On Fri, 24 May 2024, Richard Kojedzinszky wrote:
> Dear devs,
>
> I am attaching a stripped down version of the little program which
> triggers the bug very quickly, in a few minutes in my test lab. It
> turned out that a single NFS mountpoint is enough. Just start the
> program giving it the NFS mount as first argument. It will chdir there,
> and do file operations, which will trigger a lockup in a few minutes.
I couldn't get the go code to run. But then it is a long time since I
played with go and I didn't try very hard.
If you could provide simple instructions and a list of package
dependencies that I need to install (on Debian), I can give it a try.
Or you could try this patch. It might help, but I don't have high
hopes. It adds some memory barriers and fixes a bug which would cause a
problem if memory allocation failed (but memory allocation never fails).
NeilBrown
diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c
index ac505671efbd..5bcc0d14d519 100644
--- a/fs/nfs/dir.c
+++ b/fs/nfs/dir.c
@@ -1804,7 +1804,7 @@ __nfs_lookup_revalidate(struct dentry *dentry, unsigned int flags,
} else {
/* Wait for unlink to complete */
wait_var_event(&dentry->d_fsdata,
- dentry->d_fsdata != NFS_FSDATA_BLOCKED);
+ smp_load_acquire(&dentry->d_fsdata) != NFS_FSDATA_BLOCKED);
parent = dget_parent(dentry);
ret = reval(d_inode(parent), dentry, flags);
dput(parent);
@@ -2508,7 +2508,7 @@ int nfs_unlink(struct inode *dir, struct dentry *dentry)
spin_unlock(&dentry->d_lock);
error = nfs_safe_remove(dentry);
nfs_dentry_remove_handle_error(dir, dentry, error);
- dentry->d_fsdata = NULL;
+ smp_store_release(&dentry->d_fsdata, NULL);
wake_up_var(&dentry->d_fsdata);
out:
trace_nfs_unlink_exit(dir, dentry, error);
@@ -2616,7 +2616,7 @@ nfs_unblock_rename(struct rpc_task *task, struct nfs_renamedata *data)
{
struct dentry *new_dentry = data->new_dentry;
- new_dentry->d_fsdata = NULL;
+ smp_store_release(&new_dentry->d_fsdata, NULL);
wake_up_var(&new_dentry->d_fsdata);
}
@@ -2717,6 +2717,10 @@ int nfs_rename(struct mnt_idmap *idmap, struct inode *old_dir,
task = nfs_async_rename(old_dir, new_dir, old_dentry, new_dentry,
must_unblock ? nfs_unblock_rename : NULL);
if (IS_ERR(task)) {
+ if (must_unlock) {
+ smp_store_release(&new_dentry->d_fsdata, NULL);
+ wake_up_var(&new_dentry->d_fsdata);
+ }
error = PTR_ERR(task);
goto out;
}
