Re: [regression] NFS readdir change break fully cached nfs root

[Trond Myklebust <Trond.Myklebust@netapp.com>]

On Tue, 2010-11-02 at 19:00 +0100, Andi Kleen wrote:
> My NFS root test systems stopped booting with 2.6.37-rc1. It just
> hangs after entering user space.
> 
> The NFS root setup uses a slightly fancy parameter setup to minimize 
> network traffic:
> 
> nfsroot=10.23.204.1:/home/nfsroot/edwin,nocto,acregmin=86400,acregmax=86400,acdirmin=86400,acdirmax=86400 root=/dev/nfs
> 
> I bisected it down to this commit from Bryan.
> 
> Unfortunately it's not trivially revertable because that conflicts
> with later patches.

Does the following patch help?

Cheers
  Trond
------------------------------------------------------------------------
NFS: Fix a couple of regressions in readdir.

From: Trond Myklebust <Trond.Myklebust@netapp.com>

Fix up the issue that array->eof_index needs to be able to be set
even if array->size == 0.

Ensure that we catch all important memory allocation error conditions
and/or kmap() failures.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
---

 fs/nfs/dir.c |   73 ++++++++++++++++++++++++++++++++++++++--------------------
 1 files changed, 48 insertions(+), 25 deletions(-)


diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c
index 07ac384..8c22d60 100644
--- a/fs/nfs/dir.c
+++ b/fs/nfs/dir.c
@@ -194,9 +194,13 @@ typedef struct {
 static
 struct nfs_cache_array *nfs_readdir_get_array(struct page *page)
 {
+	void *ptr;
 	if (page == NULL)
 		return ERR_PTR(-EIO);
-	return (struct nfs_cache_array *)kmap(page);
+	ptr = kmap(page);
+	if (ptr == NULL)
+		return ERR_PTR(-ENOMEM);
+	return ptr;
 }
 
 static
@@ -213,6 +217,9 @@ int nfs_readdir_clear_array(struct page *page, gfp_t mask)
 {
 	struct nfs_cache_array *array = nfs_readdir_get_array(page);
 	int i;
+
+	if (IS_ERR(array))
+		return PTR_ERR(array);
 	for (i = 0; i < array->size; i++)
 		kfree(array->array[i].string.name);
 	nfs_readdir_release_array(page);
@@ -244,7 +251,7 @@ int nfs_readdir_add_to_array(struct nfs_entry *entry, struct page *page)
 
 	if (IS_ERR(array))
 		return PTR_ERR(array);
-	ret = -EIO;
+	ret = -ENOSPC;
 	if (array->size >= MAX_READDIR_ARRAY)
 		goto out;
 
@@ -255,9 +262,9 @@ int nfs_readdir_add_to_array(struct nfs_entry *entry, struct page *page)
 	if (ret)
 		goto out;
 	array->last_cookie = entry->cookie;
+	array->size++;
 	if (entry->eof == 1)
 		array->eof_index = array->size;
-	array->size++;
 out:
 	nfs_readdir_release_array(page);
 	return ret;
@@ -272,7 +279,7 @@ int nfs_readdir_search_for_pos(struct nfs_cache_array *array, nfs_readdir_descri
 	if (diff < 0)
 		goto out_eof;
 	if (diff >= array->size) {
-		if (array->eof_index > 0)
+		if (array->eof_index >= 0)
 			goto out_eof;
 		desc->current_index += array->size;
 		return -EAGAIN;
@@ -281,8 +288,6 @@ 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;
-	if (index == array->eof_index)
-		desc->eof = 1;
 	return 0;
 out_eof:
 	desc->eof = 1;
@@ -296,17 +301,17 @@ int nfs_readdir_search_for_cookie(struct nfs_cache_array *array, nfs_readdir_des
 	int status = -EAGAIN;
 
 	for (i = 0; i < array->size; i++) {
-		if (i == array->eof_index) {
-			desc->eof = 1;
-			status = -EBADCOOKIE;
-		}
 		if (array->array[i].cookie == *desc->dir_cookie) {
 			desc->cache_entry_index = i;
 			status = 0;
-			break;
+			goto out;
 		}
 	}
-
+	if (i == array->eof_index) {
+		desc->eof = 1;
+		status = -EBADCOOKIE;
+	}
+out:
 	return status;
 }
 
@@ -449,7 +454,7 @@ out:
 
 /* Perform conversion from xdr to cache array */
 static
-void nfs_readdir_page_filler(nfs_readdir_descriptor_t *desc, struct nfs_entry *entry,
+int nfs_readdir_page_filler(nfs_readdir_descriptor_t *desc, struct nfs_entry *entry,
 				void *xdr_page, struct page *page, unsigned int buflen)
 {
 	struct xdr_stream stream;
@@ -471,21 +476,29 @@ void nfs_readdir_page_filler(nfs_readdir_descriptor_t *desc, struct nfs_entry *e
 
 	do {
 		status = xdr_decode(desc, entry, &stream);
-		if (status != 0)
+		if (status != 0) {
+			if (status == -EAGAIN)
+				status = 0;
 			break;
+		}
 
-		if (nfs_readdir_add_to_array(entry, page) == -1)
-			break;
 		if (desc->plus == 1)
 			nfs_prime_dcache(desc->file->f_path.dentry, entry);
+
+		status = nfs_readdir_add_to_array(entry, page);
+		if (status != 0)
+			break;
 	} while (!entry->eof);
 
 	if (status == -EBADCOOKIE && entry->eof) {
 		array = nfs_readdir_get_array(page);
-		array->eof_index = array->size - 1;
-		status = 0;
-		nfs_readdir_release_array(page);
+		if (!IS_ERR(array)) {
+			array->eof_index = array->size;
+			status = 0;
+			nfs_readdir_release_array(page);
+		}
 	}
+	return status;
 }
 
 static
@@ -549,9 +562,14 @@ int nfs_readdir_xdr_to_array(nfs_readdir_descriptor_t *desc, struct page *page,
 		goto out;
 
 	array = nfs_readdir_get_array(page);
+	if (IS_ERR(array)) {
+		status = PTR_ERR(array);
+		goto out;
+	}
 	memset(array, 0, sizeof(struct nfs_cache_array));
 	array->eof_index = -1;
 
+	status = -ENOMEM;
 	pages_ptr = nfs_readdir_large_page(pages, array_size);
 	if (!pages_ptr)
 		goto out_release_array;
@@ -560,8 +578,13 @@ int nfs_readdir_xdr_to_array(nfs_readdir_descriptor_t *desc, struct page *page,
 
 		if (status < 0)
 			break;
-		nfs_readdir_page_filler(desc, &entry, pages_ptr, page, array_size * PAGE_SIZE);
-	} while (array->eof_index < 0 && array->size < MAX_READDIR_ARRAY);
+		status = nfs_readdir_page_filler(desc, &entry, pages_ptr, page, array_size * PAGE_SIZE);
+		if (status < 0) {
+			if (status == -ENOSPC)
+				status = 0;
+			break;
+		}
+	} while (array->eof_index < 0);
 
 	nfs_readdir_free_large_page(pages_ptr, pages, array_size);
 out_release_array:
@@ -670,6 +693,8 @@ int nfs_do_filldir(nfs_readdir_descriptor_t *desc, void *dirent,
 	struct dentry *dentry = NULL;
 
 	array = nfs_readdir_get_array(desc->page);
+	if (IS_ERR(array))
+		return PTR_ERR(array);
 
 	for (i = desc->cache_entry_index; i < array->size; i++) {
 		d_type = DT_UNKNOWN;
@@ -685,11 +710,9 @@ 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 (i == array->eof_index) {
-			desc->eof = 1;
-			break;
-		}
 	}
+	if (i == array->eof_index)
+		desc->eof = 1;
 
 	nfs_readdir_release_array(desc->page);
 	cache_page_release(desc);