cb_lock.lock));
+ if (cbi) {
+ afs_put_cb_interest(afs_i2net(inode), cbi);
+ rcu_assign_pointer(vnode->cb_interest, NULL);
}
+ write_sequnlock(&vnode->cb_lock);
while (!list_empty(&vnode->wb_keys)) {
struct afs_wb_key *wbk = list_entry(vnode->wb_keys.next,