btrfs: tree-checker: Fix wrong check on max devid

commit 8bb177d18f114358a57d8ae7e206861b48b8b4de upstream.

[BUG]
The following script will cause false alert on devid check.
  #!/bin/bash

  dev1=/dev/test/test
  dev2=/dev/test/scratch1
  mnt=/mnt/btrfs

  umount $dev1 &> /dev/null
  umount $dev2 &> /dev/null
  umount $mnt &> /dev/null

  mkfs.btrfs -f $dev1

  mount $dev1 $mnt

  _fail()
  {
          echo "!!! FAILED !!!"
          exit 1
  }

  for ((i = 0; i < 4096; i++)); do
          btrfs dev add -f $dev2 $mnt || _fail
          btrfs dev del $dev1 $mnt || _fail
          dev_tmp=$dev1
          dev1=$dev2
          dev2=$dev_tmp
  done

[CAUSE]
Tree-checker uses BTRFS_MAX_DEVS() and BTRFS_MAX_DEVS_SYS_CHUNK() as
upper limit for devid.  But we can have devid holes just like above
script.

So the check for devid is incorrect and could cause false alert.

[FIX]
Just remove the whole devid check.  We don't have any hard requirement
for devid assignment.

Furthermore, even devid could get corrupted by a bitflip, we still have
dev extents verification at mount time, so corrupted data won't sneak
in.

This fixes fstests btrfs/194.

Reported-by: Anand Jain <anand.jain@oracle.com>
Fixes: ab4ba2e13346 ("btrfs: tree-checker: Verify dev item")
CC: stable@vger.kernel.org # 5.2+
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
[bwh: Backported to 4.19: adjust context]
Signed-off-by: Ben Hutchings <ben.hutchings@codethink.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/fs/btrfs/tree-checker.c b/fs/btrfs/tree-checker.c
index b5e7caeb28a2892a717d4f16e529db1e8d547c94..a0222e6a11c542308ccfa562c64d26a7c66ef9b5 100644 (file)
--- a/fs/btrfs/tree-checker.c
+++ b/fs/btrfs/tree-checker.c
@@ -629,7 +629,6 @@ static int check_dev_item(struct btrfs_fs_info *fs_info,
                          struct btrfs_key *key, int slot)
 {
        struct btrfs_dev_item *ditem;
-       u64 max_devid = max(BTRFS_MAX_DEVS(fs_info), BTRFS_MAX_DEVS_SYS_CHUNK);
 
        if (key->objectid != BTRFS_DEV_ITEMS_OBJECTID) {
                dev_item_err(fs_info, leaf, slot,
@@ -637,12 +636,6 @@ static int check_dev_item(struct btrfs_fs_info *fs_info,
                             key->objectid, BTRFS_DEV_ITEMS_OBJECTID);
                return -EUCLEAN;
        }
-       if (key->offset > max_devid) {
-               dev_item_err(fs_info, leaf, slot,
-                            "invalid devid: has=%llu expect=[0, %llu]",
-                            key->offset, max_devid);
-               return -EUCLEAN;
-       }
        ditem = btrfs_item_ptr(leaf, slot, struct btrfs_dev_item);
        if (btrfs_device_id(leaf, ditem) != key->offset) {
                dev_item_err(fs_info, leaf, slot,