| From 42383020beb1cfb05f5d330cc311931bc4917a97 Mon Sep 17 00:00:00 2001 |
| From: Sage Weil <sage@redhat.com> |
| Date: Fri, 26 Sep 2014 08:30:06 -0700 |
| Subject: Btrfs: fix race in WAIT_SYNC ioctl |
| |
| From: Sage Weil <sage@redhat.com> |
| |
| commit 42383020beb1cfb05f5d330cc311931bc4917a97 upstream. |
| |
| 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: Sage Weil <sage@redhat.com> |
| Signed-off-by: Chris Mason <clm@fb.com> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| |
| --- |
| fs/btrfs/transaction.c | 12 +++++++++--- |
| 1 file changed, 9 insertions(+), 3 deletions(-) |
| |
| --- a/fs/btrfs/transaction.c |
| +++ b/fs/btrfs/transaction.c |
| @@ -609,7 +609,6 @@ int btrfs_wait_for_commit(struct btrfs_r |
| if (transid <= root->fs_info->last_trans_committed) |
| goto out; |
| |
| - ret = -EINVAL; |
| /* find specified transaction */ |
| spin_lock(&root->fs_info->trans_lock); |
| list_for_each_entry(t, &root->fs_info->trans_list, list) { |
| @@ -625,9 +624,16 @@ int btrfs_wait_for_commit(struct btrfs_r |
| } |
| } |
| 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; |
| + } |
| } else { |
| /* find newest transaction that is committing | committed */ |
| spin_lock(&root->fs_info->trans_lock); |