NFS: Fix spurious readdir cookie loop messages

If the directory contents change, then we have to accept that the
file->f_pos value may shrink if we do a 'search-by-cookie'. In that
case, we should turn off the loop detection and let the NFS client
try to recover.

The patch also fixes a second loop detection bug by ensuring
that after turning on the ctx->duped flag, we read at least one new
cookie into ctx->dir_cookie before attempting to match with
ctx->dup_cookie.

Reported-by: Petr Vandrovec <petr@vandrovec.name>
Cc: stable@kernel.org [2.6.39+]
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

2 files changed, 35 insertions, 24 deletions

diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c
index 57f578e2560a..d23108b1e338 100644
--- a/fs/nfs/dir.c
+++ b/fs/nfs/dir.c
@@ -134,18 +134,19 @@ const struct inode_operations nfs4_dir_inode_operations = {
 
 #endif /* CONFIG_NFS_V4 */
 
-static struct nfs_open_dir_context *alloc_nfs_open_dir_context(struct rpc_cred *cred)
+static struct nfs_open_dir_context *alloc_nfs_open_dir_context(struct inode *dir, struct rpc_cred *cred)
 {
         struct nfs_open_dir_context *ctx;
         ctx = kmalloc(sizeof(*ctx), GFP_KERNEL);
         if (ctx != NULL) {
                 ctx->duped = 0;
+                ctx->attr_gencount = NFS_I(dir)->attr_gencount;
                 ctx->dir_cookie = 0;
                 ctx->dup_cookie = 0;
                 ctx->cred = get_rpccred(cred);
-        } else
-                ctx = ERR_PTR(-ENOMEM);
-        return ctx;
+                return ctx;
+        }
+        return  ERR_PTR(-ENOMEM);
 }
 
 static void put_nfs_open_dir_context(struct nfs_open_dir_context *ctx)
@@ -173,7 +174,7 @@ nfs_opendir(struct inode *inode, struct file *filp)
         cred = rpc_lookup_cred();
         if (IS_ERR(cred))
                 return PTR_ERR(cred);
-        ctx = alloc_nfs_open_dir_context(cred);
+        ctx = alloc_nfs_open_dir_context(inode, cred);
         if (IS_ERR(ctx)) {
                 res = PTR_ERR(ctx);
                 goto out;
@@ -323,7 +324,6 @@ int nfs_readdir_search_for_pos(struct nfs_cache_array *array, nfs_readdir_descri
 {
         loff_t diff = desc->file->f_pos - desc->current_index;
         unsigned int index;
-        struct nfs_open_dir_context *ctx = desc->file->private_data;
 
         if (diff < 0)
                 goto out_eof;
@@ -336,7 +336,6 @@ int nfs_readdir_search_for_pos(struct nfs_cache_array *array, nfs_readdir_descri
         index = (unsigned int)diff;
         *desc->dir_cookie = array->array[index].cookie;
         desc->cache_entry_index = index;
-        ctx->duped = 0;
         return 0;
 out_eof:
         desc->eof = 1;
@@ -349,14 +348,33 @@ int nfs_readdir_search_for_cookie(struct nfs_cache_array *array, nfs_readdir_des
         int i;
         loff_t new_pos;
         int status = -EAGAIN;
-        struct nfs_open_dir_context *ctx = desc->file->private_data;
 
         for (i = 0; i < array->size; i++) {
                 if (array->array[i].cookie == *desc->dir_cookie) {
+                        struct nfs_inode *nfsi = NFS_I(desc->file->f_path.dentry->d_inode);
+                        struct nfs_open_dir_context *ctx = desc->file->private_data;
+
                         new_pos = desc->current_index + i;
-                        if (new_pos < desc->file->f_pos) {
+                        if (ctx->attr_gencount != nfsi->attr_gencount
+                            || (nfsi->cache_validity & (NFS_INO_INVALID_ATTR|NFS_INO_INVALID_DATA))) {
+                                ctx->duped = 0;
+                                ctx->attr_gencount = nfsi->attr_gencount;
+                        } else if (new_pos < desc->file->f_pos) {
+                                if (ctx->duped > 0
+                                    && ctx->dup_cookie == *desc->dir_cookie) {
+                                        if (printk_ratelimit()) {
+                                                pr_notice("NFS: directory %s/%s contains a readdir loop."
+                                                                "Please contact your server vendor.  "
+                                                                "Offending cookie: %llu\n",
+                                                                desc->file->f_dentry->d_parent->d_name.name,
+                                                                desc->file->f_dentry->d_name.name,
+                                                                *desc->dir_cookie);
+                                        }
+                                        status = -ELOOP;
+                                        goto out;
+                                }
                                 ctx->dup_cookie = *desc->dir_cookie;
-                                ctx->duped = 1;
+                                ctx->duped = -1;
                         }
                         desc->file->f_pos = new_pos;
                         desc->cache_entry_index = i;
@@ -368,6 +386,7 @@ int nfs_readdir_search_for_cookie(struct nfs_cache_array *array, nfs_readdir_des
                 if (*desc->dir_cookie == array->last_cookie)
                         desc->eof = 1;
         }
+out:
         return status;
 }
 
@@ -740,19 +759,6 @@ int nfs_do_filldir(nfs_readdir_descriptor_t *desc, void *dirent,
         struct nfs_cache_array *array = NULL;
         struct nfs_open_dir_context *ctx = file->private_data;
 
-        if (ctx->duped != 0 && ctx->dup_cookie == *desc->dir_cookie) {
-                if (printk_ratelimit()) {
-                        pr_notice("NFS: directory %s/%s contains a readdir loop.  "
-                                "Please contact your server vendor.  "
-                                "Offending cookie: %llu\n",
-                                file->f_dentry->d_parent->d_name.name,
-                                file->f_dentry->d_name.name,
-                                *desc->dir_cookie);
-                }
-                res = -ELOOP;
-                goto out;
-        }
-
         array = nfs_readdir_get_array(desc->page);
         if (IS_ERR(array)) {
                 res = PTR_ERR(array);
@@ -774,6 +780,8 @@ int nfs_do_filldir(nfs_readdir_descriptor_t *desc, void *dirent,
                         *desc->dir_cookie = array->array[i+1].cookie;
                 else
                         *desc->dir_cookie = array->last_cookie;
+                if (ctx->duped != 0)
+                        ctx->duped = 1;
         }
         if (array->eof_index >= 0)
                 desc->eof = 1;
@@ -805,6 +813,7 @@ int uncached_readdir(nfs_readdir_descriptor_t *desc, void *dirent,
         struct page     *page = NULL;
         int             status;
         struct inode *inode = desc->file->f_path.dentry->d_inode;
+        struct nfs_open_dir_context *ctx = desc->file->private_data;
 
         dfprintk(DIRCACHE, "NFS: uncached_readdir() searching for cookie %Lu\n",
                         (unsigned long long)*desc->dir_cookie);
@@ -818,6 +827,7 @@ int uncached_readdir(nfs_readdir_descriptor_t *desc, void *dirent,
         desc->page_index = 0;
         desc->last_cookie = *desc->dir_cookie;
         desc->page = page;
+        ctx->duped = 0;
 
         status = nfs_readdir_xdr_to_array(desc, page, inode);
         if (status < 0)
diff --git a/include/linux/nfs_fs.h b/include/linux/nfs_fs.h
index 8b579beb6358..b96fb99072ff 100644
--- a/include/linux/nfs_fs.h
+++ b/include/linux/nfs_fs.h
@@ -99,9 +99,10 @@ struct nfs_open_context {
 
 struct nfs_open_dir_context {
         struct rpc_cred *cred;
+        unsigned long attr_gencount;
         __u64 dir_cookie;
         __u64 dup_cookie;
-        int duped;
+        signed char duped;
 };
 
 /*