[PATCH] NFS: Hide NFS server-generated readdir cookies from userland
NFSv3 currently returns the unsigned 64-bit cookie directly to
userspace. The following patch causes the kernel to generate
loff_t offsets for the benefit of userland.
The current server-generated READDIR cookie is cached in the
nfs_open_context instead of in filp->f_pos, so we still end up work
correctly under directory insertions/deletion.
Signed-off-by: Olivier Galibert <galibert@pobox.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c
index 2c6a959..fceef29 100644
--- a/fs/nfs/dir.c
+++ b/fs/nfs/dir.c
@@ -141,7 +141,9 @@
struct page *page;
unsigned long page_index;
u32 *ptr;
- u64 target;
+ u64 target_cookie;
+ int target_index;
+ int current_index;
struct nfs_entry *entry;
decode_dirent_t decode;
int plus;
@@ -225,14 +227,14 @@
/*
* Given a pointer to a buffer that has already been filled by a call
- * to readdir, find the next entry.
+ * to readdir, find the next entry with cookie 'desc->target_cookie'.
*
* If the end of the buffer has been reached, return -EAGAIN, if not,
* return the offset within the buffer of the next entry to be
* read.
*/
static inline
-int find_dirent(nfs_readdir_descriptor_t *desc, struct page *page)
+int find_dirent(nfs_readdir_descriptor_t *desc)
{
struct nfs_entry *entry = desc->entry;
int loop_count = 0,
@@ -240,7 +242,7 @@
while((status = dir_decode(desc)) == 0) {
dfprintk(VFS, "NFS: found cookie %Lu\n", (long long)entry->cookie);
- if (entry->prev_cookie == desc->target)
+ if (entry->prev_cookie == desc->target_cookie)
break;
if (loop_count++ > 200) {
loop_count = 0;
@@ -252,8 +254,44 @@
}
/*
- * Find the given page, and call find_dirent() in order to try to
- * return the next entry.
+ * Given a pointer to a buffer that has already been filled by a call
+ * to readdir, find the entry at offset 'desc->target_index'.
+ *
+ * If the end of the buffer has been reached, return -EAGAIN, if not,
+ * return the offset within the buffer of the next entry to be
+ * read.
+ */
+static inline
+int find_dirent_index(nfs_readdir_descriptor_t *desc)
+{
+ struct nfs_entry *entry = desc->entry;
+ int loop_count = 0,
+ status;
+
+ for(;;) {
+ status = dir_decode(desc);
+ if (status)
+ break;
+
+ dfprintk(VFS, "NFS: found cookie %Lu at index %d\n", (long long)entry->cookie, desc->current_index);
+
+ if (desc->target_index == desc->current_index) {
+ desc->target_cookie = entry->cookie;
+ break;
+ }
+ desc->current_index++;
+ if (loop_count++ > 200) {
+ loop_count = 0;
+ schedule();
+ }
+ }
+ dfprintk(VFS, "NFS: find_dirent_index() returns %d\n", status);
+ return status;
+}
+
+/*
+ * Find the given page, and call find_dirent() or find_dirent_index in
+ * order to try to return the next entry.
*/
static inline
int find_dirent_page(nfs_readdir_descriptor_t *desc)
@@ -276,7 +314,10 @@
/* NOTE: Someone else may have changed the READDIRPLUS flag */
desc->page = page;
desc->ptr = kmap(page); /* matching kunmap in nfs_do_filldir */
- status = find_dirent(desc, page);
+ if (desc->target_cookie)
+ status = find_dirent(desc);
+ else
+ status = find_dirent_index(desc);
if (status < 0)
dir_page_release(desc);
out:
@@ -291,7 +332,8 @@
* Recurse through the page cache pages, and return a
* filled nfs_entry structure of the next directory entry if possible.
*
- * The target for the search is 'desc->target'.
+ * The target for the search is 'desc->target_cookie' if non-0,
+ * 'desc->target_index' otherwise
*/
static inline
int readdir_search_pagecache(nfs_readdir_descriptor_t *desc)
@@ -299,7 +341,19 @@
int loop_count = 0;
int res;
- dfprintk(VFS, "NFS: readdir_search_pagecache() searching for cookie %Lu\n", (long long)desc->target);
+ if (desc->target_cookie)
+ dfprintk(VFS, "NFS: readdir_search_pagecache() searching for cookie %Lu\n", (long long)desc->target_cookie);
+ else
+ dfprintk(VFS, "NFS: readdir_search_pagecache() searching for cookie number %d\n", desc->target_index);
+
+ /* Always search-by-index from the beginning of the cache */
+ if (!(desc->target_cookie)) {
+ desc->page_index = 0;
+ desc->entry->cookie = desc->entry->prev_cookie = 0;
+ desc->entry->eof = 0;
+ desc->current_index = 0;
+ }
+
for (;;) {
res = find_dirent_page(desc);
if (res != -EAGAIN)
@@ -332,11 +386,12 @@
struct file *file = desc->file;
struct nfs_entry *entry = desc->entry;
struct dentry *dentry = NULL;
+ struct nfs_open_context *ctx = file->private_data;
unsigned long fileid;
int loop_count = 0,
res;
- dfprintk(VFS, "NFS: nfs_do_filldir() filling starting @ cookie %Lu\n", (long long)desc->target);
+ dfprintk(VFS, "NFS: nfs_do_filldir() filling starting @ cookie %Lu\n", (long long)entry->cookie);
for(;;) {
unsigned d_type = DT_UNKNOWN;
@@ -356,10 +411,11 @@
}
res = filldir(dirent, entry->name, entry->len,
- entry->prev_cookie, fileid, d_type);
+ file->f_pos, fileid, d_type);
if (res < 0)
break;
- file->f_pos = desc->target = entry->cookie;
+ file->f_pos++;
+ desc->target_cookie = entry->cookie;
if (dir_decode(desc) != 0) {
desc->page_index ++;
break;
@@ -369,10 +425,12 @@
schedule();
}
}
+ ctx->dir_pos = file->f_pos;
+ ctx->dir_cookie = desc->target_cookie;
dir_page_release(desc);
if (dentry != NULL)
dput(dentry);
- dfprintk(VFS, "NFS: nfs_do_filldir() filling ended @ cookie %Lu; returning = %d\n", (long long)desc->target, res);
+ dfprintk(VFS, "NFS: nfs_do_filldir() filling ended @ cookie %Lu; returning = %d\n", (long long)desc->target_cookie, res);
return res;
}
@@ -398,14 +456,14 @@
struct page *page = NULL;
int status;
- dfprintk(VFS, "NFS: uncached_readdir() searching for cookie %Lu\n", (long long)desc->target);
+ dfprintk(VFS, "NFS: uncached_readdir() searching for cookie %Lu\n", (long long)desc->target_cookie);
page = alloc_page(GFP_HIGHUSER);
if (!page) {
status = -ENOMEM;
goto out;
}
- desc->error = NFS_PROTO(inode)->readdir(file->f_dentry, cred, desc->target,
+ desc->error = NFS_PROTO(inode)->readdir(file->f_dentry, cred, desc->target_cookie,
page,
NFS_SERVER(inode)->dtsize,
desc->plus);
@@ -414,7 +472,7 @@
desc->ptr = kmap(page); /* matching kunmap in nfs_do_filldir */
if (desc->error >= 0) {
if ((status = dir_decode(desc)) == 0)
- desc->entry->prev_cookie = desc->target;
+ desc->entry->prev_cookie = desc->target_cookie;
} else
status = -EIO;
if (status < 0)
@@ -435,13 +493,15 @@
goto out;
}
-/* The file offset position is now represented as a true offset into the
- * page cache as is the case in most of the other filesystems.
+/* The file offset position represents the dirent entry number. A
+ last cookie cache takes care of the common case of reading the
+ whole directory.
*/
static int nfs_readdir(struct file *filp, void *dirent, filldir_t filldir)
{
struct dentry *dentry = filp->f_dentry;
struct inode *inode = dentry->d_inode;
+ struct nfs_open_context *ctx = filp->private_data;
nfs_readdir_descriptor_t my_desc,
*desc = &my_desc;
struct nfs_entry my_entry;
@@ -458,17 +518,22 @@
}
/*
- * filp->f_pos points to the file offset in the page cache.
- * but if the cache has meanwhile been zapped, we need to
- * read from the last dirent to revalidate f_pos
- * itself.
+ * filp->f_pos points to the dirent entry number.
+ * ctx->dir_pos has the number of the cached cookie. We have
+ * to either find the entry with the appropriate number or
+ * revalidate the cookie.
*/
memset(desc, 0, sizeof(*desc));
desc->file = filp;
- desc->target = filp->f_pos;
desc->decode = NFS_PROTO(inode)->decode_dirent;
desc->plus = NFS_USE_READDIRPLUS(inode);
+ desc->target_index = filp->f_pos;
+
+ if (filp->f_pos == ctx->dir_pos)
+ desc->target_cookie = ctx->dir_cookie;
+ else
+ desc->target_cookie = 0;
my_entry.cookie = my_entry.prev_cookie = 0;
my_entry.eof = 0;
@@ -478,9 +543,10 @@
while(!desc->entry->eof) {
res = readdir_search_pagecache(desc);
+
if (res == -EBADCOOKIE) {
/* This means either end of directory */
- if (desc->entry->cookie != desc->target) {
+ if (desc->target_cookie && desc->entry->cookie != desc->target_cookie) {
/* Or that the server has 'lost' a cookie */
res = uncached_readdir(desc, dirent, filldir);
if (res >= 0)
diff --git a/fs/nfs/inode.c b/fs/nfs/inode.c
index 8a8d57d..9fa02e7 100644
--- a/fs/nfs/inode.c
+++ b/fs/nfs/inode.c
@@ -891,6 +891,8 @@
ctx->state = NULL;
ctx->lockowner = current->files;
ctx->error = 0;
+ ctx->dir_pos = 0;
+ ctx->dir_cookie = 0;
}
return ctx;
}
diff --git a/include/linux/nfs_fs.h b/include/linux/nfs_fs.h
index 4ceac9d..f810195 100644
--- a/include/linux/nfs_fs.h
+++ b/include/linux/nfs_fs.h
@@ -84,6 +84,9 @@
int error;
struct list_head list;
+
+ int dir_pos; /* Directory cookie cache */
+ __u64 dir_cookie;
};
/*