On Mon, Feb 2, 2015 at 12:41 PM, Al Viro <viro@xxxxxxxxxxxxxxxxxx> wrote: > > On Mon, Feb 02, 2015 at 11:23:58AM +0800, Yan, Zheng wrote: > > > we should _never_ create multiple dentries pointing to directory inode, so > > > d_instantiate() in there isn't mitigating anything - it's actively breaking > > > things as far as the rest of the kernel is concerned... What are you > > > trying to do there? > > > > ceph_handle_notrace_create() is for case: Ceph Metadata server restarted, > > client re-sent a request. Ceph MDS found the request has already completed, > > so it sent a traceless reply to client. (traceless reply contains no information > > for the dentry and the newly created inode). It's hard to handle this case > > elegantly, because MDS may have done other operation, which moved the > > newly created file/directory to other place. > > > > For multiple dentries pointing to directory inode, maybe we can return an error > > (-ENOENT or -ESTALE). > > IDGI... Suppose we got non-NULL from ceph_lookup() there. So we'd sent either > CEPH_MDS_OP_LOOKUP or CEPH_MDS_OP_LOOKUPSNAP and got ->r_dentry changed > (presumably in ceph_fill_trace(), after it got the sucker from splice_dentry(), > i.e. ultimately d_splice_alias()). Right? In theory, yes. But I think it never happens in reality. Because parent directory of the newly created file/directory is locked, client has no other way to lookup the newly created file/directory. Now, we have acquired a reference > to it (in ceph_finish_lookup()). So far, so good; for one thing, we definitely > do *NOT* want to forget about that reference. For another, we've got > a good and valid dentry; so why are we playing with the originally passed > one? Just unhash the original and be done with that... > I think the reason is that VFS still uses the original dentry. (for example, after calling filesystem's mkdir callback, vfs_mkdir() calls fsnotify_mkdir() and passing the original dentry to it) > Looking at the code downstream from the calls of ceph_handle_notrace_create(), > ceph_mkdir() looks very dubious - we do ceph_init_inode_acls(dentry->d_inode, > &acls); there, after having set ->d_inode to that of a preexisting alias. > Is that really correct in the case when such an alias used to exist? you are right, it's incorrect. how about make ceph_handle_notrace_create() return an error when it gets an non-NULL from ceph_lookup() ? this method is not perfect but should work in most case. Regards Yan, Zheng -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
