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Qu Wenruo d139ded8b9 btrfs: qgroup: always free reserved space for extent records
[BUG]
If qgroup is marked inconsistent (e.g. caused by operations needing full
subtree rescan, like creating a snapshot and assign to a higher level
qgroup), btrfs would immediately start leaking its data reserved space.

The following script can easily reproduce it:

  mkfs.btrfs -O quota -f $dev
  mount $dev $mnt
  btrfs subvolume create $mnt/subv1
  btrfs qgroup create 1/0 $mnt

  # This snapshot creation would mark qgroup inconsistent,
  # as the ownership involves different higher level qgroup, thus
  # we have to rescan both source and snapshot, which can be very
  # time consuming, thus here btrfs just choose to mark qgroup
  # inconsistent, and let users to determine when to do the rescan.
  btrfs subv snapshot -i 1/0 $mnt/subv1 $mnt/snap1

  # Now this write would lead to qgroup rsv leak.
  xfs_io -f -c "pwrite 0 64k" $mnt/file1

  # And at unmount time, btrfs would report 64K DATA rsv space leaked.
  umount $mnt

And we would have the following dmesg output for the unmount:

  BTRFS info (device dm-1): last unmount of filesystem 14a3d84e-f47b-4f72-b053-a8a36eef74d3
  BTRFS warning (device dm-1): qgroup 0/5 has unreleased space, type 0 rsv 65536

[CAUSE]
Since commit e15e9f43c7 ("btrfs: introduce
BTRFS_QGROUP_RUNTIME_FLAG_NO_ACCOUNTING to skip qgroup accounting"),
we introduce a mode for btrfs qgroup to skip the timing consuming
backref walk, if the qgroup is already inconsistent.

But this skip also covered the data reserved freeing, thus the qgroup
reserved space for each newly created data extent would not be freed,
thus cause the leakage.

[FIX]
Make the data extent reserved space freeing mandatory.

The qgroup reserved space handling is way cheaper compared to the
backref walking part, and we always have the super sensitive leak
detector, thus it's definitely worth to always free the qgroup
reserved data space.

Reported-by: Fabian Vogt <fvogt@suse.com>
Fixes: e15e9f43c7 ("btrfs: introduce BTRFS_QGROUP_RUNTIME_FLAG_NO_ACCOUNTING to skip qgroup accounting")
CC: stable@vger.kernel.org # 6.1+
Link: https://bugzilla.suse.com/show_bug.cgi?id=1216196
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2024-03-05 17:13:23 +01:00
arch powerpc fixes for 6.8 #5 2024-03-03 09:47:19 -08:00
block block: sed-opal: handle empty atoms when parsing response 2024-02-16 15:52:45 -07:00
certs This update includes the following changes: 2023-11-02 16:15:30 -10:00
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Documentation Including fixes from bluetooth, WiFi and netfilter. 2024-02-29 12:40:20 -08:00
drivers phy second set of fixes for 6.8 2024-03-03 09:56:49 -08:00
fs btrfs: qgroup: always free reserved space for extent records 2024-03-05 17:13:23 +01:00
include block: define bvec_iter as __packed __aligned(4) 2024-03-02 09:15:01 -08:00
init update workarounds for gcc "asm goto" issue 2024-02-15 11:14:33 -08:00
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virt Generic: 2024-01-17 13:03:37 -08:00
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.cocciconfig
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COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: supplement of zswap maintainers update 2024-01-25 23:52:21 -08:00
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MAINTAINERS RISC-V Fixes for 6.8-rc7 2024-03-01 12:44:33 -08:00
Makefile Linux 6.8-rc7 2024-03-03 13:02:52 -08:00
README

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.