Patch "nfsd: track filehandle aliasing in nfs4_files" has been added to the 5.10-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    nfsd: track filehandle aliasing in nfs4_files

to the 5.10-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     nfsd-track-filehandle-aliasing-in-nfs4_files.patch
and it can be found in the queue-5.10 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit d9661e72f07c0cc0d194ba7f0f1de8b927052cfa
Author: J. Bruce Fields <bfields@xxxxxxxxxxxx>
Date:   Fri Apr 16 14:00:16 2021 -0400

    nfsd: track filehandle aliasing in nfs4_files
    
    [ Upstream commit a0ce48375a367222989c2618fe68bf34db8c7bb7 ]
    
    It's unusual but possible for multiple filehandles to point to the same
    file.  In that case, we may end up with multiple nfs4_files referencing
    the same inode.
    
    For delegation purposes it will turn out to be useful to flag those
    cases.
    
    Signed-off-by: J. Bruce Fields <bfields@xxxxxxxxxx>
    Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
index 8d2d6e90bfc5e..89d5669ce1463 100644
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -4120,6 +4120,8 @@ static void nfsd4_init_file(struct svc_fh *fh, unsigned int hashval,
 	fp->fi_share_deny = 0;
 	memset(fp->fi_fds, 0, sizeof(fp->fi_fds));
 	memset(fp->fi_access, 0, sizeof(fp->fi_access));
+	fp->fi_aliased = false;
+	fp->fi_inode = d_inode(fh->fh_dentry);
 #ifdef CONFIG_NFSD_PNFS
 	INIT_LIST_HEAD(&fp->fi_lo_states);
 	atomic_set(&fp->fi_lo_recalls, 0);
@@ -4472,6 +4474,31 @@ find_file_locked(struct svc_fh *fh, unsigned int hashval)
 	return NULL;
 }
 
+static struct nfs4_file *insert_file(struct nfs4_file *new, struct svc_fh *fh,
+				     unsigned int hashval)
+{
+	struct nfs4_file *fp;
+	struct nfs4_file *ret = NULL;
+	bool alias_found = false;
+
+	spin_lock(&state_lock);
+	hlist_for_each_entry_rcu(fp, &file_hashtbl[hashval], fi_hash,
+				 lockdep_is_held(&state_lock)) {
+		if (fh_match(&fp->fi_fhandle, &fh->fh_handle)) {
+			if (refcount_inc_not_zero(&fp->fi_ref))
+				ret = fp;
+		} else if (d_inode(fh->fh_dentry) == fp->fi_inode)
+			fp->fi_aliased = alias_found = true;
+	}
+	if (likely(ret == NULL)) {
+		nfsd4_init_file(fh, hashval, new);
+		new->fi_aliased = alias_found;
+		ret = new;
+	}
+	spin_unlock(&state_lock);
+	return ret;
+}
+
 static struct nfs4_file * find_file(struct svc_fh *fh)
 {
 	struct nfs4_file *fp;
@@ -4495,15 +4522,7 @@ find_or_add_file(struct nfs4_file *new, struct svc_fh *fh)
 	if (fp)
 		return fp;
 
-	spin_lock(&state_lock);
-	fp = find_file_locked(fh, hashval);
-	if (likely(fp == NULL)) {
-		nfsd4_init_file(fh, hashval, new);
-		fp = new;
-	}
-	spin_unlock(&state_lock);
-
-	return fp;
+	return insert_file(new, fh, hashval);
 }
 
 /*
diff --git a/fs/nfsd/state.h b/fs/nfsd/state.h
index 61a2d95d79233..e73bdbb1634ab 100644
--- a/fs/nfsd/state.h
+++ b/fs/nfsd/state.h
@@ -516,6 +516,8 @@ struct nfs4_clnt_odstate {
  */
 struct nfs4_file {
 	refcount_t		fi_ref;
+	struct inode *		fi_inode;
+	bool			fi_aliased;
 	spinlock_t		fi_lock;
 	struct hlist_node       fi_hash;	/* hash on fi_fhandle */
 	struct list_head        fi_stateids;