Btrfs doesn't reuse devid, thus if we add and delete device in a loop, we can increase devid to higher value, triggering tree checker to give a false alert.
But we still don't want to give up the devid check, so here we compromise by setting a larger devid upper limit, 1<<32. So crazy scripts can't bump devid to that high value easily, while we can still detect obviously wrong devid. Reported-by: Anand Jain <[email protected]> Fixes: ab4ba2e13346 ("btrfs: tree-checker: Verify dev item") Signed-off-by: Qu Wenruo <[email protected]> --- fs/btrfs/tree-checker.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/fs/btrfs/tree-checker.c b/fs/btrfs/tree-checker.c index 43e488f5d063..f9d24f01801e 100644 --- a/fs/btrfs/tree-checker.c +++ b/fs/btrfs/tree-checker.c @@ -686,9 +686,14 @@ 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); + /* + * Btrfs doesn't really reuse devid, thus devid can increase to any + * value, but we don't believe a devid higher than (1<<32) is really + * valid. This could at least detect bitflip at the higher + * 32 bits while still consider high devid valid. + */ + u64 max_devid = (1ULL << 32); if (key->objectid != BTRFS_DEV_ITEMS_OBJECTID) { dev_item_err(leaf, slot, -- 2.23.0
