diff options
| -rw-r--r-- | fs/file_table.c | 19 |
1 files changed, 14 insertions, 5 deletions
diff --git a/fs/file_table.c b/fs/file_table.c index b8a0bb63cbd7..2fc3b3c08911 100644 --- a/fs/file_table.c +++ b/fs/file_table.c @@ -298,11 +298,20 @@ struct file *fget(unsigned int fd) EXPORT_SYMBOL(fget); /* - * Lightweight file lookup - no refcnt increment if fd table isn't shared. - * You can use this only if it is guranteed that the current task already - * holds a refcnt to that file. That check has to be done at fget() only - * and a flag is returned to be passed to the corresponding fput_light(). - * There must not be a cloning between an fget_light/fput_light pair. + * Lightweight file lookup - no refcnt increment if fd table isn't shared. + * + * You can use this instead of fget if you satisfy all of the following + * conditions: + * 1) You must call fput_light before exiting the syscall and returning control + * to userspace (i.e. you cannot remember the returned struct file * after + * returning to userspace). + * 2) You must not call filp_close on the returned struct file * in between + * calls to fget_light and fput_light. + * 3) You must not clone the current task in between the calls to fget_light + * and fput_light. + * + * The fput_needed flag returned by fget_light should be passed to the + * corresponding fput_light. */ struct file *fget_light(unsigned int fd, int *fput_needed) { |