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-rw-r--r--fs/btrfs/ctree.c29
1 files changed, 23 insertions, 6 deletions
diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c
index 72745235896f..4252e89df6ae 100644
--- a/fs/btrfs/ctree.c
+++ b/fs/btrfs/ctree.c
@@ -2587,14 +2587,27 @@ static struct extent_buffer *btrfs_search_slot_get_root(struct btrfs_root *root,
root_lock = BTRFS_READ_LOCK;
if (p->search_commit_root) {
- /* The commit roots are read only so we always do read locks */
- if (p->need_commit_sem)
+ /*
+ * The commit roots are read only so we always do read locks,
+ * and we always must hold the commit_root_sem when doing
+ * searches on them, the only exception is send where we don't
+ * want to block transaction commits for a long time, so
+ * we need to clone the commit root in order to avoid races
+ * with transaction commits that create a snapshot of one of
+ * the roots used by a send operation.
+ */
+ if (p->need_commit_sem) {
down_read(&fs_info->commit_root_sem);
- b = root->commit_root;
- extent_buffer_get(b);
- level = btrfs_header_level(b);
- if (p->need_commit_sem)
+ b = btrfs_clone_extent_buffer(root->commit_root);
up_read(&fs_info->commit_root_sem);
+ if (!b)
+ return ERR_PTR(-ENOMEM);
+
+ } else {
+ b = root->commit_root;
+ extent_buffer_get(b);
+ }
+ level = btrfs_header_level(b);
/*
* Ensure that all callers have set skip_locking when
* p->search_commit_root = 1.
@@ -2720,6 +2733,10 @@ int btrfs_search_slot(struct btrfs_trans_handle *trans, struct btrfs_root *root,
again:
prev_cmp = -1;
b = btrfs_search_slot_get_root(root, p, write_lock_level);
+ if (IS_ERR(b)) {
+ ret = PTR_ERR(b);
+ goto done;
+ }
while (b) {
level = btrfs_header_level(b);