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authorXiubo Li <xiubli@redhat.com>2022-02-19 14:56:17 +0800
committerIlya Dryomov <idryomov@gmail.com>2022-03-01 18:26:37 +0100
commit74a31df4f1f16807a93e414a322baf6eceddb60d (patch)
treeb015b33598f76d03cbd442985e788885bd219aa7 /fs/ceph
parent2e586641c950e7f3e7e008404bd783a466b9b590 (diff)
ceph: eliminate the recursion when rebuilding the snap context
Use a list instead of recursion to avoid possible stack overflow. Signed-off-by: Xiubo Li <xiubli@redhat.com> Reviewed-by: Jeff Layton <jlayton@kernel.org> Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Diffstat (limited to 'fs/ceph')
-rw-r--r--fs/ceph/snap.c57
-rw-r--r--fs/ceph/super.h2
2 files changed, 50 insertions, 9 deletions
diff --git a/fs/ceph/snap.c b/fs/ceph/snap.c
index 5fd79ae96f34..66a1a92cf579 100644
--- a/fs/ceph/snap.c
+++ b/fs/ceph/snap.c
@@ -127,6 +127,7 @@ static struct ceph_snap_realm *ceph_create_snap_realm(
INIT_LIST_HEAD(&realm->child_item);
INIT_LIST_HEAD(&realm->empty_item);
INIT_LIST_HEAD(&realm->dirty_item);
+ INIT_LIST_HEAD(&realm->rebuild_item);
INIT_LIST_HEAD(&realm->inodes_with_caps);
spin_lock_init(&realm->inodes_with_caps_lock);
__insert_snap_realm(&mdsc->snap_realms, realm);
@@ -320,7 +321,8 @@ static int cmpu64_rev(const void *a, const void *b)
* build the snap context for a given realm.
*/
static int build_snap_context(struct ceph_snap_realm *realm,
- struct list_head* dirty_realms)
+ struct list_head *realm_queue,
+ struct list_head *dirty_realms)
{
struct ceph_snap_realm *parent = realm->parent;
struct ceph_snap_context *snapc;
@@ -334,9 +336,9 @@ static int build_snap_context(struct ceph_snap_realm *realm,
*/
if (parent) {
if (!parent->cached_context) {
- err = build_snap_context(parent, dirty_realms);
- if (err)
- goto fail;
+ /* add to the queue head */
+ list_add(&parent->rebuild_item, realm_queue);
+ return 1;
}
num += parent->cached_context->num_snaps;
}
@@ -420,13 +422,50 @@ fail:
static void rebuild_snap_realms(struct ceph_snap_realm *realm,
struct list_head *dirty_realms)
{
- struct ceph_snap_realm *child;
+ LIST_HEAD(realm_queue);
+ int last = 0;
+ bool skip = false;
- dout("rebuild_snap_realms %llx %p\n", realm->ino, realm);
- build_snap_context(realm, dirty_realms);
+ list_add_tail(&realm->rebuild_item, &realm_queue);
- list_for_each_entry(child, &realm->children, child_item)
- rebuild_snap_realms(child, dirty_realms);
+ while (!list_empty(&realm_queue)) {
+ struct ceph_snap_realm *_realm, *child;
+
+ _realm = list_first_entry(&realm_queue,
+ struct ceph_snap_realm,
+ rebuild_item);
+
+ /*
+ * If the last building failed dues to memory
+ * issue, just empty the realm_queue and return
+ * to avoid infinite loop.
+ */
+ if (last < 0) {
+ list_del_init(&_realm->rebuild_item);
+ continue;
+ }
+
+ last = build_snap_context(_realm, &realm_queue, dirty_realms);
+ dout("rebuild_snap_realms %llx %p, %s\n", _realm->ino, _realm,
+ last > 0 ? "is deferred" : !last ? "succeeded" : "failed");
+
+ /* is any child in the list ? */
+ list_for_each_entry(child, &_realm->children, child_item) {
+ if (!list_empty(&child->rebuild_item)) {
+ skip = true;
+ break;
+ }
+ }
+
+ if (!skip) {
+ list_for_each_entry(child, &_realm->children, child_item)
+ list_add_tail(&child->rebuild_item, &realm_queue);
+ }
+
+ /* last == 1 means need to build parent first */
+ if (last <= 0)
+ list_del_init(&_realm->rebuild_item);
+ }
}
diff --git a/fs/ceph/super.h b/fs/ceph/super.h
index a2caa7beca4f..ef9f32ec905e 100644
--- a/fs/ceph/super.h
+++ b/fs/ceph/super.h
@@ -883,6 +883,8 @@ struct ceph_snap_realm {
struct list_head dirty_item; /* if realm needs new context */
+ struct list_head rebuild_item; /* rebuild snap realms _downward_ in hierarchy */
+
/* the current set of snaps for this realm */
struct ceph_snap_context *cached_context;