linux-kernel - [PATCH v2 08/11] teach page_get

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Message-Id: <1449639295-20512-8-git-send-email-viro@ZenIV.linux.org.uk>
Date:	Wed,  9 Dec 2015 05:34:52 +0000
From:	Al Viro <viro@...IV.linux.org.uk>
To:	linux-kernel@...r.kernel.org
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Neil Brown <neilb@...e.com>, linux-fsdevel@...r.kernel.org
Subject: [PATCH v2 08/11] teach page_get_link() to work in RCU mode

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

more or less along the lines of Neil's patchset, sans the insanity
around kmap().

Signed-off-by: Al Viro <viro@...iv.linux.org.uk>
---
 fs/namei.c | 19 +++++++++++++------
 1 file changed, 13 insertions(+), 6 deletions(-)

diff --git a/fs/namei.c b/fs/namei.c
index 1da3064..8f51788 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -4533,12 +4533,19 @@ const char *page_get_link(struct dentry *dentry, struct inode *inode,
 	struct page *page;
 	struct address_space *mapping = inode->i_mapping;
 
-	if (!dentry)
-		return ERR_PTR(-ECHILD);
-
-	page = read_mapping_page(mapping, 0, NULL);
-	if (IS_ERR(page))
-		return (char*)page;
+	if (!dentry) {
+		page = find_get_page(mapping, 0);
+		if (!page)
+			return ERR_PTR(-ECHILD);
+		if (!PageUptodate(page)) {
+			put_page(page);
+			return ERR_PTR(-ECHILD);
+		}
+	} else {
+		page = read_mapping_page(mapping, 0, NULL);
+		if (IS_ERR(page))
+			return (char*)page;
+	}
 	*cookie = page;
 	BUG_ON(mapping_gfp_mask(mapping) & __GFP_HIGHMEM);
 	kaddr = page_address(page);
-- 
2.1.4

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