[PATCH] NFS: Fix races in nfs_revalidate_mapping()

Prevent the call to invalidate_inode_pages2() from racing with file writes
by taking the inode->i_mutex across the page cache flush and invalidate.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c
index dee3d6c..d9ba8cb 100644 (file)
--- a/fs/nfs/dir.c
+++ b/fs/nfs/dir.c
@@ -532,7 +532,7 @@ static int nfs_readdir(struct file *filp, void *dirent, filldir_t filldir)
 
        lock_kernel();
 
-       res = nfs_revalidate_mapping(inode, filp->f_mapping);
+       res = nfs_revalidate_mapping_nolock(inode, filp->f_mapping);
        if (res < 0) {
                unlock_kernel();
                return res;

diff --git a/fs/nfs/inode.c b/fs/nfs/inode.c
index 63e4702..d834982 100644 (file)
--- a/fs/nfs/inode.c
+++ b/fs/nfs/inode.c
@@ -665,49 +665,86 @@ int nfs_revalidate_inode(struct nfs_server *server, struct inode *inode)
        return __nfs_revalidate_inode(server, inode);
 }
 
+static int nfs_invalidate_mapping_nolock(struct inode *inode, struct address_space *mapping)
+{
+       struct nfs_inode *nfsi = NFS_I(inode);
+       
+       if (mapping->nrpages != 0) {
+               int ret = invalidate_inode_pages2(mapping);
+               if (ret < 0)
+                       return ret;
+       }
+       spin_lock(&inode->i_lock);
+       nfsi->cache_validity &= ~NFS_INO_INVALID_DATA;
+       if (S_ISDIR(inode->i_mode)) {
+               memset(nfsi->cookieverf, 0, sizeof(nfsi->cookieverf));
+               /* This ensures we revalidate child dentries */
+               nfsi->cache_change_attribute = jiffies;
+       }
+       spin_unlock(&inode->i_lock);
+       nfs_inc_stats(inode, NFSIOS_DATAINVALIDATE);
+       dfprintk(PAGECACHE, "NFS: (%s/%Ld) data cache invalidated\n",
+                       inode->i_sb->s_id, (long long)NFS_FILEID(inode));
+       return 0;
+}
+
+static int nfs_invalidate_mapping(struct inode *inode, struct address_space *mapping)
+{
+       int ret = 0;
+
+       mutex_lock(&inode->i_mutex);
+       if (NFS_I(inode)->cache_validity & NFS_INO_INVALID_DATA) {
+               ret = nfs_sync_mapping(mapping);
+               if (ret == 0)
+                       ret = nfs_invalidate_mapping_nolock(inode, mapping);
+       }
+       mutex_unlock(&inode->i_mutex);
+       return ret;
+}
+
 /**
- * nfs_revalidate_mapping - Revalidate the pagecache
+ * nfs_revalidate_mapping_nolock - Revalidate the pagecache
  * @inode - pointer to host inode
  * @mapping - pointer to mapping
  */
-int nfs_revalidate_mapping(struct inode *inode, struct address_space *mapping)
+int nfs_revalidate_mapping_nolock(struct inode *inode, struct address_space *mapping)
 {
        struct nfs_inode *nfsi = NFS_I(inode);
        int ret = 0;
 
-       if (NFS_STALE(inode))
-               ret = -ESTALE;
        if ((nfsi->cache_validity & NFS_INO_REVAL_PAGECACHE)
-                       || nfs_attribute_timeout(inode))
+                       || nfs_attribute_timeout(inode) || NFS_STALE(inode)) {
                ret = __nfs_revalidate_inode(NFS_SERVER(inode), inode);
-       if (ret < 0)
-               goto out;
+               if (ret < 0)
+                       goto out;
+       }
+       if (nfsi->cache_validity & NFS_INO_INVALID_DATA)
+               ret = nfs_invalidate_mapping_nolock(inode, mapping);
+out:
+       return ret;
+}
 
-       if (nfsi->cache_validity & NFS_INO_INVALID_DATA) {
-               if (mapping->nrpages != 0) {
-                       if (S_ISREG(inode->i_mode)) {
-                               ret = nfs_sync_mapping(mapping);
-                               if (ret < 0)
-                                       goto out;
-                       }
-                       ret = invalidate_inode_pages2(mapping);
-                       if (ret < 0)
-                               goto out;
-               }
-               spin_lock(&inode->i_lock);
-               nfsi->cache_validity &= ~NFS_INO_INVALID_DATA;
-               if (S_ISDIR(inode->i_mode)) {
-                       memset(nfsi->cookieverf, 0, sizeof(nfsi->cookieverf));
-                       /* This ensures we revalidate child dentries */
-                       nfsi->cache_change_attribute = jiffies;
-               }
-               spin_unlock(&inode->i_lock);
+/**
+ * nfs_revalidate_mapping - Revalidate the pagecache
+ * @inode - pointer to host inode
+ * @mapping - pointer to mapping
+ *
+ * This version of the function will take the inode->i_mutex and attempt to
+ * flush out all dirty data if it needs to invalidate the page cache.
+ */
+int nfs_revalidate_mapping(struct inode *inode, struct address_space *mapping)
+{
+       struct nfs_inode *nfsi = NFS_I(inode);
+       int ret = 0;
 
-               nfs_inc_stats(inode, NFSIOS_DATAINVALIDATE);
-               dfprintk(PAGECACHE, "NFS: (%s/%Ld) data cache invalidated\n",
-                               inode->i_sb->s_id,
-                               (long long)NFS_FILEID(inode));
+       if ((nfsi->cache_validity & NFS_INO_REVAL_PAGECACHE)
+                       || nfs_attribute_timeout(inode) || NFS_STALE(inode)) {
+               ret = __nfs_revalidate_inode(NFS_SERVER(inode), inode);
+               if (ret < 0)
+                       goto out;
        }
+       if (nfsi->cache_validity & NFS_INO_INVALID_DATA)
+               ret = nfs_invalidate_mapping(inode, mapping);
 out:
        return ret;
 }

diff --git a/fs/nfs/symlink.c b/fs/nfs/symlink.c
index 6c68611..525c136 100644 (file)
--- a/fs/nfs/symlink.c
+++ b/fs/nfs/symlink.c
@@ -50,7 +50,9 @@ static void *nfs_follow_link(struct dentry *dentry, struct nameidata *nd)
 {
        struct inode *inode = dentry->d_inode;
        struct page *page;
-       void *err = ERR_PTR(nfs_revalidate_mapping(inode, inode->i_mapping));
+       void *err;
+
+       err = ERR_PTR(nfs_revalidate_mapping_nolock(inode, inode->i_mapping));
        if (err)
                goto read_failed;
        page = read_cache_page(&inode->i_data, 0,

diff --git a/include/linux/nfs_fs.h b/include/linux/nfs_fs.h
index 0496306..c5d4084 100644 (file)
--- a/include/linux/nfs_fs.h
+++ b/include/linux/nfs_fs.h
@@ -308,6 +308,7 @@ extern int nfs_attribute_timeout(struct inode *inode);
 extern int nfs_revalidate_inode(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_nolock(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);
 extern void nfs_begin_attr_update(struct inode *);