From 74a31df4f1f16807a93e414a322baf6eceddb60d Mon Sep 17 00:00:00 2001 From: Xiubo Li Date: Sat, 19 Feb 2022 14:56:17 +0800 Subject: 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 Reviewed-by: Jeff Layton Signed-off-by: Ilya Dryomov --- fs/ceph/snap.c | 57 ++++++++++++++++++++++++++++++++++++++++++++++++--------- fs/ceph/super.h | 2 ++ 2 files changed, 50 insertions(+), 9 deletions(-) (limited to 'fs/ceph') 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; -- cgit v1.2.3