From: Al Viro <viro@zeniv.linux.org.uk>
Date: Wed, 18 Nov 2015 02:14:24 +0000 (-0500)
Subject: teach nfs_get_link() to work in RCU mode
X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=0d0def49d05ae988936268b0e57d19aeef8c3ad2;p=GitHub%2Fmoto-9609%2Fandroid_kernel_motorola_exynos9610.git

teach nfs_get_link() to work in RCU mode

based upon the corresponding patch from Neil's March patchset,
again with kmap-related horrors removed.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---

diff --git a/fs/nfs/inode.c b/fs/nfs/inode.c
index ae9aa0b8155c..aa828e8b6e04 100644
--- a/fs/nfs/inode.c
+++ b/fs/nfs/inode.c
@@ -1087,6 +1087,27 @@ static bool nfs_mapping_need_revalidate_inode(struct inode *inode)
 		|| NFS_STALE(inode);
 }
 
+int nfs_revalidate_mapping_rcu(struct inode *inode)
+{
+	struct nfs_inode *nfsi = NFS_I(inode);
+	unsigned long *bitlock = &nfsi->flags;
+	int ret = 0;
+
+	if (IS_SWAPFILE(inode))
+		goto out;
+	if (nfs_mapping_need_revalidate_inode(inode)) {
+		ret = -ECHILD;
+		goto out;
+	}
+	spin_lock(&inode->i_lock);
+	if (test_bit(NFS_INO_INVALIDATING, bitlock) ||
+	    (nfsi->cache_validity & NFS_INO_INVALID_DATA))
+		ret = -ECHILD;
+	spin_unlock(&inode->i_lock);
+out:
+	return ret;
+}
+
 /**
  * __nfs_revalidate_mapping - Revalidate the pagecache
  * @inode - pointer to host inode
diff --git a/fs/nfs/symlink.c b/fs/nfs/symlink.c
index 8ade8a812607..95c69af7e4d0 100644
--- a/fs/nfs/symlink.c
+++ b/fs/nfs/symlink.c
@@ -48,16 +48,26 @@ static const char *nfs_get_link(struct dentry *dentry,
 	struct page *page;
 	void *err;
 
-	if (!dentry)
-		return ERR_PTR(-ECHILD);
-
-	err = ERR_PTR(nfs_revalidate_mapping(inode, inode->i_mapping));
-	if (err)
-		return err;
-	page = read_cache_page(&inode->i_data, 0,
-				(filler_t *)nfs_symlink_filler, inode);
-	if (IS_ERR(page))
-		return ERR_CAST(page);
+	if (!dentry) {
+		err = ERR_PTR(nfs_revalidate_mapping_rcu(inode));
+		if (err)
+			return err;
+		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 {
+		err = ERR_PTR(nfs_revalidate_mapping(inode, inode->i_mapping));
+		if (err)
+			return err;
+		page = read_cache_page(&inode->i_data, 0,
+					(filler_t *)nfs_symlink_filler, inode);
+		if (IS_ERR(page))
+			return ERR_CAST(page);
+	}
 	*cookie = page;
 	return page_address(page);
 }
diff --git a/include/linux/nfs_fs.h b/include/linux/nfs_fs.h
index c0e961474a52..37a3d2981352 100644
--- a/include/linux/nfs_fs.h
+++ b/include/linux/nfs_fs.h
@@ -359,6 +359,7 @@ extern int nfs_revalidate_inode(struct nfs_server *server, struct inode *inode);
 extern int nfs_revalidate_inode_rcu(struct nfs_server *server, struct inode *inode);
 extern int __nfs_revalidate_inode(struct nfs_server *, struct inode *);
 extern int nfs_revalidate_mapping(struct inode *inode, struct address_space *mapping);
+extern int nfs_revalidate_mapping_rcu(struct inode *inode);
 extern int nfs_revalidate_mapping_protected(struct inode *inode, struct address_space *mapping);
 extern int nfs_setattr(struct dentry *, struct iattr *);
 extern void nfs_setattr_update_inode(struct inode *inode, struct iattr *attr, struct nfs_fattr *);