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[PATCH 08/13] teach page_get_link() to work in RCU mode

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

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

Signed-off-by: Al Viro <viro@zeniv.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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Thread

[RFC] ->get_link(), ->put_link() and cookies Al Viro <viro@ZenIV.linux.org.uk> - 2016-01-01 07:40 +0100
  [PATCH 02/13] logfs: don't duplicate page_symlink_inode_operations Al Viro <viro@ZenIV.linux.org.uk> - 2016-01-01 07:40 +0100
  [PATCH 11/13] teach nfs_get_link() to work in RCU mode Al Viro <viro@ZenIV.linux.org.uk> - 2016-01-01 07:40 +0100
  [PATCH 03/13] udf: don't duplicate page_symlink_inode_operations Al Viro <viro@ZenIV.linux.org.uk> - 2016-01-01 07:40 +0100
    Re: [PATCH 03/13] udf: don't duplicate page_symlink_inode_operations Jan Kara <jack@suse.cz> - 2016-01-05 17:30 +0100
  [PATCH 01/13] switch befs long symlinks to page_symlink_operations Al Viro <viro@ZenIV.linux.org.uk> - 2016-01-01 07:40 +0100
  [PATCH 09/13] teach shmem_get_link() to work in RCU mode Al Viro <viro@ZenIV.linux.org.uk> - 2016-01-01 07:40 +0100
  [PATCH 06/13] don't put symlink bodies in pagecache into highmem Al Viro <viro@ZenIV.linux.org.uk> - 2016-01-01 07:40 +0100
  [PATCH 12/13] kill free_page_put_link() Al Viro <viro@ZenIV.linux.org.uk> - 2016-01-01 07:50 +0100
  [PATCH 05/13] namei: page_getlink() and page_follow_link_light() are the same thing Al Viro <viro@ZenIV.linux.org.uk> - 2016-01-01 07:50 +0100
  [PATCH 10/13] teach proc_self_get_link()/proc_thread_self_get_link() to work in RCU mode Al Viro <viro@ZenIV.linux.org.uk> - 2016-01-01 07:50 +0100
  [PATCH 08/13] teach page_get_link() to work in RCU mode Al Viro <viro@ZenIV.linux.org.uk> - 2016-01-01 07:50 +0100
  [PATCH 04/13] ufs: get rid of ->setattr() for symlinks Al Viro <viro@ZenIV.linux.org.uk> - 2016-01-01 07:50 +0100
  Re: [RFC] ->get_link(), ->put_link() and cookies Linus Torvalds <torvalds@linux-foundation.org> - 2016-01-03 21:00 +0100
    Re: [RFC] ->get_link(), ->put_link() and cookies Al Viro <viro@ZenIV.linux.org.uk> - 2016-01-03 21:30 +0100
      Re: [RFC] ->get_link(), ->put_link() and cookies Linus Torvalds <torvalds@linux-foundation.org> - 2016-01-03 21:50 +0100
        Re: [RFC] ->get_link(), ->put_link() and cookies Al Viro <viro@ZenIV.linux.org.uk> - 2016-01-03 22:50 +0100

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