linux.git/fs/btrfs/relocation.c, branch v5.4

btrfs: qgroup: Always free PREALLOC META reserve in btrfs_delalloc_release_extents()

2019-10-15T16:50:07+00:00

[Background]
Btrfs qgroup uses two types of reserved space for METADATA space,
PERTRANS and PREALLOC.

PERTRANS is metadata space reserved for each transaction started by
btrfs_start_transaction().
While PREALLOC is for delalloc, where we reserve space before joining a
transaction, and finally it will be converted to PERTRANS after the
writeback is done.

[Inconsistency]
However there is inconsistency in how we handle PREALLOC metadata space.

The most obvious one is:
In btrfs_buffered_write():
	btrfs_delalloc_release_extents(BTRFS_I(inode), reserve_bytes, true);

We always free qgroup PREALLOC meta space.

While in btrfs_truncate_block():
	btrfs_delalloc_release_extents(BTRFS_I(inode), blocksize, (ret != 0));

We only free qgroup PREALLOC meta space when something went wrong.

[The Correct Behavior]
The correct behavior should be the one in btrfs_buffered_write(), we
should always free PREALLOC metadata space.

The reason is, the btrfs_delalloc_* mechanism works by:
- Reserve metadata first, even it's not necessary
  In btrfs_delalloc_reserve_metadata()

- Free the unused metadata space
  Normally in:
  btrfs_delalloc_release_extents()
  |- btrfs_inode_rsv_release()
     Here we do calculation on whether we should release or not.

E.g. for 64K buffered write, the metadata rsv works like:

/* The first page */
reserve_meta:	num_bytes=calc_inode_reservations()
free_meta:	num_bytes=0
total:		num_bytes=calc_inode_reservations()
/* The first page caused one outstanding extent, thus needs metadata
   rsv */

/* The 2nd page */
reserve_meta:	num_bytes=calc_inode_reservations()
free_meta:	num_bytes=calc_inode_reservations()
total:		not changed
/* The 2nd page doesn't cause new outstanding extent, needs no new meta
   rsv, so we free what we have reserved */

/* The 3rd~16th pages */
reserve_meta:	num_bytes=calc_inode_reservations()
free_meta:	num_bytes=calc_inode_reservations()
total:		not changed (still space for one outstanding extent)

This means, if btrfs_delalloc_release_extents() determines to free some
space, then those space should be freed NOW.
So for qgroup, we should call btrfs_qgroup_free_meta_prealloc() other
than btrfs_qgroup_convert_reserved_meta().

The good news is:
- The callers are not that hot
  The hottest caller is in btrfs_buffered_write(), which is already
  fixed by commit 336a8bb8e36a ("btrfs: Fix wrong
  btrfs_delalloc_release_extents parameter"). Thus it's not that
  easy to cause false EDQUOT.

- The trans commit in advance for qgroup would hide the bug
  Since commit f5fef4593653 ("btrfs: qgroup: Make qgroup async transaction
  commit more aggressive"), when btrfs qgroup metadata free space is slow,
  it will try to commit transaction and free the wrongly converted
  PERTRANS space, so it's not that easy to hit such bug.

[FIX]
So to fix the problem, remove the @qgroup_free parameter for
btrfs_delalloc_release_extents(), and always pass true to
btrfs_inode_rsv_release().

Reported-by: Filipe Manana 
Fixes: 43b18595d660 ("btrfs: qgroup: Use separate meta reservation type for delalloc")
CC: stable@vger.kernel.org # 4.19+
Reviewed-by: Filipe Manana 
Signed-off-by: Qu Wenruo 
Signed-off-by: David Sterba

Btrfs: add missing extents release on file extent cluster relocation error

2019-10-11T17:49:11+00:00

If we error out when finding a page at relocate_file_extent_cluster(), we
need to release the outstanding extents counter on the relocation inode,
set by the previous call to btrfs_delalloc_reserve_metadata(), otherwise
the inode's block reserve size can never decrease to zero and metadata
space is leaked. Therefore add a call to btrfs_delalloc_release_extents()
in case we can't find the target page.

Fixes: 8b62f87bad9c ("Btrfs: rework outstanding_extents")
CC: stable@vger.kernel.org # 4.19+
Signed-off-by: Filipe Manana 
Reviewed-by: David Sterba 
Signed-off-by: David Sterba

btrfs: relocation: fix use-after-free on dead relocation roots

2019-09-25T13:23:42+00:00

[BUG]
One user reported a reproducible KASAN report about use-after-free:

  BTRFS info (device sdi1): balance: start -dvrange=1256811659264..1256811659265
  BTRFS info (device sdi1): relocating block group 1256811659264 flags data|raid0
  ==================================================================
  BUG: KASAN: use-after-free in btrfs_init_reloc_root+0x2cd/0x340 [btrfs]
  Write of size 8 at addr ffff88856f671710 by task kworker/u24:10/261579

  CPU: 2 PID: 261579 Comm: kworker/u24:10 Tainted: P           OE     5.2.11-arch1-1-kasan #4
  Hardware name: To Be Filled By O.E.M. To Be Filled By O.E.M./X99 Extreme4, BIOS P3.80 04/06/2018
  Workqueue: btrfs-endio-write btrfs_endio_write_helper [btrfs]
  Call Trace:
   dump_stack+0x7b/0xba
   print_address_description+0x6c/0x22e
   ? btrfs_init_reloc_root+0x2cd/0x340 [btrfs]
   __kasan_report.cold+0x1b/0x3b
   ? btrfs_init_reloc_root+0x2cd/0x340 [btrfs]
   kasan_report+0x12/0x17
   __asan_report_store8_noabort+0x17/0x20
   btrfs_init_reloc_root+0x2cd/0x340 [btrfs]
   record_root_in_trans+0x2a0/0x370 [btrfs]
   btrfs_record_root_in_trans+0xf4/0x140 [btrfs]
   start_transaction+0x1ab/0xe90 [btrfs]
   btrfs_join_transaction+0x1d/0x20 [btrfs]
   btrfs_finish_ordered_io+0x7bf/0x18a0 [btrfs]
   ? lock_repin_lock+0x400/0x400
   ? __kmem_cache_shutdown.cold+0x140/0x1ad
   ? btrfs_unlink_subvol+0x9b0/0x9b0 [btrfs]
   finish_ordered_fn+0x15/0x20 [btrfs]
   normal_work_helper+0x1bd/0xca0 [btrfs]
   ? process_one_work+0x819/0x1720
   ? kasan_check_read+0x11/0x20
   btrfs_endio_write_helper+0x12/0x20 [btrfs]
   process_one_work+0x8c9/0x1720
   ? pwq_dec_nr_in_flight+0x2f0/0x2f0
   ? worker_thread+0x1d9/0x1030
   worker_thread+0x98/0x1030
   kthread+0x2bb/0x3b0
   ? process_one_work+0x1720/0x1720
   ? kthread_park+0x120/0x120
   ret_from_fork+0x35/0x40

  Allocated by task 369692:
   __kasan_kmalloc.part.0+0x44/0xc0
   __kasan_kmalloc.constprop.0+0xba/0xc0
   kasan_kmalloc+0x9/0x10
   kmem_cache_alloc_trace+0x138/0x260
   btrfs_read_tree_root+0x92/0x360 [btrfs]
   btrfs_read_fs_root+0x10/0xb0 [btrfs]
   create_reloc_root+0x47d/0xa10 [btrfs]
   btrfs_init_reloc_root+0x1e2/0x340 [btrfs]
   record_root_in_trans+0x2a0/0x370 [btrfs]
   btrfs_record_root_in_trans+0xf4/0x140 [btrfs]
   start_transaction+0x1ab/0xe90 [btrfs]
   btrfs_start_transaction+0x1e/0x20 [btrfs]
   __btrfs_prealloc_file_range+0x1c2/0xa00 [btrfs]
   btrfs_prealloc_file_range+0x13/0x20 [btrfs]
   prealloc_file_extent_cluster+0x29f/0x570 [btrfs]
   relocate_file_extent_cluster+0x193/0xc30 [btrfs]
   relocate_data_extent+0x1f8/0x490 [btrfs]
   relocate_block_group+0x600/0x1060 [btrfs]
   btrfs_relocate_block_group+0x3a0/0xa00 [btrfs]
   btrfs_relocate_chunk+0x9e/0x180 [btrfs]
   btrfs_balance+0x14e4/0x2fc0 [btrfs]
   btrfs_ioctl_balance+0x47f/0x640 [btrfs]
   btrfs_ioctl+0x119d/0x8380 [btrfs]
   do_vfs_ioctl+0x9f5/0x1060
   ksys_ioctl+0x67/0x90
   __x64_sys_ioctl+0x73/0xb0
   do_syscall_64+0xa5/0x370
   entry_SYSCALL_64_after_hwframe+0x44/0xa9

  Freed by task 369692:
   __kasan_slab_free+0x14f/0x210
   kasan_slab_free+0xe/0x10
   kfree+0xd8/0x270
   btrfs_drop_snapshot+0x154c/0x1eb0 [btrfs]
   clean_dirty_subvols+0x227/0x340 [btrfs]
   relocate_block_group+0x972/0x1060 [btrfs]
   btrfs_relocate_block_group+0x3a0/0xa00 [btrfs]
   btrfs_relocate_chunk+0x9e/0x180 [btrfs]
   btrfs_balance+0x14e4/0x2fc0 [btrfs]
   btrfs_ioctl_balance+0x47f/0x640 [btrfs]
   btrfs_ioctl+0x119d/0x8380 [btrfs]
   do_vfs_ioctl+0x9f5/0x1060
   ksys_ioctl+0x67/0x90
   __x64_sys_ioctl+0x73/0xb0
   do_syscall_64+0xa5/0x370
   entry_SYSCALL_64_after_hwframe+0x44/0xa9

  The buggy address belongs to the object at ffff88856f671100
   which belongs to the cache kmalloc-4k of size 4096
  The buggy address is located 1552 bytes inside of
   4096-byte region [ffff88856f671100, ffff88856f672100)
  The buggy address belongs to the page:
  page:ffffea0015bd9c00 refcount:1 mapcount:0 mapping:ffff88864400e600 index:0x0 compound_mapcount: 0
  flags: 0x2ffff0000010200(slab|head)
  raw: 02ffff0000010200 dead000000000100 dead000000000200 ffff88864400e600
  raw: 0000000000000000 0000000000070007 00000001ffffffff 0000000000000000
  page dumped because: kasan: bad access detected

  Memory state around the buggy address:
   ffff88856f671600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
   ffff88856f671680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
  >ffff88856f671700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                           ^
   ffff88856f671780: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
   ffff88856f671800: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
  ==================================================================
  BTRFS info (device sdi1): 1 enospc errors during balance
  BTRFS info (device sdi1): balance: ended with status: -28

[CAUSE]
The problem happens when finish_ordered_io() get called with balance
still running, while the reloc root of that subvolume is already dead.
(Tree is swap already done, but tree not yet deleted for possible qgroup
usage.)

That means root->reloc_root still exists, but that reloc_root can be
under btrfs_drop_snapshot(), thus we shouldn't access it.

The following race could cause the use-after-free problem:

                CPU1              |                CPU2
--------------------------------------------------------------------------
                                  | relocate_block_group()
                                  | |- unset_reloc_control(rc)
                                  | |- btrfs_commit_transaction()
btrfs_finish_ordered_io()         | |- clean_dirty_subvols()
|- btrfs_join_transaction()       |    |
   |- record_root_in_trans()      |    |
      |- btrfs_init_reloc_root()  |    |
         |- if (root->reloc_root) |    |
         |                        |    |- root->reloc_root = NULL
         |                        |    |- btrfs_drop_snapshot(reloc_root);
         |- reloc_root->last_trans|
                 = trans->transid |
	    ^^^^^^^^^^^^^^^^^^^^^^
            Use after free

[FIX]
Fix it by the following modifications:

- Test if the root has dead reloc tree before accessing root->reloc_root
  If the root has BTRFS_ROOT_DEAD_RELOC_TREE, then we don't need to
  create or update root->reloc_tree

- Clear the BTRFS_ROOT_DEAD_RELOC_TREE flag until we have fully dropped
  reloc tree
  To co-operate with above modification, so as long as
  BTRFS_ROOT_DEAD_RELOC_TREE is still set, we won't try to re-create
  reloc tree at record_root_in_trans().

Reported-by: Cebtenzzre 
Fixes: d2311e698578 ("btrfs: relocation: Delay reloc tree deletion after merge_reloc_roots")
CC: stable@vger.kernel.org # 5.1+
Reviewed-by: Josef Bacik 
Reviewed-by: Filipe Manana 
Signed-off-by: Qu Wenruo 
Reviewed-by: David Sterba 
Signed-off-by: David Sterba

btrfs: move basic block_group definitions to their own header

2019-09-09T12:59:03+00:00

This is prep work for moving all of the block group cache code into its
own file.

Signed-off-by: Josef Bacik 
Reviewed-by: David Sterba 
[ minor comment updates ]
Signed-off-by: David Sterba

btrfs: Remove leftover of in-band dedupe

2019-09-09T12:58:59+00:00

It's unlikely in-band dedupe is going to land so just remove any
leftovers - dedupe.h header as well as the 'dedupe' parameter to
btrfs_set_extent_delalloc.

Signed-off-by: Nikolay Borisov 
Reviewed-by: David Sterba 
Signed-off-by: David Sterba

btrfs: migrate the delalloc space stuff to it's own home

2019-07-04T15:26:17+00:00

We have code for data and metadata reservations for delalloc.  There's
quite a bit of code here, and it's used in a lot of places so I've
separated it out to it's own file.  inode.c and file.c are already
pretty large, and this code is complicated enough to live in its own
space.

Signed-off-by: Josef Bacik 
Signed-off-by: David Sterba

btrfs: reloc: Also queue orphan reloc tree for cleanup to avoid BUG_ON()

2019-05-28T16:54:10+00:00

[BUG]
When a fs has orphan reloc tree along with unfinished balance:
  ...
        item 16 key (TREE_RELOC ROOT_ITEM FS_TREE) itemoff 12090 itemsize 439
                generation 12 root_dirid 256 bytenr 300400640 level 1 refs 0 <<<
                lastsnap 8 byte_limit 0 bytes_used 1359872 flags 0x0(none)
                uuid 7c48d938-33a3-4aae-ab19-6e5c9d406e46
        item 17 key (BALANCE TEMPORARY_ITEM 0) itemoff 11642 itemsize 448
                temporary item objectid BALANCE offset 0
                balance status flags 14

Then at mount time, we can hit the following kernel BUG_ON():
  BTRFS info (device dm-3): relocating block group 298844160 flags metadata|dup
  ------------[ cut here ]------------
  kernel BUG at fs/btrfs/relocation.c:1413!
  invalid opcode: 0000 [#1] PREEMPT SMP NOPTI
  CPU: 1 PID: 897 Comm: btrfs-balance Tainted: G           O      5.2.0-rc1-custom #15
  RIP: 0010:create_reloc_root+0x1eb/0x200 [btrfs]
  Call Trace:
   btrfs_init_reloc_root+0x96/0xb0 [btrfs]
   record_root_in_trans+0xb2/0xe0 [btrfs]
   btrfs_record_root_in_trans+0x55/0x70 [btrfs]
   select_reloc_root+0x7e/0x230 [btrfs]
   do_relocation+0xc4/0x620 [btrfs]
   relocate_tree_blocks+0x592/0x6a0 [btrfs]
   relocate_block_group+0x47b/0x5d0 [btrfs]
   btrfs_relocate_block_group+0x183/0x2f0 [btrfs]
   btrfs_relocate_chunk+0x4e/0xe0 [btrfs]
   btrfs_balance+0x864/0xfa0 [btrfs]
   balance_kthread+0x3b/0x50 [btrfs]
   kthread+0x123/0x140
   ret_from_fork+0x27/0x50

[CAUSE]
In btrfs, reloc trees are used to record swapped tree blocks during
balance.
Reloc tree either get merged (replace old tree blocks of its parent
subvolume) in next transaction if its ref is 1 (fresh).
Or is already merged and will be cleaned up if its ref is 0 (orphan).

After commit d2311e698578 ("btrfs: relocation: Delay reloc tree deletion
after merge_reloc_roots"), reloc tree cleanup is delayed until one block
group is balanced.

Since fresh reloc roots are recorded during merge, as long as there
is no power loss, those orphan reloc roots converted from fresh ones are
handled without problem.

However when power loss happens, orphan reloc roots can be recorded
on-disk, thus at next mount time, we will have orphan reloc roots from
on-disk data directly, and ignored by clean_dirty_subvols() routine.

Then when background balance starts to balance another block group, and
needs to create new reloc root for the same root, btrfs_insert_item()
returns -EEXIST, and trigger that BUG_ON().

[FIX]
For orphan reloc roots, also queue them to rc->dirty_subvol_roots, so
all reloc roots no matter orphan or not, can be cleaned up properly and
avoid above BUG_ON().

And to cooperate with above change, clean_dirty_subvols() will check if
the queued root is a reloc root or a subvol root.
For a subvol root, do the old work, and for a orphan reloc root, clean it
up.

Fixes: d2311e698578 ("btrfs: relocation: Delay reloc tree deletion after merge_reloc_roots")
CC: stable@vger.kernel.org # 5.1
Signed-off-by: Qu Wenruo 
Signed-off-by: David Sterba

btrfs: extent-tree: Use btrfs_ref to refactor btrfs_free_extent()

2019-04-29T17:02:49+00:00

Similar to btrfs_inc_extent_ref(), use btrfs_ref to replace the long
parameter list and the confusing @owner parameter.

Signed-off-by: Qu Wenruo 
Reviewed-by: David Sterba 
Signed-off-by: David Sterba

btrfs: extent-tree: Use btrfs_ref to refactor btrfs_inc_extent_ref()

2019-04-29T17:02:49+00:00

Use the new btrfs_ref structure and replace parameter list to clean up
the usage of owner and level to distinguish the extent types.

Signed-off-by: Qu Wenruo 
Reviewed-by: David Sterba 
Signed-off-by: David Sterba

btrfs: get fs_info from block group in lookup_free_space_inode

2019-04-29T17:02:45+00:00

We can read fs_info from the block group cache structure and can drop it
from the parameters.

Signed-off-by: David Sterba