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fs/anon_inodes.c
4.56 KB
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// SPDX-License-Identifier: GPL-2.0-only |
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/* * fs/anon_inodes.c * * Copyright (C) 2007 Davide Libenzi <davidel@xmailserver.org> * * Thanks to Arnd Bergmann for code review and suggestions. * More changes for Thomas Gleixner suggestions. * */ |
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#include <linux/cred.h> |
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#include <linux/file.h> #include <linux/poll.h> |
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#include <linux/sched.h> |
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#include <linux/init.h> #include <linux/fs.h> #include <linux/mount.h> #include <linux/module.h> #include <linux/kernel.h> #include <linux/magic.h> #include <linux/anon_inodes.h> |
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#include <linux/pseudo_fs.h> |
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#include <linux/uaccess.h> |
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static struct vfsmount *anon_inode_mnt __read_mostly; static struct inode *anon_inode_inode; |
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/* * anon_inodefs_dname() is called from d_path(). */ static char *anon_inodefs_dname(struct dentry *dentry, char *buffer, int buflen) { return dynamic_dname(dentry, buffer, buflen, "anon_inode:%s", dentry->d_name.name); } |
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static const struct dentry_operations anon_inodefs_dentry_operations = { .d_dname = anon_inodefs_dname, }; |
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static int anon_inodefs_init_fs_context(struct fs_context *fc) |
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{ |
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struct pseudo_fs_context *ctx = init_pseudo(fc, ANON_INODE_FS_MAGIC); if (!ctx) return -ENOMEM; ctx->dops = &anon_inodefs_dentry_operations; return 0; |
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} static struct file_system_type anon_inode_fs_type = { .name = "anon_inodefs", |
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.init_fs_context = anon_inodefs_init_fs_context, |
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.kill_sb = kill_anon_super, }; |
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/** |
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* anon_inode_getfile - creates a new file instance by hooking it up to an * anonymous inode, and a dentry that describe the "class" * of the file |
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* |
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* @name: [in] name of the "class" of the new file |
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* @fops: [in] file operations for the new file * @priv: [in] private data for the new file (will be file's private_data) * @flags: [in] flags |
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* * Creates a new file by hooking it on a single inode. This is useful for files * that do not need to have a full-fledged inode in order to operate correctly. |
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* All the files created with anon_inode_getfile() will share a single inode, |
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* hence saving memory and avoiding code duplication for the file/inode/dentry |
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* setup. Returns the newly created file* or an error pointer. |
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*/ |
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struct file *anon_inode_getfile(const char *name, const struct file_operations *fops, void *priv, int flags) |
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{ |
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struct file *file; |
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if (IS_ERR(anon_inode_inode)) |
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return ERR_PTR(-ENODEV); |
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if (fops->owner && !try_module_get(fops->owner)) |
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return ERR_PTR(-ENOENT); |
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/* |
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* We know the anon_inode inode count is always greater than zero, |
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* so ihold() is safe. |
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*/ |
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ihold(anon_inode_inode); |
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file = alloc_file_pseudo(anon_inode_inode, anon_inode_mnt, name, flags & (O_ACCMODE | O_NONBLOCK), fops); |
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if (IS_ERR(file)) |
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goto err; |
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file->f_mapping = anon_inode_inode->i_mapping; |
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file->private_data = priv; |
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return file; |
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err: iput(anon_inode_inode); |
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module_put(fops->owner); |
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return file; |
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} EXPORT_SYMBOL_GPL(anon_inode_getfile); /** * anon_inode_getfd - creates a new file instance by hooking it up to an * anonymous inode, and a dentry that describe the "class" * of the file * * @name: [in] name of the "class" of the new file * @fops: [in] file operations for the new file * @priv: [in] private data for the new file (will be file's private_data) * @flags: [in] flags * * Creates a new file by hooking it on a single inode. This is useful for files * that do not need to have a full-fledged inode in order to operate correctly. * All the files created with anon_inode_getfd() will share a single inode, * hence saving memory and avoiding code duplication for the file/inode/dentry * setup. Returns new descriptor or an error code. */ int anon_inode_getfd(const char *name, const struct file_operations *fops, void *priv, int flags) { int error, fd; struct file *file; error = get_unused_fd_flags(flags); if (error < 0) return error; fd = error; file = anon_inode_getfile(name, fops, priv, flags); if (IS_ERR(file)) { error = PTR_ERR(file); goto err_put_unused_fd; } |
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fd_install(fd, file); |
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return fd; |
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err_put_unused_fd: put_unused_fd(fd); |
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return error; } |
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EXPORT_SYMBOL_GPL(anon_inode_getfd); |
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static int __init anon_inode_init(void) { |
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anon_inode_mnt = kern_mount(&anon_inode_fs_type); |
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if (IS_ERR(anon_inode_mnt)) panic("anon_inode_init() kernel mount failed (%ld) ", PTR_ERR(anon_inode_mnt)); |
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anon_inode_inode = alloc_anon_inode(anon_inode_mnt->mnt_sb); if (IS_ERR(anon_inode_inode)) panic("anon_inode_init() inode allocation failed (%ld) ", PTR_ERR(anon_inode_inode)); return 0; |
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} fs_initcall(anon_inode_init); |