From f8f91342dc0ee344a9249786e180e7acd00a04ac Mon Sep 17 00:00:00 2001
From: Qu Wenruo <wqu@suse.com>
Date: Thu, 16 Sep 2021 20:43:29 +0800
Subject: [PATCH] btrfs: prevent __btrfs_dump_space_info() to underflow its free space
Git-commit: 0619b7901473c380abc05d45cf9c70bee0707db3
Patch-mainline: v5.15-rc3
References: stable-5.14.9
commit 0619b7901473c380abc05d45cf9c70bee0707db3 upstream.
It's not uncommon where __btrfs_dump_space_info() gets called
under over-commit situations.
In that case free space would underflow as total allocated space is not
enough to handle all the over-committed space.
Such underflow values can sometimes cause confusion for users enabled
enospc_debug mount option, and takes some seconds for developers to
convert the underflow value to signed result.
Just output the free space as s64 to avoid such problem.
Reported-by: Eli V <eliventer@gmail.com>
Link: https://lore.kernel.org/linux-btrfs/CAJtFHUSy4zgyhf-4d9T+KdJp9w=UgzC2A0V=VtmaeEpcGgm1-Q@mail.gmail.com/
Cc: stable@vger.kernel.org # 5.4+
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: Takashi Iwai <tiwai@suse.de>
---
fs/btrfs/space-info.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/fs/btrfs/space-info.c b/fs/btrfs/space-info.c
index 46e8415fa2c5..0842efa6f712 100644
--- a/fs/btrfs/space-info.c
+++ b/fs/btrfs/space-info.c
@@ -414,9 +414,10 @@ static void __btrfs_dump_space_info(struct btrfs_fs_info *fs_info,
{
lockdep_assert_held(&info->lock);
- btrfs_info(fs_info, "space_info %llu has %llu free, is %sfull",
+ /* The free space could be negative in case of overcommit */
+ btrfs_info(fs_info, "space_info %llu has %lld free, is %sfull",
info->flags,
- info->total_bytes - btrfs_space_info_used(info, true),
+ (s64)(info->total_bytes - btrfs_space_info_used(info, true)),
info->full ? "" : "not ");
btrfs_info(fs_info,
"space_info total=%llu, used=%llu, pinned=%llu, reserved=%llu, may_use=%llu, readonly=%llu zone_unusable=%llu",
--
2.26.2