dir.c

linux 内核源代码

		return -ENOMEM;
	}

	kaddr = kmap_atomic(page, KM_USER0);
	memcpy(kaddr, symname, pathlen);
	if (pathlen < PAGE_SIZE)
		memset(kaddr + pathlen, 0, PAGE_SIZE - pathlen);
	kunmap_atomic(kaddr, KM_USER0);

	error = NFS_PROTO(dir)->symlink(dir, dentry, page, pathlen, &attr);
	if (error != 0) {
		dfprintk(VFS, "NFS: symlink(%s/%ld, %s, %s) error %d\n",
			dir->i_sb->s_id, dir->i_ino,
			dentry->d_name.name, symname, error);
		d_drop(dentry);
		__free_page(page);
		unlock_kernel();
		return error;
	}

	/*
	 * No big deal if we can't add this page to the page cache here.
	 * READLINK will get the missing page from the server if needed.
	 */
	pagevec_init(&lru_pvec, 0);
	if (!add_to_page_cache(page, dentry->d_inode->i_mapping, 0,
							GFP_KERNEL)) {
		pagevec_add(&lru_pvec, page);
		pagevec_lru_add(&lru_pvec);
		SetPageUptodate(page);
		unlock_page(page);
	} else
		__free_page(page);

	unlock_kernel();
	return 0;
}

static int 
nfs_link(struct dentry *old_dentry, struct inode *dir, struct dentry *dentry)
{
	struct inode *inode = old_dentry->d_inode;
	int error;

	dfprintk(VFS, "NFS: link(%s/%s -> %s/%s)\n",
		old_dentry->d_parent->d_name.name, old_dentry->d_name.name,
		dentry->d_parent->d_name.name, dentry->d_name.name);

	lock_kernel();
	d_drop(dentry);
	error = NFS_PROTO(dir)->link(inode, dir, &dentry->d_name);
	if (error == 0) {
		atomic_inc(&inode->i_count);
		d_add(dentry, inode);
	}
	unlock_kernel();
	return error;
}

/*
 * RENAME
 * FIXME: Some nfsds, like the Linux user space nfsd, may generate a
 * different file handle for the same inode after a rename (e.g. when
 * moving to a different directory). A fail-safe method to do so would
 * be to look up old_dir/old_name, create a link to new_dir/new_name and
 * rename the old file using the sillyrename stuff. This way, the original
 * file in old_dir will go away when the last process iput()s the inode.
 *
 * FIXED.
 * 
 * It actually works quite well. One needs to have the possibility for
 * at least one ".nfs..." file in each directory the file ever gets
 * moved or linked to which happens automagically with the new
 * implementation that only depends on the dcache stuff instead of
 * using the inode layer
 *
 * Unfortunately, things are a little more complicated than indicated
 * above. For a cross-directory move, we want to make sure we can get
 * rid of the old inode after the operation.  This means there must be
 * no pending writes (if it's a file), and the use count must be 1.
 * If these conditions are met, we can drop the dentries before doing
 * the rename.
 */
static int nfs_rename(struct inode *old_dir, struct dentry *old_dentry,
		      struct inode *new_dir, struct dentry *new_dentry)
{
	struct inode *old_inode = old_dentry->d_inode;
	struct inode *new_inode = new_dentry->d_inode;
	struct dentry *dentry = NULL, *rehash = NULL;
	int error = -EBUSY;

	/*
	 * To prevent any new references to the target during the rename,
	 * we unhash the dentry and free the inode in advance.
	 */
	lock_kernel();
	if (!d_unhashed(new_dentry)) {
		d_drop(new_dentry);
		rehash = new_dentry;
	}

	dfprintk(VFS, "NFS: rename(%s/%s -> %s/%s, ct=%d)\n",
		 old_dentry->d_parent->d_name.name, old_dentry->d_name.name,
		 new_dentry->d_parent->d_name.name, new_dentry->d_name.name,
		 atomic_read(&new_dentry->d_count));

	/*
	 * First check whether the target is busy ... we can't
	 * safely do _any_ rename if the target is in use.
	 *
	 * For files, make a copy of the dentry and then do a 
	 * silly-rename. If the silly-rename succeeds, the
	 * copied dentry is hashed and becomes the new target.
	 */
	if (!new_inode)
		goto go_ahead;
	if (S_ISDIR(new_inode->i_mode)) {
		error = -EISDIR;
		if (!S_ISDIR(old_inode->i_mode))
			goto out;
	} else if (atomic_read(&new_dentry->d_count) > 2) {
		int err;
		/* copy the target dentry's name */
		dentry = d_alloc(new_dentry->d_parent,
				 &new_dentry->d_name);
		if (!dentry)
			goto out;

		/* silly-rename the existing target ... */
		err = nfs_sillyrename(new_dir, new_dentry);
		if (!err) {
			new_dentry = rehash = dentry;
			new_inode = NULL;
			/* instantiate the replacement target */
			d_instantiate(new_dentry, NULL);
		} else if (atomic_read(&new_dentry->d_count) > 1)
			/* dentry still busy? */
			goto out;
	} else
		drop_nlink(new_inode);

go_ahead:
	/*
	 * ... prune child dentries and writebacks if needed.
	 */
	if (atomic_read(&old_dentry->d_count) > 1) {
		if (S_ISREG(old_inode->i_mode))
			nfs_wb_all(old_inode);
		shrink_dcache_parent(old_dentry);
	}
	nfs_inode_return_delegation(old_inode);

	if (new_inode != NULL) {
		nfs_inode_return_delegation(new_inode);
		d_delete(new_dentry);
	}

	error = NFS_PROTO(old_dir)->rename(old_dir, &old_dentry->d_name,
					   new_dir, &new_dentry->d_name);
	nfs_mark_for_revalidate(old_inode);
out:
	if (rehash)
		d_rehash(rehash);
	if (!error) {
		d_move(old_dentry, new_dentry);
		nfs_set_verifier(new_dentry,
					nfs_save_change_attribute(new_dir));
	}

	/* new dentry created? */
	if (dentry)
		dput(dentry);
	unlock_kernel();
	return error;
}

static DEFINE_SPINLOCK(nfs_access_lru_lock);
static LIST_HEAD(nfs_access_lru_list);
static atomic_long_t nfs_access_nr_entries;

static void nfs_access_free_entry(struct nfs_access_entry *entry)
{
	put_rpccred(entry->cred);
	kfree(entry);
	smp_mb__before_atomic_dec();
	atomic_long_dec(&nfs_access_nr_entries);
	smp_mb__after_atomic_dec();
}

int nfs_access_cache_shrinker(int nr_to_scan, gfp_t gfp_mask)
{
	LIST_HEAD(head);
	struct nfs_inode *nfsi;
	struct nfs_access_entry *cache;

restart:
	spin_lock(&nfs_access_lru_lock);
	list_for_each_entry(nfsi, &nfs_access_lru_list, access_cache_inode_lru) {
		struct inode *inode;

		if (nr_to_scan-- == 0)
			break;
		inode = igrab(&nfsi->vfs_inode);
		if (inode == NULL)
			continue;
		spin_lock(&inode->i_lock);
		if (list_empty(&nfsi->access_cache_entry_lru))
			goto remove_lru_entry;
		cache = list_entry(nfsi->access_cache_entry_lru.next,
				struct nfs_access_entry, lru);
		list_move(&cache->lru, &head);
		rb_erase(&cache->rb_node, &nfsi->access_cache);
		if (!list_empty(&nfsi->access_cache_entry_lru))
			list_move_tail(&nfsi->access_cache_inode_lru,
					&nfs_access_lru_list);
		else {
remove_lru_entry:
			list_del_init(&nfsi->access_cache_inode_lru);
			clear_bit(NFS_INO_ACL_LRU_SET, &nfsi->flags);
		}
		spin_unlock(&inode->i_lock);
		spin_unlock(&nfs_access_lru_lock);
		iput(inode);
		goto restart;
	}
	spin_unlock(&nfs_access_lru_lock);
	while (!list_empty(&head)) {
		cache = list_entry(head.next, struct nfs_access_entry, lru);
		list_del(&cache->lru);
		nfs_access_free_entry(cache);
	}
	return (atomic_long_read(&nfs_access_nr_entries) / 100) * sysctl_vfs_cache_pressure;
}

static void __nfs_access_zap_cache(struct inode *inode)
{
	struct nfs_inode *nfsi = NFS_I(inode);
	struct rb_root *root_node = &nfsi->access_cache;
	struct rb_node *n, *dispose = NULL;
	struct nfs_access_entry *entry;

	/* Unhook entries from the cache */
	while ((n = rb_first(root_node)) != NULL) {
		entry = rb_entry(n, struct nfs_access_entry, rb_node);
		rb_erase(n, root_node);
		list_del(&entry->lru);
		n->rb_left = dispose;
		dispose = n;
	}
	nfsi->cache_validity &= ~NFS_INO_INVALID_ACCESS;
	spin_unlock(&inode->i_lock);

	/* Now kill them all! */
	while (dispose != NULL) {
		n = dispose;
		dispose = n->rb_left;
		nfs_access_free_entry(rb_entry(n, struct nfs_access_entry, rb_node));
	}
}

void nfs_access_zap_cache(struct inode *inode)
{
	/* Remove from global LRU init */
	if (test_and_clear_bit(NFS_INO_ACL_LRU_SET, &NFS_FLAGS(inode))) {
		spin_lock(&nfs_access_lru_lock);
		list_del_init(&NFS_I(inode)->access_cache_inode_lru);
		spin_unlock(&nfs_access_lru_lock);
	}

	spin_lock(&inode->i_lock);
	/* This will release the spinlock */
	__nfs_access_zap_cache(inode);
}

static struct nfs_access_entry *nfs_access_search_rbtree(struct inode *inode, struct rpc_cred *cred)
{
	struct rb_node *n = NFS_I(inode)->access_cache.rb_node;
	struct nfs_access_entry *entry;

	while (n != NULL) {
		entry = rb_entry(n, struct nfs_access_entry, rb_node);

		if (cred < entry->cred)
			n = n->rb_left;
		else if (cred > entry->cred)
			n = n->rb_right;
		else
			return entry;
	}
	return NULL;
}

static int nfs_access_get_cached(struct inode *inode, struct rpc_cred *cred, struct nfs_access_entry *res)
{
	struct nfs_inode *nfsi = NFS_I(inode);
	struct nfs_access_entry *cache;
	int err = -ENOENT;

	spin_lock(&inode->i_lock);
	if (nfsi->cache_validity & NFS_INO_INVALID_ACCESS)
		goto out_zap;
	cache = nfs_access_search_rbtree(inode, cred);
	if (cache == NULL)
		goto out;
	if (!time_in_range(jiffies, cache->jiffies, cache->jiffies + nfsi->attrtimeo))
		goto out_stale;
	res->jiffies = cache->jiffies;
	res->cred = cache->cred;
	res->mask = cache->mask;
	list_move_tail(&cache->lru, &nfsi->access_cache_entry_lru);
	err = 0;
out:
	spin_unlock(&inode->i_lock);
	return err;
out_stale:
	rb_erase(&cache->rb_node, &nfsi->access_cache);
	list_del(&cache->lru);
	spin_unlock(&inode->i_lock);
	nfs_access_free_entry(cache);
	return -ENOENT;
out_zap:
	/* This will release the spinlock */
	__nfs_access_zap_cache(inode);
	return -ENOENT;
}

static void nfs_access_add_rbtree(struct inode *inode, struct nfs_access_entry *set)
{
	struct nfs_inode *nfsi = NFS_I(inode);
	struct rb_root *root_node = &nfsi->access_cache;
	struct rb_node **p = &root_node->rb_node;
	struct rb_node *parent = NULL;
	struct nfs_access_entry *entry;

	spin_lock(&inode->i_lock);
	while (*p != NULL) {
		parent = *p;
		entry = rb_entry(parent, struct nfs_access_entry, rb_node);

		if (set->cred < entry->cred)
			p = &parent->rb_left;
		else if (set->cred > entry->cred)
			p = &parent->rb_right;
		else
			goto found;
	}
	rb_link_node(&set->rb_node, parent, p);
	rb_insert_color(&set->rb_node, root_node);
	list_add_tail(&set->lru, &nfsi->access_cache_entry_lru);
	spin_unlock(&inode->i_lock);
	return;
found:
	rb_replace_node(parent, &set->rb_node, root_node);
	list_add_tail(&set->lru, &nfsi->access_cache_entry_lru);
	list_del(&entry->lru);
	spin_unlock(&inode->i_lock);
	nfs_access_free_entry(entry);
}

static void nfs_access_add_cache(struct inode *inode, struct nfs_access_entry *set)
{
	struct nfs_access_entry *cache = kmalloc(sizeof(*cache), GFP_KERNEL);
	if (cache == NULL)
		return;
	RB_CLEAR_NODE(&cache->rb_node);
	cache->jiffies = set->jiffies;
	cache->cred = get_rpccred(set->cred);
	cache->mask = set->mask;

	nfs_access_add_rbtree(inode, cache);

	/* Update accounting */
	smp_mb__before_atomic_inc();
	atomic_long_inc(&nfs_access_nr_entries);
	smp_mb__after_atomic_inc();

	/* Add inode to global LRU list */
	if (!test_and_set_bit(NFS_INO_ACL_LRU_SET, &NFS_FLAGS(inode))) {
		spin_lock(&nfs_access_lru_lock);
		list_add_tail(&NFS_I(inode)->access_cache_inode_lru, &nfs_access_lru_list);
		spin_unlock(&nfs_access_lru_lock);
	}
}

static int nfs_do_access(struct inode *inode, struct rpc_cred *cred, int mask)
{
	struct nfs_access_entry cache;
	int status;

	status = nfs_access_get_cached(inode, cred, &cache);
	if (status == 0)
		goto out;

	/* Be clever: ask server to check for all possible rights */
	cache.mask = MAY_EXEC | MAY_WRITE | MAY_READ;
	cache.cred = cred;
	cache.jiffies = jiffies;
	status = NFS_PROTO(inode)->access(inode, &cache);
	if (status != 0)
		return status;
	nfs_access_add_cache(inode, &cache);
out:
	if ((cache.mask & mask) == mask)
		return 0;
	return -EACCES;
}

static int nfs_open_permission_mask(int openflags)
{
	int mask = 0;

	if (openflags & FMODE_READ)
		mask |= MAY_READ;
	if (openflags & FMODE_WRITE)
		mask |= MAY_WRITE;
	if (openflags & FMODE_EXEC)
		mask |= MAY_EXEC;
	return mask;
}

int nfs_may_open(struct inode *inode, struct rpc_cred *cred, int openflags)
{
	return nfs_do_access(inode, cred, nfs_open_permission_mask(openflags));
}

int nfs_permission(struct inode *inode, int mask, struct nameidata *nd)
{
	struct rpc_cred *cred;
	int res = 0;

	nfs_inc_stats(inode, NFSIOS_VFSACCESS);

	if (mask == 0)
		goto out;
	/* Is this sys_access() ? */
	if (nd != NULL && (nd->flags & LOOKUP_ACCESS))
		goto force_lookup;

	switch (inode->i_mode & S_IFMT) {
		case S_IFLNK:
			goto out;
		case S_IFREG:
			/* NFSv4 has atomic_open... */
			if (nfs_server_capable(inode, NFS_CAP_ATOMIC_OPEN)
					&& nd != NULL
					&& (nd->flags & LOOKUP_OPEN))
				goto out;
			break;
		case S_IFDIR:
			/*
			 * Optimize away all write operations, since the server
			 * will check permissions when we perform the op.
			 */
			if ((mask & MAY_WRITE) && !(mask & MAY_READ))
				goto out;
	}

force_lookup:
	lock_kernel();

	if (!NFS_PROTO(inode)->access)
		goto out_notsup;

	cred = rpcauth_lookupcred(NFS_CLIENT(inode)->cl_auth, 0);
	if (!IS_ERR(cred)) {
		res = nfs_do_access(inode, cred, mask);
		put_rpccred(cred);
	} else
		res = PTR_ERR(cred);
	unlock_kernel();
out:
	dfprintk(VFS, "NFS: permission(%s/%ld), mask=0x%x, res=%d\n",
		inode->i_sb->s_id, inode->i_ino, mask, res);
	return res;
out_notsup:
	res = nfs_revalidate_inode(NFS_SERVER(inode), inode);
	if (res == 0)
		res = generic_permission(inode, mask, NULL);
	unlock_kernel();
	goto out;
}

/*
 * Local variables:
 *  version-control: t
 *  kept-new-versions: 5
 * End:
 */