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afs: Make vnode->cb_interest RCU safe

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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>
This commit is contained in:
David Howells
2019-05-13 16:14:32 +01:00
parent c925bd0ac4
commit f642404a04
7 changed files with 99 additions and 58 deletions
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21
fs/afs/callback.c
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@@ -94,15 +94,15 @@ int afs_register_server_cb_interest(struct afs_vnode *vnode,
struct afs_server *server = entry->server;
again:
if (vnode->cb_interest &&
likely(vnode->cb_interest == entry->cb_interest))
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);
vcbi = vnode->cb_interest;
if (vcbi) {
if (vcbi == cbi) {
afs_put_cb_interest(afs_v2net(vnode), cbi);
@@ -114,8 +114,9 @@ again:
*/
if (cbi && vcbi->server == cbi->server) {
write_seqlock(&vnode->cb_lock);
old = vnode->cb_interest;
vnode->cb_interest = cbi;
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;
@@ -160,8 +161,9 @@ again:
*/
write_seqlock(&vnode->cb_lock);
old = vnode->cb_interest;
vnode->cb_interest = cbi;
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);
@@ -191,10 +193,11 @@ void afs_put_cb_interest(struct afs_net *net, struct afs_cb_interest *cbi)
vi = NULL;
write_unlock(&cbi->server->cb_break_lock);
kfree(vi);
if (vi)
kfree_rcu(vi, rcu);
afs_put_server(net, cbi->server);
}
kfree(cbi);
kfree_rcu(cbi, rcu);
}
}