releases/4.18.6/btrfs-fix-btrfs_write_inode-vs-delayed-iput-deadlock.patch

   1 From 3c4276936f6fbe52884b4ea4e6cc120b890a0f9f Mon Sep 17 00:00:00 2001
   2 From: Josef Bacik <jbacik@fb.com>
   3 Date: Fri, 20 Jul 2018 11:46:10 -0700
   4 Subject: Btrfs: fix btrfs_write_inode vs delayed iput deadlock
   5
   6 From: Josef Bacik <jbacik@fb.com>
   7
   8 commit 3c4276936f6fbe52884b4ea4e6cc120b890a0f9f upstream.
   9
  10 We recently ran into the following deadlock involving
  11 btrfs_write_inode():
  12
  13 [  +0.005066]  __schedule+0x38e/0x8c0
  14 [  +0.007144]  schedule+0x36/0x80
  15 [  +0.006447]  bit_wait+0x11/0x60
  16 [  +0.006446]  __wait_on_bit+0xbe/0x110
  17 [  +0.007487]  ? bit_wait_io+0x60/0x60
  18 [  +0.007319]  __inode_wait_for_writeback+0x96/0xc0
  19 [  +0.009568]  ? autoremove_wake_function+0x40/0x40
  20 [  +0.009565]  inode_wait_for_writeback+0x21/0x30
  21 [  +0.009224]  evict+0xb0/0x190
  22 [  +0.006099]  iput+0x1a8/0x210
  23 [  +0.006103]  btrfs_run_delayed_iputs+0x73/0xc0
  24 [  +0.009047]  btrfs_commit_transaction+0x799/0x8c0
  25 [  +0.009567]  btrfs_write_inode+0x81/0xb0
  26 [  +0.008008]  __writeback_single_inode+0x267/0x320
  27 [  +0.009569]  writeback_sb_inodes+0x25b/0x4e0
  28 [  +0.008702]  wb_writeback+0x102/0x2d0
  29 [  +0.007487]  wb_workfn+0xa4/0x310
  30 [  +0.006794]  ? wb_workfn+0xa4/0x310
  31 [  +0.007143]  process_one_work+0x150/0x410
  32 [  +0.008179]  worker_thread+0x6d/0x520
  33 [  +0.007490]  kthread+0x12c/0x160
  34 [  +0.006620]  ? put_pwq_unlocked+0x80/0x80
  35 [  +0.008185]  ? kthread_park+0xa0/0xa0
  36 [  +0.007484]  ? do_syscall_64+0x53/0x150
  37 [  +0.007837]  ret_from_fork+0x29/0x40
  38
  39 Writeback calls:
  40
  41 btrfs_write_inode
  42   btrfs_commit_transaction
  43     btrfs_run_delayed_iputs
  44
  45 If iput() is called on that same inode, evict() will wait for writeback
  46 forever.
  47
  48 btrfs_write_inode() was originally added way back in 4730a4bc5bf3
  49 ("btrfs_dirty_inode") to support O_SYNC writes. However, ->write_inode()
  50 hasn't been used for O_SYNC since 148f948ba877 ("vfs: Introduce new
  51 helpers for syncing after writing to O_SYNC file or IS_SYNC inode"), so
  52 btrfs_write_inode() is actually unnecessary (and leads to a bunch of
  53 unnecessary commits). Get rid of it, which also gets rid of the
  54 deadlock.
  55
  56 CC: stable@vger.kernel.org # 3.2+
  57 Signed-off-by: Josef Bacik <jbacik@fb.com>
  58 [Omar: new commit message]
  59 Signed-off-by: Omar Sandoval <osandov@fb.com>
  60 Signed-off-by: David Sterba <dsterba@suse.com>
  61 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  62
  63 ---
  64  fs/btrfs/inode.c |   26 --------------------------
  65  fs/btrfs/super.c |    1 -
  66  2 files changed, 27 deletions(-)
  67
  68 --- a/fs/btrfs/inode.c
  69 +++ b/fs/btrfs/inode.c
  70 @@ -6027,32 +6027,6 @@ err:
  71         return ret;
  72  }
  73
  74 -int btrfs_write_inode(struct inode *inode, struct writeback_control *wbc)
  75 -{
  76 -       struct btrfs_root *root = BTRFS_I(inode)->root;
  77 -       struct btrfs_trans_handle *trans;
  78 -       int ret = 0;
  79 -       bool nolock = false;
  80 -
  81 -       if (test_bit(BTRFS_INODE_DUMMY, &BTRFS_I(inode)->runtime_flags))
  82 -               return 0;
  83 -
  84 -       if (btrfs_fs_closing(root->fs_info) &&
  85 -                       btrfs_is_free_space_inode(BTRFS_I(inode)))
  86 -               nolock = true;
  87 -
  88 -       if (wbc->sync_mode == WB_SYNC_ALL) {
  89 -               if (nolock)
  90 -                       trans = btrfs_join_transaction_nolock(root);
  91 -               else
  92 -                       trans = btrfs_join_transaction(root);
  93 -               if (IS_ERR(trans))
  94 -                       return PTR_ERR(trans);
  95 -               ret = btrfs_commit_transaction(trans);
  96 -       }
  97 -       return ret;
  98 -}
  99 -
 100  /*
 101   * This is somewhat expensive, updating the tree every time the
 102   * inode changes.  But, it is most likely to find the inode in cache.
 103 --- a/fs/btrfs/super.c
 104 +++ b/fs/btrfs/super.c
 105 @@ -2331,7 +2331,6 @@ static const struct super_operations btr
 106         .sync_fs        = btrfs_sync_fs,
 107         .show_options   = btrfs_show_options,
 108         .show_devname   = btrfs_show_devname,
 109 -       .write_inode    = btrfs_write_inode,
 110         .alloc_inode    = btrfs_alloc_inode,
 111         .destroy_inode  = btrfs_destroy_inode,
 112         .statfs         = btrfs_statfs,