4.9-stable patches

added patches:
	btrfs-fix-lockdep-splat-when-reading-qgroup-config-on-mount.patch

diff --git a/queue-4.9/btrfs-fix-lockdep-splat-when-reading-qgroup-config-on-mount.patch b/queue-4.9/btrfs-fix-lockdep-splat-when-reading-qgroup-config-on-mount.patch
new file mode 100644 (file)
index 0000000..49e2520
--- /dev/null
+++ b/queue-4.9/btrfs-fix-lockdep-splat-when-reading-qgroup-config-on-mount.patch
@@ -0,0 +1,162 @@
+From 3d05cad3c357a2b749912914356072b38435edfa Mon Sep 17 00:00:00 2001
+From: Filipe Manana <fdmanana@suse.com>
+Date: Mon, 23 Nov 2020 14:28:44 +0000
+Subject: btrfs: fix lockdep splat when reading qgroup config on mount
+
+From: Filipe Manana <fdmanana@suse.com>
+
+commit 3d05cad3c357a2b749912914356072b38435edfa upstream.
+
+Lockdep reported the following splat when running test btrfs/190 from
+fstests:
+
+  [ 9482.126098] ======================================================
+  [ 9482.126184] WARNING: possible circular locking dependency detected
+  [ 9482.126281] 5.10.0-rc4-btrfs-next-73 #1 Not tainted
+  [ 9482.126365] ------------------------------------------------------
+  [ 9482.126456] mount/24187 is trying to acquire lock:
+  [ 9482.126534] ffffa0c869a7dac0 (&fs_info->qgroup_rescan_lock){+.+.}-{3:3}, at: qgroup_rescan_init+0x43/0xf0 [btrfs]
+  [ 9482.126647]
+                but task is already holding lock:
+  [ 9482.126777] ffffa0c892ebd3a0 (btrfs-quota-00){++++}-{3:3}, at: __btrfs_tree_read_lock+0x27/0x120 [btrfs]
+  [ 9482.126886]
+                which lock already depends on the new lock.
+
+  [ 9482.127078]
+                the existing dependency chain (in reverse order) is:
+  [ 9482.127213]
+                -> #1 (btrfs-quota-00){++++}-{3:3}:
+  [ 9482.127366]        lock_acquire+0xd8/0x490
+  [ 9482.127436]        down_read_nested+0x45/0x220
+  [ 9482.127528]        __btrfs_tree_read_lock+0x27/0x120 [btrfs]
+  [ 9482.127613]        btrfs_read_lock_root_node+0x41/0x130 [btrfs]
+  [ 9482.127702]        btrfs_search_slot+0x514/0xc30 [btrfs]
+  [ 9482.127788]        update_qgroup_status_item+0x72/0x140 [btrfs]
+  [ 9482.127877]        btrfs_qgroup_rescan_worker+0xde/0x680 [btrfs]
+  [ 9482.127964]        btrfs_work_helper+0xf1/0x600 [btrfs]
+  [ 9482.128039]        process_one_work+0x24e/0x5e0
+  [ 9482.128110]        worker_thread+0x50/0x3b0
+  [ 9482.128181]        kthread+0x153/0x170
+  [ 9482.128256]        ret_from_fork+0x22/0x30
+  [ 9482.128327]
+                -> #0 (&fs_info->qgroup_rescan_lock){+.+.}-{3:3}:
+  [ 9482.128464]        check_prev_add+0x91/0xc60
+  [ 9482.128551]        __lock_acquire+0x1740/0x3110
+  [ 9482.128623]        lock_acquire+0xd8/0x490
+  [ 9482.130029]        __mutex_lock+0xa3/0xb30
+  [ 9482.130590]        qgroup_rescan_init+0x43/0xf0 [btrfs]
+  [ 9482.131577]        btrfs_read_qgroup_config+0x43a/0x550 [btrfs]
+  [ 9482.132175]        open_ctree+0x1228/0x18a0 [btrfs]
+  [ 9482.132756]        btrfs_mount_root.cold+0x13/0xed [btrfs]
+  [ 9482.133325]        legacy_get_tree+0x30/0x60
+  [ 9482.133866]        vfs_get_tree+0x28/0xe0
+  [ 9482.134392]        fc_mount+0xe/0x40
+  [ 9482.134908]        vfs_kern_mount.part.0+0x71/0x90
+  [ 9482.135428]        btrfs_mount+0x13b/0x3e0 [btrfs]
+  [ 9482.135942]        legacy_get_tree+0x30/0x60
+  [ 9482.136444]        vfs_get_tree+0x28/0xe0
+  [ 9482.136949]        path_mount+0x2d7/0xa70
+  [ 9482.137438]        do_mount+0x75/0x90
+  [ 9482.137923]        __x64_sys_mount+0x8e/0xd0
+  [ 9482.138400]        do_syscall_64+0x33/0x80
+  [ 9482.138873]        entry_SYSCALL_64_after_hwframe+0x44/0xa9
+  [ 9482.139346]
+                other info that might help us debug this:
+
+  [ 9482.140735]  Possible unsafe locking scenario:
+
+  [ 9482.141594]        CPU0                    CPU1
+  [ 9482.142011]        ----                    ----
+  [ 9482.142411]   lock(btrfs-quota-00);
+  [ 9482.142806]                                lock(&fs_info->qgroup_rescan_lock);
+  [ 9482.143216]                                lock(btrfs-quota-00);
+  [ 9482.143629]   lock(&fs_info->qgroup_rescan_lock);
+  [ 9482.144056]
+                 *** DEADLOCK ***
+
+  [ 9482.145242] 2 locks held by mount/24187:
+  [ 9482.145637]  #0: ffffa0c8411c40e8 (&type->s_umount_key#44/1){+.+.}-{3:3}, at: alloc_super+0xb9/0x400
+  [ 9482.146061]  #1: ffffa0c892ebd3a0 (btrfs-quota-00){++++}-{3:3}, at: __btrfs_tree_read_lock+0x27/0x120 [btrfs]
+  [ 9482.146509]
+                stack backtrace:
+  [ 9482.147350] CPU: 1 PID: 24187 Comm: mount Not tainted 5.10.0-rc4-btrfs-next-73 #1
+  [ 9482.147788] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014
+  [ 9482.148709] Call Trace:
+  [ 9482.149169]  dump_stack+0x8d/0xb5
+  [ 9482.149628]  check_noncircular+0xff/0x110
+  [ 9482.150090]  check_prev_add+0x91/0xc60
+  [ 9482.150561]  ? kvm_clock_read+0x14/0x30
+  [ 9482.151017]  ? kvm_sched_clock_read+0x5/0x10
+  [ 9482.151470]  __lock_acquire+0x1740/0x3110
+  [ 9482.151941]  ? __btrfs_tree_read_lock+0x27/0x120 [btrfs]
+  [ 9482.152402]  lock_acquire+0xd8/0x490
+  [ 9482.152887]  ? qgroup_rescan_init+0x43/0xf0 [btrfs]
+  [ 9482.153354]  __mutex_lock+0xa3/0xb30
+  [ 9482.153826]  ? qgroup_rescan_init+0x43/0xf0 [btrfs]
+  [ 9482.154301]  ? qgroup_rescan_init+0x43/0xf0 [btrfs]
+  [ 9482.154768]  ? qgroup_rescan_init+0x43/0xf0 [btrfs]
+  [ 9482.155226]  qgroup_rescan_init+0x43/0xf0 [btrfs]
+  [ 9482.155690]  btrfs_read_qgroup_config+0x43a/0x550 [btrfs]
+  [ 9482.156160]  open_ctree+0x1228/0x18a0 [btrfs]
+  [ 9482.156643]  btrfs_mount_root.cold+0x13/0xed [btrfs]
+  [ 9482.157108]  ? rcu_read_lock_sched_held+0x5d/0x90
+  [ 9482.157567]  ? kfree+0x31f/0x3e0
+  [ 9482.158030]  legacy_get_tree+0x30/0x60
+  [ 9482.158489]  vfs_get_tree+0x28/0xe0
+  [ 9482.158947]  fc_mount+0xe/0x40
+  [ 9482.159403]  vfs_kern_mount.part.0+0x71/0x90
+  [ 9482.159875]  btrfs_mount+0x13b/0x3e0 [btrfs]
+  [ 9482.160335]  ? rcu_read_lock_sched_held+0x5d/0x90
+  [ 9482.160805]  ? kfree+0x31f/0x3e0
+  [ 9482.161260]  ? legacy_get_tree+0x30/0x60
+  [ 9482.161714]  legacy_get_tree+0x30/0x60
+  [ 9482.162166]  vfs_get_tree+0x28/0xe0
+  [ 9482.162616]  path_mount+0x2d7/0xa70
+  [ 9482.163070]  do_mount+0x75/0x90
+  [ 9482.163525]  __x64_sys_mount+0x8e/0xd0
+  [ 9482.163986]  do_syscall_64+0x33/0x80
+  [ 9482.164437]  entry_SYSCALL_64_after_hwframe+0x44/0xa9
+  [ 9482.164902] RIP: 0033:0x7f51e907caaa
+
+This happens because at btrfs_read_qgroup_config() we can call
+qgroup_rescan_init() while holding a read lock on a quota btree leaf,
+acquired by the previous call to btrfs_search_slot_for_read(), and
+qgroup_rescan_init() acquires the mutex qgroup_rescan_lock.
+
+A qgroup rescan worker does the opposite: it acquires the mutex
+qgroup_rescan_lock, at btrfs_qgroup_rescan_worker(), and then tries to
+update the qgroup status item in the quota btree through the call to
+update_qgroup_status_item(). This inversion of locking order
+between the qgroup_rescan_lock mutex and quota btree locks causes the
+splat.
+
+Fix this simply by releasing and freeing the path before calling
+qgroup_rescan_init() at btrfs_read_qgroup_config().
+
+CC: stable@vger.kernel.org # 4.4+
+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: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+
+---
+ fs/btrfs/qgroup.c |    2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+--- a/fs/btrfs/qgroup.c
++++ b/fs/btrfs/qgroup.c
+@@ -461,13 +461,13 @@ next2:
+                       break;
+       }
+ out:
++      btrfs_free_path(path);
+       fs_info->qgroup_flags |= flags;
+       if (!(fs_info->qgroup_flags & BTRFS_QGROUP_STATUS_FLAG_ON))
+               clear_bit(BTRFS_FS_QUOTA_ENABLED, &fs_info->flags);
+       else if (fs_info->qgroup_flags & BTRFS_QGROUP_STATUS_FLAG_RESCAN &&
+                ret >= 0)
+               ret = qgroup_rescan_init(fs_info, rescan_progress, 0);
+-      btrfs_free_path(path);
+ 
+       if (ret < 0) {
+               ulist_free(fs_info->qgroup_ulist);

diff --git a/queue-4.9/series b/queue-4.9/series
index 8dc2bb307fe27ad04168fa9f443f1fc3a456d680..e542f665651ac3c118ce1510430ec3e174ac5e67 100644 (file)
--- a/queue-4.9/series
+++ b/queue-4.9/series
@@ -1,2 +1,3 @@
 perf-event-check-ref_reloc_sym-before-using-it.patch
 mm-userfaultfd-do-not-access-vma-vm_mm-after-calling-handle_userfault.patch
+btrfs-fix-lockdep-splat-when-reading-qgroup-config-on-mount.patch