![David Howells](/assets/img/avatar_default.png)
Extend the get_sb() filesystem operation to take an extra argument that permits the VFS to pass in the target vfsmount that defines the mountpoint. The filesystem is then required to manually set the superblock and root dentry pointers. For most filesystems, this should be done with simple_set_mnt() which will set the superblock pointer and then set the root dentry to the superblock's s_root (as per the old default behaviour). The get_sb() op now returns an integer as there's now no need to return the superblock pointer. This patch permits a superblock to be implicitly shared amongst several mount points, such as can be done with NFS to avoid potential inode aliasing. In such a case, simple_set_mnt() would not be called, and instead the mnt_root and mnt_sb would be set directly. The patch also makes the following changes: (*) the get_sb_*() convenience functions in the core kernel now take a vfsmount pointer argument and return an integer, so most filesystems have to change very little. (*) If one of the convenience function is not used, then get_sb() should normally call simple_set_mnt() to instantiate the vfsmount. This will always return 0, and so can be tail-called from get_sb(). (*) generic_shutdown_super() now calls shrink_dcache_sb() to clean up the dcache upon superblock destruction rather than shrink_dcache_anon(). This is required because the superblock may now have multiple trees that aren't actually bound to s_root, but that still need to be cleaned up. The currently called functions assume that the whole tree is rooted at s_root, and that anonymous dentries are not the roots of trees which results in dentries being left unculled. However, with the way NFS superblock sharing are currently set to be implemented, these assumptions are violated: the root of the filesystem is simply a dummy dentry and inode (the real inode for '/' may well be inaccessible), and all the vfsmounts are rooted on anonymous[*] dentries with child trees. [*] Anonymous until discovered from another tree. (*) The documentation has been adjusted, including the additional bit of changing ext2_* into foo_* in the documentation. [akpm@osdl.org: convert ipath_fs, do other stuff] Signed-off-by: David Howells <dhowells@redhat.com> Acked-by: Al Viro <viro@zeniv.linux.org.uk> Cc: Nathan Scott <nathans@sgi.com> Cc: Roland Dreier <rolandd@cisco.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
320 lines
8.9 KiB
C
320 lines
8.9 KiB
C
/*
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* file.c - part of debugfs, a tiny little debug file system
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*
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* Copyright (C) 2004 Greg Kroah-Hartman <greg@kroah.com>
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* Copyright (C) 2004 IBM Inc.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License version
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* 2 as published by the Free Software Foundation.
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*
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* debugfs is for people to use instead of /proc or /sys.
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* See Documentation/DocBook/kernel-api for more details.
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*
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*/
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/* uncomment to get debug messages from the debug filesystem, ah the irony. */
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/* #define DEBUG */
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#include <linux/config.h>
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#include <linux/module.h>
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#include <linux/fs.h>
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#include <linux/mount.h>
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#include <linux/pagemap.h>
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#include <linux/init.h>
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#include <linux/namei.h>
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#include <linux/debugfs.h>
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#define DEBUGFS_MAGIC 0x64626720
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/* declared over in file.c */
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extern struct file_operations debugfs_file_operations;
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static struct vfsmount *debugfs_mount;
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static int debugfs_mount_count;
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static struct inode *debugfs_get_inode(struct super_block *sb, int mode, dev_t dev)
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{
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struct inode *inode = new_inode(sb);
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if (inode) {
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inode->i_mode = mode;
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inode->i_uid = 0;
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inode->i_gid = 0;
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inode->i_blksize = PAGE_CACHE_SIZE;
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inode->i_blocks = 0;
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inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
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switch (mode & S_IFMT) {
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default:
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init_special_inode(inode, mode, dev);
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break;
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case S_IFREG:
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inode->i_fop = &debugfs_file_operations;
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break;
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case S_IFDIR:
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inode->i_op = &simple_dir_inode_operations;
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inode->i_fop = &simple_dir_operations;
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/* directory inodes start off with i_nlink == 2 (for "." entry) */
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inode->i_nlink++;
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break;
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}
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}
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return inode;
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}
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/* SMP-safe */
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static int debugfs_mknod(struct inode *dir, struct dentry *dentry,
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int mode, dev_t dev)
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{
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struct inode *inode;
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int error = -EPERM;
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if (dentry->d_inode)
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return -EEXIST;
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inode = debugfs_get_inode(dir->i_sb, mode, dev);
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if (inode) {
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d_instantiate(dentry, inode);
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dget(dentry);
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error = 0;
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}
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return error;
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}
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static int debugfs_mkdir(struct inode *dir, struct dentry *dentry, int mode)
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{
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int res;
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mode = (mode & (S_IRWXUGO | S_ISVTX)) | S_IFDIR;
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res = debugfs_mknod(dir, dentry, mode, 0);
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if (!res)
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dir->i_nlink++;
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return res;
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}
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static int debugfs_create(struct inode *dir, struct dentry *dentry, int mode)
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{
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mode = (mode & S_IALLUGO) | S_IFREG;
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return debugfs_mknod(dir, dentry, mode, 0);
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}
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static inline int debugfs_positive(struct dentry *dentry)
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{
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return dentry->d_inode && !d_unhashed(dentry);
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}
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static int debug_fill_super(struct super_block *sb, void *data, int silent)
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{
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static struct tree_descr debug_files[] = {{""}};
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return simple_fill_super(sb, DEBUGFS_MAGIC, debug_files);
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}
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static int debug_get_sb(struct file_system_type *fs_type,
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int flags, const char *dev_name,
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void *data, struct vfsmount *mnt)
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{
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return get_sb_single(fs_type, flags, data, debug_fill_super, mnt);
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}
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static struct file_system_type debug_fs_type = {
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.owner = THIS_MODULE,
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.name = "debugfs",
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.get_sb = debug_get_sb,
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.kill_sb = kill_litter_super,
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};
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static int debugfs_create_by_name(const char *name, mode_t mode,
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struct dentry *parent,
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struct dentry **dentry)
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{
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int error = 0;
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/* If the parent is not specified, we create it in the root.
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* We need the root dentry to do this, which is in the super
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* block. A pointer to that is in the struct vfsmount that we
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* have around.
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*/
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if (!parent ) {
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if (debugfs_mount && debugfs_mount->mnt_sb) {
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parent = debugfs_mount->mnt_sb->s_root;
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}
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}
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if (!parent) {
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pr_debug("debugfs: Ah! can not find a parent!\n");
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return -EFAULT;
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}
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*dentry = NULL;
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mutex_lock(&parent->d_inode->i_mutex);
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*dentry = lookup_one_len(name, parent, strlen(name));
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if (!IS_ERR(dentry)) {
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if ((mode & S_IFMT) == S_IFDIR)
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error = debugfs_mkdir(parent->d_inode, *dentry, mode);
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else
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error = debugfs_create(parent->d_inode, *dentry, mode);
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} else
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error = PTR_ERR(dentry);
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mutex_unlock(&parent->d_inode->i_mutex);
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return error;
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}
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/**
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* debugfs_create_file - create a file in the debugfs filesystem
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*
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* @name: a pointer to a string containing the name of the file to create.
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* @mode: the permission that the file should have
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* @parent: a pointer to the parent dentry for this file. This should be a
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* directory dentry if set. If this paramater is NULL, then the
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* file will be created in the root of the debugfs filesystem.
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* @data: a pointer to something that the caller will want to get to later
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* on. The inode.u.generic_ip pointer will point to this value on
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* the open() call.
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* @fops: a pointer to a struct file_operations that should be used for
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* this file.
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*
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* This is the basic "create a file" function for debugfs. It allows for a
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* wide range of flexibility in createing a file, or a directory (if you
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* want to create a directory, the debugfs_create_dir() function is
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* recommended to be used instead.)
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*
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* This function will return a pointer to a dentry if it succeeds. This
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* pointer must be passed to the debugfs_remove() function when the file is
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* to be removed (no automatic cleanup happens if your module is unloaded,
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* you are responsible here.) If an error occurs, NULL will be returned.
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*
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* If debugfs is not enabled in the kernel, the value -ENODEV will be
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* returned. It is not wise to check for this value, but rather, check for
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* NULL or !NULL instead as to eliminate the need for #ifdef in the calling
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* code.
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*/
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struct dentry *debugfs_create_file(const char *name, mode_t mode,
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struct dentry *parent, void *data,
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const struct file_operations *fops)
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{
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struct dentry *dentry = NULL;
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int error;
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pr_debug("debugfs: creating file '%s'\n",name);
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error = simple_pin_fs("debugfs", &debugfs_mount, &debugfs_mount_count);
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if (error)
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goto exit;
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error = debugfs_create_by_name(name, mode, parent, &dentry);
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if (error) {
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dentry = NULL;
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goto exit;
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}
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if (dentry->d_inode) {
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if (data)
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dentry->d_inode->u.generic_ip = data;
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if (fops)
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dentry->d_inode->i_fop = fops;
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}
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exit:
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return dentry;
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}
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EXPORT_SYMBOL_GPL(debugfs_create_file);
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/**
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* debugfs_create_dir - create a directory in the debugfs filesystem
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*
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* @name: a pointer to a string containing the name of the directory to
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* create.
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* @parent: a pointer to the parent dentry for this file. This should be a
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* directory dentry if set. If this paramater is NULL, then the
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* directory will be created in the root of the debugfs filesystem.
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*
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* This function creates a directory in debugfs with the given name.
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*
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* This function will return a pointer to a dentry if it succeeds. This
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* pointer must be passed to the debugfs_remove() function when the file is
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* to be removed (no automatic cleanup happens if your module is unloaded,
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* you are responsible here.) If an error occurs, NULL will be returned.
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*
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* If debugfs is not enabled in the kernel, the value -ENODEV will be
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* returned. It is not wise to check for this value, but rather, check for
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* NULL or !NULL instead as to eliminate the need for #ifdef in the calling
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* code.
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*/
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struct dentry *debugfs_create_dir(const char *name, struct dentry *parent)
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{
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return debugfs_create_file(name,
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S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO,
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parent, NULL, NULL);
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}
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EXPORT_SYMBOL_GPL(debugfs_create_dir);
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/**
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* debugfs_remove - removes a file or directory from the debugfs filesystem
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*
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* @dentry: a pointer to a the dentry of the file or directory to be
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* removed.
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*
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* This function removes a file or directory in debugfs that was previously
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* created with a call to another debugfs function (like
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* debufs_create_file() or variants thereof.)
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*
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* This function is required to be called in order for the file to be
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* removed, no automatic cleanup of files will happen when a module is
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* removed, you are responsible here.
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*/
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void debugfs_remove(struct dentry *dentry)
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{
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struct dentry *parent;
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if (!dentry)
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return;
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parent = dentry->d_parent;
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if (!parent || !parent->d_inode)
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return;
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mutex_lock(&parent->d_inode->i_mutex);
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if (debugfs_positive(dentry)) {
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if (dentry->d_inode) {
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if (S_ISDIR(dentry->d_inode->i_mode))
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simple_rmdir(parent->d_inode, dentry);
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else
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simple_unlink(parent->d_inode, dentry);
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dput(dentry);
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}
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}
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mutex_unlock(&parent->d_inode->i_mutex);
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simple_release_fs(&debugfs_mount, &debugfs_mount_count);
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}
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EXPORT_SYMBOL_GPL(debugfs_remove);
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static decl_subsys(debug, NULL, NULL);
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static int __init debugfs_init(void)
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{
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int retval;
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kset_set_kset_s(&debug_subsys, kernel_subsys);
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retval = subsystem_register(&debug_subsys);
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if (retval)
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return retval;
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retval = register_filesystem(&debug_fs_type);
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if (retval)
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subsystem_unregister(&debug_subsys);
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return retval;
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}
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static void __exit debugfs_exit(void)
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{
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simple_release_fs(&debugfs_mount, &debugfs_mount_count);
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unregister_filesystem(&debug_fs_type);
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subsystem_unregister(&debug_subsys);
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}
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core_initcall(debugfs_init);
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module_exit(debugfs_exit);
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MODULE_LICENSE("GPL");
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