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Subject[PATCH 4.19 27/71] btrfs: tree-checker: Fix wrong check on max devid
Date
From: Qu Wenruo <wqu@suse.com>

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>
---
fs/btrfs/tree-checker.c | 7 -------
1 file changed, 7 deletions(-)

--- a/fs/btrfs/tree-checker.c
+++ b/fs/btrfs/tree-checker.c
@@ -629,7 +629,6 @@ static int check_dev_item(struct btrfs_f
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_f
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,

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