Commit 42383020 authored by Sage Weil's avatar Sage Weil Committed by Chris Mason

Btrfs: fix race in WAIT_SYNC ioctl

We check whether transid is already committed via last_trans_committed and
then search through trans_list for pending transactions.  If
last_trans_committed is updated by btrfs_commit_transaction after we check
it (there is no locking), we will fail to find the committed transaction
and return EINVAL to the caller.  This has been observed occasionally by
ceph-osd (which uses this ioctl heavily).

Fix by rechecking whether the provided transid <= last_trans_committed
after the search fails, and if so return 0.
Signed-off-by: default avatarSage Weil <sage@redhat.com>
Signed-off-by: default avatarChris Mason <clm@fb.com>
parent 656f30db
...@@ -609,7 +609,6 @@ int btrfs_wait_for_commit(struct btrfs_root *root, u64 transid) ...@@ -609,7 +609,6 @@ int btrfs_wait_for_commit(struct btrfs_root *root, u64 transid)
if (transid <= root->fs_info->last_trans_committed) if (transid <= root->fs_info->last_trans_committed)
goto out; goto out;
ret = -EINVAL;
/* find specified transaction */ /* find specified transaction */
spin_lock(&root->fs_info->trans_lock); spin_lock(&root->fs_info->trans_lock);
list_for_each_entry(t, &root->fs_info->trans_list, list) { list_for_each_entry(t, &root->fs_info->trans_list, list) {
...@@ -625,9 +624,16 @@ int btrfs_wait_for_commit(struct btrfs_root *root, u64 transid) ...@@ -625,9 +624,16 @@ int btrfs_wait_for_commit(struct btrfs_root *root, u64 transid)
} }
} }
spin_unlock(&root->fs_info->trans_lock); spin_unlock(&root->fs_info->trans_lock);
/* The specified transaction doesn't exist */
if (!cur_trans) /*
* The specified transaction doesn't exist, or we
* raced with btrfs_commit_transaction
*/
if (!cur_trans) {
if (transid > root->fs_info->last_trans_committed)
ret = -EINVAL;
goto out; goto out;
}
} else { } else {
/* find newest transaction that is committing | committed */ /* find newest transaction that is committing | committed */
spin_lock(&root->fs_info->trans_lock); spin_lock(&root->fs_info->trans_lock);
......
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