dir.c

FUSE文件系统开发工具,将内核层面的文件系统开发过程平移到应用层面上来。

/*
  FUSE: Filesystem in Userspace
  Copyright (C) 2001-2007  Miklos Szeredi <[e-mail]>

  This program can be distributed under the terms of the GNU GPL.
  See the file COPYING.
*/

#include "fuse_i.h"

#include <linux/pagemap.h>
#include <linux/file.h>
#include <linux/gfp.h>
#include <linux/sched.h>
#include <linux/namei.h>

#if BITS_PER_LONG >= 64
static inline void fuse_dentry_settime(struct dentry *entry, u64 time)
{
	entry->d_time = time;
}

static inline u64 fuse_dentry_time(struct dentry *entry)
{
	return entry->d_time;
}
#else
/*
 * On 32 bit archs store the high 32 bits of time in d_fsdata
 */
static void fuse_dentry_settime(struct dentry *entry, u64 time)
{
	entry->d_time = time;
	entry->d_fsdata = (void *) (unsigned long) (time >> 32);
}

static u64 fuse_dentry_time(struct dentry *entry)
{
	return (u64) entry->d_time +
		((u64) (unsigned long) entry->d_fsdata << 32);
}
#endif

/*
 * FUSE caches dentries and attributes with separate timeout.  The
 * time in jiffies until the dentry/attributes are valid is stored in
 * dentry->d_time and fuse_inode->i_time respectively.
 */

/*
 * Calculate the time in jiffies until a dentry/attributes are valid
 */
static u64 time_to_jiffies(unsigned long sec, unsigned long nsec)
{
	if (sec || nsec) {
		struct timespec ts = {sec, nsec};
		return get_jiffies_64() + timespec_to_jiffies(&ts);
	} else
		return 0;
}

/*
 * Set dentry and possibly attribute timeouts from the lookup/mk*
 * replies
 */
static void fuse_change_timeout(struct dentry *entry, struct fuse_entry_out *o)
{
	fuse_dentry_settime(entry,
		time_to_jiffies(o->entry_valid, o->entry_valid_nsec));
	if (entry->d_inode)
		get_fuse_inode(entry->d_inode)->i_time =
			time_to_jiffies(o->attr_valid, o->attr_valid_nsec);
}

/*
 * Mark the attributes as stale, so that at the next call to
 * ->getattr() they will be fetched from userspace
 */
void fuse_invalidate_attr(struct inode *inode)
{
	get_fuse_inode(inode)->i_time = 0;
}

/*
 * Just mark the entry as stale, so that a next attempt to look it up
 * will result in a new lookup call to userspace
 *
 * This is called when a dentry is about to become negative and the
 * timeout is unknown (unlink, rmdir, rename and in some cases
 * lookup)
 */
static void fuse_invalidate_entry_cache(struct dentry *entry)
{
	fuse_dentry_settime(entry, 0);
}

/*
 * Same as fuse_invalidate_entry_cache(), but also try to remove the
 * dentry from the hash
 */
static void fuse_invalidate_entry(struct dentry *entry)
{
	d_invalidate(entry);
	fuse_invalidate_entry_cache(entry);
}

static void fuse_lookup_init(struct fuse_req *req, struct inode *dir,
			     struct dentry *entry,
			     struct fuse_entry_out *outarg)
{
	req->in.h.opcode = FUSE_LOOKUP;
	req->in.h.nodeid = get_node_id(dir);
	req->in.numargs = 1;
	req->in.args[0].size = entry->d_name.len + 1;
	req->in.args[0].value = entry->d_name.name;
	req->out.numargs = 1;
	req->out.args[0].size = sizeof(struct fuse_entry_out);
	req->out.args[0].value = outarg;
}

/*
 * Check whether the dentry is still valid
 *
 * If the entry validity timeout has expired and the dentry is
 * positive, try to redo the lookup.  If the lookup results in a
 * different inode, then let the VFS invalidate the dentry and redo
 * the lookup once more.  If the lookup results in the same inode,
 * then refresh the attributes, timeouts and mark the dentry valid.
 */
static int fuse_dentry_revalidate(struct dentry *entry, struct nameidata *nd)
{
	struct inode *inode = entry->d_inode;

	if (inode && is_bad_inode(inode))
		return 0;
	else if (fuse_dentry_time(entry) < get_jiffies_64()) {
		int err;
		struct fuse_entry_out outarg;
		struct fuse_conn *fc;
		struct fuse_req *req;
		struct fuse_req *forget_req;
		struct dentry *parent;

		/* For negative dentries, always do a fresh lookup */
		if (!inode)
			return 0;

		fc = get_fuse_conn(inode);
		req = fuse_get_req(fc);
		if (IS_ERR(req))
			return 0;

		forget_req = fuse_get_req(fc);
		if (IS_ERR(forget_req)) {
			fuse_put_request(fc, req);
			return 0;
		}

		parent = dget_parent(entry);
		fuse_lookup_init(req, parent->d_inode, entry, &outarg);
		request_send(fc, req);
		dput(parent);
		err = req->out.h.error;
		fuse_put_request(fc, req);
		/* Zero nodeid is same as -ENOENT */
		if (!err && !outarg.nodeid)
			err = -ENOENT;
		if (!err) {
			struct fuse_inode *fi = get_fuse_inode(inode);
			if (outarg.nodeid != get_node_id(inode)) {
				fuse_send_forget(fc, forget_req,
						 outarg.nodeid, 1);
				return 0;
			}
			spin_lock(&fc->lock);
			fi->nlookup ++;
			spin_unlock(&fc->lock);
		}
		fuse_put_request(fc, forget_req);
		if (err || (outarg.attr.mode ^ inode->i_mode) & S_IFMT)
			return 0;

		fuse_change_attributes(inode, &outarg.attr);
		fuse_change_timeout(entry, &outarg);
	}
	return 1;
}

static int invalid_nodeid(u64 nodeid)
{
	return !nodeid || nodeid == FUSE_ROOT_ID;
}

struct dentry_operations fuse_dentry_operations = {
	.d_revalidate	= fuse_dentry_revalidate,
};

int fuse_valid_type(int m)
{
	return S_ISREG(m) || S_ISDIR(m) || S_ISLNK(m) || S_ISCHR(m) ||
		S_ISBLK(m) || S_ISFIFO(m) || S_ISSOCK(m);
}

/*
 * Add a directory inode to a dentry, ensuring that no other dentry
 * refers to this inode.  Called with fc->inst_mutex.
 */
static struct dentry *fuse_d_add_directory(struct dentry *entry,
					   struct inode *inode)
{
	struct dentry *alias = d_find_alias(inode);
	if (alias && !(alias->d_flags & DCACHE_DISCONNECTED)) {
		/* This tries to shrink the subtree below alias */
		fuse_invalidate_entry(alias);
		dput(alias);
		if (!list_empty(&inode->i_dentry))
			return ERR_PTR(-EBUSY);
	} else
		dput(alias);
	return d_splice_alias(inode, entry);
}

static struct dentry *fuse_lookup(struct inode *dir, struct dentry *entry,
				  struct nameidata *nd)
{
	int err;
	struct fuse_entry_out outarg;
	struct inode *inode = NULL;
	struct dentry *newent;
	struct fuse_conn *fc = get_fuse_conn(dir);
	struct fuse_req *req;
	struct fuse_req *forget_req;

	if (entry->d_name.len > FUSE_NAME_MAX)
		return ERR_PTR(-ENAMETOOLONG);

	req = fuse_get_req(fc);
	if (IS_ERR(req))
		return ERR_PTR(PTR_ERR(req));

	forget_req = fuse_get_req(fc);
	if (IS_ERR(forget_req)) {
		fuse_put_request(fc, req);
		return ERR_PTR(PTR_ERR(forget_req));
	}

	fuse_lookup_init(req, dir, entry, &outarg);
	request_send(fc, req);
	err = req->out.h.error;
	fuse_put_request(fc, req);
	/* Zero nodeid is same as -ENOENT, but with valid timeout */
	if (!err && outarg.nodeid &&
	    (invalid_nodeid(outarg.nodeid) ||
	     !fuse_valid_type(outarg.attr.mode)))
		err = -EIO;
	if (!err && outarg.nodeid) {
		inode = fuse_iget(dir->i_sb, outarg.nodeid, outarg.generation,
				  &outarg.attr);
		if (!inode) {
			fuse_send_forget(fc, forget_req, outarg.nodeid, 1);
			return ERR_PTR(-ENOMEM);
		}
	}
	fuse_put_request(fc, forget_req);
	if (err && err != -ENOENT)
		return ERR_PTR(err);

	if (inode && S_ISDIR(inode->i_mode)) {
		mutex_lock(&fc->inst_mutex);
		newent = fuse_d_add_directory(entry, inode);
		mutex_unlock(&fc->inst_mutex);
		if (IS_ERR(newent)) {
			iput(inode);
			return newent;
		}
	} else
		newent = d_splice_alias(inode, entry);

	entry = newent ? newent : entry;
	entry->d_op = &fuse_dentry_operations;
	if (!err)
		fuse_change_timeout(entry, &outarg);
	else
		fuse_invalidate_entry_cache(entry);
	return newent;
}

#ifdef HAVE_LOOKUP_INSTANTIATE_FILP
/*
 * Synchronous release for the case when something goes wrong in CREATE_OPEN
 */
static void fuse_sync_release(struct fuse_conn *fc, struct fuse_file *ff,
			      u64 nodeid, int flags)
{
	struct fuse_req *req;

	req = fuse_release_fill(ff, nodeid, flags, FUSE_RELEASE);
	req->force = 1;
	request_send(fc, req);
	fuse_put_request(fc, req);
}

/*
 * Atomic create+open operation
 *
 * If the filesystem doesn't support this, then fall back to separate
 * 'mknod' + 'open' requests.
 */
static int fuse_create_open(struct inode *dir, struct dentry *entry, int mode,
			    struct nameidata *nd)
{
	int err;
	struct inode *inode;
	struct fuse_conn *fc = get_fuse_conn(dir);
	struct fuse_req *req;
	struct fuse_req *forget_req;
	struct fuse_open_in inarg;
	struct fuse_open_out outopen;
	struct fuse_entry_out outentry;
	struct fuse_file *ff;
	struct file *file;
	int flags = nd->intent.open.flags - 1;

	if (fc->no_create)
		return -ENOSYS;

	forget_req = fuse_get_req(fc);
	if (IS_ERR(forget_req))
		return PTR_ERR(forget_req);

	req = fuse_get_req(fc);
	err = PTR_ERR(req);
	if (IS_ERR(req))
		goto out_put_forget_req;

	err = -ENOMEM;
	ff = fuse_file_alloc();
	if (!ff)
		goto out_put_request;

	flags &= ~O_NOCTTY;
	memset(&inarg, 0, sizeof(inarg));
	inarg.flags = flags;
	inarg.mode = mode;
	req->in.h.opcode = FUSE_CREATE;
	req->in.h.nodeid = get_node_id(dir);
	req->in.numargs = 2;
	req->in.args[0].size = sizeof(inarg);
	req->in.args[0].value = &inarg;
	req->in.args[1].size = entry->d_name.len + 1;
	req->in.args[1].value = entry->d_name.name;
	req->out.numargs = 2;
	req->out.args[0].size = sizeof(outentry);
	req->out.args[0].value = &outentry;
	req->out.args[1].size = sizeof(outopen);
	req->out.args[1].value = &outopen;
	request_send(fc, req);
	err = req->out.h.error;
	if (err) {
		if (err == -ENOSYS)
			fc->no_create = 1;
		goto out_free_ff;
	}

	err = -EIO;
	if (!S_ISREG(outentry.attr.mode) || invalid_nodeid(outentry.nodeid))
		goto out_free_ff;

	fuse_put_request(fc, req);
	inode = fuse_iget(dir->i_sb, outentry.nodeid, outentry.generation,
			  &outentry.attr);
	if (!inode) {
		flags &= ~(O_CREAT | O_EXCL | O_TRUNC);
		ff->fh = outopen.fh;
		fuse_sync_release(fc, ff, outentry.nodeid, flags);
		fuse_send_forget(fc, forget_req, outentry.nodeid, 1);
		return -ENOMEM;
	}
	fuse_put_request(fc, forget_req);
	d_instantiate(entry, inode);
	fuse_invalidate_attr(dir);
	fuse_change_timeout(entry, &outentry);
	file = lookup_instantiate_filp(nd, entry, generic_file_open);
	if (IS_ERR(file)) {
		ff->fh = outopen.fh;
		fuse_sync_release(fc, ff, outentry.nodeid, flags);
		return PTR_ERR(file);
	}
	fuse_finish_open(inode, file, ff, &outopen);
	return 0;

 out_free_ff:
	fuse_file_free(ff);
 out_put_request:
	fuse_put_request(fc, req);
 out_put_forget_req:
	fuse_put_request(fc, forget_req);
	return err;
}
#endif

/*
 * Code shared between mknod, mkdir, symlink and link
 */
static int create_new_entry(struct fuse_conn *fc, struct fuse_req *req,
			    struct inode *dir, struct dentry *entry,
			    int mode)
{
	struct fuse_entry_out outarg;
	struct inode *inode;
	int err;
	struct fuse_req *forget_req;

	forget_req = fuse_get_req(fc);
	if (IS_ERR(forget_req)) {
		fuse_put_request(fc, req);
		return PTR_ERR(forget_req);
	}

	req->in.h.nodeid = get_node_id(dir);
	req->out.numargs = 1;
	req->out.args[0].size = sizeof(outarg);
	req->out.args[0].value = &outarg;
	request_send(fc, req);
	err = req->out.h.error;
	fuse_put_request(fc, req);
	if (err)
		goto out_put_forget_req;

	err = -EIO;
	if (invalid_nodeid(outarg.nodeid))
		goto out_put_forget_req;

	if ((outarg.attr.mode ^ mode) & S_IFMT)
		goto out_put_forget_req;

	inode = fuse_iget(dir->i_sb, outarg.nodeid, outarg.generation,
			  &outarg.attr);
	if (!inode) {
		fuse_send_forget(fc, forget_req, outarg.nodeid, 1);
		return -ENOMEM;
	}
	fuse_put_request(fc, forget_req);

	if (S_ISDIR(inode->i_mode)) {
		struct dentry *alias;
		mutex_lock(&fc->inst_mutex);
		alias = d_find_alias(inode);
		if (alias) {
			/* New directory must have moved since mkdir */
			mutex_unlock(&fc->inst_mutex);
			dput(alias);
			iput(inode);
			return -EBUSY;
		}
		d_instantiate(entry, inode);
		mutex_unlock(&fc->inst_mutex);
	} else
		d_instantiate(entry, inode);