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Commit 0ef97dcf authored by Miklos Szeredi's avatar Miklos Szeredi Committed by Al Viro
Browse files

nfs: don't open in ->d_revalidate 



NFSv4 can't do reliable opens in d_revalidate, since it cannot know whether a
mount needs to be followed or not.  It does check d_mountpoint() on the dentry,
which can result in a weird error if the VFS found that the mount does not in
fact need to be followed, e.g.:

  # mount --bind /mnt/nfs /mnt/nfs-clone
  # echo something > /mnt/nfs/tmp/bar
  # echo x > /tmp/file
  # mount --bind /tmp/file /mnt/nfs-clone/tmp/bar
  # cat  /mnt/nfs/tmp/bar
  cat: /mnt/nfs/tmp/bar: Not a directory

Which should, by any sane filesystem, result in "something" being printed.

So instead do the open in f_op->open() and in the unlikely case that the cached
dentry turned out to be invalid, drop the dentry and return EOPENSTALE to let
the VFS retry.

Signed-off-by: default avatarMiklos Szeredi <mszeredi@suse.cz>
CC: Trond Myklebust <Trond.Myklebust@netapp.com>
Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent 16b1c1cd

fs/nfs/dir.c

+5 −51
Original line number Diff line number Diff line
@@ -1354,10 +1354,10 @@ static struct dentry *nfs_lookup(struct inode *dir, struct dentry * dentry, stru 
}



#ifdef CONFIG_NFS_V4

static int nfs_open_revalidate(struct dentry *, struct nameidata *);

static int nfs4_lookup_revalidate(struct dentry *, struct nameidata *);



const struct dentry_operations nfs4_dentry_operations = {

	.d_revalidate	= nfs_open_revalidate,

	.d_revalidate	= nfs4_lookup_revalidate,

	.d_delete	= nfs_dentry_delete,

	.d_iput		= nfs_dentry_iput,

	.d_automount	= nfs_d_automount,
@@ -1519,13 +1519,11 @@ static struct dentry *nfs_atomic_lookup(struct inode *dir, struct dentry *dentry 
	return nfs_lookup(dir, dentry, nd);

}



static int nfs_open_revalidate(struct dentry *dentry, struct nameidata *nd)

static int nfs4_lookup_revalidate(struct dentry *dentry, struct nameidata *nd)

{

	struct dentry *parent = NULL;

	struct inode *inode;

	struct inode *dir;

	struct nfs_open_context *ctx;

	struct iattr attr;

	int openflags, ret = 0;



	if (nd->flags & LOOKUP_RCU)
@@ -1554,57 +1552,13 @@ static int nfs_open_revalidate(struct dentry *dentry, struct nameidata *nd) 
	/* We cannot do exclusive creation on a positive dentry */

	if ((openflags & (O_CREAT|O_EXCL)) == (O_CREAT|O_EXCL))

		goto no_open_dput;

	/* We can't create new files here */

	openflags &= ~(O_CREAT|O_EXCL);



	ctx = create_nfs_open_context(dentry, openflags);

	ret = PTR_ERR(ctx);

	if (IS_ERR(ctx))

		goto out;



	attr.ia_valid = ATTR_OPEN;

	if (openflags & O_TRUNC) {

		attr.ia_valid |= ATTR_SIZE;

		attr.ia_size = 0;

		nfs_wb_all(inode);

	}



	/*

	 * Note: we're not holding inode->i_mutex and so may be racing with

	 * operations that change the directory. We therefore save the

	 * change attribute *before* we do the RPC call.

	 */

	inode = NFS_PROTO(dir)->open_context(dir, ctx, openflags, &attr);

	if (IS_ERR(inode)) {

		ret = PTR_ERR(inode);

		switch (ret) {

		case -EPERM:

		case -EACCES:

		case -EDQUOT:

		case -ENOSPC:

		case -EROFS:

			goto out_put_ctx;

		default:

			goto out_drop;

		}

	}

	iput(inode);

	if (inode != dentry->d_inode)

		goto out_drop;



	nfs_set_verifier(dentry, nfs_save_change_attribute(dir));

	ret = nfs_intent_set_file(nd, ctx);

	if (ret >= 0)

	/* Let f_op->open() actually open (and revalidate) the file */

	ret = 1;



out:

	dput(parent);

	return ret;

out_drop:

	d_drop(dentry);

	ret = 0;

out_put_ctx:

	put_nfs_open_context(ctx);

	goto out;



no_open_dput:

	dput(parent);

fs/nfs/file.c

+73 −4
Original line number Diff line number Diff line
@@ -879,12 +879,81 @@ const struct file_operations nfs_file_operations = { 
static int

nfs4_file_open(struct inode *inode, struct file *filp)

{

	struct nfs_open_context *ctx;

	struct dentry *dentry = filp->f_path.dentry;

	struct dentry *parent = NULL;

	struct inode *dir;

	unsigned openflags = filp->f_flags;

	struct iattr attr;

	int err;



	BUG_ON(inode != dentry->d_inode);

	/*

	 * NFSv4 opens are handled in d_lookup and d_revalidate. If we get to

	 * this point, then something is very wrong

	 * If no cached dentry exists or if it's negative, NFSv4 handled the

	 * opens in ->lookup() or ->create().

	 *

	 * We only get this far for a cached positive dentry.  We skipped

	 * revalidation, so handle it here by dropping the dentry and returning

	 * -EOPENSTALE.  The VFS will retry the lookup/create/open.

	 */

	dprintk("NFS: %s called! inode=%p filp=%p\n", __func__, inode, filp);

	return -ENOTDIR;



	dprintk("NFS: open file(%s/%s)\n",

		dentry->d_parent->d_name.name,

		dentry->d_name.name);



	if ((openflags & O_ACCMODE) == 3)

		openflags--;



	/* We can't create new files here */

	openflags &= ~(O_CREAT|O_EXCL);



	parent = dget_parent(dentry);

	dir = parent->d_inode;



	ctx = alloc_nfs_open_context(filp->f_path.dentry, filp->f_mode);

	err = PTR_ERR(ctx);

	if (IS_ERR(ctx))

		goto out;



	attr.ia_valid = ATTR_OPEN;

	if (openflags & O_TRUNC) {

		attr.ia_valid |= ATTR_SIZE;

		attr.ia_size = 0;

		nfs_wb_all(inode);

	}



	inode = NFS_PROTO(dir)->open_context(dir, ctx, openflags, &attr);

	if (IS_ERR(inode)) {

		err = PTR_ERR(inode);

		switch (err) {

		case -EPERM:

		case -EACCES:

		case -EDQUOT:

		case -ENOSPC:

		case -EROFS:

			goto out_put_ctx;

		default:

			goto out_drop;

		}

	}

	iput(inode);

	if (inode != dentry->d_inode)

		goto out_drop;



	nfs_set_verifier(dentry, nfs_save_change_attribute(dir));

	nfs_file_set_open_context(filp, ctx);

	err = 0;



out_put_ctx:

	put_nfs_open_context(ctx);

out:

	dput(parent);

	return err;



out_drop:

	d_drop(dentry);

	err = -EOPENSTALE;

	goto out_put_ctx;

}



const struct file_operations nfs4_file_operations = {