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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 <neilb@suse.de>
This commit is contained in:
NeilBrown 2015-02-02 11:37:59 +11:00
parent 2c58f06e6f
commit a79cfe12c6
1 changed files with 29 additions and 9 deletions
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38
drivers/md/raid5.c
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@ -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;
}