[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 2c6a959456849f16141928f44fdb728893d9d60a..fceef29c65a3e4c7a4b478f3c812c5889cd00c72 100644 (file)
--- a/fs/nfs/dir.c
+++ b/fs/nfs/dir.c
@@ -141,7 +141,9 @@ typedef struct {
        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 @@ void dir_page_release(nfs_readdir_descriptor_t *desc)
 
 /*
  * 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 @@ int find_dirent(nfs_readdir_descriptor_t *desc, struct page *page)
 
        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 @@ int find_dirent(nfs_readdir_descriptor_t *desc, struct page *page)
 }
 
 /*
- * 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 @@ int find_dirent_page(nfs_readdir_descriptor_t *desc)
        /* 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 @@ int find_dirent_page(nfs_readdir_descriptor_t *desc)
  * 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 readdir_search_pagecache(nfs_readdir_descriptor_t *desc)
        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 @@ int nfs_do_filldir(nfs_readdir_descriptor_t *desc, void *dirent,
        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 @@ int nfs_do_filldir(nfs_readdir_descriptor_t *desc, void *dirent,
                }
 
                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 @@ int nfs_do_filldir(nfs_readdir_descriptor_t *desc, void *dirent,
                        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 @@ int uncached_readdir(nfs_readdir_descriptor_t *desc, void *dirent,
        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 @@ int uncached_readdir(nfs_readdir_descriptor_t *desc, void *dirent,
        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 @@ int uncached_readdir(nfs_readdir_descriptor_t *desc, void *dirent,
        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 @@ static int nfs_readdir(struct file *filp, void *dirent, filldir_t filldir)
        }
 
        /*
-        * 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 @@ static int nfs_readdir(struct file *filp, void *dirent, filldir_t filldir)
 
        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 8a8d57d9d6604a458d2243e9c373f9f8dd6ce6e0..9fa02e7984ac7a1e2c970c7233409ec01fff6a36 100644 (file)
--- a/fs/nfs/inode.c
+++ b/fs/nfs/inode.c
@@ -891,6 +891,8 @@ struct nfs_open_context *alloc_nfs_open_context(struct dentry *dentry, struct rp
                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 4ceac9ddac932904d7dfbb0970b824cfac1175e3..f810195ef7ad9b4d85da443f4e217573ce0f729a 100644 (file)
--- a/include/linux/nfs_fs.h
+++ b/include/linux/nfs_fs.h
@@ -84,6 +84,9 @@ struct nfs_open_context {
        int error;
 
        struct list_head list;
+
+       int dir_pos;            /* Directory cookie cache */
+       __u64 dir_cookie;
 };
 
 /*