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authorDavid Howells <dhowells@redhat.com>2018-05-10 10:43:04 +0300
committerDavid Howells <dhowells@redhat.com>2018-05-14 15:17:35 +0300
commitd4a96bec7a7362834ef5c31d7b2cc9bf36eb0570 (patch)
tree003ec92ab854c87f1ebbdbb4ee38e7b8a99e870a
parentf2686b09269ec1a6f23028b5675d87c3b4579a4c (diff)
downloadlinux-d4a96bec7a7362834ef5c31d7b2cc9bf36eb0570.tar.xz
afs: Fix refcounting in callback registration
The refcounting on afs_cb_interest struct objects in afs_register_server_cb_interest() is wrong as it uses the server list entry's call back interest pointer without regard for the fact that it might be replaced at any time and the object thrown away. Fix this by: (1) Put a lock on the afs_server_list struct that can be used to mediate access to the callback interest pointers in the servers array. (2) Keep a ref on the callback interest that we get from the entry. (3) Dropping the old reference held by vnode->cb_interest if we replace the pointer. Fixes: c435ee34551e ("afs: Overhaul the callback handling") Signed-off-by: David Howells <dhowells@redhat.com>
-rw-r--r--fs/afs/callback.c56
-rw-r--r--fs/afs/internal.h7
-rw-r--r--fs/afs/rotate.c4
-rw-r--r--fs/afs/server_list.c7
4 files changed, 52 insertions, 22 deletions
diff --git a/fs/afs/callback.c b/fs/afs/callback.c
index abd9a84f4e88..09332945d322 100644
--- a/fs/afs/callback.c
+++ b/fs/afs/callback.c
@@ -23,36 +23,55 @@
/*
* Set up an interest-in-callbacks record for a volume on a server and
* register it with the server.
- * - Called with volume->server_sem held.
+ * - Called with vnode->io_lock held.
*/
int afs_register_server_cb_interest(struct afs_vnode *vnode,
- struct afs_server_entry *entry)
+ struct afs_server_list *slist,
+ unsigned int index)
{
- struct afs_cb_interest *cbi = entry->cb_interest, *vcbi, *new, *x;
+ struct afs_server_entry *entry = &slist->servers[index];
+ struct afs_cb_interest *cbi, *vcbi, *new, *old;
struct afs_server *server = entry->server;
again:
+ if (vnode->cb_interest &&
+ likely(vnode->cb_interest == 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)
+ 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);
- vnode->cb_interest = afs_get_cb_interest(cbi);
+ old = vnode->cb_interest;
+ vnode->cb_interest = cbi;
write_sequnlock(&vnode->cb_lock);
- afs_put_cb_interest(afs_v2net(vnode), cbi);
+ afs_put_cb_interest(afs_v2net(vnode), old);
return 0;
}
+ /* Re-use the one attached to the vnode. */
if (!cbi && vcbi->server == server) {
- afs_get_cb_interest(vcbi);
- x = cmpxchg(&entry->cb_interest, cbi, vcbi);
- if (x != cbi) {
- cbi = x;
- afs_put_cb_interest(afs_v2net(vnode), vcbi);
+ 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;
}
}
@@ -72,13 +91,16 @@ again:
list_add_tail(&new->cb_link, &server->cb_interests);
write_unlock(&server->cb_break_lock);
- x = cmpxchg(&entry->cb_interest, cbi, new);
- if (x == cbi) {
+ write_lock(&slist->lock);
+ if (!entry->cb_interest) {
+ entry->cb_interest = afs_get_cb_interest(new);
cbi = new;
+ new = NULL;
} else {
- cbi = x;
- afs_put_cb_interest(afs_v2net(vnode), new);
+ cbi = afs_get_cb_interest(entry->cb_interest);
}
+ write_unlock(&slist->lock);
+ afs_put_cb_interest(afs_v2net(vnode), new);
}
ASSERT(cbi);
@@ -88,11 +110,13 @@ again:
*/
write_seqlock(&vnode->cb_lock);
- vnode->cb_interest = afs_get_cb_interest(cbi);
+ old = vnode->cb_interest;
+ vnode->cb_interest = cbi;
vnode->cb_s_break = cbi->server->cb_s_break;
clear_bit(AFS_VNODE_CB_PROMISED, &vnode->flags);
write_sequnlock(&vnode->cb_lock);
+ afs_put_cb_interest(afs_v2net(vnode), old);
return 0;
}
diff --git a/fs/afs/internal.h b/fs/afs/internal.h
index 8de04b29bec1..e75e57e13320 100644
--- a/fs/afs/internal.h
+++ b/fs/afs/internal.h
@@ -434,6 +434,7 @@ struct afs_server_list {
unsigned short index; /* Server currently in use */
unsigned short vnovol_mask; /* Servers to be skipped due to VNOVOL */
unsigned int seq; /* Set to ->servers_seq when installed */
+ rwlock_t lock;
struct afs_server_entry servers[];
};
@@ -649,13 +650,15 @@ extern void afs_init_callback_state(struct afs_server *);
extern void afs_break_callback(struct afs_vnode *);
extern void afs_break_callbacks(struct afs_server *, size_t, struct afs_callback_break*);
-extern int afs_register_server_cb_interest(struct afs_vnode *, struct afs_server_entry *);
+extern int afs_register_server_cb_interest(struct afs_vnode *,
+ struct afs_server_list *, unsigned int);
extern void afs_put_cb_interest(struct afs_net *, struct afs_cb_interest *);
extern void afs_clear_callback_interests(struct afs_net *, struct afs_server_list *);
static inline struct afs_cb_interest *afs_get_cb_interest(struct afs_cb_interest *cbi)
{
- refcount_inc(&cbi->usage);
+ if (cbi)
+ refcount_inc(&cbi->usage);
return cbi;
}
diff --git a/fs/afs/rotate.c b/fs/afs/rotate.c
index ac0feac9d746..4a26d51b2968 100644
--- a/fs/afs/rotate.c
+++ b/fs/afs/rotate.c
@@ -350,8 +350,8 @@ use_server:
* break request before we've finished decoding the reply and
* installing the vnode.
*/
- fc->ac.error = afs_register_server_cb_interest(
- vnode, &fc->server_list->servers[fc->index]);
+ fc->ac.error = afs_register_server_cb_interest(vnode, fc->server_list,
+ fc->index);
if (fc->ac.error < 0)
goto failed;
diff --git a/fs/afs/server_list.c b/fs/afs/server_list.c
index 0f8dc4c8f07c..8a5760aa5832 100644
--- a/fs/afs/server_list.c
+++ b/fs/afs/server_list.c
@@ -49,6 +49,7 @@ struct afs_server_list *afs_alloc_server_list(struct afs_cell *cell,
goto error;
refcount_set(&slist->usage, 1);
+ rwlock_init(&slist->lock);
/* Make sure a records exists for each server in the list. */
for (i = 0; i < vldb->nr_servers; i++) {
@@ -64,9 +65,11 @@ struct afs_server_list *afs_alloc_server_list(struct afs_cell *cell,
goto error_2;
}
- /* Insertion-sort by server pointer */
+ /* Insertion-sort by UUID */
for (j = 0; j < slist->nr_servers; j++)
- if (slist->servers[j].server >= server)
+ if (memcmp(&slist->servers[j].server->uuid,
+ &server->uuid,
+ sizeof(server->uuid)) >= 0)
break;
if (j < slist->nr_servers) {
if (slist->servers[j].server == server) {