257 lines
7.9 KiB
C
257 lines
7.9 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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/*
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* Wrapper functions for accessing the file_struct fd array.
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*/
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#ifndef __LINUX_FILE_H
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#define __LINUX_FILE_H
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#include <linux/compiler.h>
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#include <linux/types.h>
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#include <linux/posix_types.h>
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#include <linux/errno.h>
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#include <linux/cleanup.h>
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#include <linux/err.h>
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struct file;
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extern void fput(struct file *);
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struct file_operations;
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struct task_struct;
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struct vfsmount;
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struct dentry;
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struct inode;
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struct path;
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extern struct file *alloc_file_pseudo(struct inode *, struct vfsmount *,
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const char *, int flags, const struct file_operations *);
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extern struct file *alloc_file_pseudo_noaccount(struct inode *, struct vfsmount *,
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const char *, int flags, const struct file_operations *);
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extern struct file *alloc_file_clone(struct file *, int flags,
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const struct file_operations *);
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/* either a reference to struct file + flags
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* (cloned vs. borrowed, pos locked), with
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* flags stored in lower bits of value,
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* or empty (represented by 0).
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*/
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struct fd {
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unsigned long word;
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};
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#define FDPUT_FPUT 1
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#define FDPUT_POS_UNLOCK 2
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#define fd_file(f) ((struct file *)((f).word & ~(FDPUT_FPUT|FDPUT_POS_UNLOCK)))
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static inline bool fd_empty(struct fd f)
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{
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return unlikely(!f.word);
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}
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#define EMPTY_FD (struct fd){0}
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static inline struct fd BORROWED_FD(struct file *f)
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{
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return (struct fd){(unsigned long)f};
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}
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static inline struct fd CLONED_FD(struct file *f)
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{
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return (struct fd){(unsigned long)f | FDPUT_FPUT};
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}
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static inline void fdput(struct fd fd)
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{
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if (unlikely(fd.word & FDPUT_FPUT))
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fput(fd_file(fd));
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}
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extern struct file *fget(unsigned int fd);
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extern struct file *fget_raw(unsigned int fd);
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extern struct file *fget_task(struct task_struct *task, unsigned int fd);
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extern struct file *fget_task_next(struct task_struct *task, unsigned int *fd);
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extern void __f_unlock_pos(struct file *);
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struct fd fdget(unsigned int fd);
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struct fd fdget_raw(unsigned int fd);
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struct fd fdget_pos(unsigned int fd);
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static inline void fdput_pos(struct fd f)
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{
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if (f.word & FDPUT_POS_UNLOCK)
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__f_unlock_pos(fd_file(f));
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fdput(f);
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}
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DEFINE_CLASS(fd, struct fd, fdput(_T), fdget(fd), int fd)
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DEFINE_CLASS(fd_raw, struct fd, fdput(_T), fdget_raw(fd), int fd)
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DEFINE_CLASS(fd_pos, struct fd, fdput_pos(_T), fdget_pos(fd), int fd)
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extern int f_dupfd(unsigned int from, struct file *file, unsigned flags);
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extern int replace_fd(unsigned fd, struct file *file, unsigned flags);
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extern void set_close_on_exec(unsigned int fd, int flag);
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extern bool get_close_on_exec(unsigned int fd);
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extern int __get_unused_fd_flags(unsigned flags, unsigned long nofile);
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extern int get_unused_fd_flags(unsigned flags);
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extern void put_unused_fd(unsigned int fd);
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DEFINE_CLASS(get_unused_fd, int, if (_T >= 0) put_unused_fd(_T),
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get_unused_fd_flags(flags), unsigned flags)
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DEFINE_FREE(fput, struct file *, if (!IS_ERR_OR_NULL(_T)) fput(_T))
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/*
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* take_fd() will take care to set @fd to -EBADF ensuring that
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* CLASS(get_unused_fd) won't call put_unused_fd(). This makes it
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* easier to rely on CLASS(get_unused_fd):
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*
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* struct file *f;
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*
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* CLASS(get_unused_fd, fd)(O_CLOEXEC);
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* if (fd < 0)
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* return fd;
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*
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* f = dentry_open(&path, O_RDONLY, current_cred());
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* if (IS_ERR(f))
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* return PTR_ERR(f);
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*
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* fd_install(fd, f);
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* return take_fd(fd);
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*/
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#define take_fd(fd) __get_and_null(fd, -EBADF)
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extern void fd_install(unsigned int fd, struct file *file);
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int receive_fd(struct file *file, int __user *ufd, unsigned int o_flags);
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int receive_fd_replace(int new_fd, struct file *file, unsigned int o_flags);
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extern void flush_delayed_fput(void);
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extern void __fput_sync(struct file *);
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extern unsigned int sysctl_nr_open_min, sysctl_nr_open_max;
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/*
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* fd_prepare: Combined fd + file allocation cleanup class.
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* @err: Error code to indicate if allocation succeeded.
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* @__fd: Allocated fd (may not be accessed directly)
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* @__file: Allocated struct file pointer (may not be accessed directly)
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*
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* Allocates an fd and a file together. On error paths, automatically cleans
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* up whichever resource was successfully allocated. Allows flexible file
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* allocation with different functions per usage.
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*
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* Do not use directly.
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*/
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struct fd_prepare {
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s32 err;
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s32 __fd; /* do not access directly */
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struct file *__file; /* do not access directly */
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};
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/* Typedef for fd_prepare cleanup guards. */
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typedef struct fd_prepare class_fd_prepare_t;
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/*
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* Accessors for fd_prepare class members.
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* _Generic() is used for zero-cost type safety.
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*/
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#define fd_prepare_fd(_fdf) \
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(_Generic((_fdf), struct fd_prepare: (_fdf).__fd))
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#define fd_prepare_file(_fdf) \
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(_Generic((_fdf), struct fd_prepare: (_fdf).__file))
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/* Do not use directly. */
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static inline void class_fd_prepare_destructor(const struct fd_prepare *fdf)
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{
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if (unlikely(fdf->err)) {
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if (likely(fdf->__fd >= 0))
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put_unused_fd(fdf->__fd);
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if (unlikely(!IS_ERR_OR_NULL(fdf->__file)))
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fput(fdf->__file);
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}
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}
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/* Do not use directly. */
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static inline int class_fd_prepare_lock_err(const struct fd_prepare *fdf)
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{
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if (unlikely(fdf->err))
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return fdf->err;
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if (unlikely(fdf->__fd < 0))
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return fdf->__fd;
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if (unlikely(IS_ERR(fdf->__file)))
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return PTR_ERR(fdf->__file);
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if (unlikely(!fdf->__file))
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return -ENOMEM;
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return 0;
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}
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/*
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* __FD_PREPARE_INIT - Helper to initialize fd_prepare class.
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* @_fd_flags: flags for get_unused_fd_flags()
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* @_file_owned: expression that returns struct file *
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*
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* Returns a struct fd_prepare with fd, file, and err set.
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* If fd allocation fails, fd will be negative and err will be set. If
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* fd succeeds but file_init_expr fails, file will be ERR_PTR and err
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* will be set. The err field is the single source of truth for error
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* checking.
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*/
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#define __FD_PREPARE_INIT(_fd_flags, _file_owned) \
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({ \
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struct fd_prepare fdf = { \
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.__fd = get_unused_fd_flags((_fd_flags)), \
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}; \
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if (likely(fdf.__fd >= 0)) \
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fdf.__file = (_file_owned); \
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fdf.err = ACQUIRE_ERR(fd_prepare, &fdf); \
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fdf; \
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})
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/*
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* FD_PREPARE - Macro to declare and initialize an fd_prepare variable.
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*
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* Declares and initializes an fd_prepare variable with automatic
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* cleanup. No separate scope required - cleanup happens when variable
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* goes out of scope.
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*
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* @_fdf: name of struct fd_prepare variable to define
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* @_fd_flags: flags for get_unused_fd_flags()
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* @_file_owned: struct file to take ownership of (can be expression)
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*/
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#define FD_PREPARE(_fdf, _fd_flags, _file_owned) \
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CLASS_INIT(fd_prepare, _fdf, __FD_PREPARE_INIT(_fd_flags, _file_owned))
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/*
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* fd_publish - Publish prepared fd and file to the fd table.
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* @_fdf: struct fd_prepare variable
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*/
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#define fd_publish(_fdf) \
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({ \
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struct fd_prepare *fdp = &(_fdf); \
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VFS_WARN_ON_ONCE(fdp->err); \
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VFS_WARN_ON_ONCE(fdp->__fd < 0); \
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VFS_WARN_ON_ONCE(IS_ERR_OR_NULL(fdp->__file)); \
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fd_install(fdp->__fd, fdp->__file); \
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fdp->__fd; \
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})
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/* Do not use directly. */
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#define __FD_ADD(_fdf, _fd_flags, _file_owned) \
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({ \
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FD_PREPARE(_fdf, _fd_flags, _file_owned); \
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s32 ret = _fdf.err; \
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if (likely(!ret)) \
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ret = fd_publish(_fdf); \
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ret; \
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})
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/*
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* FD_ADD - Allocate and install an fd and file in one step.
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* @_fd_flags: flags for get_unused_fd_flags()
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* @_file_owned: struct file to take ownership of
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*
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* Returns the allocated fd number, or negative error code on failure.
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*/
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#define FD_ADD(_fd_flags, _file_owned) \
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__FD_ADD(__UNIQUE_ID(fd_prepare), _fd_flags, _file_owned)
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#endif /* __LINUX_FILE_H */
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