@@ -1858,8 +1858,6 @@ int btrfs_commit_transaction(struct btrfs_trans_handle *trans,
btrfs_wait_delalloc_flush(root->fs_info);
- btrfs_wait_pending_ordered(cur_trans, root->fs_info);
-
btrfs_scrub_pause(root);
/*
* Ok now we need to make sure to block out any other joins while we
@@ -1872,6 +1870,8 @@ int btrfs_commit_transaction(struct btrfs_trans_handle *trans,
wait_event(cur_trans->writer_wait,
atomic_read(&cur_trans->num_writers) == 1);
+ btrfs_wait_pending_ordered(cur_trans, root->fs_info);
+
/* ->aborted might be set after the previous check, so check it */
if (unlikely(ACCESS_ONCE(cur_trans->aborted))) {
ret = cur_trans->aborted;
There's a short time window where a race can happen between two or more tasks that hold a transaction handle for the same transaction and where one starts the transaction commit before the other tasks attempt to split their pending ordered extents list into the transaction's pending ordered extents lists. This results in the transaction commit not waiting for those ordered extents to complete, in memory leaks of ordered extent structures and therefore inode leaks too, since an iput for the ordered extent's inode is done only when the ordered extent's refcount drops to zero. This race is described by the following sequence diagram: CPU 1 CPU 2 btrfs_start_transaction() started transaction N with trans->transaction->num_writers == 1 and trans->transaction->state == TRANS_STATE_RUNNING btrfs_sync_file() btrfs_start_transaction() --> returns transaction handle pointing to transaction N --> Now transaction N's num_writers == 2 btrfs_sync_log() btrfs_commit_transaction() btrfs_wait_pending_ordered() --> transaction N's ->pending_ordered processed and is now an empty list set transaction state to TRANS_STATE_COMMIT_DOING wait for trans->transaction->num_writers == 1 btrfs_wait_logged_extents() --> adds ordered extents to trans->ordered list btrfs_end_transaction() --> trans->ordered list is spliced into transaction N's list pending_ordered --> transaction N's num_writers becomes 1 now wait finished, num_writers == 1 transaction is committed and it doesn't wait for the ordered extents from CPU 2's task to complete, nor does it decrement their last reference, resulting in memory leaks and inode leaks (the iput on the ordered extent's inode is done only when the ordered extent's refcount drops to zero) So fix this by processing the transaction's pending_order list after the number of writers decreases to 1. I ran into this issue while running xfstests/generic/113 in a loop, which failed about 1 out of 10 runs with the following warning in dmesg: [ 2612.440038] WARNING: CPU: 4 PID: 22057 at fs/btrfs/disk-io.c:3558 free_fs_root+0x36/0x133 [btrfs]() [ 2612.442810] Modules linked in: btrfs crc32c_generic xor raid6_pq nfsd auth_rpcgss oid_registry nfs_acl nfs lockd grace fscache sunrpc loop processor parport_pc parport psmouse thermal_sys i2c_piix4 serio_raw pcspkr evdev microcode button i2c_core ext4 crc16 jbd2 mbcache sd_mod sg sr_mod cdrom virtio_scsi ata_generic virtio_pci ata_piix virtio_ring libata virtio floppy e1000 scsi_mod [last unloaded: btrfs] [ 2612.452711] CPU: 4 PID: 22057 Comm: umount Tainted: G W 3.19.0-rc5-btrfs-next-4+ #1 [ 2612.454921] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.7.5-0-ge51488c-20140602_164612-nilsson.home.kraxel.org 04/01/2014 [ 2612.457709] 0000000000000009 ffff8801342c3c78 ffffffff8142425e ffff88023ec8f2d8 [ 2612.459829] 0000000000000000 ffff8801342c3cb8 ffffffff81045308 ffff880046460000 [ 2612.461564] ffffffffa036da56 ffff88003d07b000 ffff880046460000 ffff880046460068 [ 2612.463163] Call Trace: [ 2612.463719] [<ffffffff8142425e>] dump_stack+0x4c/0x65 [ 2612.464789] [<ffffffff81045308>] warn_slowpath_common+0xa1/0xbb [ 2612.466026] [<ffffffffa036da56>] ? free_fs_root+0x36/0x133 [btrfs] [ 2612.467247] [<ffffffff810453c5>] warn_slowpath_null+0x1a/0x1c [ 2612.468416] [<ffffffffa036da56>] free_fs_root+0x36/0x133 [btrfs] [ 2612.469625] [<ffffffffa036f2a7>] btrfs_drop_and_free_fs_root+0x93/0x9b [btrfs] [ 2612.471251] [<ffffffffa036f353>] btrfs_free_fs_roots+0xa4/0xd6 [btrfs] [ 2612.472536] [<ffffffff8142612e>] ? wait_for_completion+0x24/0x26 [ 2612.473742] [<ffffffffa0370bbc>] close_ctree+0x1f3/0x33c [btrfs] [ 2612.475477] [<ffffffff81059d1d>] ? destroy_workqueue+0x148/0x1ba [ 2612.476695] [<ffffffffa034e3da>] btrfs_put_super+0x19/0x1b [btrfs] [ 2612.477911] [<ffffffff81153e53>] generic_shutdown_super+0x73/0xef [ 2612.479106] [<ffffffff811540e2>] kill_anon_super+0x13/0x1e [ 2612.480226] [<ffffffffa034e1e3>] btrfs_kill_super+0x17/0x23 [btrfs] [ 2612.481471] [<ffffffff81154307>] deactivate_locked_super+0x3b/0x50 [ 2612.482686] [<ffffffff811547a7>] deactivate_super+0x3f/0x43 [ 2612.483791] [<ffffffff8116b3ed>] cleanup_mnt+0x59/0x78 [ 2612.484842] [<ffffffff8116b44c>] __cleanup_mnt+0x12/0x14 [ 2612.485900] [<ffffffff8105d019>] task_work_run+0x8f/0xbc [ 2612.486960] [<ffffffff810028d8>] do_notify_resume+0x5a/0x6b [ 2612.488083] [<ffffffff81236e5b>] ? trace_hardirqs_on_thunk+0x3a/0x3f [ 2612.489333] [<ffffffff8142a17f>] int_signal+0x12/0x17 [ 2612.490353] ---[ end trace 54a960a6bdcb8d93 ]--- [ 2612.557253] VFS: Busy inodes after unmount of sdb. Self-destruct in 5 seconds. Have a nice day... This happened because evict_inodes (VFS) skipped eviction of one inode because that inode had an i_count > 0. This prevented btrfs_destroy_inode from being called against that inode, and the non-zero i_count was because one ordered extent didn't get its refcount dropped to 0, which is when a delayed iput is scheduled for the inode. Kmemleak also complained about this, namely the leak of the ordered extent structure and btrfs inode specific structures, like the delayed inode: $ cat /sys/kernel/debug/kmemleak unreferenced object 0xffff880154290db0 (size 576): comm "btrfsck", pid 21980, jiffies 4295542503 (age 1273.412s) hex dump (first 32 bytes): 01 40 00 00 01 00 00 00 b0 1d f1 4e 01 88 ff ff .@.........N.... 00 00 00 00 00 00 00 00 c8 0d 29 54 01 88 ff ff ..........)T.... backtrace: [<ffffffff8141d74d>] kmemleak_update_trace+0x4c/0x6a [<ffffffff8122f2c0>] radix_tree_node_alloc+0x6d/0x83 [<ffffffff8122fb26>] __radix_tree_create+0x109/0x190 [<ffffffff8122fbdd>] radix_tree_insert+0x30/0xac [<ffffffffa03b9bde>] btrfs_get_or_create_delayed_node+0x130/0x187 [btrfs] [<ffffffffa03bb82d>] btrfs_delayed_delete_inode_ref+0x32/0xac [btrfs] [<ffffffffa0379dae>] __btrfs_unlink_inode+0xee/0x288 [btrfs] [<ffffffffa037c715>] btrfs_unlink_inode+0x1e/0x40 [btrfs] [<ffffffffa037c797>] btrfs_unlink+0x60/0x9b [btrfs] [<ffffffff8115d7f0>] vfs_unlink+0x9c/0xed [<ffffffff8115f5de>] do_unlinkat+0x12c/0x1fa [<ffffffff811601a7>] SyS_unlinkat+0x29/0x2b [<ffffffff81429e92>] system_call_fastpath+0x12/0x17 [<ffffffffffffffff>] 0xffffffffffffffff unreferenced object 0xffff88014ef11db0 (size 576): comm "rm", pid 22009, jiffies 4295542593 (age 1273.052s) hex dump (first 32 bytes): 02 00 00 00 01 00 00 00 00 00 00 00 00 00 00 00 ................ 00 00 00 00 00 00 00 00 c8 1d f1 4e 01 88 ff ff ...........N.... backtrace: [<ffffffff8141d74d>] kmemleak_update_trace+0x4c/0x6a [<ffffffff8122f2c0>] radix_tree_node_alloc+0x6d/0x83 [<ffffffff8122fb26>] __radix_tree_create+0x109/0x190 [<ffffffff8122fbdd>] radix_tree_insert+0x30/0xac [<ffffffffa03b9bde>] btrfs_get_or_create_delayed_node+0x130/0x187 [btrfs] [<ffffffffa03bb82d>] btrfs_delayed_delete_inode_ref+0x32/0xac [btrfs] [<ffffffffa0379dae>] __btrfs_unlink_inode+0xee/0x288 [btrfs] [<ffffffffa037c715>] btrfs_unlink_inode+0x1e/0x40 [btrfs] [<ffffffffa037c797>] btrfs_unlink+0x60/0x9b [btrfs] [<ffffffff8115d7f0>] vfs_unlink+0x9c/0xed [<ffffffff8115f5de>] do_unlinkat+0x12c/0x1fa [<ffffffff811601a7>] SyS_unlinkat+0x29/0x2b [<ffffffff81429e92>] system_call_fastpath+0x12/0x17 [<ffffffffffffffff>] 0xffffffffffffffff unreferenced object 0xffff8800336feda8 (size 584): comm "aio-stress", pid 22031, jiffies 4295543006 (age 1271.400s) hex dump (first 32 bytes): 00 40 3e 00 00 00 00 00 00 00 8f 42 00 00 00 00 .@>........B.... 00 00 01 00 00 00 00 00 00 00 01 00 00 00 00 00 ................ backtrace: [<ffffffff8114eb34>] create_object+0x172/0x29a [<ffffffff8141d790>] kmemleak_alloc+0x25/0x41 [<ffffffff81141ae6>] kmemleak_alloc_recursive.constprop.52+0x16/0x18 [<ffffffff81145288>] kmem_cache_alloc+0xf7/0x198 [<ffffffffa0389243>] __btrfs_add_ordered_extent+0x43/0x309 [btrfs] [<ffffffffa038968b>] btrfs_add_ordered_extent_dio+0x12/0x14 [btrfs] [<ffffffffa03810e2>] btrfs_get_blocks_direct+0x3ef/0x571 [btrfs] [<ffffffff81181349>] do_blockdev_direct_IO+0x62a/0xb47 [<ffffffff8118189a>] __blockdev_direct_IO+0x34/0x36 [<ffffffffa03776e5>] btrfs_direct_IO+0x16a/0x1e8 [btrfs] [<ffffffff81100373>] generic_file_direct_write+0xb8/0x12d [<ffffffffa038615c>] btrfs_file_write_iter+0x24b/0x42f [btrfs] [<ffffffff8118bb0d>] aio_run_iocb+0x2b7/0x32e [<ffffffff8118c99a>] do_io_submit+0x26e/0x2ff [<ffffffff8118ca3b>] SyS_io_submit+0x10/0x12 [<ffffffff81429e92>] system_call_fastpath+0x12/0x17 This race was introduced with the following change (added in 3.19 and backported to stable 3.18 and 3.17): Btrfs: make sure logged extents complete in the current transaction V3 commit 50d9aa99bd35c77200e0e3dd7a72274f8304701f CC: <stable@vger.kernel.org> # 3.19, 3.18 and 3.17 Signed-off-by: Filipe Manana <fdmanana@suse.com> --- fs/btrfs/transaction.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)