| From | Greg Kroah-Hartman <> | Subject | [PATCH 3.17 012/146] Btrfs: fix race in WAIT_SYNC ioctl | Date | Tue, 28 Oct 2014 11:32:34 +0800 |
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3.17-stable review patch. If anyone has any objections, please let me know.
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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);
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