Commit 8bb177d1 authored Aug 28, 2019 by Qu Wenruo Committed by David Sterba Oct 25, 2019

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



[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: ab4ba2e1 ("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>

parent c17add7a

fs/btrfs/tree-checker.c

+0 −8

Original line number	Diff line number	Diff line
		@@ -686,9 +686,7 @@ static void dev_item_err(const struct extent_buffer *eb, int slot,
		static int check_dev_item(struct extent_buffer *leaf,
		struct btrfs_key *key, int slot)
		{
		struct btrfs_fs_info *fs_info = leaf->fs_info;
		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(leaf, slot,
		@@ -696,12 +694,6 @@ static int check_dev_item(struct extent_buffer *leaf,
		key->objectid, BTRFS_DEV_ITEMS_OBJECTID);
		return -EUCLEAN;
		}
		if (key->offset > max_devid) {
		dev_item_err(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(leaf, slot,

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