[PATCH 20/20] NFS: support LOOKUP_RCU in nfs_follow_link.

NeilBrown
2015-03-23T02:40:07Z

If the inode is valid and the page has been read in,
then we can follow a link in RCU-walk.

Signed-off-by: NeilBrown <neilb@suse.de>
---
fs/nfs/inode.c | 21 +++++++++++++++++++++
fs/nfs/symlink.c | 20 ++++++++++++++++++--
include/linux/nfs_fs.h | 1 +
3 files changed, 40 insertions(+), 2 deletions(-)

diff --git a/fs/nfs/inode.c b/fs/nfs/inode.c
index d42dff6d5e98..430899a789c6 100644
--- a/fs/nfs/inode.c
+++ b/fs/nfs/inode.c
@@ -1162,6 +1162,27 @@ int nfs_revalidate_mapping_protected(struct inode *inode, struct address_space *
return __nfs_revalidate_mapping(inode, mapping, true);
}

+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;
+}
+
static unsigned long nfs_wcc_update_inode(struct inode *inode, struct nfs_fattr *fattr)
{
struct nfs_inode *nfsi = NFS_I(inode);
diff --git a/fs/nfs/symlink.c b/fs/nfs/symlink.c
index 32bbac1bb4bc..1c0a94b3d12e 100644
--- a/fs/nfs/symlink.c
+++ b/fs/nfs/symlink.c
@@ -49,8 +49,24 @@ static void *nfs_follow_link(struct dentry *dentry, struct inode *inode,
struct page *page;
void *err;

- if (flags & LOOKUP_RCU)
- return ERR_PTR(-ECHILD);
+ if (flags & LOOKUP_RCU) {
+ err = ERR_PTR(nfs_revalidate_mapping_rcu(inode));
+ if (err)
+ goto read_failed;
+ page = find_get_page(inode->i_mapping, 0);
+ if (page &&
+ (!PageUptodate(page) || PageHighMem(page))) {
+ put_page(page);
+ page = NULL;
+ }
+ if (!page) {
+ err = ERR_PTR(-ECHILD);
+ goto read_failed;
+ }
+ nd_set_link(page_address(page));
+ page = (void *)((unsigned long)page | 1);
+ return page;
+ }
err = ERR_PTR(nfs_revalidate_mapping(inode, inode->i_mapping));
if (err)
goto read_failed;
diff --git a/include/linux/nfs_fs.h b/include/linux/nfs_fs.h
index b01ccf371fdc..2eea59456ebb 100644
--- a/include/linux/nfs_fs.h
+++ b/include/linux/nfs_fs.h
@@ -357,6 +357,7 @@ extern int nfs_revalidate_inode_rcu(struct nfs_server *server, struct inode *ino
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_protected(struct inode *inode, struct address_space *mapping);
+extern int nfs_revalidate_mapping_rcu(struct inode *inode);
extern int nfs_setattr(struct dentry *, struct iattr *);
extern void nfs_setattr_update_inode(struct inode *inode, struct iattr *attr, struct nfs_fattr *);
extern void nfs_setsecurity(struct inode *inode, struct nfs_fattr *fattr,