patches/fs-dcache-use-swait_queue-instead-of-waitqueue.patch

From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Date: Wed, 14 Sep 2016 14:35:49 +0200
Subject: [PATCH] fs/dcache: use swait_queue instead of waitqueue

__d_lookup_done() invokes wake_up_all() while holding a hlist_bl_lock()
which disables preemption. As a workaround convert it to swait.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
 fs/cifs/readdir.c       |    2 +-
 fs/dcache.c             |   27 +++++++++++++++------------
 fs/fuse/dir.c           |    2 +-
 fs/namei.c              |    4 ++--
 fs/nfs/dir.c            |    4 ++--
 fs/nfs/unlink.c         |    4 ++--
 fs/proc/base.c          |    2 +-
 fs/proc/proc_sysctl.c   |    2 +-
 include/linux/dcache.h  |    4 ++--
 include/linux/nfs_xdr.h |    2 +-
 kernel/sched/swait.c    |    1 +
 11 files changed, 29 insertions(+), 25 deletions(-)

--- a/fs/cifs/readdir.c
+++ b/fs/cifs/readdir.c
@@ -80,7 +80,7 @@ cifs_prime_dcache(struct dentry *parent,
 	struct inode *inode;
 	struct super_block *sb = parent->d_sb;
 	struct cifs_sb_info *cifs_sb = CIFS_SB(sb);
-	DECLARE_WAIT_QUEUE_HEAD_ONSTACK(wq);
+	DECLARE_SWAIT_QUEUE_HEAD_ONSTACK(wq);
 
 	cifs_dbg(FYI, "%s: for %s\n", __func__, name->name);
 
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -2403,21 +2403,24 @@ static inline void end_dir_add(struct in
 
 static void d_wait_lookup(struct dentry *dentry)
 {
-	if (d_in_lookup(dentry)) {
-		DECLARE_WAITQUEUE(wait, current);
-		add_wait_queue(dentry->d_wait, &wait);
-		do {
-			set_current_state(TASK_UNINTERRUPTIBLE);
-			spin_unlock(&dentry->d_lock);
-			schedule();
-			spin_lock(&dentry->d_lock);
-		} while (d_in_lookup(dentry));
-	}
+	struct swait_queue __wait;
+
+	if (!d_in_lookup(dentry))
+		return;
+
+	INIT_LIST_HEAD(&__wait.task_list);
+	do {
+		prepare_to_swait(dentry->d_wait, &__wait, TASK_UNINTERRUPTIBLE);
+		spin_unlock(&dentry->d_lock);
+		schedule();
+		spin_lock(&dentry->d_lock);
+	} while (d_in_lookup(dentry));
+	finish_swait(dentry->d_wait, &__wait);
 }
 
 struct dentry *d_alloc_parallel(struct dentry *parent,
 				const struct qstr *name,
-				wait_queue_head_t *wq)
+				struct swait_queue_head *wq)
 {
 	unsigned int hash = name->hash;
 	struct hlist_bl_head *b = in_lookup_hash(parent, hash);
@@ -2526,7 +2529,7 @@ void __d_lookup_done(struct dentry *dent
 	hlist_bl_lock(b);
 	dentry->d_flags &= ~DCACHE_PAR_LOOKUP;
 	__hlist_bl_del(&dentry->d_u.d_in_lookup_hash);
-	wake_up_all(dentry->d_wait);
+	swake_up_all(dentry->d_wait);
 	dentry->d_wait = NULL;
 	hlist_bl_unlock(b);
 	INIT_HLIST_NODE(&dentry->d_u.d_alias);
--- a/fs/fuse/dir.c
+++ b/fs/fuse/dir.c
@@ -1191,7 +1191,7 @@ static int fuse_direntplus_link(struct f
 	struct inode *dir = d_inode(parent);
 	struct fuse_conn *fc;
 	struct inode *inode;
-	DECLARE_WAIT_QUEUE_HEAD_ONSTACK(wq);
+	DECLARE_SWAIT_QUEUE_HEAD_ONSTACK(wq);
 
 	if (!o->nodeid) {
 		/*
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -1628,7 +1628,7 @@ static struct dentry *lookup_slow(const
 {
 	struct dentry *dentry = ERR_PTR(-ENOENT), *old;
 	struct inode *inode = dir->d_inode;
-	DECLARE_WAIT_QUEUE_HEAD_ONSTACK(wq);
+	DECLARE_SWAIT_QUEUE_HEAD_ONSTACK(wq);
 
 	inode_lock_shared(inode);
 	/* Don't go there if it's already dead */
@@ -3069,7 +3069,7 @@ static int lookup_open(struct nameidata
 	struct dentry *dentry;
 	int error, create_error = 0;
 	umode_t mode = op->mode;
-	DECLARE_WAIT_QUEUE_HEAD_ONSTACK(wq);
+	DECLARE_SWAIT_QUEUE_HEAD_ONSTACK(wq);
 
 	if (unlikely(IS_DEADDIR(dir_inode)))
 		return -ENOENT;
--- a/fs/nfs/dir.c
+++ b/fs/nfs/dir.c
@@ -491,7 +491,7 @@ static
 void nfs_prime_dcache(struct dentry *parent, struct nfs_entry *entry)
 {
 	struct qstr filename = QSTR_INIT(entry->name, entry->len);
-	DECLARE_WAIT_QUEUE_HEAD_ONSTACK(wq);
+	DECLARE_SWAIT_QUEUE_HEAD_ONSTACK(wq);
 	struct dentry *dentry;
 	struct dentry *alias;
 	struct inode *dir = d_inode(parent);
@@ -1493,7 +1493,7 @@ int nfs_atomic_open(struct inode *dir, s
 		    struct file *file, unsigned open_flags,
 		    umode_t mode, int *opened)
 {
-	DECLARE_WAIT_QUEUE_HEAD_ONSTACK(wq);
+	DECLARE_SWAIT_QUEUE_HEAD_ONSTACK(wq);
 	struct nfs_open_context *ctx;
 	struct dentry *res;
 	struct iattr attr = { .ia_valid = ATTR_OPEN };
--- a/fs/nfs/unlink.c
+++ b/fs/nfs/unlink.c
@@ -12,7 +12,7 @@
 #include <linux/sunrpc/clnt.h>
 #include <linux/nfs_fs.h>
 #include <linux/sched.h>
-#include <linux/wait.h>
+#include <linux/swait.h>
 #include <linux/namei.h>
 #include <linux/fsnotify.h>
 
@@ -205,7 +205,7 @@ nfs_async_unlink(struct dentry *dentry,
 		goto out_free_name;
 	}
 	data->res.dir_attr = &data->dir_attr;
-	init_waitqueue_head(&data->wq);
+	init_swait_queue_head(&data->wq);
 
 	status = -EBUSY;
 	spin_lock(&dentry->d_lock);
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -1836,7 +1836,7 @@ bool proc_fill_cache(struct file *file,
 
 	child = d_hash_and_lookup(dir, &qname);
 	if (!child) {
-		DECLARE_WAIT_QUEUE_HEAD_ONSTACK(wq);
+		DECLARE_SWAIT_QUEUE_HEAD_ONSTACK(wq);
 		child = d_alloc_parallel(dir, &qname, &wq);
 		if (IS_ERR(child))
 			goto end_instantiate;
--- a/fs/proc/proc_sysctl.c
+++ b/fs/proc/proc_sysctl.c
@@ -682,7 +682,7 @@ static bool proc_sys_fill_cache(struct f
 
 	child = d_lookup(dir, &qname);
 	if (!child) {
-		DECLARE_WAIT_QUEUE_HEAD_ONSTACK(wq);
+		DECLARE_SWAIT_QUEUE_HEAD_ONSTACK(wq);
 		child = d_alloc_parallel(dir, &qname, &wq);
 		if (IS_ERR(child))
 			return false;
--- a/include/linux/dcache.h
+++ b/include/linux/dcache.h
@@ -101,7 +101,7 @@ struct dentry {
 
 	union {
 		struct list_head d_lru;		/* LRU list */
-		wait_queue_head_t *d_wait;	/* in-lookup ones only */
+		struct swait_queue_head *d_wait;	/* in-lookup ones only */
 	};
 	struct list_head d_child;	/* child of parent list */
 	struct list_head d_subdirs;	/* our children */
@@ -231,7 +231,7 @@ extern void d_set_d_op(struct dentry *de
 extern struct dentry * d_alloc(struct dentry *, const struct qstr *);
 extern struct dentry * d_alloc_pseudo(struct super_block *, const struct qstr *);
 extern struct dentry * d_alloc_parallel(struct dentry *, const struct qstr *,
-					wait_queue_head_t *);
+					struct swait_queue_head *);
 extern struct dentry * d_splice_alias(struct inode *, struct dentry *);
 extern struct dentry * d_add_ci(struct dentry *, struct inode *, struct qstr *);
 extern struct dentry * d_exact_alias(struct dentry *, struct inode *);
--- a/include/linux/nfs_xdr.h
+++ b/include/linux/nfs_xdr.h
@@ -1513,7 +1513,7 @@ struct nfs_unlinkdata {
 	struct nfs_removeargs args;
 	struct nfs_removeres res;
 	struct dentry *dentry;
-	wait_queue_head_t wq;
+	struct swait_queue_head wq;
 	struct rpc_cred	*cred;
 	struct nfs_fattr dir_attr;
 	long timeout;
--- a/kernel/sched/swait.c
+++ b/kernel/sched/swait.c
@@ -74,6 +74,7 @@ void swake_up_all(struct swait_queue_hea
 	if (!swait_active(q))
 		return;
 
+	WARN_ON(irqs_disabled());
 	raw_spin_lock_irq(&q->lock);
 	list_splice_init(&q->task_list, &tmp);
 	while (!list_empty(&tmp)) {