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Subject[080/102] NFS: Fix spurious readdir cookie loop messages
3.0-stable review patch.  If anyone has any objections, please let us know.

------------------

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

commit 0c0308066ca53fdf1423895f3a42838b67b3a5a8 upstream.

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>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
fs/nfs/dir.c | 56 ++++++++++++++++++++++++++++---------------------
include/linux/nfs_fs.h | 3 +-
2 files changed, 35 insertions(+), 24 deletions(-)

--- a/fs/nfs/dir.c
+++ b/fs/nfs/dir.c
@@ -134,18 +134,19 @@ const struct inode_operations nfs4_dir_i

#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
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 nf
{
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 nf
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
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
if (*desc->dir_cookie == array->last_cookie)
desc->eof = 1;
}
+out:
return status;
}

@@ -740,19 +759,6 @@ int nfs_do_filldir(nfs_readdir_descripto
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_descripto
*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_descrip
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_descrip
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)
--- 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;
};

/*



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