From: Sasha Levin <sashal@kernel.org>
To: linux-kernel@vger.kernel.org, stable@vger.kernel.org
Cc: Filipe Manana <fdmanana@suse.com>,
David Sterba <dsterba@suse.com>, Sasha Levin <sashal@kernel.org>,
linux-btrfs@vger.kernel.org
Subject: [PATCH AUTOSEL 4.20 075/117] Btrfs: fix access to available allocation bits when starting balance
Date: Tue, 8 Jan 2019 14:25:43 -0500 [thread overview]
Message-ID: <20190108192628.121270-75-sashal@kernel.org> (raw)
In-Reply-To: <20190108192628.121270-1-sashal@kernel.org>
From: Filipe Manana <fdmanana@suse.com>
[ Upstream commit 5a8067c0d17feb7579db0476191417b441a8996e ]
The available allocation bits members from struct btrfs_fs_info are
protected by a sequence lock, and when starting balance we access them
incorrectly in two different ways:
1) In the read sequence lock loop at btrfs_balance() we use the values we
read from fs_info->avail_*_alloc_bits and we can immediately do actions
that have side effects and can not be undone (printing a message and
jumping to a label). This is wrong because a retry might be needed, so
our actions must not have side effects and must be repeatable as long
as read_seqretry() returns a non-zero value. In other words, we were
essentially ignoring the sequence lock;
2) Right below the read sequence lock loop, we were reading the values
from avail_metadata_alloc_bits and avail_data_alloc_bits without any
protection from concurrent writers, that is, reading them outside of
the read sequence lock critical section.
So fix this by making sure we only read the available allocation bits
while in a read sequence lock critical section and that what we do in the
critical section is repeatable (has nothing that can not be undone) so
that any eventual retry that is needed is handled properly.
Fixes: de98ced9e743 ("Btrfs: use seqlock to protect fs_info->avail_{data, metadata, system}_alloc_bits")
Fixes: 14506127979a ("btrfs: fix a bogus warning when converting only data or metadata")
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
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>
---
fs/btrfs/volumes.c | 39 +++++++++++++++++++++++----------------
1 file changed, 23 insertions(+), 16 deletions(-)
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 1797a82eb7df..ea5fa9df9405 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -3724,6 +3724,7 @@ int btrfs_balance(struct btrfs_fs_info *fs_info,
int ret;
u64 num_devices;
unsigned seq;
+ bool reducing_integrity;
if (btrfs_fs_closing(fs_info) ||
atomic_read(&fs_info->balance_pause_req) ||
@@ -3803,24 +3804,30 @@ int btrfs_balance(struct btrfs_fs_info *fs_info,
!(bctl->sys.target & allowed)) ||
((bctl->meta.flags & BTRFS_BALANCE_ARGS_CONVERT) &&
(fs_info->avail_metadata_alloc_bits & allowed) &&
- !(bctl->meta.target & allowed))) {
- if (bctl->flags & BTRFS_BALANCE_FORCE) {
- btrfs_info(fs_info,
- "balance: force reducing metadata integrity");
- } else {
- btrfs_err(fs_info,
- "balance: reduces metadata integrity, use --force if you want this");
- ret = -EINVAL;
- goto out;
- }
- }
+ !(bctl->meta.target & allowed)))
+ reducing_integrity = true;
+ else
+ reducing_integrity = false;
+
+ /* if we're not converting, the target field is uninitialized */
+ meta_target = (bctl->meta.flags & BTRFS_BALANCE_ARGS_CONVERT) ?
+ bctl->meta.target : fs_info->avail_metadata_alloc_bits;
+ data_target = (bctl->data.flags & BTRFS_BALANCE_ARGS_CONVERT) ?
+ bctl->data.target : fs_info->avail_data_alloc_bits;
} while (read_seqretry(&fs_info->profiles_lock, seq));
- /* if we're not converting, the target field is uninitialized */
- meta_target = (bctl->meta.flags & BTRFS_BALANCE_ARGS_CONVERT) ?
- bctl->meta.target : fs_info->avail_metadata_alloc_bits;
- data_target = (bctl->data.flags & BTRFS_BALANCE_ARGS_CONVERT) ?
- bctl->data.target : fs_info->avail_data_alloc_bits;
+ if (reducing_integrity) {
+ if (bctl->flags & BTRFS_BALANCE_FORCE) {
+ btrfs_info(fs_info,
+ "balance: force reducing metadata integrity");
+ } else {
+ btrfs_err(fs_info,
+ "balance: reduces metadata integrity, use --force if you want this");
+ ret = -EINVAL;
+ goto out;
+ }
+ }
+
if (btrfs_get_num_tolerated_disk_barrier_failures(meta_target) <
btrfs_get_num_tolerated_disk_barrier_failures(data_target)) {
int meta_index = btrfs_bg_flags_to_raid_index(meta_target);
--
2.19.1
next prev parent reply other threads:[~2019-01-08 19:28 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20190108192628.121270-1-sashal@kernel.org>
2019-01-08 19:25 ` [PATCH AUTOSEL 4.20 071/117] btrfs: volumes: Make sure there is no overlap of dev extents at mount time Sasha Levin
2019-01-08 19:25 ` [PATCH AUTOSEL 4.20 072/117] btrfs: alloc_chunk: fix more DUP stripe size handling Sasha Levin
2019-01-08 23:52 ` Hans van Kranenburg
2019-01-23 14:37 ` Sasha Levin
2019-01-23 15:54 ` Hans van Kranenburg
2019-01-23 17:41 ` David Sterba
2019-01-23 18:18 ` Sasha Levin
2019-01-23 19:32 ` Hans van Kranenburg
2019-11-19 15:23 ` Ben Hutchings
2019-01-08 19:25 ` [PATCH AUTOSEL 4.20 073/117] btrfs: fix use-after-free due to race between replace start and cancel Sasha Levin
2019-01-08 19:25 ` [PATCH AUTOSEL 4.20 074/117] Btrfs: fix deadlock when enabling quotas due to concurrent snapshot creation Sasha Levin
2019-01-08 19:25 ` Sasha Levin [this message]
2019-01-08 19:25 ` [PATCH AUTOSEL 4.20 076/117] btrfs: improve error handling of btrfs_add_link Sasha Levin
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