1. 28 Aug, 2020 13 commits
  2. 26 Aug, 2020 2 commits
  3. 21 Aug, 2020 23 commits
  4. 18 Aug, 2020 2 commits
    • Dmitry Monakhov's avatar
      bfq: fix blkio cgroup leakage v4 · 2de791ab
      Dmitry Monakhov authored
      Changes from v1:
          - update commit description with proper ref-accounting justification
      
      commit db37a34c ("block, bfq: get a ref to a group when adding it to a service tree")
      introduce leak forbfq_group and blkcg_gq objects because of get/put
      imbalance.
      In fact whole idea of original commit is wrong because bfq_group entity
      can not dissapear under us because it is referenced by child bfq_queue's
      entities from here:
       -> bfq_init_entity()
          ->bfqg_and_blkg_get(bfqg);
          ->entity->parent = bfqg->my_entity
      
       -> bfq_put_queue(bfqq)
          FINAL_PUT
          ->bfqg_and_blkg_put(bfqq_group(bfqq))
          ->kmem_cache_free(bfq_pool, bfqq);
      
      So parent entity can not disappear while child entity is in tree,
      and child entities already has proper protection.
      This patch revert commit db37a34c ("block, bfq: get a ref to a group when adding it to a service tree")
      
      bfq_group leak trace caused by bad commit:
      -> blkg_alloc
         -> bfq_pq_alloc
           -> bfqg_get (+1)
      ->bfq_activate_bfqq
        ->bfq_activate_requeue_entity
          -> __bfq_activate_entity
             ->bfq_get_entity
               ->bfqg_and_blkg_get (+1)  <==== : Note1
      ->bfq_del_bfqq_busy
        ->bfq_deactivate_entity+0x53/0xc0 [bfq]
          ->__bfq_deactivate_entity+0x1b8/0x210 [bfq]
            -> bfq_forget_entity(is_in_service = true)
      	 entity->on_st_or_in_serv = false   <=== :Note2
      	 if (is_in_service)
      	     return;  ==> do not touch reference
      -> blkcg_css_offline
       -> blkcg_destroy_blkgs
        -> blkg_destroy
         -> bfq_pd_offline
          -> __bfq_deactivate_entity
               if (!entity->on_st_or_in_serv) /* true, because (Note2)
      		return false;
       -> bfq_pd_free
          -> bfqg_put() (-1, byt bfqg->ref == 2) because of (Note2)
      So bfq_group and blkcg_gq  will leak forever, see test-case below.
      
      ##TESTCASE_BEGIN:
      #!/bin/bash
      
      max_iters=${1:-100}
      #prep cgroup mounts
      mount -t tmpfs cgroup_root /sys/fs/cgroup
      mkdir /sys/fs/cgroup/blkio
      mount -t cgroup -o blkio none /sys/fs/cgroup/blkio
      
      # Prepare blkdev
      grep blkio /proc/cgroups
      truncate -s 1M img
      losetup /dev/loop0 img
      echo bfq > /sys/block/loop0/queue/scheduler
      
      grep blkio /proc/cgroups
      for ((i=0;i<max_iters;i++))
      do
          mkdir -p /sys/fs/cgroup/blkio/a
          echo 0 > /sys/fs/cgroup/blkio/a/cgroup.procs
          dd if=/dev/loop0 bs=4k count=1 of=/dev/null iflag=direct 2> /dev/null
          echo 0 > /sys/fs/cgroup/blkio/cgroup.procs
          rmdir /sys/fs/cgroup/blkio/a
          grep blkio /proc/cgroups
      done
      ##TESTCASE_END:
      
      Fixes: db37a34c ("block, bfq: get a ref to a group when adding it to a service tree")
      Tested-by: default avatarOleksandr Natalenko <oleksandr@natalenko.name>
      Signed-off-by: default avatarDmitry Monakhov <dmtrmonakhov@yandex-team.ru>
      Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
      2de791ab
    • Matthew Wilcox (Oracle)'s avatar
      block: Fix page_is_mergeable() for compound pages · d8166519
      Matthew Wilcox (Oracle) authored
      If we pass in an offset which is larger than PAGE_SIZE, then
      page_is_mergeable() thinks it's not mergeable with the previous bio_vec,
      leading to a large number of bio_vecs being used.  Use a slightly more
      obvious test that the two pages are compatible with each other.
      
      Fixes: 52d52d1c ("block: only allow contiguous page structs in a bio_vec")
      Signed-off-by: default avatarMatthew Wilcox (Oracle) <willy@infradead.org>
      Reviewed-by: default avatarMing Lei <ming.lei@redhat.com>
      Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
      d8166519