From a79cfe12c619aa0fc401f9148d78faa6fc61a331 Mon Sep 17 00:00:00 2001 From: NeilBrown Date: Mon, 2 Feb 2015 11:37:59 +1100 Subject: [PATCH] md/raid5: separate out the easy conditions in need_this_block. Some of the conditions in need_this_block have very straight forward motivation. Separate those out and document them. Signed-off-by: NeilBrown --- drivers/md/raid5.c | 38 +++++++++++++++++++++++++++++--------- 1 file changed, 29 insertions(+), 9 deletions(-) diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c index 5a980fe7c982..21c1e796a0d6 100644 --- a/drivers/md/raid5.c +++ b/drivers/md/raid5.c @@ -2903,14 +2903,34 @@ static int need_this_block(struct stripe_head *sh, struct stripe_head_state *s, struct r5dev *fdev[2] = { &sh->dev[s->failed_num[0]], &sh->dev[s->failed_num[1]] }; - if (!test_bit(R5_LOCKED, &dev->flags) && - !test_bit(R5_UPTODATE, &dev->flags) && - (dev->toread || - (dev->towrite && !test_bit(R5_OVERWRITE, &dev->flags)) || - s->syncing || s->expanding || - (s->replacing && want_replace(sh, disk_idx)) || - (s->failed >= 1 && fdev[0]->toread) || - (s->failed >= 2 && fdev[1]->toread) || + + if (test_bit(R5_LOCKED, &dev->flags) || + test_bit(R5_UPTODATE, &dev->flags)) + /* No point reading this as we already have it or have + * decided to get it. + */ + return 0; + + if (dev->toread || + (dev->towrite && !test_bit(R5_OVERWRITE, &dev->flags))) + /* We need this block to directly satisfy a request */ + return 1; + + if (s->syncing || s->expanding || + (s->replacing && want_replace(sh, disk_idx))) + /* When syncing, or expanding we read everything. + * When replacing, we need the replaced block. + */ + return 1; + + if ((s->failed >= 1 && fdev[0]->toread) || + (s->failed >= 2 && fdev[1]->toread)) + /* If we want to read from a failed device, then + * we need to actually read every other device. + */ + return 1; + + if ( (sh->raid_conf->level <= 5 && s->failed && fdev[0]->towrite && (!test_bit(R5_Insync, &dev->flags) || test_bit(STRIPE_PREREAD_ACTIVE, &sh->state)) && !test_bit(R5_OVERWRITE, &fdev[0]->flags)) || @@ -2919,7 +2939,7 @@ static int need_this_block(struct stripe_head *sh, struct stripe_head_state *s, && s->failed && s->to_write && (s->to_write - s->non_overwrite < sh->raid_conf->raid_disks - sh->raid_conf->max_degraded) && - (!test_bit(R5_Insync, &dev->flags) || test_bit(STRIPE_PREREAD_ACTIVE, &sh->state))))) + (!test_bit(R5_Insync, &dev->flags) || test_bit(STRIPE_PREREAD_ACTIVE, &sh->state)))) return 1; return 0; } -- 2.20.1