linux-stable.git/fs/btrfs/dev-replace.c, branch v5.2

btrfs: Ensure replaced device doesn't have pending chunk allocation

2019-05-28T16:54:00+00:00

Recent FITRIM work, namely bbbf7243d62d ("btrfs: combine device update
operations during transaction commit") combined the way certain
operations are recoded in a transaction. As a result an ASSERT was added
in dev_replace_finish to ensure the new code works correctly.
Unfortunately I got reports that it's possible to trigger the assert,
meaning that during a device replace it's possible to have an unfinished
chunk allocation on the source device.

This is supposed to be prevented by the fact that a transaction is
committed before finishing the replace oepration and alter acquiring the
chunk mutex. This is not sufficient since by the time the transaction is
committed and the chunk mutex acquired it's possible to allocate a chunk
depending on the workload being executed on the replaced device. This
bug has been present ever since device replace was introduced but there
was never code which checks for it.

The correct way to fix is to ensure that there is no pending device
modification operation when the chunk mutex is acquire and if there is
repeat transaction commit. Unfortunately it's not possible to just
exclude the source device from btrfs_fs_devices::dev_alloc_list since
this causes ENOSPC to be hit in transaction commit.

Fixing that in another way would need to add special cases to handle the
last writes and forbid new ones. The looped transaction fix is more
obvious, and can be easily backported. The runtime of dev-replace is
long so there's no noticeable delay caused by that.

Reported-by: David Sterba
Fixes: 391cd9df81ac ("Btrfs: fix unprotected alloc list insertion during the finishing procedure of replace")
CC: stable@vger.kernel.org # 4.4+
Signed-off-by: Nikolay Borisov
Reviewed-by: David Sterba
Signed-off-by: David Sterba

btrfs: get fs_info from device in btrfs_rm_dev_replace_free_srcdev

2019-04-29T17:02:48+00:00

We can read fs_info from the device and can drop it from the parameters.

Signed-off-by: David Sterba

btrfs: get fs_info from trans in btrfs_run_dev_replace

2019-04-29T17:02:43+00:00

We can read fs_info from the transaction and can drop it from the
parameters.

Signed-off-by: David Sterba

btrfs: combine device update operations during transaction commit

2019-04-29T17:02:36+00:00

We currently overload the pending_chunks list to handle updating
btrfs_device->commit_bytes used.  We don't actually care about the
extent mapping or even the device mapping for the chunk - we just need
the device, and we can end up processing it multiple times.  The
fs_devices->resized_list does more or less the same thing, but with the
disk size.  They are called consecutively during commit and have more or
less the same purpose.

We can combine the two lists into a single list that attaches to the
transaction and contains a list of devices that need updating.  Since we
always add the device to a list when we change bytes_used or
disk_total_size, there's no harm in copying both values at once.

Signed-off-by: Nikolay Borisov 
Reviewed-by: David Sterba 
Signed-off-by: David Sterba

btrfs: drop the lock on error in btrfs_dev_replace_cancel

2019-02-25T13:13:41+00:00

We should drop the lock on this error path.  This has been found by a
static tool.

The lock needs to be released, it's there to protect access to the
dev_replace members and is not supposed to be left locked. The value of
state that's being switched would need to be artifically changed to an
invalid value so the default: branch is taken.

Fixes: d189dd70e255 ("btrfs: fix use-after-free due to race between replace start and cancel")
CC: stable@vger.kernel.org # 5.0+
Reviewed-by: Anand Jain 
Signed-off-by: Dan Carpenter 
Reviewed-by: David Sterba 
Signed-off-by: David Sterba

btrfs: merge btrfs_find_device and find_device

2019-02-25T13:13:24+00:00

Both btrfs_find_device() and find_device() does the same thing except
that the latter does not take the seed device onto account in the device
scanning context. We can merge them.

Signed-off-by: Anand Jain 
Reviewed-by: David Sterba 
Signed-off-by: David Sterba

btrfs: refactor btrfs_find_device() take fs_devices as argument

2019-02-25T13:13:23+00:00

btrfs_find_device() accepts fs_info as an argument and retrieves
fs_devices from fs_info.

Instead use fs_devices, so that this function can be used in non-mount
(during device scanning) context as well.

Signed-off-by: Anand Jain 
Reviewed-by: David Sterba 
Signed-off-by: David Sterba

btrfs: Fix typos in comments and strings

2018-12-17T13:51:50+00:00

The typos accumulate over time so once in a while time they get fixed in
a large patch.

Signed-off-by: Andrea Gelmini 
Reviewed-by: David Sterba 
Signed-off-by: David Sterba

btrfs: dev-replace: open code trivial locking helpers

2018-12-17T13:51:45+00:00

The dev-replace locking functions are now trivial wrappers around rw
semaphore that can be used directly everywhere. No functional change.

Signed-off-by: David Sterba

btrfs: dev-replace: remove custom read/write blocking scheme

2018-12-17T13:51:45+00:00

After the rw semaphore has been added, the custom blocking using
::blocking_readers and ::read_lock_wq is redundant.

The blocking logic in __btrfs_map_block is replaced by extending the
time the semaphore is held, that has the same blocking effect on writes
as the previous custom scheme that waited until ::blocking_readers was
zero.

Signed-off-by: David Sterba