linux-kernel - [PATCH v3 106/110] namei: don't unlazy until get

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Message-Id: <1431367690-5223-106-git-send-email-viro@ZenIV.linux.org.uk>
Date:	Mon, 11 May 2015 19:08:06 +0100
From:	Al Viro <viro@...IV.linux.org.uk>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Neil Brown <neilb@...e.de>, Christoph Hellwig <hch@...radead.org>,
	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: [PATCH v3 106/110] namei: don't unlazy until get_link()

From: Al Viro <viro@...iv.linux.org.uk>

Signed-off-by: Al Viro <viro@...iv.linux.org.uk>
---
 fs/namei.c | 37 ++++++++++++++++++++++++++-----------
 1 file changed, 26 insertions(+), 11 deletions(-)

diff --git a/fs/namei.c b/fs/namei.c
index 090214b..4d6065d 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -536,10 +536,19 @@ static void restore_nameidata(struct nameidata *old)
 
 static int __nd_alloc_stack(struct nameidata *nd)
 {
-	struct saved *p = kmalloc(MAXSYMLINKS * sizeof(struct saved),
+	struct saved *p;
+
+	if (nd->flags & LOOKUP_RCU) {
+		p= kmalloc(MAXSYMLINKS * sizeof(struct saved),
+				  GFP_ATOMIC);
+		if (unlikely(!p))
+			return -ECHILD;
+	} else {
+		p= kmalloc(MAXSYMLINKS * sizeof(struct saved),
 				  GFP_KERNEL);
-	if (unlikely(!p))
-		return -ENOMEM;
+		if (unlikely(!p))
+			return -ENOMEM;
+	}
 	memcpy(p, nd->internal, sizeof(nd->internal));
 	nd->stack = p;
 	return 0;
@@ -949,8 +958,10 @@ const char *get_link(struct nameidata *nd)
 	int error;
 	const char *res;
 
-	BUG_ON(nd->flags & LOOKUP_RCU);
-
+	if (nd->flags & LOOKUP_RCU) {
+		if (unlikely(unlazy_walk(nd, NULL, 0)))
+			return ERR_PTR(-ECHILD);
+	}
 	cond_resched();
 
 	touch_atime(&last->link);
@@ -1632,17 +1643,21 @@ static int pick_link(struct nameidata *nd, struct path *link,
 		path_to_nameidata(link, nd);
 		return -ELOOP;
 	}
-	if (nd->flags & LOOKUP_RCU) {
-		if (unlikely(unlazy_link(nd, link, seq)))
-			return -ECHILD;
-	} else {
+	if (!(nd->flags & LOOKUP_RCU)) {
 		if (link->mnt == nd->path.mnt)
 			mntget(link->mnt);
 	}
 	error = nd_alloc_stack(nd);
 	if (unlikely(error)) {
-		path_put(link);
-		return error;
+		if (error == -ECHILD) {
+			if (unlikely(unlazy_link(nd, link, seq)))
+				return -ECHILD;
+			error = nd_alloc_stack(nd);
+		}
+		if (error) {
+			path_put(link);
+			return error;
+		}
 	}
 
 	last = nd->stack + nd->depth++;
-- 
2.1.4

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