From 4d41cef279f72f3965140fffa6b48f2a7d51408c Mon Sep 17 00:00:00 2001 From: "Yan, Zheng" Date: Wed, 4 Feb 2015 15:10:48 +0800 Subject: [PATCH] ceph: return error for traceless reply race When we receives traceless reply for request that created new inode, we re-send a lookup request to MDS get information of the newly created inode. (VFS expects FS' callback return an inode in create case) This breaks one request into two requests. Other client may modify or move to the new inode in the middle. When the race happens, ceph_handle_notrace_create() unconditionally links the dentry for 'create' operation to the inode returned by lookup. This may confuse VFS when the inode is a directory (VFS does not allow multiple linkages for directory inode). This patch makes ceph_handle_notrace_create() when it detect a race. This event should be rare and it happens only when we talk to old MDS. Recent MDS does not send traceless reply for request that creates new inode. Signed-off-by: Yan, Zheng --- fs/ceph/dir.c | 15 +++++++++------ 1 file changed, 9 insertions(+), 6 deletions(-) diff --git a/fs/ceph/dir.c b/fs/ceph/dir.c index 77eeb768f95a..0411dbb15815 100644 --- a/fs/ceph/dir.c +++ b/fs/ceph/dir.c @@ -670,14 +670,17 @@ int ceph_handle_notrace_create(struct inode *dir, struct dentry *dentry) /* * We created the item, then did a lookup, and found * it was already linked to another inode we already - * had in our cache (and thus got spliced). Link our - * dentry to that inode, but don't hash it, just in - * case the VFS wants to dereference it. + * had in our cache (and thus got spliced). To not + * confuse VFS (especially when inode is a directory), + * we don't link our dentry to that inode, return an + * error instead. + * + * This event should be rare and it happens only when + * we talk to old MDS. Recent MDS does not send traceless + * reply for request that creates new inode. */ - BUG_ON(!result->d_inode); - d_instantiate(dentry, result->d_inode); d_drop(result); - return 0; + return -ESTALE; } return PTR_ERR(result); } -- 2.20.1