It looks like this patch was totally forgotten? I don't see it in neither vfs nor nfs trees and yet it fixes a very easy to cause crash in nfs code. And I think it's unrelated to the other parallel case too.
On Jun 3, 2016, at 1:56 AM, Al Viro wrote: > On Fri, Jun 03, 2016 at 12:58:10AM -0400, Oleg Drokin wrote: > >> This one cures the insta-crash I was having, and I see no other ill-effects >> so far. > > OK... I can take it through vfs.git, but I think it'd be better off in > NFS tree. Is everyone OK with something like the following? > > make nfs_atomic_open() call d_drop() on all ->open_context() errors. > > In "NFSv4: Move dentry instantiation into the NFSv4-specific atomic open code" > unconditional d_drop() after the ->open_context() had been removed. It had > been correct for success cases (there ->open_context() itself had been doing > dcache manipulations), but not for error ones. Only one of those (ENOENT) > got a compensatory d_drop() added in that commit, but in fact it should've > been done for all errors. As it is, the case of O_CREAT non-exclusive open > on a hashed negative dentry racing with e.g. symlink creation from another > client ended up with ->open_context() getting an error and proceeding to > call nfs_lookup(). On a hashed dentry, which would've instantly triggered > BUG_ON() in d_materialise_unique() (or, these days, its equivalent in > d_splice_alias()). > > Cc: [email protected] # v3.10+ > Tested-by: Oleg Drokin <[email protected]> > Signed-off-by: Al Viro <[email protected]> > --- > diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c > index aaf7bd0..6e3a6f4 100644 > --- a/fs/nfs/dir.c > +++ b/fs/nfs/dir.c > @@ -1536,9 +1536,9 @@ int nfs_atomic_open(struct inode *dir, struct dentry > *dentry, > err = PTR_ERR(inode); > trace_nfs_atomic_open_exit(dir, ctx, open_flags, err); > put_nfs_open_context(ctx); > + d_drop(dentry); > switch (err) { > case -ENOENT: > - d_drop(dentry); > d_add(dentry, NULL); > nfs_set_verifier(dentry, > nfs_save_change_attribute(dir)); > break;
