Hi Anand,
I found that btrfs/125 test case can only pass if we enabled space cache.
If using nospace_cache or space_cache=v2 mount option, it will get
blocked forever with the following callstack(the only blocked process):
[11382.046978] btrfs D11128 6705 6057 0x00000000
[11382.047356] Call Trace:
[11382.047668] __schedule+0x2d4/0xae0
[11382.047956] schedule+0x3d/0x90
[11382.048283] btrfs_start_ordered_extent+0x160/0x200 [btrfs]
[11382.048630] ? wake_atomic_t_function+0x60/0x60
[11382.048958] btrfs_wait_ordered_range+0x113/0x210 [btrfs]
[11382.049360] btrfs_relocate_block_group+0x260/0x2b0 [btrfs]
[11382.049703] btrfs_relocate_chunk+0x51/0xf0 [btrfs]
[11382.050073] btrfs_balance+0xaa9/0x1610 [btrfs]
[11382.050404] ? btrfs_ioctl_balance+0x3a0/0x3b0 [btrfs]
[11382.050739] btrfs_ioctl_balance+0x3a0/0x3b0 [btrfs]
[11382.051109] btrfs_ioctl+0xbe7/0x27f0 [btrfs]
[11382.051430] ? trace_hardirqs_on+0xd/0x10
[11382.051747] ? free_object+0x74/0xa0
[11382.052084] ? debug_object_free+0xf2/0x130
[11382.052413] do_vfs_ioctl+0x94/0x710
[11382.052750] ? enqueue_hrtimer+0x160/0x160
[11382.053090] ? do_nanosleep+0x71/0x130
[11382.053431] SyS_ioctl+0x79/0x90
[11382.053735] entry_SYSCALL_64_fastpath+0x18/0xad
[11382.054570] RIP: 0033:0x7f397d7a6787
I also found in the test case, we only have 3 continuous data extents,
whose sizes are 1M, 68.5M and 31.5M respectively.
Original data block group:
0 1M 64M 69.5M 101M 128M
| Ext A | Extent B(68.5M) | Extent C(31.5M) |
While relocation write them in 4 extents:
0~1M :same as Extent A. (1st)
1M~68.3438M :smaller than Extent B (2nd)
68.3438M~69.5M :tail part of Extent B (3rd)
69.5M~ 101M :same as Extent C. (4th)
However only ordered extent of (3rd) and (4th) get finished.
While ordered extent of (1st) and (2nd) never reached finish_ordered_io().
So relocation will wait for no one to finish the these two ordered
extent, and get blocked.
Did you experienced the same bug submitting the test case?
Is there any known fix for it?
Thanks,
Qu
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