[BUG]
For the following operation, qgroup is guaranteed to be screwed up due
to snapshot adding to a new qgroup:
# mkfs.btrfs -f $dev
# mount $dev $mnt
# btrfs qgroup en $mnt
# btrfs subv create $mnt/src
# xfs_io -f -c "pwrite 0 1m" $mnt/src/file
# sync
# btrfs qgroup create 1/0 $mnt/src
# btrfs subv snapshot -i 1/0 $mnt/src $mnt/snapshot
# btrfs qgroup show -prce $mnt/src
qgroupid rfer excl max_rfer max_excl parent child
-------- ---- ---- -------- -------- ------ -----
0/5 16.00KiB 16.00KiB none none --- ---
0/257 1.02MiB 16.00KiB none none --- ---
0/258 1.02MiB 16.00KiB none none 1/0 ---
1/0 0.00B 0.00B none none --- 0/258
^^^^^^^^^^^^^^^^^^^^
[CAUSE]
The problem is in btrfs_qgroup_inherit(), we don't have good enough
check to determine if the new relation would break the existing
accounting.
Unlike btrfs_add_qgroup_relation(), which has proper check to determine
if we can do quick update without a rescan, in btrfs_qgroup_inherit() we
can even assign a snapshot to multiple qgroups.
[FIX]
Fix it by manually marking qgroup inconsistent for snapshot inheritance.
For subvolume creation, since all its extents are exclusively owned, we
don't need to rescan.
In theory, we should call relation check like quick_update_accounting()
when doing qgroup inheritance and inform user about qgroup accounting
inconsistency.
But we don't have good mechanism to relay that back to the user in the
snapshot creation context, thus we can only silently mark the qgroup
inconsistent.
Anyway, user shouldn't use qgroup inheritance during snapshot creation,
and should add qgroup relationship after snapshot creation by 'btrfs
qgroup assign', which has a much better UI to inform user about qgroup
inconsistent and kick in rescan automatically.
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
There are a few different ways to free roots, either you allocated them
yourself and you just do
free_extent_buffer(root->node);
free_extent_buffer(root->commit_node);
btrfs_put_root(root);
Which is the pattern for log roots. Or for snapshots/subvolumes that
are being dropped you simply call btrfs_free_fs_root() which does all
the cleanup for you.
Unify this all into btrfs_put_root(), so that we don't free up things
associated with the root until the last reference is dropped. This
makes the root freeing code much more significant.
The only caveat is at close_ctree() time we have to free the extent
buffers for all of our main roots (extent_root, chunk_root, etc) because
we have to drop the btree_inode and we'll run into issues if we hold
onto those nodes until ->kill_sb() time. This will be addressed in the
future when we kill the btree_inode.
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
After the previous patch, qgroup_rescan_running is protected by
btrfs_fs_info::qgroup_rescan_lock, thus no need for the extra spinlock.
Suggested-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
[BUG]
There are some reports about btrfs wait forever to unmount itself, with
the following call trace:
INFO: task umount:4631 blocked for more than 491 seconds.
Tainted: G X 5.3.8-2-default #1
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
umount D 0 4631 3337 0x00000000
Call Trace:
([<00000000174adf7a>] __schedule+0x342/0x748)
[<00000000174ae3ca>] schedule+0x4a/0xd8
[<00000000174b1f08>] schedule_timeout+0x218/0x420
[<00000000174af10c>] wait_for_common+0x104/0x1d8
[<000003ff804d6994>] btrfs_qgroup_wait_for_completion+0x84/0xb0 [btrfs]
[<000003ff8044a616>] close_ctree+0x4e/0x380 [btrfs]
[<0000000016fa3136>] generic_shutdown_super+0x8e/0x158
[<0000000016fa34d6>] kill_anon_super+0x26/0x40
[<000003ff8041ba88>] btrfs_kill_super+0x28/0xc8 [btrfs]
[<0000000016fa39f8>] deactivate_locked_super+0x68/0x98
[<0000000016fcb198>] cleanup_mnt+0xc0/0x140
[<0000000016d6a846>] task_work_run+0xc6/0x110
[<0000000016d04f76>] do_notify_resume+0xae/0xb8
[<00000000174b30ae>] system_call+0xe2/0x2c8
[CAUSE]
The problem happens when we have called qgroup_rescan_init(), but
not queued the worker. It can be caused mostly by error handling.
Qgroup ioctl thread | Unmount thread
----------------------------------------+-----------------------------------
|
btrfs_qgroup_rescan() |
|- qgroup_rescan_init() |
| |- qgroup_rescan_running = true; |
| |
|- trans = btrfs_join_transaction() |
| Some error happened |
| |
|- btrfs_qgroup_rescan() returns error |
But qgroup_rescan_running == true; |
| close_ctree()
| |- btrfs_qgroup_wait_for_completion()
| |- running == true;
| |- wait_for_completion();
btrfs_qgroup_rescan_worker is never queued, thus no one is going to wake
up close_ctree() and we get a deadlock.
All involved qgroup_rescan_init() callers are:
- btrfs_qgroup_rescan()
The example above. It's possible to trigger the deadlock when error
happened.
- btrfs_quota_enable()
Not possible. Just after qgroup_rescan_init() we queue the work.
- btrfs_read_qgroup_config()
It's possible to trigger the deadlock. It only init the work, the
work queueing happens in btrfs_qgroup_rescan_resume().
Thus if error happened in between, deadlock is possible.
We shouldn't set fs_info->qgroup_rescan_running just in
qgroup_rescan_init(), as at that stage we haven't yet queued qgroup
rescan worker to run.
[FIX]
Set qgroup_rescan_running before queueing the work, so that we ensure
the rescan work is queued when we wait for it.
Fixes: 8d9eddad19 ("Btrfs: fix qgroup rescan worker initialization")
Signed-off-by: Jeff Mahoney <jeffm@suse.com>
[ Change subject and cause analyse, use a smaller fix ]
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
We are now using these for all roots, rename them to btrfs_put_root()
and btrfs_grab_root();
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
If we are going to track leaked roots we need to free them all the same
way, so don't kfree() roots directly, use btrfs_put_fs_root.
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
We clean up the delayed references when we abort a transaction but we
leave the pending qgroup extent records behind, leaking memory.
This patch destroys the extent records when we destroy the delayed refs
and makes sure ensure they're gone before releasing the transaction.
Fixes: 3368d001ba ("btrfs: qgroup: Record possible quota-related extent for qgroup.")
CC: stable@vger.kernel.org # 4.4+
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Jeff Mahoney <jeffm@suse.com>
[ Rebased to latest upstream, remove to_qgroup() helper, use
rbtree_postorder_for_each_entry_safe() wrapper ]
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
[PROBLEM]
qgroup create/remove code is currently returning EINVAL when the user
tries to create a qgroup on a subvolume without quota enabled. EINVAL is
already being used for too many error scenarios so that is hard to
depict what is the problem.
[FIX]
Currently scrub and balance code return -ENOTCONN when the user tries to
cancel/pause and no scrub or balance is currently running for the
desired subvolume. Do the same here by returning -ENOTCONN when a user
tries to create/delete/assing/list a qgroup on a subvolume without quota
enabled.
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Marcos Paulo de Souza <mpdesouza@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Remove some variables that are set only to be checked later, and never
used.
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Marcos Paulo de Souza <mpdesouza@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
When running xfstests on the current btrfs I get the following splat from
kmemleak:
unreferenced object 0xffff88821b2404e0 (size 32):
comm "kworker/u4:7", pid 26663, jiffies 4295283698 (age 8.776s)
hex dump (first 32 bytes):
01 00 00 00 00 00 00 00 10 ff fd 26 82 88 ff ff ...........&....
10 ff fd 26 82 88 ff ff 20 ff fd 26 82 88 ff ff ...&.... ..&....
backtrace:
[<00000000f94fd43f>] ulist_alloc+0x25/0x60 [btrfs]
[<00000000fd023d99>] btrfs_find_all_roots_safe+0x41/0x100 [btrfs]
[<000000008f17bd32>] btrfs_find_all_roots+0x52/0x70 [btrfs]
[<00000000b7660afb>] btrfs_qgroup_rescan_worker+0x343/0x680 [btrfs]
[<0000000058e66778>] btrfs_work_helper+0xac/0x1e0 [btrfs]
[<00000000f0188930>] process_one_work+0x1cf/0x350
[<00000000af5f2f8e>] worker_thread+0x28/0x3c0
[<00000000b55a1add>] kthread+0x109/0x120
[<00000000f88cbd17>] ret_from_fork+0x35/0x40
This corresponds to:
(gdb) l *(btrfs_find_all_roots_safe+0x41)
0x8d7e1 is in btrfs_find_all_roots_safe (fs/btrfs/backref.c:1413).
1408
1409 tmp = ulist_alloc(GFP_NOFS);
1410 if (!tmp)
1411 return -ENOMEM;
1412 *roots = ulist_alloc(GFP_NOFS);
1413 if (!*roots) {
1414 ulist_free(tmp);
1415 return -ENOMEM;
1416 }
1417
Following the lifetime of the allocated 'roots' ulist, it gets freed
again in btrfs_qgroup_account_extent().
But this does not happen if the function is called with the
'BTRFS_FS_QUOTA_ENABLED' flag cleared, then btrfs_qgroup_account_extent()
does a short leave and directly returns.
Instead of directly returning we should jump to the 'out_free' in order to
free all resources as expected.
CC: stable@vger.kernel.org # 4.14+
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
[ add comment ]
Signed-off-by: David Sterba <dsterba@suse.com>
The branch of qgroup_rescan_init which is executed from the mount
path prints wrong errors messages. The textual print out in case
BTRFS_QGROUP_STATUS_FLAG_RESCAN/BTRFS_QGROUP_STATUS_FLAG_ON are not
set are transposed. Fix it by exchanging their place.
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
The type name is misleading, a single entry is named 'cache' while this
normally means a collection of objects. Rename that everywhere. Also the
identifier was quite long, making function prototypes harder to format.
Suggested-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
The helper is trivial and we can understand what the atomic_inc on
something named refs does.
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Commit 9e0af23764 ("Btrfs: fix task hang under heavy compressed
write") worked around the issue that a recycled work item could get a
false dependency on the original work item due to how the workqueue code
guarantees non-reentrancy. It did so by giving different work functions
to different types of work.
However, the fixes in the previous few patches are more complete, as
they prevent a work item from being recycled at all (except for a tiny
window that the kernel workqueue code handles for us). This obsoletes
the previous fix, so we don't need the unique helpers for correctness.
The only other reason to keep them would be so they show up in stack
traces, but they always seem to be optimized to a tail call, so they
don't show up anyways. So, let's just get rid of the extra indirection.
While we're here, rename normal_work_helper() to the more informative
btrfs_work_helper().
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Omar Sandoval <osandov@fb.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Commit fc97fab0ea ("btrfs: Replace fs_info->qgroup_rescan_worker
workqueue with btrfs_workqueue.") converted qgroup_rescan_work to be
initialized with btrfs_init_work(), but it left behind an unnecessary
memset(). Get rid of the memset().
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: Omar Sandoval <osandov@fb.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
[BUG]
For btrfs:qgroup_meta_reserve event, the trace event can output garbage:
qgroup_meta_reserve: 9c7f6acc-b342-4037-bc47-7f6e4d2232d7: refroot=5(FS_TREE) type=DATA diff=2
The diff should always be alinged to sector size (4k), so there is
definitely something wrong.
[CAUSE]
For the wrong @diff, it's caused by wrong parameter order.
The correct parameters are:
struct btrfs_root, s64 diff, int type.
However the parameters used are:
struct btrfs_root, int type, s64 diff.
Fixes: 4ee0d8832c ("btrfs: qgroup: Update trace events for metadata reservation")
CC: stable@vger.kernel.org # 4.19+
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
[BUG]
The following script can cause btrfs qgroup data space leak:
mkfs.btrfs -f $dev
mount $dev -o nospace_cache $mnt
btrfs subv create $mnt/subv
btrfs quota en $mnt
btrfs quota rescan -w $mnt
btrfs qgroup limit 128m $mnt/subv
for (( i = 0; i < 3; i++)); do
# Create 3 64M holes for latter fallocate to fail
truncate -s 192m $mnt/subv/file
xfs_io -c "pwrite 64m 4k" $mnt/subv/file > /dev/null
xfs_io -c "pwrite 128m 4k" $mnt/subv/file > /dev/null
sync
# it's supposed to fail, and each failure will leak at least 64M
# data space
xfs_io -f -c "falloc 0 192m" $mnt/subv/file &> /dev/null
rm $mnt/subv/file
sync
done
# Shouldn't fail after we removed the file
xfs_io -f -c "falloc 0 64m" $mnt/subv/file
[CAUSE]
Btrfs qgroup data reserve code allow multiple reservations to happen on
a single extent_changeset:
E.g:
btrfs_qgroup_reserve_data(inode, &data_reserved, 0, SZ_1M);
btrfs_qgroup_reserve_data(inode, &data_reserved, SZ_1M, SZ_2M);
btrfs_qgroup_reserve_data(inode, &data_reserved, 0, SZ_4M);
Btrfs qgroup code has its internal tracking to make sure we don't
double-reserve in above example.
The only pattern utilizing this feature is in the main while loop of
btrfs_fallocate() function.
However btrfs_qgroup_reserve_data()'s error handling has a bug in that
on error it clears all ranges in the io_tree with EXTENT_QGROUP_RESERVED
flag but doesn't free previously reserved bytes.
This bug has a two fold effect:
- Clearing EXTENT_QGROUP_RESERVED ranges
This is the correct behavior, but it prevents
btrfs_qgroup_check_reserved_leak() to catch the leakage as the
detector is purely EXTENT_QGROUP_RESERVED flag based.
- Leak the previously reserved data bytes.
The bug manifests when N calls to btrfs_qgroup_reserve_data are made and
the last one fails, leaking space reserved in the previous ones.
[FIX]
Also free previously reserved data bytes when btrfs_qgroup_reserve_data
fails.
Fixes: 5247255370 ("btrfs: qgroup: Introduce btrfs_qgroup_reserve_data function")
CC: stable@vger.kernel.org # 4.4+
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
[BUG]
Under the following case with qgroup enabled, if some error happened
after we have reserved delalloc space, then in error handling path, we
could cause qgroup data space leakage:
From btrfs_truncate_block() in inode.c:
ret = btrfs_delalloc_reserve_space(inode, &data_reserved,
block_start, blocksize);
if (ret)
goto out;
again:
page = find_or_create_page(mapping, index, mask);
if (!page) {
btrfs_delalloc_release_space(inode, data_reserved,
block_start, blocksize, true);
btrfs_delalloc_release_extents(BTRFS_I(inode), blocksize, true);
ret = -ENOMEM;
goto out;
}
[CAUSE]
In the above case, btrfs_delalloc_reserve_space() will call
btrfs_qgroup_reserve_data() and mark the io_tree range with
EXTENT_QGROUP_RESERVED flag.
In the error handling path, we have the following call stack:
btrfs_delalloc_release_space()
|- btrfs_free_reserved_data_space()
|- btrsf_qgroup_free_data()
|- __btrfs_qgroup_release_data(reserved=@reserved, free=1)
|- qgroup_free_reserved_data(reserved=@reserved)
|- clear_record_extent_bits();
|- freed += changeset.bytes_changed;
However due to a completion bug, qgroup_free_reserved_data() will clear
EXTENT_QGROUP_RESERVED flag in BTRFS_I(inode)->io_failure_tree, other
than the correct BTRFS_I(inode)->io_tree.
Since io_failure_tree is never marked with that flag,
btrfs_qgroup_free_data() will not free any data reserved space at all,
causing a leakage.
This type of error handling can only be triggered by errors outside of
qgroup code. So EDQUOT error from qgroup can't trigger it.
[FIX]
Fix the wrong target io_tree.
Reported-by: Josef Bacik <josef@toxicpanda.com>
Fixes: bc42bda223 ("btrfs: qgroup: Fix qgroup reserved space underflow by only freeing reserved ranges")
CC: stable@vger.kernel.org # 4.14+
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
There is a race between setting up a qgroup rescan worker and completing
a qgroup rescan worker that can lead to callers of the qgroup rescan wait
ioctl to either not wait for the rescan worker to complete or to hang
forever due to missing wake ups. The following diagram shows a sequence
of steps that illustrates the race.
CPU 1 CPU 2 CPU 3
btrfs_ioctl_quota_rescan()
btrfs_qgroup_rescan()
qgroup_rescan_init()
mutex_lock(&fs_info->qgroup_rescan_lock)
spin_lock(&fs_info->qgroup_lock)
fs_info->qgroup_flags |=
BTRFS_QGROUP_STATUS_FLAG_RESCAN
init_completion(
&fs_info->qgroup_rescan_completion)
fs_info->qgroup_rescan_running = true
mutex_unlock(&fs_info->qgroup_rescan_lock)
spin_unlock(&fs_info->qgroup_lock)
btrfs_init_work()
--> starts the worker
btrfs_qgroup_rescan_worker()
mutex_lock(&fs_info->qgroup_rescan_lock)
fs_info->qgroup_flags &=
~BTRFS_QGROUP_STATUS_FLAG_RESCAN
mutex_unlock(&fs_info->qgroup_rescan_lock)
starts transaction, updates qgroup status
item, etc
btrfs_ioctl_quota_rescan()
btrfs_qgroup_rescan()
qgroup_rescan_init()
mutex_lock(&fs_info->qgroup_rescan_lock)
spin_lock(&fs_info->qgroup_lock)
fs_info->qgroup_flags |=
BTRFS_QGROUP_STATUS_FLAG_RESCAN
init_completion(
&fs_info->qgroup_rescan_completion)
fs_info->qgroup_rescan_running = true
mutex_unlock(&fs_info->qgroup_rescan_lock)
spin_unlock(&fs_info->qgroup_lock)
btrfs_init_work()
--> starts another worker
mutex_lock(&fs_info->qgroup_rescan_lock)
fs_info->qgroup_rescan_running = false
mutex_unlock(&fs_info->qgroup_rescan_lock)
complete_all(&fs_info->qgroup_rescan_completion)
Before the rescan worker started by the task at CPU 3 completes, if
another task calls btrfs_ioctl_quota_rescan(), it will get -EINPROGRESS
because the flag BTRFS_QGROUP_STATUS_FLAG_RESCAN is set at
fs_info->qgroup_flags, which is expected and correct behaviour.
However if other task calls btrfs_ioctl_quota_rescan_wait() before the
rescan worker started by the task at CPU 3 completes, it will return
immediately without waiting for the new rescan worker to complete,
because fs_info->qgroup_rescan_running is set to false by CPU 2.
This race is making test case btrfs/171 (from fstests) to fail often:
btrfs/171 9s ... - output mismatch (see /home/fdmanana/git/hub/xfstests/results//btrfs/171.out.bad)
--- tests/btrfs/171.out 2018-09-16 21:30:48.505104287 +0100
+++ /home/fdmanana/git/hub/xfstests/results//btrfs/171.out.bad 2019-09-19 02:01:36.938486039 +0100
@@ -1,2 +1,3 @@
QA output created by 171
+ERROR: quota rescan failed: Operation now in progress
Silence is golden
...
(Run 'diff -u /home/fdmanana/git/hub/xfstests/tests/btrfs/171.out /home/fdmanana/git/hub/xfstests/results//btrfs/171.out.bad' to see the entire diff)
That is because the test calls the btrfs-progs commands "qgroup quota
rescan -w", "qgroup assign" and "qgroup remove" in a sequence that makes
calls to the rescan start ioctl fail with -EINPROGRESS (note the "btrfs"
commands 'qgroup assign' and 'qgroup remove' often call the rescan start
ioctl after calling the qgroup assign ioctl,
btrfs_ioctl_qgroup_assign()), since previous waits didn't actually wait
for a rescan worker to complete.
Another problem the race can cause is missing wake ups for waiters,
since the call to complete_all() happens outside a critical section and
after clearing the flag BTRFS_QGROUP_STATUS_FLAG_RESCAN. In the sequence
diagram above, if we have a waiter for the first rescan task (executed
by CPU 2), then fs_info->qgroup_rescan_completion.wait is not empty, and
if after the rescan worker clears BTRFS_QGROUP_STATUS_FLAG_RESCAN and
before it calls complete_all() against
fs_info->qgroup_rescan_completion, the task at CPU 3 calls
init_completion() against fs_info->qgroup_rescan_completion which
re-initilizes its wait queue to an empty queue, therefore causing the
rescan worker at CPU 2 to call complete_all() against an empty queue,
never waking up the task waiting for that rescan worker.
Fix this by clearing BTRFS_QGROUP_STATUS_FLAG_RESCAN and setting
fs_info->qgroup_rescan_running to false in the same critical section,
delimited by the mutex fs_info->qgroup_rescan_lock, as well as doing the
call to complete_all() in that same critical section. This gives the
protection needed to avoid rescan wait ioctl callers not waiting for a
running rescan worker and the lost wake ups problem, since setting that
rescan flag and boolean as well as initializing the wait queue is done
already in a critical section delimited by that mutex (at
qgroup_rescan_init()).
Fixes: 57254b6ebc ("Btrfs: add ioctl to wait for qgroup rescan completion")
Fixes: d2c609b834 ("btrfs: properly track when rescan worker is running")
CC: stable@vger.kernel.org # 4.4+
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
When we try to delete qgroups, we're pretty cautious, we make sure both
qgroups exist and there is a relationship between them, then try to
delete the relation.
This behavior is OK, but the problem is we need to two relation items,
and if we failed the first item deletion, we error out, leaving the
other relation item in qgroup tree.
Sometimes the error from del_qgroup_relation_item() could just be
-ENOENT, thus we can ignore that error and continue without any problem.
Further more, such cautious behavior makes qgroup relation deletion
impossible for orphan relation items.
This patch will enhance __del_qgroup_relation():
- If both qgroups and their relation items exist
Go the regular deletion routine and update their accounting if needed.
- If any qgroup or relation item doesn't exist
Then we still try to delete the orphan items anyway, but don't trigger
the accounting update.
By this, we try our best to remove relation items, and can handle orphan
relation items properly, while still keep the existing behavior for good
qgroup tree.
Reported-by: Andrei Borzenkov <arvidjaar@gmail.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This is prep work for moving all of the block group cache code into its
own file.
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
[ minor comment updates ]
Signed-off-by: David Sterba <dsterba@suse.com>
[BUG]
Lockdep will report the following circular locking dependency:
WARNING: possible circular locking dependency detected
5.2.0-rc2-custom #24 Tainted: G O
------------------------------------------------------
btrfs/8631 is trying to acquire lock:
000000002536438c (&fs_info->qgroup_ioctl_lock#2){+.+.}, at: btrfs_qgroup_inherit+0x40/0x620 [btrfs]
but task is already holding lock:
000000003d52cc23 (&fs_info->tree_log_mutex){+.+.}, at: create_pending_snapshot+0x8b6/0xe60 [btrfs]
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #2 (&fs_info->tree_log_mutex){+.+.}:
__mutex_lock+0x76/0x940
mutex_lock_nested+0x1b/0x20
btrfs_commit_transaction+0x475/0xa00 [btrfs]
btrfs_commit_super+0x71/0x80 [btrfs]
close_ctree+0x2bd/0x320 [btrfs]
btrfs_put_super+0x15/0x20 [btrfs]
generic_shutdown_super+0x72/0x110
kill_anon_super+0x18/0x30
btrfs_kill_super+0x16/0xa0 [btrfs]
deactivate_locked_super+0x3a/0x80
deactivate_super+0x51/0x60
cleanup_mnt+0x3f/0x80
__cleanup_mnt+0x12/0x20
task_work_run+0x94/0xb0
exit_to_usermode_loop+0xd8/0xe0
do_syscall_64+0x210/0x240
entry_SYSCALL_64_after_hwframe+0x49/0xbe
-> #1 (&fs_info->reloc_mutex){+.+.}:
__mutex_lock+0x76/0x940
mutex_lock_nested+0x1b/0x20
btrfs_commit_transaction+0x40d/0xa00 [btrfs]
btrfs_quota_enable+0x2da/0x730 [btrfs]
btrfs_ioctl+0x2691/0x2b40 [btrfs]
do_vfs_ioctl+0xa9/0x6d0
ksys_ioctl+0x67/0x90
__x64_sys_ioctl+0x1a/0x20
do_syscall_64+0x65/0x240
entry_SYSCALL_64_after_hwframe+0x49/0xbe
-> #0 (&fs_info->qgroup_ioctl_lock#2){+.+.}:
lock_acquire+0xa7/0x190
__mutex_lock+0x76/0x940
mutex_lock_nested+0x1b/0x20
btrfs_qgroup_inherit+0x40/0x620 [btrfs]
create_pending_snapshot+0x9d7/0xe60 [btrfs]
create_pending_snapshots+0x94/0xb0 [btrfs]
btrfs_commit_transaction+0x415/0xa00 [btrfs]
btrfs_mksubvol+0x496/0x4e0 [btrfs]
btrfs_ioctl_snap_create_transid+0x174/0x180 [btrfs]
btrfs_ioctl_snap_create_v2+0x11c/0x180 [btrfs]
btrfs_ioctl+0xa90/0x2b40 [btrfs]
do_vfs_ioctl+0xa9/0x6d0
ksys_ioctl+0x67/0x90
__x64_sys_ioctl+0x1a/0x20
do_syscall_64+0x65/0x240
entry_SYSCALL_64_after_hwframe+0x49/0xbe
other info that might help us debug this:
Chain exists of:
&fs_info->qgroup_ioctl_lock#2 --> &fs_info->reloc_mutex --> &fs_info->tree_log_mutex
Possible unsafe locking scenario:
CPU0 CPU1
---- ----
lock(&fs_info->tree_log_mutex);
lock(&fs_info->reloc_mutex);
lock(&fs_info->tree_log_mutex);
lock(&fs_info->qgroup_ioctl_lock#2);
*** DEADLOCK ***
6 locks held by btrfs/8631:
#0: 00000000ed8f23f6 (sb_writers#12){.+.+}, at: mnt_want_write_file+0x28/0x60
#1: 000000009fb1597a (&type->i_mutex_dir_key#10/1){+.+.}, at: btrfs_mksubvol+0x70/0x4e0 [btrfs]
#2: 0000000088c5ad88 (&fs_info->subvol_sem){++++}, at: btrfs_mksubvol+0x128/0x4e0 [btrfs]
#3: 000000009606fc3e (sb_internal#2){.+.+}, at: start_transaction+0x37a/0x520 [btrfs]
#4: 00000000f82bbdf5 (&fs_info->reloc_mutex){+.+.}, at: btrfs_commit_transaction+0x40d/0xa00 [btrfs]
#5: 000000003d52cc23 (&fs_info->tree_log_mutex){+.+.}, at: create_pending_snapshot+0x8b6/0xe60 [btrfs]
[CAUSE]
Due to the delayed subvolume creation, we need to call
btrfs_qgroup_inherit() inside commit transaction code, with a lot of
other mutex hold.
This hell of lock chain can lead to above problem.
[FIX]
On the other hand, we don't really need to hold qgroup_ioctl_lock if
we're in the context of create_pending_snapshot().
As in that context, we're the only one being able to modify qgroup.
All other qgroup functions which needs qgroup_ioctl_lock are either
holding a transaction handle, or will start a new transaction:
Functions will start a new transaction():
* btrfs_quota_enable()
* btrfs_quota_disable()
Functions hold a transaction handler:
* btrfs_add_qgroup_relation()
* btrfs_del_qgroup_relation()
* btrfs_create_qgroup()
* btrfs_remove_qgroup()
* btrfs_limit_qgroup()
* btrfs_qgroup_inherit() call inside create_subvol()
So we have a higher level protection provided by transaction, thus we
don't need to always hold qgroup_ioctl_lock in btrfs_qgroup_inherit().
Only the btrfs_qgroup_inherit() call in create_subvol() needs to hold
qgroup_ioctl_lock, while the btrfs_qgroup_inherit() call in
create_pending_snapshot() is already protected by transaction.
So the fix is to detect the context by checking
trans->transaction->state.
If we're at TRANS_STATE_COMMIT_DOING, then we're in commit transaction
context and no need to get the mutex.
Reported-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
[BUG]
When mounting a fs with reloc tree and has qgroup enabled, it can cause
NULL pointer dereference at mount time:
BUG: kernel NULL pointer dereference, address: 00000000000000a8
#PF: supervisor read access in kernel mode
#PF: error_code(0x0000) - not-present page
PGD 0 P4D 0
Oops: 0000 [#1] PREEMPT SMP NOPTI
RIP: 0010:btrfs_qgroup_add_swapped_blocks+0x186/0x300 [btrfs]
Call Trace:
replace_path.isra.23+0x685/0x900 [btrfs]
merge_reloc_root+0x26e/0x5f0 [btrfs]
merge_reloc_roots+0x10a/0x1a0 [btrfs]
btrfs_recover_relocation+0x3cd/0x420 [btrfs]
open_ctree+0x1bc8/0x1ed0 [btrfs]
btrfs_mount_root+0x544/0x680 [btrfs]
legacy_get_tree+0x34/0x60
vfs_get_tree+0x2d/0xf0
fc_mount+0x12/0x40
vfs_kern_mount.part.12+0x61/0xa0
vfs_kern_mount+0x13/0x20
btrfs_mount+0x16f/0x860 [btrfs]
legacy_get_tree+0x34/0x60
vfs_get_tree+0x2d/0xf0
do_mount+0x81f/0xac0
ksys_mount+0xbf/0xe0
__x64_sys_mount+0x25/0x30
do_syscall_64+0x65/0x240
entry_SYSCALL_64_after_hwframe+0x49/0xbe
[CAUSE]
In btrfs_recover_relocation(), we don't have enough info to determine
which block group we're relocating, but only to merge existing reloc
trees.
Thus in btrfs_recover_relocation(), rc->block_group is NULL.
btrfs_qgroup_add_swapped_blocks() hasn't taken this into consideration,
and causes a NULL pointer dereference.
The bug is introduced by commit 3d0174f78e ("btrfs: qgroup: Only trace
data extents in leaves if we're relocating data block group"), and
later qgroup refactoring still keeps this optimization.
[FIX]
Thankfully in the context of btrfs_recover_relocation(), there is no
other progress can modify tree blocks, thus those swapped tree blocks
pair will never affect qgroup numbers, no matter whatever we set for
block->trace_leaf.
So we only need to check if @bg is NULL before accessing @bg->flags.
Reported-by: Juan Erbes <jerbes@gmail.com>
Link: https://bugzilla.opensuse.org/show_bug.cgi?id=1134806
Fixes: 3d0174f78e ("btrfs: qgroup: Only trace data extents in leaves if we're relocating data block group")
CC: stable@vger.kernel.org # 4.20+
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
If 'cur_level' is 7 then the bound checking at the top of the function
will actually pass. Later on, it's possible to dereference
ds_path->nodes[cur_level+1] which will be an out of bounds.
The correct check will be cur_level >= BTRFS_MAX_LEVEL - 1 .
Fixes-coverty-id: 1440918
Fixes-coverty-id: 1440911
Fixes: ea49f3e73c ("btrfs: qgroup: Introduce function to find all new tree blocks of reloc tree")
CC: stable@vger.kernel.org # 4.20+
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
The allocation happens with GFP_KERNEL after a transaction has been
started, this can potentially cause deadlock if reclaim tries to get the
memory by flushing filesystem data.
The fs_info::qgroup_ulist is not used during transaction start when
quotas are not enabled. The status bit BTRFS_FS_QUOTA_ENABLED is set
later in btrfs_quota_enable so it's safe to move it before the
transaction start.
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
[BUG]
Btrfs qgroup will still hit EDQUOT under the following case:
$ dev=/dev/test/test
$ mnt=/mnt/btrfs
$ umount $mnt &> /dev/null
$ umount $dev &> /dev/null
$ mkfs.btrfs -f $dev
$ mount $dev $mnt -o nospace_cache
$ btrfs subv create $mnt/subv
$ btrfs quota enable $mnt
$ btrfs quota rescan -w $mnt
$ btrfs qgroup limit -e 1G $mnt/subv
$ fallocate -l 900M $mnt/subv/padding
$ sync
$ rm $mnt/subv/padding
# Hit EDQUOT
$ xfs_io -f -c "pwrite 0 512M" $mnt/subv/real_file
[CAUSE]
Since commit a514d63882 ("btrfs: qgroup: Commit transaction in advance
to reduce early EDQUOT"), btrfs is not forced to commit transaction to
reclaim more quota space.
Instead, we just check pertrans metadata reservation against some
threshold and try to do asynchronously transaction commit.
However in above case, the pertrans metadata reservation is pretty small
thus it will never trigger asynchronous transaction commit.
[FIX]
Instead of only accounting pertrans metadata reservation, we calculate
how much free space we have, and if there isn't much free space left,
commit transaction asynchronously to try to free some space.
This may slow down the fs when we have less than 32M free qgroup space,
but should reduce a lot of false EDQUOT, so the cost should be
acceptable.
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
[BUG]
Btrfs/139 will fail with a high probability if the testing machine (VM)
has only 2G RAM.
Resulting the final write success while it should fail due to EDQUOT,
and the fs will have quota exceeding the limit by 16K.
The simplified reproducer will be: (needs a 2G ram VM)
$ mkfs.btrfs -f $dev
$ mount $dev $mnt
$ btrfs subv create $mnt/subv
$ btrfs quota enable $mnt
$ btrfs quota rescan -w $mnt
$ btrfs qgroup limit -e 1G $mnt/subv
$ for i in $(seq -w 1 8); do
xfs_io -f -c "pwrite 0 128M" $mnt/subv/file_$i > /dev/null
echo "file $i written" > /dev/kmsg
done
$ sync
$ btrfs qgroup show -pcre --raw $mnt
The last pwrite will not trigger EDQUOT and final 'qgroup show' will
show something like:
qgroupid rfer excl max_rfer max_excl parent child
-------- ---- ---- -------- -------- ------ -----
0/5 16384 16384 none none --- ---
0/256 1073758208 1073758208 none 1073741824 --- ---
And 1073758208 is larger than
> 1073741824.
[CAUSE]
It's a bug in btrfs qgroup data reserved space management.
For quota limit, we must ensure that:
reserved (data + metadata) + rfer/excl <= limit
Since rfer/excl is only updated at transaction commmit time, reserved
space needs to be taken special care.
One important part of reserved space is data, and for a new data extent
written to disk, we still need to take the reserved space until
rfer/excl numbers get updated.
Originally when an ordered extent finishes, we migrate the reserved
qgroup data space from extent_io tree to delayed ref head of the data
extent, expecting delayed ref will only be cleaned up at commit
transaction time.
However for small RAM machine, due to memory pressure dirty pages can be
flushed back to disk without committing a transaction.
The related events will be something like:
file 1 written
btrfs_finish_ordered_io: ino=258 ordered offset=0 len=54947840
btrfs_finish_ordered_io: ino=258 ordered offset=54947840 len=5636096
btrfs_finish_ordered_io: ino=258 ordered offset=61153280 len=57344
btrfs_finish_ordered_io: ino=258 ordered offset=61210624 len=8192
btrfs_finish_ordered_io: ino=258 ordered offset=60583936 len=569344
cleanup_ref_head: num_bytes=54947840
cleanup_ref_head: num_bytes=5636096
cleanup_ref_head: num_bytes=569344
cleanup_ref_head: num_bytes=57344
cleanup_ref_head: num_bytes=8192
^^^^^^^^^^^^^^^^ This will free qgroup data reserved space
file 2 written
...
file 8 written
cleanup_ref_head: num_bytes=8192
...
btrfs_commit_transaction <<< the only transaction committed during
the test
When file 2 is written, we have already freed 128M reserved qgroup data
space for ino 258. Thus later write won't trigger EDQUOT.
This allows us to write more data beyond qgroup limit.
In my 2G ram VM, it could reach about 1.2G before hitting EDQUOT.
[FIX]
By moving reserved qgroup data space from btrfs_delayed_ref_head to
btrfs_qgroup_extent_record, we can ensure that reserved qgroup data
space won't be freed half way before commit transaction, thus fix the
problem.
Fixes: f64d5ca868 ("btrfs: delayed_ref: Add new function to record reserved space into delayed ref")
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Inside qgroup_rsv_add/release(), we have trace events
trace_qgroup_update_reserve() to catch reserved space update.
However we still have two manual trace_qgroup_update_reserve() calls
just outside these functions. Remove these duplicated calls.
Fixes: 64ee4e751a ("btrfs: qgroup: Update trace events to use new separate rsv types")
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
We can use the right helper where the lock type is a fixed parameter.
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: David Sterba <dsterba@suse.com>
Since it's replaced by new delayed subtree swap code, remove the
original code.
The cleanup is small since most of its core function is still used by
delayed subtree swap trace.
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Before this patch, qgroup code traces the whole subtree of subvolume and
reloc trees unconditionally.
This makes qgroup numbers consistent, but it could cause tons of
unnecessary extent tracing, which causes a lot of overhead.
However for subtree swap of balance, just swap both subtrees because
they contain the same contents and tree structure, so qgroup numbers
won't change.
It's the race window between subtree swap and transaction commit could
cause qgroup number change.
This patch will delay the qgroup subtree scan until COW happens for the
subtree root.
So if there is no other operations for the fs, balance won't cause extra
qgroup overhead. (best case scenario)
Depending on the workload, most of the subtree scan can still be
avoided.
Only for worst case scenario, it will fall back to old subtree swap
overhead. (scan all swapped subtrees)
[[Benchmark]]
Hardware:
VM 4G vRAM, 8 vCPUs,
disk is using 'unsafe' cache mode,
backing device is SAMSUNG 850 evo SSD.
Host has 16G ram.
Mkfs parameter:
--nodesize 4K (To bump up tree size)
Initial subvolume contents:
4G data copied from /usr and /lib.
(With enough regular small files)
Snapshots:
16 snapshots of the original subvolume.
each snapshot has 3 random files modified.
balance parameter:
-m
So the content should be pretty similar to a real world root fs layout.
And after file system population, there is no other activity, so it
should be the best case scenario.
| v4.20-rc1 | w/ patchset | diff
-----------------------------------------------------------------------
relocated extents | 22615 | 22457 | -0.1%
qgroup dirty extents | 163457 | 121606 | -25.6%
time (sys) | 22.884s | 18.842s | -17.6%
time (real) | 27.724s | 22.884s | -17.5%
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
To allow delayed subtree swap rescan, btrfs needs to record per-root
information about which tree blocks get swapped. This patch introduces
the required infrastructure.
The designed workflow will be:
1) Record the subtree root block that gets swapped.
During subtree swap:
O = Old tree blocks
N = New tree blocks
reloc tree subvolume tree X
Root Root
/ \ / \
NA OB OA OB
/ | | \ / | | \
NC ND OE OF OC OD OE OF
In this case, NA and OA are going to be swapped, record (NA, OA) into
subvolume tree X.
2) After subtree swap.
reloc tree subvolume tree X
Root Root
/ \ / \
OA OB NA OB
/ | | \ / | | \
OC OD OE OF NC ND OE OF
3a) COW happens for OB
If we are going to COW tree block OB, we check OB's bytenr against
tree X's swapped_blocks structure.
If it doesn't fit any, nothing will happen.
3b) COW happens for NA
Check NA's bytenr against tree X's swapped_blocks, and get a hit.
Then we do subtree scan on both subtrees OA and NA.
Resulting 6 tree blocks to be scanned (OA, OC, OD, NA, NC, ND).
Then no matter what we do to subvolume tree X, qgroup numbers will
still be correct.
Then NA's record gets removed from X's swapped_blocks.
4) Transaction commit
Any record in X's swapped_blocks gets removed, since there is no
modification to swapped subtrees, no need to trigger heavy qgroup
subtree rescan for them.
This will introduce 128 bytes overhead for each btrfs_root even qgroup
is not enabled. This is to reduce memory allocations and potential
failures.
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Refactor btrfs_qgroup_trace_subtree_swap() into
qgroup_trace_subtree_swap(), which only needs two extent buffer and some
other bool to control the behavior.
This provides the basis for later delayed subtree scan work.
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
The typos accumulate over time so once in a while time they get fixed in
a large patch.
Signed-off-by: Andrea Gelmini <andrea.gelmini@gelma.net>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
If the quota enable and snapshot creation ioctls are called concurrently
we can get into a deadlock where the task enabling quotas will deadlock
on the fs_info->qgroup_ioctl_lock mutex because it attempts to lock it
twice, or the task creating a snapshot tries to commit the transaction
while the task enabling quota waits for the former task to commit the
transaction while holding the mutex. The following time diagrams show how
both cases happen.
First scenario:
CPU 0 CPU 1
btrfs_ioctl()
btrfs_ioctl_quota_ctl()
btrfs_quota_enable()
mutex_lock(fs_info->qgroup_ioctl_lock)
btrfs_start_transaction()
btrfs_ioctl()
btrfs_ioctl_snap_create_v2
create_snapshot()
--> adds snapshot to the
list pending_snapshots
of the current
transaction
btrfs_commit_transaction()
create_pending_snapshots()
create_pending_snapshot()
qgroup_account_snapshot()
btrfs_qgroup_inherit()
mutex_lock(fs_info->qgroup_ioctl_lock)
--> deadlock, mutex already locked
by this task at
btrfs_quota_enable()
Second scenario:
CPU 0 CPU 1
btrfs_ioctl()
btrfs_ioctl_quota_ctl()
btrfs_quota_enable()
mutex_lock(fs_info->qgroup_ioctl_lock)
btrfs_start_transaction()
btrfs_ioctl()
btrfs_ioctl_snap_create_v2
create_snapshot()
--> adds snapshot to the
list pending_snapshots
of the current
transaction
btrfs_commit_transaction()
--> waits for task at
CPU 0 to release
its transaction
handle
btrfs_commit_transaction()
--> sees another task started
the transaction commit first
--> releases its transaction
handle
--> waits for the transaction
commit to be completed by
the task at CPU 1
create_pending_snapshot()
qgroup_account_snapshot()
btrfs_qgroup_inherit()
mutex_lock(fs_info->qgroup_ioctl_lock)
--> deadlock, task at CPU 0
has the mutex locked but
it is waiting for us to
finish the transaction
commit
So fix this by setting the quota enabled flag in fs_info after committing
the transaction at btrfs_quota_enable(). This ends up serializing quota
enable and snapshot creation as if the snapshot creation happened just
before the quota enable request. The quota rescan task, scheduled after
committing the transaction in btrfs_quote_enable(), will do the accounting.
Fixes: 6426c7ad69 ("btrfs: qgroup: Fix qgroup accounting when creating snapshot")
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
In qgroup_rescan_leaf a copy is made of the target leaf by calling
btrfs_clone_extent_buffer. The latter allocates a new buffer and
attaches a new set of pages and copies the content of the source buffer.
The new scratch buffer is only used to iterate it's items, it's not
published anywhere and cannot be accessed by a third party.
Hence, it's not necessary to perform any locking on it whatsoever.
Furthermore, remove the extra extent_buffer_get call since the new
buffer is always allocated with a reference count of 1 which is
sufficient here. No functional changes.
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
We have a race between enabling quotas end subvolume creation that cause
subvolume creation to fail with -EINVAL, and the following diagram shows
how it happens:
CPU 0 CPU 1
btrfs_ioctl()
btrfs_ioctl_quota_ctl()
btrfs_quota_enable()
mutex_lock(fs_info->qgroup_ioctl_lock)
btrfs_ioctl()
create_subvol()
btrfs_qgroup_inherit()
-> save fs_info->quota_root
into quota_root
-> stores a NULL value
-> tries to lock the mutex
qgroup_ioctl_lock
-> blocks waiting for
the task at CPU0
-> sets BTRFS_FS_QUOTA_ENABLED in fs_info
-> sets quota_root in fs_info->quota_root
(non-NULL value)
mutex_unlock(fs_info->qgroup_ioctl_lock)
-> checks quota enabled
flag is set
-> returns -EINVAL because
fs_info->quota_root was
NULL before it acquired
the mutex
qgroup_ioctl_lock
-> ioctl returns -EINVAL
Returning -EINVAL to user space will be confusing if all the arguments
passed to the subvolume creation ioctl were valid.
Fix it by grabbing the value from fs_info->quota_root after acquiring
the mutex.
CC: stable@vger.kernel.org # 4.4+
Reviewed-by: Qu Wenruo <wqu@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>
There is no reason to put this check in (!qgroup)'s else branch because
if qgroup is null, it will goto out directly. So move it out to reduce
indentation level. No functional change.
Signed-off-by: Lu Fengqi <lufq.fnst@cn.fujitsu.com>
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Some qgroup trace events like btrfs_qgroup_release_data() and
btrfs_qgroup_free_delayed_ref() can still be triggered even if qgroup is
not enabled.
This is caused by the lack of qgroup status check before calling some
qgroup functions. Thankfully the functions can handle quota disabled
case well and just do nothing for qgroup disabled case.
This patch will do earlier check before triggering related trace events.
And for enabled <-> disabled race case:
1) For enabled->disabled case
Disable will wipe out all qgroups data including reservation and
excl/rfer. Even if we leak some reservation or numbers, it will
still be cleared, so nothing will go wrong.
2) For disabled -> enabled case
Current btrfs_qgroup_release_data() will use extent_io tree to ensure
we won't underflow reservation. And for delayed_ref we use
head->qgroup_reserved to record the reserved space, so in that case
head->qgroup_reserved should be 0 and we won't underflow.
CC: stable@vger.kernel.org # 4.14+
Reported-by: Chris Murphy <lists@colorremedies.com>
Link: https://lore.kernel.org/linux-btrfs/CAJCQCtQau7DtuUUeycCkZ36qjbKuxNzsgqJ7+sJ6W0dK_NLE3w@mail.gmail.com/
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
For qgroup_trace_extent_swap(), if we find one leaf that needs to be
traced, we will also iterate all file extents and trace them.
This is OK if we're relocating data block groups, but if we're
relocating metadata block groups, balance code itself has ensured that
both subtree of file tree and reloc tree contain the same contents.
That's to say, if we're relocating metadata block groups, all file
extents in reloc and file tree should match, thus no need to trace them.
This should reduce the total number of dirty extents processed in metadata
block group balance.
[[Benchmark]] (with all previous enhancement)
Hardware:
VM 4G vRAM, 8 vCPUs,
disk is using 'unsafe' cache mode,
backing device is SAMSUNG 850 evo SSD.
Host has 16G ram.
Mkfs parameter:
--nodesize 4K (To bump up tree size)
Initial subvolume contents:
4G data copied from /usr and /lib.
(With enough regular small files)
Snapshots:
16 snapshots of the original subvolume.
each snapshot has 3 random files modified.
balance parameter:
-m
So the content should be pretty similar to a real world root fs layout.
| v4.19-rc1 | w/ patchset | diff (*)
---------------------------------------------------------------
relocated extents | 22929 | 22851 | -0.3%
qgroup dirty extents | 227757 | 140886 | -38.1%
time (sys) | 65.253s | 37.464s | -42.6%
time (real) | 74.032s | 44.722s | -39.6%
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Before this patch, with quota enabled during balance, we need to mark
the whole subtree dirty for quota.
E.g.
OO = Old tree blocks (from file tree)
NN = New tree blocks (from reloc tree)
File tree (src) Reloc tree (dst)
OO (a) NN (a)
/ \ / \
(b) OO OO (c) (b) NN NN (c)
/ \ / \ / \ / \
OO OO OO OO (d) OO OO OO NN (d)
For old balance + quota case, quota will mark the whole src and dst tree
dirty, including all the 3 old tree blocks in reloc tree.
It's doable for small file tree or new tree blocks are all located at
lower level.
But for large file tree or new tree blocks are all located at higher
level, this will lead to mark the whole tree dirty, and be unbelievably
slow.
This patch will change how we handle such balance with quota enabled
case.
Now we will search from (b) and (c) for any new tree blocks whose
generation is equal to @last_snapshot, and only mark them dirty.
In above case, we only need to trace tree blocks NN(b), NN(c) and NN(d).
(NN(a) will be traced when COW happens for nodeptr modification). And
also for tree blocks OO(b), OO(c), OO(d). (OO(a) will be traced when COW
happens for nodeptr modification.)
For above case, we could skip 3 tree blocks, but for larger tree, we can
skip tons of unmodified tree blocks, and hugely speed up balance.
This patch will introduce a new function,
btrfs_qgroup_trace_subtree_swap(), which will do the following main
work:
1) Read out real root eb
And setup basic dst_path for later calls
2) Call qgroup_trace_new_subtree_blocks()
To trace all new tree blocks in reloc tree and their counter
parts in the file tree.
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Introduce new function, qgroup_trace_new_subtree_blocks(), to iterate
all new tree blocks in a reloc tree.
So that qgroup could skip unrelated tree blocks during balance, which
should hugely speedup balance speed when quota is enabled.
The function qgroup_trace_new_subtree_blocks() itself only cares about
new tree blocks in reloc tree.
All its main works are:
1) Read out tree blocks according to parent pointers
2) Do recursive depth-first search
Will call the same function on all its children tree blocks, with
search level set to current level -1.
And will also skip all children whose generation is smaller than
@last_snapshot.
3) Call qgroup_trace_extent_swap() to trace tree blocks
So although we have parameter list related to source file tree, it's not
used at all, but only passed to qgroup_trace_extent_swap().
Thus despite the tree read code, the core should be pretty short and all
about recursive depth-first search.
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Introduce a new function, qgroup_trace_extent_swap(), which will be used
later for balance qgroup speedup.
The basis idea of balance is swapping tree blocks between reloc tree and
the real file tree.
The swap will happen in highest tree block, but there may be a lot of
tree blocks involved.
For example:
OO = Old tree blocks
NN = New tree blocks allocated during balance
File tree (257) Reloc tree for 257
L2 OO NN
/ \ / \
L1 OO OO (a) OO NN (a)
/ \ / \ / \ / \
L0 OO OO OO OO OO OO NN NN
(b) (c) (b) (c)
When calling qgroup_trace_extent_swap(), we will pass:
@src_eb = OO(a)
@dst_path = [ nodes[1] = NN(a), nodes[0] = NN(c) ]
@dst_level = 0
@root_level = 1
In that case, qgroup_trace_extent_swap() will search from OO(a) to
reach OO(c), then mark both OO(c) and NN(c) as qgroup dirty.
The main work of qgroup_trace_extent_swap() can be split into 3 parts:
1) Tree search from @src_eb
It should acts as a simplified btrfs_search_slot().
The key for search can be extracted from @dst_path->nodes[dst_level]
(first key).
2) Mark the final tree blocks in @src_path and @dst_path qgroup dirty
NOTE: In above case, OO(a) and NN(a) won't be marked qgroup dirty.
They should be marked during preivous (@dst_level = 1) iteration.
3) Mark file extents in leaves dirty
We don't have good way to pick out new file extents only.
So we still follow the old method by scanning all file extents in
the leave.
This function can free us from keeping two pathes, thus later we only need
to care about how to iterate all new tree blocks in reloc tree.
Signed-off-by: Qu Wenruo <wqu@suse.com>
[ copy changelog to function comment ]
Signed-off-by: David Sterba <dsterba@suse.com>
Number of qgroup dirty extents is directly linked to the performance
overhead, so add a new trace event, trace_qgroup_num_dirty_extents(), to
record how many dirty extents is processed in
btrfs_qgroup_account_extents().
This will be pretty handy to analyze later balance performance
improvement.
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
[BUG]
In the following case, rescan won't zero out the number of qgroup 1/0:
$ mkfs.btrfs -fq $DEV
$ mount $DEV /mnt
$ btrfs quota enable /mnt
$ btrfs qgroup create 1/0 /mnt
$ btrfs sub create /mnt/sub
$ btrfs qgroup assign 0/257 1/0 /mnt
$ dd if=/dev/urandom of=/mnt/sub/file bs=1k count=1000
$ btrfs sub snap /mnt/sub /mnt/snap
$ btrfs quota rescan -w /mnt
$ btrfs qgroup show -pcre /mnt
qgroupid rfer excl max_rfer max_excl parent child
-------- ---- ---- -------- -------- ------ -----
0/5 16.00KiB 16.00KiB none none --- ---
0/257 1016.00KiB 16.00KiB none none 1/0 ---
0/258 1016.00KiB 16.00KiB none none --- ---
1/0 1016.00KiB 16.00KiB none none --- 0/257
So far so good, but:
$ btrfs qgroup remove 0/257 1/0 /mnt
WARNING: quotas may be inconsistent, rescan needed
$ btrfs quota rescan -w /mnt
$ btrfs qgroup show -pcre /mnt
qgoupid rfer excl max_rfer max_excl parent child
-------- ---- ---- -------- -------- ------ -----
0/5 16.00KiB 16.00KiB none none --- ---
0/257 1016.00KiB 16.00KiB none none --- ---
0/258 1016.00KiB 16.00KiB none none --- ---
1/0 1016.00KiB 16.00KiB none none --- ---
^^^^^^^^^^ ^^^^^^^^ not cleared
[CAUSE]
Before rescan we call qgroup_rescan_zero_tracking() to zero out all
qgroups' accounting numbers.
However we don't mark all qgroups dirty, but rely on rescan to do so.
If we have any high level qgroup without children, it won't be marked
dirty during rescan, since we cannot reach that qgroup.
This will cause QGROUP_INFO items of childless qgroups never get updated
in the quota tree, thus their numbers will stay the same in "btrfs
qgroup show" output.
[FIX]
Just mark all qgroups dirty in qgroup_rescan_zero_tracking(), so even if
we have childless qgroups, their QGROUP_INFO items will still get
updated during rescan.
Reported-by: Misono Tomohiro <misono.tomohiro@jp.fujitsu.com>
CC: stable@vger.kernel.org # 4.4+
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: Misono Tomohiro <misono.tomohiro@jp.fujitsu.com>
Tested-by: Misono Tomohiro <misono.tomohiro@jp.fujitsu.com>
Signed-off-by: David Sterba <dsterba@suse.com>
There are two members in struct btrfs_root which indicate root's
objectid: objectid and root_key.objectid.
They are both set to the same value in __setup_root():
static void __setup_root(struct btrfs_root *root,
struct btrfs_fs_info *fs_info,
u64 objectid)
{
...
root->objectid = objectid;
...
root->root_key.objectid = objecitd;
...
}
and not changed to other value after initialization.
grep in btrfs directory shows both are used in many places:
$ grep -rI "root->root_key.objectid" | wc -l
133
$ grep -rI "root->objectid" | wc -l
55
(4.17, inc. some noise)
It is confusing to have two similar variable names and it seems
that there is no rule about which should be used in a certain case.
Since ->root_key itself is needed for tree reloc tree, let's remove
'objecitd' member and unify code to use ->root_key.objectid in all places.
Signed-off-by: Misono Tomohiro <misono.tomohiro@jp.fujitsu.com>
Reviewed-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
The issue here is that btrfs_commit_transaction() frees "trans" on both
the error and the success path. So the problem would be if
btrfs_commit_transaction() succeeds, and then qgroup_rescan_init()
fails. That means that "ret" is non-zero and "trans" is non-NULL and it
leads to a use after free inside the btrfs_end_transaction() macro.
Fixes: 340f1aa27f ("btrfs: qgroups: Move transaction management inside btrfs_quota_enable/disable")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
It can be referenced from the passed transaction handle.
Signed-off-by: Lu Fengqi <lufq.fnst@cn.fujitsu.com>
Signed-off-by: David Sterba <dsterba@suse.com>
