Commit f3ac8bf7ce1c5abd763ea762e95d1cdcf7799372
1 parent
046abeede7
Exists in
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md: tidy up device searches in read_balance.
The code for searching through the device list to read-balance in raid1 is rather clumsy and hard to follow. Try to simplify it a bit. No important functionality change here. Signed-off-by: NeilBrown <neilb@suse.de>
Showing 1 changed file with 36 additions and 56 deletions Side-by-side Diff
drivers/md/raid1.c
| ... | ... | @@ -419,11 +419,13 @@ |
| 419 | 419 | static int read_balance(conf_t *conf, r1bio_t *r1_bio) |
| 420 | 420 | { |
| 421 | 421 | const sector_t this_sector = r1_bio->sector; |
| 422 | - int new_disk = conf->last_used, disk = new_disk; | |
| 423 | - int wonly_disk = -1; | |
| 424 | 422 | const int sectors = r1_bio->sectors; |
| 423 | + int new_disk = -1; | |
| 424 | + int start_disk; | |
| 425 | + int i; | |
| 425 | 426 | sector_t new_distance, current_distance; |
| 426 | 427 | mdk_rdev_t *rdev; |
| 428 | + int choose_first; | |
| 427 | 429 | |
| 428 | 430 | rcu_read_lock(); |
| 429 | 431 | /* |
| 430 | 432 | |
| 431 | 433 | |
| 432 | 434 | |
| 433 | 435 | |
| 434 | 436 | |
| 435 | 437 | |
| 436 | 438 | |
| ... | ... | @@ -434,54 +436,33 @@ |
| 434 | 436 | retry: |
| 435 | 437 | if (conf->mddev->recovery_cp < MaxSector && |
| 436 | 438 | (this_sector + sectors >= conf->next_resync)) { |
| 437 | - /* Choose the first operational device, for consistancy */ | |
| 438 | - new_disk = 0; | |
| 439 | - | |
| 440 | - for (rdev = rcu_dereference(conf->mirrors[new_disk].rdev); | |
| 441 | - r1_bio->bios[new_disk] == IO_BLOCKED || | |
| 442 | - !rdev || !test_bit(In_sync, &rdev->flags) | |
| 443 | - || test_bit(WriteMostly, &rdev->flags); | |
| 444 | - rdev = rcu_dereference(conf->mirrors[++new_disk].rdev)) { | |
| 445 | - | |
| 446 | - if (rdev && test_bit(In_sync, &rdev->flags) && | |
| 447 | - r1_bio->bios[new_disk] != IO_BLOCKED) | |
| 448 | - wonly_disk = new_disk; | |
| 449 | - | |
| 450 | - if (new_disk == conf->raid_disks - 1) { | |
| 451 | - new_disk = wonly_disk; | |
| 452 | - break; | |
| 453 | - } | |
| 454 | - } | |
| 455 | - goto rb_out; | |
| 439 | + choose_first = 1; | |
| 440 | + start_disk = 0; | |
| 441 | + } else { | |
| 442 | + choose_first = 0; | |
| 443 | + start_disk = conf->last_used; | |
| 456 | 444 | } |
| 457 | 445 | |
| 458 | - | |
| 459 | 446 | /* make sure the disk is operational */ |
| 460 | - for (rdev = rcu_dereference(conf->mirrors[new_disk].rdev); | |
| 461 | - r1_bio->bios[new_disk] == IO_BLOCKED || | |
| 462 | - !rdev || !test_bit(In_sync, &rdev->flags) || | |
| 463 | - test_bit(WriteMostly, &rdev->flags); | |
| 464 | - rdev = rcu_dereference(conf->mirrors[new_disk].rdev)) { | |
| 447 | + for (i = 0 ; i < conf->raid_disks ; i++) { | |
| 448 | + int disk = start_disk + i; | |
| 449 | + if (disk >= conf->raid_disks) | |
| 450 | + disk -= conf->raid_disks; | |
| 465 | 451 | |
| 466 | - if (rdev && test_bit(In_sync, &rdev->flags) && | |
| 467 | - r1_bio->bios[new_disk] != IO_BLOCKED) | |
| 468 | - wonly_disk = new_disk; | |
| 452 | + rdev = rcu_dereference(conf->mirrors[disk].rdev); | |
| 453 | + if (r1_bio->bios[disk] == IO_BLOCKED | |
| 454 | + || rdev == NULL | |
| 455 | + || !test_bit(In_sync, &rdev->flags)) | |
| 456 | + continue; | |
| 469 | 457 | |
| 470 | - if (new_disk <= 0) | |
| 471 | - new_disk = conf->raid_disks; | |
| 472 | - new_disk--; | |
| 473 | - if (new_disk == disk) { | |
| 474 | - new_disk = wonly_disk; | |
| 458 | + new_disk = disk; | |
| 459 | + if (!test_bit(WriteMostly, &rdev->flags)) | |
| 475 | 460 | break; |
| 476 | - } | |
| 477 | 461 | } |
| 478 | 462 | |
| 479 | - if (new_disk < 0) | |
| 463 | + if (new_disk < 0 || choose_first) | |
| 480 | 464 | goto rb_out; |
| 481 | 465 | |
| 482 | - disk = new_disk; | |
| 483 | - /* now disk == new_disk == starting point for search */ | |
| 484 | - | |
| 485 | 466 | /* |
| 486 | 467 | * Don't change to another disk for sequential reads: |
| 487 | 468 | */ |
| 488 | 469 | |
| 489 | 470 | |
| 490 | 471 | |
| ... | ... | @@ -490,20 +471,21 @@ |
| 490 | 471 | if (this_sector == conf->mirrors[new_disk].head_position) |
| 491 | 472 | goto rb_out; |
| 492 | 473 | |
| 493 | - current_distance = abs(this_sector - conf->mirrors[disk].head_position); | |
| 474 | + current_distance = abs(this_sector | |
| 475 | + - conf->mirrors[new_disk].head_position); | |
| 494 | 476 | |
| 495 | - /* Find the disk whose head is closest */ | |
| 477 | + /* look for a better disk - i.e. head is closer */ | |
| 478 | + start_disk = new_disk; | |
| 479 | + for (i = 1; i < conf->raid_disks; i++) { | |
| 480 | + int disk = start_disk + 1; | |
| 481 | + if (disk >= conf->raid_disks) | |
| 482 | + disk -= conf->raid_disks; | |
| 496 | 483 | |
| 497 | - do { | |
| 498 | - if (disk <= 0) | |
| 499 | - disk = conf->raid_disks; | |
| 500 | - disk--; | |
| 501 | - | |
| 502 | 484 | rdev = rcu_dereference(conf->mirrors[disk].rdev); |
| 503 | - | |
| 504 | - if (!rdev || r1_bio->bios[disk] == IO_BLOCKED || | |
| 505 | - !test_bit(In_sync, &rdev->flags) || | |
| 506 | - test_bit(WriteMostly, &rdev->flags)) | |
| 485 | + if (r1_bio->bios[disk] == IO_BLOCKED | |
| 486 | + || rdev == NULL | |
| 487 | + || !test_bit(In_sync, &rdev->flags) | |
| 488 | + || test_bit(WriteMostly, &rdev->flags)) | |
| 507 | 489 | continue; |
| 508 | 490 | |
| 509 | 491 | if (!atomic_read(&rdev->nr_pending)) { |
| 510 | 492 | |
| ... | ... | @@ -515,11 +497,9 @@ |
| 515 | 497 | current_distance = new_distance; |
| 516 | 498 | new_disk = disk; |
| 517 | 499 | } |
| 518 | - } while (disk != conf->last_used); | |
| 500 | + } | |
| 519 | 501 | |
| 520 | 502 | rb_out: |
| 521 | - | |
| 522 | - | |
| 523 | 503 | if (new_disk >= 0) { |
| 524 | 504 | rdev = rcu_dereference(conf->mirrors[new_disk].rdev); |
| 525 | 505 | if (!rdev) |