Syzkaller reports warning as follows:
=====================================
WARNING: CPU: 0 PID: 3612 at fs/btrfs/space-info.h:122
btrfs_space_info_free_bytes_may_use fs/btrfs/space-info.h:154 [inline]
WARNING: CPU: 0 PID: 3612 at fs/btrfs/space-info.h:122
block_rsv_release_bytes fs/btrfs/block-rsv.c:151 [inline]
WARNING: CPU: 0 PID: 3612 at fs/btrfs/space-info.h:122
btrfs_block_rsv_release+0x5d1/0x730 fs/btrfs/block-rsv.c:295
Modules linked in:
[...]
RIP: 0010:btrfs_space_info_update_bytes_may_use
fs/btrfs/space-info.h:122 [inline]
RIP: 0010:btrfs_space_info_free_bytes_may_use
fs/btrfs/space-info.h:154 [inline]
RIP: 0010:block_rsv_release_bytes
fs/btrfs/block-rsv.c:151 [inline]
RIP: 0010:btrfs_block_rsv_release+0x5d1/0x730
fs/btrfs/block-rsv.c:295
[...]
Call Trace:
<TASK>
btrfs_release_global_block_rsv+0x2f/0x250 fs/btrfs/block-rsv.c:463
btrfs_free_block_groups+0xb67/0xfd0 fs/btrfs/block-group.c:4053
close_ctree+0x6c5/0xbde fs/btrfs/disk-io.c:4710
generic_shutdown_super+0x130/0x310 fs/super.c:491
kill_anon_super+0x36/0x60 fs/super.c:1085
btrfs_kill_super+0x3d/0x50 fs/btrfs/super.c:2441
deactivate_locked_super+0xa7/0xf0 fs/super.c:331
cleanup_mnt+0x4ce/0x560 fs/namespace.c:1186
task_work_run+0x146/0x1c0 kernel/task_work.c:177
ptrace_notify+0x29a/0x340 kernel/signal.c:2354
ptrace_report_syscall include/linux/ptrace.h:420 [inline]
ptrace_report_syscall_exit include/linux/ptrace.h:482 [inline]
syscall_exit_work+0x8c/0xe0 kernel/entry/common.c:249
syscall_exit_to_user_mode_prepare+0x63/0xc0 kernel/entry/common.c:276
__syscall_exit_to_user_mode_work kernel/entry/common.c:281 [inline]
syscall_exit_to_user_mode+0xa/0x60 kernel/entry/common.c:294
do_syscall_64+0x49/0xb0 arch/x86/entry/common.c:86
entry_SYSCALL_64_after_hwframe+0x63/0xcd
[...]
</TASK>
=====================================
In btrfs_new_extent_direct(), kernel will reserves space for extent
by btrfs_reserve_extent(), and frees those space by
btrfs_free_reserved_extent() if btrfs_create_dio_extent() fails.
Yet the problem is that, it may not update the space
info correctly. To be more specific, kernel will
converts space from ->bytes_may_use to ->bytes_reserved, in
btrfs_add_reserved_bytes() when reserving space.
But when freeing those space in btrfs_free_reserved_bytes(),
kernel does not convert space from ->bytes_reserved back to
->bytes_may_use, which triggers the above warning.
This patch solves it by converting space from ->bytes_reserved
back to ->bytes_may_use in btrfs_free_reserved_bytes().
Link: https://lore.kernel.org/all/[email protected]
Reported-by: [email protected]
Tested-by: [email protected]
Signed-off-by: Hawkins Jiawei <[email protected]>
---
fs/btrfs/block-group.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/fs/btrfs/block-group.c b/fs/btrfs/block-group.c
index deebc8ddbd93..1b573ab5514b 100644
--- a/fs/btrfs/block-group.c
+++ b/fs/btrfs/block-group.c
@@ -3414,6 +3414,10 @@ void btrfs_free_reserved_bytes(struct btrfs_block_group *cache,
cache->reserved -= num_bytes;
space_info->bytes_reserved -= num_bytes;
space_info->max_extent_size = 0;
+ trace_btrfs_space_reservation(cache->fs_info, "space_info",
+ space_info->flags, -num_bytes, 1);
+ btrfs_space_info_update_bytes_may_use(cache->fs_info,
+ space_info, num_bytes);
if (delalloc)
cache->delalloc_bytes -= num_bytes;
--
2.25.1
On Mon, Oct 31, 2022 at 12:22:24AM +0800, Hawkins Jiawei wrote:
> Syzkaller reports warning as follows:
> =====================================
> WARNING: CPU: 0 PID: 3612 at fs/btrfs/space-info.h:122
> btrfs_space_info_free_bytes_may_use fs/btrfs/space-info.h:154 [inline]
> WARNING: CPU: 0 PID: 3612 at fs/btrfs/space-info.h:122
> block_rsv_release_bytes fs/btrfs/block-rsv.c:151 [inline]
> WARNING: CPU: 0 PID: 3612 at fs/btrfs/space-info.h:122
> btrfs_block_rsv_release+0x5d1/0x730 fs/btrfs/block-rsv.c:295
> Modules linked in:
> [...]
> RIP: 0010:btrfs_space_info_update_bytes_may_use
> fs/btrfs/space-info.h:122 [inline]
> RIP: 0010:btrfs_space_info_free_bytes_may_use
> fs/btrfs/space-info.h:154 [inline]
> RIP: 0010:block_rsv_release_bytes
> fs/btrfs/block-rsv.c:151 [inline]
> RIP: 0010:btrfs_block_rsv_release+0x5d1/0x730
> fs/btrfs/block-rsv.c:295
> [...]
> Call Trace:
> <TASK>
> btrfs_release_global_block_rsv+0x2f/0x250 fs/btrfs/block-rsv.c:463
> btrfs_free_block_groups+0xb67/0xfd0 fs/btrfs/block-group.c:4053
> close_ctree+0x6c5/0xbde fs/btrfs/disk-io.c:4710
> generic_shutdown_super+0x130/0x310 fs/super.c:491
> kill_anon_super+0x36/0x60 fs/super.c:1085
> btrfs_kill_super+0x3d/0x50 fs/btrfs/super.c:2441
> deactivate_locked_super+0xa7/0xf0 fs/super.c:331
> cleanup_mnt+0x4ce/0x560 fs/namespace.c:1186
> task_work_run+0x146/0x1c0 kernel/task_work.c:177
> ptrace_notify+0x29a/0x340 kernel/signal.c:2354
> ptrace_report_syscall include/linux/ptrace.h:420 [inline]
> ptrace_report_syscall_exit include/linux/ptrace.h:482 [inline]
> syscall_exit_work+0x8c/0xe0 kernel/entry/common.c:249
> syscall_exit_to_user_mode_prepare+0x63/0xc0 kernel/entry/common.c:276
> __syscall_exit_to_user_mode_work kernel/entry/common.c:281 [inline]
> syscall_exit_to_user_mode+0xa/0x60 kernel/entry/common.c:294
> do_syscall_64+0x49/0xb0 arch/x86/entry/common.c:86
> entry_SYSCALL_64_after_hwframe+0x63/0xcd
> [...]
> </TASK>
> =====================================
>
> In btrfs_new_extent_direct(), kernel will reserves space for extent
> by btrfs_reserve_extent(), and frees those space by
> btrfs_free_reserved_extent() if btrfs_create_dio_extent() fails.
>
> Yet the problem is that, it may not update the space
> info correctly. To be more specific, kernel will
> converts space from ->bytes_may_use to ->bytes_reserved, in
> btrfs_add_reserved_bytes() when reserving space.
> But when freeing those space in btrfs_free_reserved_bytes(),
> kernel does not convert space from ->bytes_reserved back to
> ->bytes_may_use, which triggers the above warning.
>
> This patch solves it by converting space from ->bytes_reserved
> back to ->bytes_may_use in btrfs_free_reserved_bytes().
>
This isn't correct. I haven't looked at the code yet, but reservations go into
->bytes_may_use, and then when we reserve the space we subtract the reservation
from ->bytes_may_use and add it to ->bytes_reserved. If we free the reserved
extent we only have to update ->bytes_reserved. What may be happening here is
we're failing to free the rest of our ->bytes_may_use resrvation, and that part
needs to be addressed. This fix as it stands however is incorrect. Thanks,
Josef
Hi Josef,
On Mon, 31 Oct 2022 at 23:12, Josef Bacik <[email protected]> wrote:
>
> On Mon, Oct 31, 2022 at 12:22:24AM +0800, Hawkins Jiawei wrote:
> > Syzkaller reports warning as follows:
> > =====================================
> > WARNING: CPU: 0 PID: 3612 at fs/btrfs/space-info.h:122
> > btrfs_space_info_free_bytes_may_use fs/btrfs/space-info.h:154 [inline]
> > WARNING: CPU: 0 PID: 3612 at fs/btrfs/space-info.h:122
> > block_rsv_release_bytes fs/btrfs/block-rsv.c:151 [inline]
> > WARNING: CPU: 0 PID: 3612 at fs/btrfs/space-info.h:122
> > btrfs_block_rsv_release+0x5d1/0x730 fs/btrfs/block-rsv.c:295
> > Modules linked in:
> > [...]
> > RIP: 0010:btrfs_space_info_update_bytes_may_use
> > fs/btrfs/space-info.h:122 [inline]
> > RIP: 0010:btrfs_space_info_free_bytes_may_use
> > fs/btrfs/space-info.h:154 [inline]
> > RIP: 0010:block_rsv_release_bytes
> > fs/btrfs/block-rsv.c:151 [inline]
> > RIP: 0010:btrfs_block_rsv_release+0x5d1/0x730
> > fs/btrfs/block-rsv.c:295
> > [...]
> > Call Trace:
> > <TASK>
> > btrfs_release_global_block_rsv+0x2f/0x250 fs/btrfs/block-rsv.c:463
> > btrfs_free_block_groups+0xb67/0xfd0 fs/btrfs/block-group.c:4053
> > close_ctree+0x6c5/0xbde fs/btrfs/disk-io.c:4710
> > generic_shutdown_super+0x130/0x310 fs/super.c:491
> > kill_anon_super+0x36/0x60 fs/super.c:1085
> > btrfs_kill_super+0x3d/0x50 fs/btrfs/super.c:2441
> > deactivate_locked_super+0xa7/0xf0 fs/super.c:331
> > cleanup_mnt+0x4ce/0x560 fs/namespace.c:1186
> > task_work_run+0x146/0x1c0 kernel/task_work.c:177
> > ptrace_notify+0x29a/0x340 kernel/signal.c:2354
> > ptrace_report_syscall include/linux/ptrace.h:420 [inline]
> > ptrace_report_syscall_exit include/linux/ptrace.h:482 [inline]
> > syscall_exit_work+0x8c/0xe0 kernel/entry/common.c:249
> > syscall_exit_to_user_mode_prepare+0x63/0xc0 kernel/entry/common.c:276
> > __syscall_exit_to_user_mode_work kernel/entry/common.c:281 [inline]
> > syscall_exit_to_user_mode+0xa/0x60 kernel/entry/common.c:294
> > do_syscall_64+0x49/0xb0 arch/x86/entry/common.c:86
> > entry_SYSCALL_64_after_hwframe+0x63/0xcd
> > [...]
> > </TASK>
> > =====================================
> >
> > In btrfs_new_extent_direct(), kernel will reserves space for extent
> > by btrfs_reserve_extent(), and frees those space by
> > btrfs_free_reserved_extent() if btrfs_create_dio_extent() fails.
> >
> > Yet the problem is that, it may not update the space
> > info correctly. To be more specific, kernel will
> > converts space from ->bytes_may_use to ->bytes_reserved, in
> > btrfs_add_reserved_bytes() when reserving space.
> > But when freeing those space in btrfs_free_reserved_bytes(),
> > kernel does not convert space from ->bytes_reserved back to
> > ->bytes_may_use, which triggers the above warning.
> >
> > This patch solves it by converting space from ->bytes_reserved
> > back to ->bytes_may_use in btrfs_free_reserved_bytes().
> >
>
> This isn't correct. I haven't looked at the code yet, but reservations go into
> ->bytes_may_use, and then when we reserve the space we subtract the reservation
> from ->bytes_may_use and add it to ->bytes_reserved. If we free the reserved
> extent we only have to update ->bytes_reserved. What may be happening here is
> we're failing to free the rest of our ->bytes_may_use resrvation, and that part
> needs to be addressed. This fix as it stands however is incorrect. Thanks,
Thanks for your explanation! I will re-analyse this bug in the way you
suggested.
>
> Josef