root.c

linux 内核源代码

/* -*- c -*- --------------------------------------------------------------- *
 *
 * linux/fs/autofs/root.c
 *
 *  Copyright 1997-1998 Transmeta Corporation -- All Rights Reserved
 *  Copyright 1999-2000 Jeremy Fitzhardinge <[e-mail]>
 *  Copyright 2001-2006 Ian Kent <[e-mail]>
 *
 * This file is part of the Linux kernel and is made available under
 * the terms of the GNU General Public License, version 2, or at your
 * option, any later version, incorporated herein by reference.
 *
 * ------------------------------------------------------------------------- */

#include <linux/capability.h>
#include <linux/errno.h>
#include <linux/stat.h>
#include <linux/param.h>
#include <linux/time.h>
#include "autofs_i.h"

static int autofs4_dir_symlink(struct inode *,struct dentry *,const char *);
static int autofs4_dir_unlink(struct inode *,struct dentry *);
static int autofs4_dir_rmdir(struct inode *,struct dentry *);
static int autofs4_dir_mkdir(struct inode *,struct dentry *,int);
static int autofs4_root_ioctl(struct inode *, struct file *,unsigned int,unsigned long);
static int autofs4_dir_open(struct inode *inode, struct file *file);
static int autofs4_dir_close(struct inode *inode, struct file *file);
static int autofs4_dir_readdir(struct file * filp, void * dirent, filldir_t filldir);
static int autofs4_root_readdir(struct file * filp, void * dirent, filldir_t filldir);
static struct dentry *autofs4_lookup(struct inode *,struct dentry *, struct nameidata *);
static void *autofs4_follow_link(struct dentry *, struct nameidata *);

const struct file_operations autofs4_root_operations = {
	.open		= dcache_dir_open,
	.release	= dcache_dir_close,
	.read		= generic_read_dir,
	.readdir	= autofs4_root_readdir,
	.ioctl		= autofs4_root_ioctl,
};

const struct file_operations autofs4_dir_operations = {
	.open		= autofs4_dir_open,
	.release	= autofs4_dir_close,
	.read		= generic_read_dir,
	.readdir	= autofs4_dir_readdir,
};

const struct inode_operations autofs4_indirect_root_inode_operations = {
	.lookup		= autofs4_lookup,
	.unlink		= autofs4_dir_unlink,
	.symlink	= autofs4_dir_symlink,
	.mkdir		= autofs4_dir_mkdir,
	.rmdir		= autofs4_dir_rmdir,
};

const struct inode_operations autofs4_direct_root_inode_operations = {
	.lookup		= autofs4_lookup,
	.unlink		= autofs4_dir_unlink,
	.mkdir		= autofs4_dir_mkdir,
	.rmdir		= autofs4_dir_rmdir,
	.follow_link	= autofs4_follow_link,
};

const struct inode_operations autofs4_dir_inode_operations = {
	.lookup		= autofs4_lookup,
	.unlink		= autofs4_dir_unlink,
	.symlink	= autofs4_dir_symlink,
	.mkdir		= autofs4_dir_mkdir,
	.rmdir		= autofs4_dir_rmdir,
};

static int autofs4_root_readdir(struct file *file, void *dirent,
				filldir_t filldir)
{
	struct autofs_sb_info *sbi = autofs4_sbi(file->f_path.dentry->d_sb);
	int oz_mode = autofs4_oz_mode(sbi);

	DPRINTK("called, filp->f_pos = %lld", file->f_pos);

	/*
	 * Don't set reghost flag if:
	 * 1) f_pos is larger than zero -- we've already been here.
	 * 2) we haven't even enabled reghosting in the 1st place.
	 * 3) this is the daemon doing a readdir
	 */
	if (oz_mode && file->f_pos == 0 && sbi->reghost_enabled)
		sbi->needs_reghost = 1;

	DPRINTK("needs_reghost = %d", sbi->needs_reghost);

	return dcache_readdir(file, dirent, filldir);
}

static int autofs4_dir_open(struct inode *inode, struct file *file)
{
	struct dentry *dentry = file->f_path.dentry;
	struct vfsmount *mnt = file->f_path.mnt;
	struct autofs_sb_info *sbi = autofs4_sbi(dentry->d_sb);
	struct dentry *cursor;
	int status;

	status = dcache_dir_open(inode, file);
	if (status)
		goto out;

	cursor = file->private_data;
	cursor->d_fsdata = NULL;

	DPRINTK("file=%p dentry=%p %.*s",
		file, dentry, dentry->d_name.len, dentry->d_name.name);

	if (autofs4_oz_mode(sbi))
		goto out;

	if (autofs4_ispending(dentry)) {
		DPRINTK("dentry busy");
		dcache_dir_close(inode, file);
		status = -EBUSY;
		goto out;
	}

	status = -ENOENT;
	if (!d_mountpoint(dentry) && dentry->d_op && dentry->d_op->d_revalidate) {
		struct nameidata nd;
		int empty, ret;

		/* In case there are stale directory dentrys from a failed mount */
		spin_lock(&dcache_lock);
		empty = list_empty(&dentry->d_subdirs);
		spin_unlock(&dcache_lock);

		if (!empty)
			d_invalidate(dentry);

		nd.flags = LOOKUP_DIRECTORY;
		ret = (dentry->d_op->d_revalidate)(dentry, &nd);

		if (ret <= 0) {
			if (ret < 0)
				status = ret;
			dcache_dir_close(inode, file);
			goto out;
		}
	}

	if (d_mountpoint(dentry)) {
		struct file *fp = NULL;
		struct vfsmount *fp_mnt = mntget(mnt);
		struct dentry *fp_dentry = dget(dentry);

		if (!autofs4_follow_mount(&fp_mnt, &fp_dentry)) {
			dput(fp_dentry);
			mntput(fp_mnt);
			dcache_dir_close(inode, file);
			goto out;
		}

		fp = dentry_open(fp_dentry, fp_mnt, file->f_flags);
		status = PTR_ERR(fp);
		if (IS_ERR(fp)) {
			dcache_dir_close(inode, file);
			goto out;
		}
		cursor->d_fsdata = fp;
	}
	return 0;
out:
	return status;
}

static int autofs4_dir_close(struct inode *inode, struct file *file)
{
	struct dentry *dentry = file->f_path.dentry;
	struct autofs_sb_info *sbi = autofs4_sbi(dentry->d_sb);
	struct dentry *cursor = file->private_data;
	int status = 0;

	DPRINTK("file=%p dentry=%p %.*s",
		file, dentry, dentry->d_name.len, dentry->d_name.name);

	if (autofs4_oz_mode(sbi))
		goto out;

	if (autofs4_ispending(dentry)) {
		DPRINTK("dentry busy");
		status = -EBUSY;
		goto out;
	}

	if (d_mountpoint(dentry)) {
		struct file *fp = cursor->d_fsdata;
		if (!fp) {
			status = -ENOENT;
			goto out;
		}
		filp_close(fp, current->files);
	}
out:
	dcache_dir_close(inode, file);
	return status;
}

static int autofs4_dir_readdir(struct file *file, void *dirent, filldir_t filldir)
{
	struct dentry *dentry = file->f_path.dentry;
	struct autofs_sb_info *sbi = autofs4_sbi(dentry->d_sb);
	struct dentry *cursor = file->private_data;
	int status;

	DPRINTK("file=%p dentry=%p %.*s",
		file, dentry, dentry->d_name.len, dentry->d_name.name);

	if (autofs4_oz_mode(sbi))
		goto out;

	if (autofs4_ispending(dentry)) {
		DPRINTK("dentry busy");
		return -EBUSY;
	}

	if (d_mountpoint(dentry)) {
		struct file *fp = cursor->d_fsdata;

		if (!fp)
			return -ENOENT;

		if (!fp->f_op || !fp->f_op->readdir)
			goto out;

		status = vfs_readdir(fp, filldir, dirent);
		file->f_pos = fp->f_pos;
		if (status)
			autofs4_copy_atime(file, fp);
		return status;
	}
out:
	return dcache_readdir(file, dirent, filldir);
}

static int try_to_fill_dentry(struct dentry *dentry, int flags)
{
	struct autofs_sb_info *sbi = autofs4_sbi(dentry->d_sb);
	struct autofs_info *ino = autofs4_dentry_ino(dentry);
	int status = 0;

	/* Block on any pending expiry here; invalidate the dentry
           when expiration is done to trigger mount request with a new
           dentry */
	if (ino && (ino->flags & AUTOFS_INF_EXPIRING)) {
		DPRINTK("waiting for expire %p name=%.*s",
			 dentry, dentry->d_name.len, dentry->d_name.name);

		status = autofs4_wait(sbi, dentry, NFY_NONE);

		DPRINTK("expire done status=%d", status);

		/*
		 * If the directory still exists the mount request must
		 * continue otherwise it can't be followed at the right
		 * time during the walk.
		 */
		status = d_invalidate(dentry);
		if (status != -EBUSY)
			return -EAGAIN;
	}

	DPRINTK("dentry=%p %.*s ino=%p",
		 dentry, dentry->d_name.len, dentry->d_name.name, dentry->d_inode);

	/*
	 * Wait for a pending mount, triggering one if there
	 * isn't one already
	 */
	if (dentry->d_inode == NULL) {
		DPRINTK("waiting for mount name=%.*s",
			 dentry->d_name.len, dentry->d_name.name);

		status = autofs4_wait(sbi, dentry, NFY_MOUNT);

		DPRINTK("mount done status=%d", status);

		/* Turn this into a real negative dentry? */
		if (status == -ENOENT) {
			spin_lock(&dentry->d_lock);
			dentry->d_flags &= ~DCACHE_AUTOFS_PENDING;
			spin_unlock(&dentry->d_lock);
			return status;
		} else if (status) {
			/* Return a negative dentry, but leave it "pending" */
			return status;
		}
	/* Trigger mount for path component or follow link */
	} else if (flags & (LOOKUP_CONTINUE | LOOKUP_DIRECTORY) ||
			current->link_count) {
		DPRINTK("waiting for mount name=%.*s",
			dentry->d_name.len, dentry->d_name.name);

		spin_lock(&dentry->d_lock);
		dentry->d_flags |= DCACHE_AUTOFS_PENDING;
		spin_unlock(&dentry->d_lock);
		status = autofs4_wait(sbi, dentry, NFY_MOUNT);

		DPRINTK("mount done status=%d", status);

		if (status) {
			spin_lock(&dentry->d_lock);
			dentry->d_flags &= ~DCACHE_AUTOFS_PENDING;
			spin_unlock(&dentry->d_lock);
			return status;
		}
	}

	/* Initialize expiry counter after successful mount */
	if (ino)
		ino->last_used = jiffies;

	spin_lock(&dentry->d_lock);
	dentry->d_flags &= ~DCACHE_AUTOFS_PENDING;
	spin_unlock(&dentry->d_lock);
	return status;
}

/* For autofs direct mounts the follow link triggers the mount */
static void *autofs4_follow_link(struct dentry *dentry, struct nameidata *nd)
{
	struct autofs_sb_info *sbi = autofs4_sbi(dentry->d_sb);
	struct autofs_info *ino = autofs4_dentry_ino(dentry);
	int oz_mode = autofs4_oz_mode(sbi);
	unsigned int lookup_type;
	int status;

	DPRINTK("dentry=%p %.*s oz_mode=%d nd->flags=%d",
		dentry, dentry->d_name.len, dentry->d_name.name, oz_mode,
		nd->flags);

	/* If it's our master or we shouldn't trigger a mount we're done */
	lookup_type = nd->flags & (LOOKUP_CONTINUE | LOOKUP_DIRECTORY);
	if (oz_mode || !lookup_type)
		goto done;

	/* If an expire request is pending wait for it. */
	if (ino && (ino->flags & AUTOFS_INF_EXPIRING)) {
		DPRINTK("waiting for active request %p name=%.*s",
			dentry, dentry->d_name.len, dentry->d_name.name);

		status = autofs4_wait(sbi, dentry, NFY_NONE);

		DPRINTK("request done status=%d", status);
	}

	/*
	 * If the dentry contains directories then it is an
	 * autofs multi-mount with no root mount offset. So
	 * don't try to mount it again.
	 */
	spin_lock(&dcache_lock);
	if (!d_mountpoint(dentry) && __simple_empty(dentry)) {
		spin_unlock(&dcache_lock);

		status = try_to_fill_dentry(dentry, 0);
		if (status)
			goto out_error;

		/*
		 * The mount succeeded but if there is no root mount
		 * it must be an autofs multi-mount with no root offset
		 * so we don't need to follow the mount.
		 */
		if (d_mountpoint(dentry)) {
			if (!autofs4_follow_mount(&nd->mnt, &nd->dentry)) {
				status = -ENOENT;
				goto out_error;
			}
		}

		goto done;
	}
	spin_unlock(&dcache_lock);

done:
	return NULL;

out_error:
	path_release(nd);
	return ERR_PTR(status);
}

/*
 * Revalidate is called on every cache lookup.  Some of those
 * cache lookups may actually happen while the dentry is not
 * yet completely filled in, and revalidate has to delay such
 * lookups..
 */
static int autofs4_revalidate(struct dentry *dentry, struct nameidata *nd)
{
	struct inode *dir = dentry->d_parent->d_inode;
	struct autofs_sb_info *sbi = autofs4_sbi(dir->i_sb);
	int oz_mode = autofs4_oz_mode(sbi);
	int flags = nd ? nd->flags : 0;
	int status = 1;

	/* Pending dentry */
	if (autofs4_ispending(dentry)) {
		/* The daemon never causes a mount to trigger */
		if (oz_mode)
			return 1;

		/*
		 * A zero status is success otherwise we have a
		 * negative error code.
		 */
		status = try_to_fill_dentry(dentry, flags);
		if (status == 0)
			return 1;

		/*
		 * A status of EAGAIN here means that the dentry has gone
		 * away while waiting for an expire to complete. If we are
		 * racing with expire lookup will wait for it so this must
		 * be a revalidate and we need to send it to lookup.
		 */
		if (status == -EAGAIN)
			return 0;

		return status;
	}

	/* Negative dentry.. invalidate if "old" */
	if (dentry->d_inode == NULL)
		return 0;

	/* Check for a non-mountpoint directory with no contents */
	spin_lock(&dcache_lock);
	if (S_ISDIR(dentry->d_inode->i_mode) &&
	    !d_mountpoint(dentry) && 
	    __simple_empty(dentry)) {
		DPRINTK("dentry=%p %.*s, emptydir",
			 dentry, dentry->d_name.len, dentry->d_name.name);
		spin_unlock(&dcache_lock);
		/* The daemon never causes a mount to trigger */
		if (oz_mode)
			return 1;

		/*
		 * A zero status is success otherwise we have a
		 * negative error code.
		 */
		status = try_to_fill_dentry(dentry, flags);
		if (status == 0)
			return 1;

		return status;
	}
	spin_unlock(&dcache_lock);

	return 1;
}

void autofs4_dentry_release(struct dentry *de)
{
	struct autofs_info *inf;

	DPRINTK("releasing %p", de);

	inf = autofs4_dentry_ino(de);
	de->d_fsdata = NULL;

	if (inf) {
		struct autofs_sb_info *sbi = autofs4_sbi(de->d_sb);

		if (sbi) {
			spin_lock(&sbi->rehash_lock);
			if (!list_empty(&inf->rehash))
				list_del(&inf->rehash);
			spin_unlock(&sbi->rehash_lock);
		}

		inf->dentry = NULL;
		inf->inode = NULL;

		autofs4_free_ino(inf);
	}
}

/* For dentries of directories in the root dir */
static struct dentry_operations autofs4_root_dentry_operations = {
	.d_revalidate	= autofs4_revalidate,
	.d_release	= autofs4_dentry_release,
};

/* For other dentries */
static struct dentry_operations autofs4_dentry_operations = {
	.d_revalidate	= autofs4_revalidate,
	.d_release	= autofs4_dentry_release,
};

static struct dentry *autofs4_lookup_unhashed(struct autofs_sb_info *sbi, struct dentry *parent, struct qstr *name)
{
	unsigned int len = name->len;
	unsigned int hash = name->hash;
	const unsigned char *str = name->name;
	struct list_head *p, *head;

	spin_lock(&dcache_lock);
	spin_lock(&sbi->rehash_lock);
	head = &sbi->rehash_list;
	list_for_each(p, head) {
		struct autofs_info *ino;
		struct dentry *dentry;
		struct qstr *qstr;