btrfs: qgroup: fix data leak caused by race between writeback and truncate
[BUG]
When running tests like generic/013 on test device with btrfs quota
enabled, it can normally lead to data leak, detected at unmount time:
BTRFS warning (device dm-3): qgroup 0/5 has unreleased space, type 0 rsv 4096
------------[ cut here ]------------
WARNING: CPU: 11 PID: 16386 at fs/btrfs/disk-io.c:4142 close_ctree+0x1dc/0x323 [btrfs]
RIP: 0010:close_ctree+0x1dc/0x323 [btrfs]
Call Trace:
btrfs_put_super+0x15/0x17 [btrfs]
generic_shutdown_super+0x72/0x110
kill_anon_super+0x18/0x30
btrfs_kill_super+0x17/0x30 [btrfs]
deactivate_locked_super+0x3b/0xa0
deactivate_super+0x40/0x50
cleanup_mnt+0x135/0x190
__cleanup_mnt+0x12/0x20
task_work_run+0x64/0xb0
__prepare_exit_to_usermode+0x1bc/0x1c0
__syscall_return_slowpath+0x47/0x230
do_syscall_64+0x64/0xb0
entry_SYSCALL_64_after_hwframe+0x44/0xa9
---[ end trace caf08beafeca2392 ]---
BTRFS error (device dm-3): qgroup reserved space leaked
[CAUSE]
In the offending case, the offending operations are:
2/6: writev f2X[269 1 0 0 0 0] [1006997,67,288] 0
2/7: truncate f2X[269 1 0 0 48 1026293] 18388 0
The following sequence of events could happen after the writev():
CPU1 (writeback) | CPU2 (truncate)
-----------------------------------------------------------------
btrfs_writepages() |
|- extent_write_cache_pages() |
|- Got page for 1003520 |
| 1003520 is Dirty, no writeback |
| So (!clear_page_dirty_for_io()) |
| gets called for it |
|- Now page 1003520 is Clean. |
| | btrfs_setattr()
| | |- btrfs_setsize()
| | |- truncate_setsize()
| | New i_size is 18388
|- __extent_writepage() |
| |- page_offset() > i_size |
|- btrfs_invalidatepage() |
|- Page is clean, so no qgroup |
callback executed
This means, the qgroup reserved data space is not properly released in
btrfs_invalidatepage() as the page is Clean.
[FIX]
Instead of checking the dirty bit of a page, call
btrfs_qgroup_free_data() unconditionally in btrfs_invalidatepage().
As qgroup rsv are completely bound to the QGROUP_RESERVED bit of
io_tree, not bound to page status, thus we won't cause double freeing
anyway.
Fixes: 0b34c261e2
("btrfs: qgroup: Prevent qgroup->reserved from going subzero")
CC: stable@vger.kernel.org # 4.14+
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
parent
580c079b57
commit
fa91e4aa17
@ -8136,20 +8136,17 @@ again:
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/*
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* Qgroup reserved space handler
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* Page here will be either
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* 1) Already written to disk
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* In this case, its reserved space is released from data rsv map
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* and will be freed by delayed_ref handler finally.
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* So even we call qgroup_free_data(), it won't decrease reserved
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* space.
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* 2) Not written to disk
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* This means the reserved space should be freed here. However,
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* if a truncate invalidates the page (by clearing PageDirty)
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* and the page is accounted for while allocating extent
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* in btrfs_check_data_free_space() we let delayed_ref to
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* free the entire extent.
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* 1) Already written to disk or ordered extent already submitted
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* Then its QGROUP_RESERVED bit in io_tree is already cleaned.
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* Qgroup will be handled by its qgroup_record then.
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* btrfs_qgroup_free_data() call will do nothing here.
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*
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* 2) Not written to disk yet
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* Then btrfs_qgroup_free_data() call will clear the QGROUP_RESERVED
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* bit of its io_tree, and free the qgroup reserved data space.
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* Since the IO will never happen for this page.
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*/
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if (PageDirty(page))
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btrfs_qgroup_free_data(inode, NULL, page_start, PAGE_SIZE);
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btrfs_qgroup_free_data(inode, NULL, page_start, PAGE_SIZE);
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if (!inode_evicting) {
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clear_extent_bit(tree, page_start, page_end, EXTENT_LOCKED |
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EXTENT_DELALLOC | EXTENT_DELALLOC_NEW |
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