btrfs: fix space cache inconsistency after error loading it from disk

stable inclusion
from stable-v5.10.181
commit 84fdaaf0d76e713d6d2e22f73358667975cfa9fa
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I8GJZJ

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=84fdaaf0d76e713d6d2e22f73358667975cfa9fa



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[ Upstream commit 0004ff15 ]

When loading a free space cache from disk, at __load_free_space_cache(),
if we fail to insert a bitmap entry, we still increment the number of
total bitmaps in the btrfs_free_space_ctl structure, which is incorrect
since we failed to add the bitmap entry. On error we then empty the
cache by calling __btrfs_remove_free_space_cache(), which will result
in getting the total bitmaps counter set to 1.

A failure to load a free space cache is not critical, so if a failure
happens we just rebuild the cache by scanning the extent tree, which
happens at block-group.c:caching_thread(). Yet the failure will result
in having the total bitmaps of the btrfs_free_space_ctl always bigger
by 1 then the number of bitmap entries we have. So fix this by having
the total bitmaps counter be incremented only if we successfully added
the bitmap entry.

Fixes: a67509c3 ("Btrfs: add a io_ctl struct and helpers for dealing with the space cache")
Reviewed-by: Anand Jain <anand.jain@oracle.com>
CC: stable@vger.kernel.org # 4.4+
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: sanglipeng <sanglipeng1@jd.com>