Reproduce the freed-list commit deadlock and show a fixed server recovers.
The alloc_fill_freed_list trigger stuffs both server_meta_freed heads
to near-full in a single commit. It claims runs of free blocks and
appends them straight into the head blocks, leaking whatever isn't
used.
Filling both heads in one commit makes the wedge reproducible. There's
no window for the drain to empty one head before the other fills. An
unfixed server is left with both heads full and wedges on the next
commit. A fixed server drains them and stays live.
Signed-off-by: Auke Kok <auke.kok@versity.com>
The server commit deadlocks when its freed allocator list head block
fills to near capacity. Both gates that decide whether a transaction has
room measure it as free slots in the clean freed head block:
- hold_commit() admits a holder only if scoutfs_alloc_meta_remaining()
reports enough freed room (2 * COMMIT_HOLD_ALLOC_BUDGET slots).
- empty_list()/fill_list()'s list_has_blocks() proceed only if the head
has extent_mod_blocks() slots.
The clean head is not what a transaction gets: the first dirtying
allocation runs dirty_alloc_blocks(), which rotates in a fresh head block
when the current head is under EMPTY_FREED_THRESH. A clean, nearly-full
head has a full block's worth of room as soon as it's touched. With the
gates refusing on the clean full head, no holder is admitted and the
drains never start, so the rotation in dirty_alloc_blocks() is never
reached. The server spins applying empty commits and the filesystem can't
mount or recover (observed at ~11k empty commits/sec; freed head first_nr
8148 of an 8184 capacity).
Fix the accounting in scoutfs_alloc_meta_remaining(): when the freed list
isn't dirtied yet and the clean head is under EMPTY_FREED_THRESH, report
the room the pending rotation will give, SCOUTFS_ALLOC_LIST_MAX_BLOCKS - 2
(a fresh block, less the old avail and freed head blocks the rotation
frees into it). list_has_blocks() routes through the same function so
fill_list()/empty_list() use identical accounting; otherwise an
avail-low, freed-full commit could still wedge because fill_list()
couldn't refill avail past the clean full freed head.
hold_commit() then admits a holder (or a drain starts) and the first
allocation rotates the full head. The avail gate and the meta_low()
loop-stop are left conservative, so genuine ENOSPC still fails and freeing
loops still commit before overflowing a head.
Signed-off-by: Auke Kok <auke.kok@versity.com>
A failed mount tears down with scoutfs_put_super(), which calls
scoutfs_srch_destroy() first. srch_destroy() does cancel_work_sync() on
the srch compact worker, but that worker can be parked in an
uninterruptible scoutfs_net_sync_request() to a server that will never
respond (e.g. the server is stuck in recovery). Nothing completes the
request: the forced-unmount drain in the net shutdown path only runs for
umount -f, and a failed mount never calls ->umount_begin, so the request
sits on the resend queue and cancel_work_sync() waits forever.
The result is an unkillable D-state mount that survives the SIGKILL a
mount timeout sends, and only clears on reboot:
systemd[1]: data-archive.mount: Killing process 15740 (mount) with signal SIGKILL.
systemd[1]: data-archive.mount: Mount process still around after SIGKILL. Ignoring.
cat /proc/26717/stack
[<0>] __flush_work+0x16f/0x240
[<0>] __cancel_work_sync+0x135/0x1a0
[<0>] scoutfs_srch_destroy+0x33/0x70 [scoutfs]
[<0>] scoutfs_put_super+0x4f/0x1a0 [scoutfs]
[<0>] scoutfs_fill_super+0x260/0x520 [scoutfs]
[<0>] mount_bdev+0xf9/0x150
[<0>] do_new_mount+0x17a/0x310
[<0>] __x64_sys_mount+0x107/0x140
The worker it waits on, blocked in the sync request that never returns:
task:kworker/u269:1 state:D
Workqueue: scoutfs_srch_compact scoutfs_srch_compact_worker [scoutfs]
Call Trace:
__wait_for_common+0x90/0x1d0
scoutfs_net_sync_request+0xdb/0xf0 [scoutfs]
scoutfs_client_srch_get_compact+0x2e/0x40 [scoutfs]
scoutfs_srch_compact_worker+0x64/0x3d0 [scoutfs]
On the fill_super error path, mark forced_unmount and shut the client
connection down before teardown. That drains pending requests with
-ECONNABORTED so the worker returns and srch_destroy()'s cancel_work_sync
completes. It is done for any failure, before the direct put_super call
and before returning to generic_shutdown_super (which calls put_super
when s_root was set), so both teardown paths are covered. sbi is
allocated before any goto out, and scoutfs_client_net_shutdown() is a
no-op when the client or connection was never set up, so early failures
are safe.
Signed-off-by: Auke Kok <auke.kok@versity.com>
A node only needs to be fenced once, but scoutfs_fence_start() can be
called for the same rid more than once. When a new leader starts it
fences the previous leader as it removes it from the quorum
(quorum_block_leader), and that same rid can also be a mounted client
that then fails to recover within the timeout (client_recovery).
The second fence call collides on that name, sysfs returns -EEXIST,
and the error is propagated to fence_pending_recov_worker() which
treats any error as fatal and shuts the server down. On the next
mount a new leader hits the same stale set and the same collision,
so the filesystem can never finish recovery.
Jun 15 09:22:35 kernel: scoutfs f.000000.r.222222: fencing previous leader f.000000.r.111111 at term 183942 in slot 3 with address x.x.x.x:6000
Jun 15 09:22:36 scoutfs-fenced[9194]: [2026-06-15 09:22:36.588037842] server f.000000.r.222222 fencing rid 1111111111111111 at IP x.x.x.x for quorum_block_leader
Jun 15 09:23:09 kernel: scoutfs f.000000.r.222222 error: 30000 ms recovery timeout expired for client rid 1111111111111111, fencing
Jun 15 09:23:09 kernel: sysfs: cannot create duplicate filename '/fs/scoutfs/f.000000.r.222222/fence/1111111111111111'
Jun 15 09:23:09 kernel: scoutfs f.000000.r.222222 error: fence returned err -17, shutting down server
Check the list for the rid and skip the duplicate before creating
sysfs. A pending fence can be freed once it is on the list, so a new
fi->mutex serializes creation against the freeing path: the duplicate
check, sysfs create, and list insert run as a unit, and a fence becomes
visible on the list only once it is fully built. scoutfs_fence_free()
and scoutfs_fence_stop() take the same mutex around removing a fence
and tearing it down, and scoutfs_fence_destroy() drains through
fence_stop() rather than walking the list unlocked.
Signed-off-by: Auke Kok <auke.kok@versity.com>
Scoutfs print segfaults walking a log_merge btree that has more than one
level. print_btree_block() prints parent (level > 0) items via
print_block_ref(), which invokes the item callback with a NULL value to
print the key portion before printing the child ref:
func(key, 0, 0, NULL, 0, arg);
print_log_merge_item immediately casts val and reads a field,
dereferencing NULL. A log_merge of a single leaf block (height 1) never
hits the parent path; one with height > 1 crashes on the first parent
item:
scoutfs[22043]: segfault at 8 ip 0000000000408ef0 sp 00007fffc5edd8b0 error 4
#0 0x0000000000408ef0 in print_log_merge_item ()
#1 0x000000000040958d in print_btree_block.constprop.0.isra ()
#2 0x000000000040a471 in print_cmd ()
#3 0x0000000000404264 in cmd_execute ()
#4 0x00000000004025c9 in main ()
print_mounted_client_entry has the same bug: it casts val and reads
mcv->addr / mcv->flags with no NULL guard, so a mounted_clients btree of
height > 1 segfaults the same way. print_srch_root_item guards NULL but
casts to scoutfs_srch_compact or scoutfs_srch_file without bounds
checking, so a short or malformed item reads past its end.
Fix all three: return early when val is NULL (printing just the key for
the parent ref where applicable), and bounds-check val_len before each
cast so a short item is reported instead of read past its end.
Signed-off-by: Auke Kok <auke.kok@versity.com>
In v1.25-49-gf6746275, we adjusted the default TCP keepalive
value for clients from 10s to 60s. The motivation for doing so
was to allow the system to withstand an - at that time - unknown
networking issue that caused intermittent fencing/disconnects.
It was later determined that lock recovery stalls were the culprit,
and those were largely addressed by ca. v1.26-21-gf0c79966 which
fixes the issue at the root of the problem. The increase from
10s to 60s however was not reverted.
We are now seeing issues when scoutfs is deployed as multiple
filesystem mounts on a cluster where e.g. the server is dropped
for a fencing test - causing a non-leader node to take over from
the fenced server. It will issue new fence requests for clients
that were previously connected in 30 seconds. But with a 60sec
TCP timeout value, any client that is still up will wait silently
for the fenced server, until the new leader fences them. This leaves
the cluster degraded in case of a 3-node quorum.
The precise timeline:
- 0sec: nmcli down on node0
- 10sec: new election issued, node1 wins, node2 remains follower
- 15sec: node0 fenced (quorum old leader fence)
- 45sec: node1 fences clients that failed to recover
never reached:
- 60sec: node2 client reconnect due to TCP timeout
In our scoutfs testing we never see this because we just call umount
in our testing script unconditionally. In a multi-fs scenario with
real fencing this is never done, and so the cluster degrades almost
entirely consistently.
Drop the value to 24sec. The new value is well below the highest
acceptable value: 45sec. We don't want to lower it too much, and we
also don't want it to be a multiple of 15/10 to avoid concurrent
intervals causing "flapping" or waves of events excluding. 24s fits
well between the minimum of 15 and maximum of 45 and isn't a straight
factor or multiple of 10, 15, or 30.
Test results: on my 3-node 3-fs setup, this 100% recovered all 3
fs's without degrading the cluster. In 1/20 tests I had to re-start
2 nodes (a "flap") in succession to recover. In the rest of the tests,
the cluster recovered as expected.
Signed-off-by: Auke Kok <auke.kok@versity.com>
RHEL7 was the only conditional user of this define, but since
support for that is removed, these can be dropped.
Signed-off-by: Auke Kok <auke.kok@versity.com>
scoutfs_rename2 was a thin shim that validated flags and forwarded
to scoutfs_rename_common. It existed because the old el7
RHEL_IOPS_WRAPPER path used a non-flag-taking .rename op alongside
.rename2; with that path gone there is only one rename method,
and the wrapper has no purpose.
Move the RENAME_NOREPLACE flag validation into scoutfs_rename_common
and point the directory inode_operations .rename slot at it directly.
The symlink inode_operations already used scoutfs_rename_common, so
this also makes symlink rename consistently reject unknown flags
instead of silently accepting them.
Signed-off-by: Auke Kok <auke.kok@versity.com>
el8 already provides stack_trace_save() and stack_trace_print()
in linux/stacktrace.h, so the legacy save_stack_trace/print_stack_trace
fallback inlines are dead. Drop the detection stanza and the inlines.
Signed-off-by: Auke Kok <auke.kok@versity.com>
el8 already provides vm_fault_t and vmf_error(), so the fallback
typedef and inline are dead. Drop the detection stanza and the
two function-signature ifdefs in data.c that switched between the
pre-v4.11 and modern fault handler prototypes.
Signed-off-by: Auke Kok <auke.kok@versity.com>
Only el7 was capable of testing this formatversion. And there
no longer is el7 support. Remove the test.
Signed-off-by: Auke Kok <auke.kok@versity.com>
We still need to keep KC_GENERIC_PERFORM_WRITE_KIOCB_IOV_ITER for
el8. So kc_generic_perform_write remains in place for now.
Signed-off-by: Auke Kok <auke.kok@versity.com>
This is a pre-el7 remnant, possibly from a really old rhel9
version, and was already effectively a stub.
Signed-off-by: Auke Kok <auke.kok@versity.com>
This depends on nfs-utils being installed on the host. Without it
it will skip, and count as a failure. It starts nfs-server and
does a bare exportfs.
- Tests basic read/write/stage/release/data wait.
- Tests setfacl/getfacl.
Signed-off-by: Auke Kok <auke.kok@versity.com>
Auke Kok
Zach BrownandGitHub