bcache: Revert "bcache: fix high CPU occupancy during journal"

This reverts commit c4dc2497d50d9c6fb16aa0d07b6a14f3b2adb1e0.

This patch enlarges a race between normal btree flush code path and
flush_btree_write(), which causes deadlock when journal space is
exhausted. Reverts this patch makes the race window from 128 btree
nodes to only 1 btree nodes.

Fixes: c4dc2497d50d ("bcache: fix high CPU occupancy during journal")
Signed-off-by: Coly Li <colyli@suse.de>
Cc: stable@vger.kernel.org
Cc: Tang Junhui <tang.junhui.linux@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/drivers/md/bcache/bcache.h b/drivers/md/bcache/bcache.h
index 73a97586a2ef8880e90c40c02de5f186d65c978d..cb268d7c6cea76224887e9cd35b5b26a90f26714 100644 (file)
--- a/drivers/md/bcache/bcache.h
+++ b/drivers/md/bcache/bcache.h
@@ -726,8 +726,6 @@ struct cache_set {
 
 #define BUCKET_HASH_BITS       12
        struct hlist_head       bucket_hash[1 << BUCKET_HASH_BITS];
-
-       DECLARE_HEAP(struct btree *, flush_btree);
 };
 
 struct bbio {

diff --git a/drivers/md/bcache/journal.c b/drivers/md/bcache/journal.c
index 11d8c93b88bb3eabb2da3a40e09c593f03992f6b..14a4e2c44de9b3e1bb906e50323ede9304022f87 100644 (file)
--- a/drivers/md/bcache/journal.c
+++ b/drivers/md/bcache/journal.c
@@ -416,12 +416,6 @@ err:
 }
 
 /* Journalling */
-#define journal_max_cmp(l, r) \
-       (fifo_idx(&c->journal.pin, btree_current_write(l)->journal) < \
-        fifo_idx(&(c)->journal.pin, btree_current_write(r)->journal))
-#define journal_min_cmp(l, r) \
-       (fifo_idx(&c->journal.pin, btree_current_write(l)->journal) > \
-        fifo_idx(&(c)->journal.pin, btree_current_write(r)->journal))
 
 static void btree_flush_write(struct cache_set *c)
 {
@@ -429,35 +423,25 @@ static void btree_flush_write(struct cache_set *c)
         * Try to find the btree node with that references the oldest journal
         * entry, best is our current candidate and is locked if non NULL:
         */
-       struct btree *b;
-       int i;
+       struct btree *b, *best;
+       unsigned int i;
 
        atomic_long_inc(&c->flush_write);
-
 retry:
-       spin_lock(&c->journal.lock);
-       if (heap_empty(&c->flush_btree)) {
-               for_each_cached_btree(b, c, i)
-                       if (btree_current_write(b)->journal) {
-                               if (!heap_full(&c->flush_btree))
-                                       heap_add(&c->flush_btree, b,
-                                                journal_max_cmp);
-                               else if (journal_max_cmp(b,
-                                        heap_peek(&c->flush_btree))) {
-                                       c->flush_btree.data[0] = b;
-                                       heap_sift(&c->flush_btree, 0,
-                                                 journal_max_cmp);
-                               }
+       best = NULL;
+
+       for_each_cached_btree(b, c, i)
+               if (btree_current_write(b)->journal) {
+                       if (!best)
+                               best = b;
+                       else if (journal_pin_cmp(c,
+                                       btree_current_write(best)->journal,
+                                       btree_current_write(b)->journal)) {
+                               best = b;
                        }
+               }
 
-               for (i = c->flush_btree.used / 2 - 1; i >= 0; --i)
-                       heap_sift(&c->flush_btree, i, journal_min_cmp);
-       }
-
-       b = NULL;
-       heap_pop(&c->flush_btree, b, journal_min_cmp);
-       spin_unlock(&c->journal.lock);
-
+       b = best;
        if (b) {
                mutex_lock(&b->write_lock);
                if (!btree_current_write(b)->journal) {
@@ -898,8 +882,7 @@ int bch_journal_alloc(struct cache_set *c)
        j->w[0].c = c;
        j->w[1].c = c;
 
-       if (!(init_heap(&c->flush_btree, 128, GFP_KERNEL)) ||
-           !(init_fifo(&j->pin, JOURNAL_PIN, GFP_KERNEL)) ||
+       if (!(init_fifo(&j->pin, JOURNAL_PIN, GFP_KERNEL)) ||
            !(j->w[0].data = (void *) __get_free_pages(GFP_KERNEL, JSET_BITS)) ||
            !(j->w[1].data = (void *) __get_free_pages(GFP_KERNEL, JSET_BITS)))
                return -ENOMEM;

diff --git a/drivers/md/bcache/util.h b/drivers/md/bcache/util.h
index 1fbced94e4cce94234ef5423ba788b9406304841..c029f744319080570704de408d0cbcfff2c788e5 100644 (file)
--- a/drivers/md/bcache/util.h
+++ b/drivers/md/bcache/util.h
@@ -113,8 +113,6 @@ do {                                                                        \
 
 #define heap_full(h)   ((h)->used == (h)->size)
 
-#define heap_empty(h)  ((h)->used == 0)
-
 #define DECLARE_FIFO(type, name)                                       \
        struct {                                                        \
                size_t front, back, size, mask;                         \