linux-kernel - [PATCH 09/10] teach shmem_get

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Message-Id: <1447801246-24588-9-git-send-email-viro@ZenIV.linux.org.uk>
Date:	Tue, 17 Nov 2015 23:00:45 +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.de>, linux-fsdevel@...r.kernel.org
Subject: [PATCH 09/10] teach shmem_get_link() to work in RCU mode

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

Signed-off-by: Al Viro <viro@...iv.linux.org.uk>
---
 mm/shmem.c | 20 ++++++++++++++------
 1 file changed, 14 insertions(+), 6 deletions(-)

diff --git a/mm/shmem.c b/mm/shmem.c
index e8220cf..e1ea5b5 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -2501,12 +2501,20 @@ static const char *shmem_get_link(struct dentry *dentry,
 {
 	struct page *page = NULL;
 	int error;
-	if (!dentry)
-		return ERR_PTR(-ECHILD);
-	error = shmem_getpage(inode, 0, &page, SGP_READ, NULL);
-	if (error)
-		return ERR_PTR(error);
-	unlock_page(page);
+	if (!dentry) {
+		page = find_get_page(inode->i_mapping, 0);
+		if (!page)
+			return ERR_PTR(-ECHILD);
+		if (!PageUptodate(page)) {
+			put_page(page);
+			return ERR_PTR(-ECHILD);
+		}
+	} else {
+		error = shmem_getpage(inode, 0, &page, SGP_READ, NULL);
+		if (error)
+			return ERR_PTR(error);
+		unlock_page(page);
+	}
 	*cookie = page;
 	return page_address(page);
 }
-- 
2.1.4

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