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ceph: eliminate the recursion when rebuilding the snap context

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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>
This commit is contained in:
Xiubo Li 2022-02-19 14:56:17 +08:00 committed by Ilya Dryomov
parent 2e586641c9
commit 74a31df4f1
2 changed files with 50 additions and 9 deletions
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57
fs/ceph/snap.c
View File

@ -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 @@ static int build_snap_context(struct ceph_snap_realm *realm,
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);
}
}

2
fs/ceph/super.h
View File

@ -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;