diff options
Diffstat (limited to 'include/linux/file.h')
| -rw-r--r-- | include/linux/file.h | 126 |
1 files changed, 126 insertions, 0 deletions
diff --git a/include/linux/file.h b/include/linux/file.h index af1768d934a0..cf389fde9bc2 100644 --- a/include/linux/file.h +++ b/include/linux/file.h @@ -127,4 +127,130 @@ extern void __fput_sync(struct file *); extern unsigned int sysctl_nr_open_min, sysctl_nr_open_max; +/* + * fd_prepare: Combined fd + file allocation cleanup class. + * @err: Error code to indicate if allocation succeeded. + * @__fd: Allocated fd (may not be accessed directly) + * @__file: Allocated struct file pointer (may not be accessed directly) + * + * Allocates an fd and a file together. On error paths, automatically cleans + * up whichever resource was successfully allocated. Allows flexible file + * allocation with different functions per usage. + * + * Do not use directly. + */ +struct fd_prepare { + s32 err; + s32 __fd; /* do not access directly */ + struct file *__file; /* do not access directly */ +}; + +/* Typedef for fd_prepare cleanup guards. */ +typedef struct fd_prepare class_fd_prepare_t; + +/* + * Accessors for fd_prepare class members. + * _Generic() is used for zero-cost type safety. + */ +#define fd_prepare_fd(_fdf) \ + (_Generic((_fdf), struct fd_prepare: (_fdf).__fd)) + +#define fd_prepare_file(_fdf) \ + (_Generic((_fdf), struct fd_prepare: (_fdf).__file)) + +/* Do not use directly. */ +static inline void class_fd_prepare_destructor(const struct fd_prepare *fdf) +{ + if (unlikely(fdf->err)) { + if (likely(fdf->__fd >= 0)) + put_unused_fd(fdf->__fd); + if (unlikely(!IS_ERR_OR_NULL(fdf->__file))) + fput(fdf->__file); + } +} + +/* Do not use directly. */ +static inline int class_fd_prepare_lock_err(const struct fd_prepare *fdf) +{ + if (unlikely(fdf->err)) + return fdf->err; + if (unlikely(fdf->__fd < 0)) + return fdf->__fd; + if (unlikely(IS_ERR(fdf->__file))) + return PTR_ERR(fdf->__file); + if (unlikely(!fdf->__file)) + return -ENOMEM; + return 0; +} + +/* + * __FD_PREPARE_INIT - Helper to initialize fd_prepare class. + * @_fd_flags: flags for get_unused_fd_flags() + * @_file_owned: expression that returns struct file * + * + * Returns a struct fd_prepare with fd, file, and err set. + * If fd allocation fails, fd will be negative and err will be set. If + * fd succeeds but file_init_expr fails, file will be ERR_PTR and err + * will be set. The err field is the single source of truth for error + * checking. + */ +#define __FD_PREPARE_INIT(_fd_flags, _file_owned) \ + ({ \ + struct fd_prepare fdf = { \ + .__fd = get_unused_fd_flags((_fd_flags)), \ + }; \ + if (likely(fdf.__fd >= 0)) \ + fdf.__file = (_file_owned); \ + fdf.err = ACQUIRE_ERR(fd_prepare, &fdf); \ + fdf; \ + }) + +/* + * FD_PREPARE - Macro to declare and initialize an fd_prepare variable. + * + * Declares and initializes an fd_prepare variable with automatic + * cleanup. No separate scope required - cleanup happens when variable + * goes out of scope. + * + * @_fdf: name of struct fd_prepare variable to define + * @_fd_flags: flags for get_unused_fd_flags() + * @_file_owned: struct file to take ownership of (can be expression) + */ +#define FD_PREPARE(_fdf, _fd_flags, _file_owned) \ + CLASS_INIT(fd_prepare, _fdf, __FD_PREPARE_INIT(_fd_flags, _file_owned)) + +/* + * fd_publish - Publish prepared fd and file to the fd table. + * @_fdf: struct fd_prepare variable + */ +#define fd_publish(_fdf) \ + ({ \ + struct fd_prepare *fdp = &(_fdf); \ + VFS_WARN_ON_ONCE(fdp->err); \ + VFS_WARN_ON_ONCE(fdp->__fd < 0); \ + VFS_WARN_ON_ONCE(IS_ERR_OR_NULL(fdp->__file)); \ + fd_install(fdp->__fd, fdp->__file); \ + fdp->__fd; \ + }) + +/* Do not use directly. */ +#define __FD_ADD(_fdf, _fd_flags, _file_owned) \ + ({ \ + FD_PREPARE(_fdf, _fd_flags, _file_owned); \ + s32 ret = _fdf.err; \ + if (likely(!ret)) \ + ret = fd_publish(_fdf); \ + ret; \ + }) + +/* + * FD_ADD - Allocate and install an fd and file in one step. + * @_fd_flags: flags for get_unused_fd_flags() + * @_file_owned: struct file to take ownership of + * + * Returns the allocated fd number, or negative error code on failure. + */ +#define FD_ADD(_fd_flags, _file_owned) \ + __FD_ADD(__UNIQUE_ID(fd_prepare), _fd_flags, _file_owned) + #endif /* __LINUX_FILE_H */ |