bcache: FUA fixes

commit e49c7c374e7aacd1f04ecbc21d9dbbeeea4a77d6 upstream.

Journal writes need to be marked FUA, not just REQ_FLUSH. And btree node
writes have... weird ordering requirements.

Signed-off-by: Kent Overstreet <koverstreet@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

3 files changed, 34 insertions, 4 deletions

diff --git a/drivers/md/bcache/btree.c b/drivers/md/bcache/btree.c
index 7b687a6f3dec..833c590806ba 100644
--- a/drivers/md/bcache/btree.c
+++ b/drivers/md/bcache/btree.c
@@ -326,10 +326,25 @@ static void do_btree_write(struct btree *b)
         i->csum         = btree_csum_set(b, i);
 
         btree_bio_init(b);
-        b->bio->bi_rw   = REQ_META|WRITE_SYNC;
+        b->bio->bi_rw   = REQ_META|WRITE_SYNC|REQ_FUA;
         b->bio->bi_size = set_blocks(i, b->c) * block_bytes(b->c);
         bch_bio_map(b->bio, i);
 
+        /*
+         * If we're appending to a leaf node, we don't technically need FUA -
+         * this write just needs to be persisted before the next journal write,
+         * which will be marked FLUSH|FUA.
+         *
+         * Similarly if we're writing a new btree root - the pointer is going to
+         * be in the next journal entry.
+         *
+         * But if we're writing a new btree node (that isn't a root) or
+         * appending to a non leaf btree node, we need either FUA or a flush
+         * when we write the parent with the new pointer. FUA is cheaper than a
+         * flush, and writes appending to leaf nodes aren't blocking anything so
+         * just make all btree node writes FUA to keep things sane.
+         */
+
         bkey_copy(&k.key, &b->key);
         SET_PTR_OFFSET(&k.key, 0, PTR_OFFSET(&k.key, 0) + bset_offset(b, i));
 
@@ -2142,6 +2157,9 @@ int bch_btree_insert(struct btree_op *op, struct cache_set *c)
 void bch_btree_set_root(struct btree *b)
 {
         unsigned i;
+        struct closure cl;
+
+        closure_init_stack(&cl);
 
         BUG_ON(!b->written);
 
@@ -2155,8 +2173,9 @@ void bch_btree_set_root(struct btree *b)
         b->c->root = b;
         __bkey_put(b->c, &b->key);
 
-        bch_journal_meta(b->c, NULL);
+        bch_journal_meta(b->c, &cl);
         pr_debug("%s for %pf", pbtree(b), __builtin_return_address(0));
+        closure_sync(&cl);
 }
 
 /* Cache lookup */
diff --git a/drivers/md/bcache/journal.c b/drivers/md/bcache/journal.c
index 8a54d3b4f517..b49abb246bb6 100644
--- a/drivers/md/bcache/journal.c
+++ b/drivers/md/bcache/journal.c
@@ -622,7 +622,7 @@ static void journal_write_unlocked(struct closure *cl)
                 bio_reset(bio);
                 bio->bi_sector  = PTR_OFFSET(k, i);
                 bio->bi_bdev    = ca->bdev;
-                bio->bi_rw      = REQ_WRITE|REQ_SYNC|REQ_META|REQ_FLUSH;
+                bio->bi_rw      = REQ_WRITE|REQ_SYNC|REQ_META|REQ_FLUSH|REQ_FUA;
                 bio->bi_size    = sectors << 9;
 
                 bio->bi_end_io  = journal_write_endio;
diff --git a/drivers/md/bcache/request.c b/drivers/md/bcache/request.c
index 2f36743ce708..afb9a998a737 100644
--- a/drivers/md/bcache/request.c
+++ b/drivers/md/bcache/request.c
@@ -1053,9 +1053,20 @@ static void request_write(struct cached_dev *dc, struct search *s)
                 trace_bcache_writethrough(s->orig_bio);
                 closure_bio_submit(bio, cl, s->d);
         } else {
-                s->op.cache_bio = bio;
                 trace_bcache_writeback(s->orig_bio);
                 bch_writeback_add(dc, bio_sectors(bio));
+
+                if (s->op.flush_journal) {
+                        /* Also need to send a flush to the backing device */
+                        s->op.cache_bio = bio_clone_bioset(bio, GFP_NOIO,
+                                                           dc->disk.bio_split);
+
+                        bio->bi_size = 0;
+                        bio->bi_vcnt = 0;
+                        closure_bio_submit(bio, cl, s->d);
+                } else {
+                        s->op.cache_bio = bio;
+                }
         }
 out:
         closure_call(&s->op.cl, bch_insert_data, NULL, cl);