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Commit 00a92642 authored by Olivier Galibert's avatar Olivier Galibert Committed by Trond Myklebust
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[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: default avatarOlivier Galibert <galibert@pobox.com>
 Signed-off-by: default avatarTrond Myklebust <Trond.Myklebust@netapp.com>
parent ae388462

fs/nfs/dir.c

+90 −24
Original line number Diff line number Diff line
@@ -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)

fs/nfs/inode.c

+2 −0
Original line number Diff line number Diff line
@@ -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;

}

include/linux/nfs_fs.h

+3 −0
Original line number Diff line number Diff line
@@ -84,6 +84,9 @@ struct nfs_open_context { 
	int error;



	struct list_head list;



	int dir_pos;		/* Directory cookie cache */

	__u64 dir_cookie;

};



/*