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bcache: fix using of loop variable in memory shrink

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In bch_mca_scan(), There are some confusion and logical error in the use of
loop variables. In this patch, we clarify them as:
1) nr: the number of btree nodes needs to scan, which will decrease after
we scan a btree node, and should not be less than 0;
2) i: the number of btree nodes have scanned, includes both
btree_cache_freeable and btree_cache, which should not be bigger than
btree_cache_used;
3) freed: the number of btree nodes have freed.

Signed-off-by: Tang Junhui <tang.junhui@zte.com.cn>
Reviewed-by: Michael Lyle <mlyle@lyle.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Tang Junhui 2018-03-18 17:36:22 -07:00 committed by Jens Axboe
parent f3641c3abd
commit ca71df3166
1 changed files with 6 additions and 3 deletions
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9
drivers/md/bcache/btree.c
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@ -665,6 +665,7 @@ static unsigned long bch_mca_scan(struct shrinker *shrink,
struct btree *b, *t;
unsigned long i, nr = sc->nr_to_scan;
unsigned long freed = 0;
unsigned int btree_cache_used;
if (c->shrinker_disabled)
return SHRINK_STOP;
@ -689,9 +690,10 @@ static unsigned long bch_mca_scan(struct shrinker *shrink,
nr = min_t(unsigned long, nr, mca_can_free(c));
i = 0;
btree_cache_used = c->btree_cache_used;
list_for_each_entry_safe(b, t, &c->btree_cache_freeable, list) {
if (freed >= nr)
break;
if (nr <= 0)
goto out;
if (++i > 3 &&
!mca_reap(b, 0, false)) {
@ -699,9 +701,10 @@ static unsigned long bch_mca_scan(struct shrinker *shrink,
rw_unlock(true, b);
freed++;
}
nr--;
}
for (i = 0; (nr--) && i < c->btree_cache_used; i++) {
for (; (nr--) && i < btree_cache_used; i++) {
if (list_empty(&c->btree_cache))
goto out;