Alloc fd
Retired DISLab
(버전 사이의 차이)
| 15번째 줄: | 15번째 줄: | ||
462 fdt = files_fdtable(files); | 462 fdt = files_fdtable(files); | ||
463 fd = start; | 463 fd = start; | ||
| − | 464 if (fd < files->next_fd) | + | 464 if (fd < files->next_fd) //file descriptor fd가 file structure구조체 files의 next_fd(비어있는 fd)보다 작다면 |
| − | 465 fd = files->next_fd; | + | 465 fd = files->next_fd; //next_fd를 fd에 할당 |
466 | 466 | ||
| − | 467 if (fd < fdt->max_fds) | + | 467 if (fd < fdt->max_fds) //fd index보다 fd가 작다면(정상적인 경우) |
| − | 468 fd = find_next_zero_bit(fdt->open_fds, fdt->max_fds, fd); | + | 468 fd = find_next_zero_bit(fdt->open_fds, fdt->max_fds, fd); //bitmap에서 bit가 0으로 되어있는 offset을 찾아 할당 |
469 | 469 | ||
470 /* | 470 /* | ||
| 25번째 줄: | 25번째 줄: | ||
472 * will limit the total number of files that can be opened. | 472 * will limit the total number of files that can be opened. | ||
473 */ | 473 */ | ||
| − | 474 error = -EMFILE; | + | 474 error = -EMFILE; //Too many open file |
475 if (fd >= end) | 475 if (fd >= end) | ||
476 goto out; | 476 goto out; | ||
477 | 477 | ||
| − | 478 error = expand_files(files, fd); | + | 478 error = expand_files(files, fd); //fdt가 부족하여 files_struct구조체를 추가하는경우 |
| − | 479 if (error < 0) | + | 479 if (error < 0) //nothing done |
480 goto out; | 480 goto out; | ||
481 | 481 | ||
| 37번째 줄: | 37번째 줄: | ||
484 * might have blocked - try again. | 484 * might have blocked - try again. | ||
485 */ | 485 */ | ||
| − | 486 if (error) | + | 486 if (error) //files were expanded |
487 goto repeat; | 487 goto repeat; | ||
488 | 488 | ||
| 43번째 줄: | 43번째 줄: | ||
490 files->next_fd = fd + 1; | 490 files->next_fd = fd + 1; | ||
491 | 491 | ||
| − | 492 __set_open_fd(fd, fdt); | + | 492 __set_open_fd(fd, fdt); //set bit |
493 if (flags & O_CLOEXEC) | 493 if (flags & O_CLOEXEC) | ||
494 __set_close_on_exec(fd, fdt); | 494 __set_close_on_exec(fd, fdt); | ||
2014년 4월 30일 (수) 19:36 현재 판
450 /* 451 * allocate a file descriptor, mark it busy. 452 */ 453 int __alloc_fd(struct files_struct *files, //struct files_struct : open file table structure 454 unsigned start, unsigned end, unsigned flags) 455 { 456 unsigned int fd; 457 int error; 458 struct fdtable *fdt; 459 460 spin_lock(&files->file_lock); 461 repeat: 462 fdt = files_fdtable(files); 463 fd = start; 464 if (fd < files->next_fd) //file descriptor fd가 file structure구조체 files의 next_fd(비어있는 fd)보다 작다면 465 fd = files->next_fd; //next_fd를 fd에 할당 466 467 if (fd < fdt->max_fds) //fd index보다 fd가 작다면(정상적인 경우) 468 fd = find_next_zero_bit(fdt->open_fds, fdt->max_fds, fd); //bitmap에서 bit가 0으로 되어있는 offset을 찾아 할당 469 470 /* 471 * N.B. For clone tasks sharing a files structure, this test 472 * will limit the total number of files that can be opened. 473 */ 474 error = -EMFILE; //Too many open file 475 if (fd >= end) 476 goto out; 477 478 error = expand_files(files, fd); //fdt가 부족하여 files_struct구조체를 추가하는경우 479 if (error < 0) //nothing done 480 goto out; 481 482 /* 483 * If we needed to expand the fs array we 484 * might have blocked - try again. 485 */ 486 if (error) //files were expanded 487 goto repeat; 488 489 if (start <= files->next_fd) 490 files->next_fd = fd + 1; 491 492 __set_open_fd(fd, fdt); //set bit 493 if (flags & O_CLOEXEC) 494 __set_close_on_exec(fd, fdt); 495 else 496 __clear_close_on_exec(fd, fdt); 497 error = fd; 498 #if 1 499 /* Sanity check */ 500 if (rcu_dereference_raw(fdt->fd[fd]) != NULL) { 501 printk(KERN_WARNING "alloc_fd: slot %d not NULL!\n", fd); 502 rcu_assign_pointer(fdt->fd[fd], NULL); 503 } 504 #endif 505 506 out: 507 spin_unlock(&files->file_lock); 508 return error; 509 }
