dm writecache: do direct write if the cache is full

If the cache device is full, we do a direct write to the origin device.
Note that we must not do it if the written block is already in the cache.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

diff --git a/drivers/md/dm-writecache.c b/drivers/md/dm-writecache.c
index a09bdc0..dc1e10c 100644 (file)
--- a/drivers/md/dm-writecache.c
+++ b/drivers/md/dm-writecache.c
@@ -1194,6 +1194,7 @@ read_next_block:
                }
        } else {
                do {
+                       bool found_entry = false;
                        if (writecache_has_error(wc))
                                goto unlock_error;
                        e = writecache_find_entry(wc, bio->bi_iter.bi_sector, 0);
@@ -1204,9 +1205,21 @@ read_next_block:
                                        wc->overwrote_committed = true;
                                        goto bio_copy;
                                }
+                               found_entry = true;
                        }
                        e = writecache_pop_from_freelist(wc, (sector_t)-1);
                        if (unlikely(!e)) {
+                               if (!found_entry) {
+                                       e = writecache_find_entry(wc, bio->bi_iter.bi_sector, WFE_RETURN_FOLLOWING);
+                                       if (e) {
+                                               sector_t next_boundary = read_original_sector(wc, e) - bio->bi_iter.bi_sector;
+                                               BUG_ON(!next_boundary);
+                                               if (next_boundary < bio->bi_iter.bi_size >> SECTOR_SHIFT) {
+                                                       dm_accept_partial_bio(bio, next_boundary);
+                                               }
+                                       }
+                                       goto unlock_remap_origin;
+                               }
                                writecache_wait_on_freelist(wc);
                                continue;
                        }