linux-toradex.git/fs/btrfs/relocation.c, branch v4.9.105

btrfs: fix NULL pointer dereference from free_reloc_roots()

2017-10-05T07:44:03+00:00

commit bb166d7207432d3c7d10c45dc052f12ba3a2121d upstream.

__del_reloc_root should be called before freeing up reloc_root->node.
If not, calling __del_reloc_root() dereference reloc_root->node, causing
the system BUG.

Fixes: 6bdf131fac23 ("Btrfs: don't leak reloc root nodes on error")
Signed-off-by: Naohiro Aota 
Reviewed-by: Nikolay Borisov 
Reviewed-by: David Sterba 
Signed-off-by: David Sterba 
Signed-off-by: Greg Kroah-Hartman

Btrfs: fix relocation incorrectly dropping data references

2017-01-06T09:40:10+00:00

commit 054570a1dc94de20e7a612cddcc5a97db9c37b6f upstream.

During relocation of a data block group we create a relocation tree
for each fs/subvol tree by making a snapshot of each tree using
btrfs_copy_root() and the tree's commit root, and then setting the last
snapshot field for the fs/subvol tree's root to the value of the current
transaction id minus 1. However this can lead to relocation later
dropping references that it did not create if we have qgroups enabled,
leaving the filesystem in an inconsistent state that keeps aborting
transactions.

Lets consider the following example to explain the problem, which requires
qgroups to be enabled.

We are relocating data block group Y, we have a subvolume with id 258 that
has a root at level 1, that subvolume is used to store directory entries
for snapshots and we are currently at transaction 3404.

When committing transaction 3404, we have a pending snapshot and therefore
we call btrfs_run_delayed_items() at transaction.c:create_pending_snapshot()
in order to create its dentry at subvolume 258. This results in COWing
leaf A from root 258 in order to add the dentry. Note that leaf A
also contains file extent items referring to extents from some other
block group X (we are currently relocating block group Y). Later on, still
at create_pending_snapshot() we call qgroup_account_snapshot(), which
switches the commit root for root 258 when it calls switch_commit_roots(),
so now the COWed version of leaf A, lets call it leaf A', is accessible
from the commit root of tree 258. At the end of qgroup_account_snapshot(),
we call record_root_in_trans() with 258 as its argument, which results
in btrfs_init_reloc_root() being called, which in turn calls
relocation.c:create_reloc_root() in order to create a relocation tree
associated to root 258, which results in assigning the value of 3403
(which is the current transaction id minus 1 = 3404 - 1) to the
last_snapshot field of root 258. When creating the relocation tree root
at ctree.c:btrfs_copy_root() we add a shared reference for leaf A',
corresponding to the relocation tree's root, when we call btrfs_inc_ref()
against the COWed root (a copy of the commit root from tree 258), which
is at level 1. So at this point leaf A' has 2 references, one normal
reference corresponding to root 258 and one shared reference corresponding
to the root of the relocation tree.

Transaction 3404 finishes its commit and transaction 3405 is started by
relocation when calling merge_reloc_root() for the relocation tree
associated to root 258. In the meanwhile leaf A' is COWed again, in
response to some filesystem operation, when we are still at transaction
3405. However when we COW leaf A', at ctree.c:update_ref_for_cow(), we
call btrfs_block_can_be_shared() in order to figure out if other trees
refer to the leaf and if any such trees exists, add a full back reference
to leaf A' - but btrfs_block_can_be_shared() incorrectly returns false
because the following condition is false:

  btrfs_header_generation(buf) <= btrfs_root_last_snapshot(&root->root_item)

which evaluates to 3404 <= 3403. So after leaf A' is COWed, it stays with
only one reference, corresponding to the shared reference we created when
we called btrfs_copy_root() to create the relocation tree's root and
btrfs_inc_ref() ends up not being called for leaf A' nor we end up setting
the flag BTRFS_BLOCK_FLAG_FULL_BACKREF in leaf A'. This results in not
adding shared references for the extents from block group X that leaf A'
refers to with its file extent items.

Later, after merging the relocation root we do a call to to
btrfs_drop_snapshot() in order to delete the relocation tree. This ends
up calling do_walk_down() when path->slots[1] points to leaf A', which
results in calling btrfs_lookup_extent_info() to get the number of
references for leaf A', which is 1 at this time (only the shared reference
exists) and this value is stored at wc->refs[0]. After this walk_up_proc()
is called when wc->level is 0 and path->nodes[0] corresponds to leaf A'.
Because the current level is 0 and wc->refs[0] is 1, it does call
btrfs_dec_ref() against leaf A', which results in removing the single
references that the extents from block group X have which are associated
to root 258 - the expectation was to have each of these extents with 2
references - one reference for root 258 and one shared reference related
to the root of the relocation tree, and so we would drop only the shared
reference (because leaf A' was supposed to have the flag
BTRFS_BLOCK_FLAG_FULL_BACKREF set).

This leaves the filesystem in an inconsistent state as we now have file
extent items in a subvolume tree that point to extents from block group X
without references in the extent tree. So later on when we try to decrement
the references for these extents, for example due to a file unlink operation,
truncate operation or overwriting ranges of a file, we fail because the
expected references do not exist in the extent tree.

This leads to warnings and transaction aborts like the following:

[  588.965795] ------------[ cut here ]------------
[  588.965815] WARNING: CPU: 2 PID: 2479 at fs/btrfs/extent-tree.c:1625 lookup_inline_extent_backref+0x432/0x5b0 [btrfs]
[  588.965816] Modules linked in: af_packet iscsi_ibft iscsi_boot_sysfs xfs libcrc32c ppdev acpi_cpufreq button tpm_tis e1000 i2c_piix4 pcspkr parport_pc
parport tpm qemu_fw_cfg joydev btrfs xor raid6_pq sr_mod cdrom ata_generic virtio_scsi ata_piix virtio_pci bochs_drm virtio_ring drm_kms_helper syscopyarea
sysfillrect sysimgblt fb_sys_fops virtio ttm serio_raw drm floppy sg
[  588.965831] CPU: 2 PID: 2479 Comm: kworker/u8:7 Not tainted 4.7.3-3-default-fdm+ #1
[  588.965832] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.9.1-0-gb3ef39f-prebuilt.qemu-project.org 04/01/2014
[  588.965844] Workqueue: btrfs-extent-refs btrfs_extent_refs_helper [btrfs]
[  588.965845]  0000000000000000 ffff8802263bfa28 ffffffff813af542 0000000000000000
[  588.965847]  0000000000000000 ffff8802263bfa68 ffffffff81081e8b 0000065900000000
[  588.965848]  ffff8801db2af000 000000012bbe2000 0000000000000000 ffff880215703b48
[  588.965849] Call Trace:
[  588.965852]  [] dump_stack+0x63/0x81
[  588.965854]  [] __warn+0xcb/0xf0
[  588.965855]  [] warn_slowpath_null+0x1d/0x20
[  588.965863]  [] lookup_inline_extent_backref+0x432/0x5b0 [btrfs]
[  588.965865]  [] ? trace_clock_local+0x10/0x30
[  588.965867]  [] ? rb_reserve_next_event+0x6f/0x460
[  588.965875]  [] insert_inline_extent_backref+0x55/0xd0 [btrfs]
[  588.965882]  [] __btrfs_inc_extent_ref.isra.55+0x8f/0x240 [btrfs]
[  588.965890]  [] __btrfs_run_delayed_refs+0x74a/0x1260 [btrfs]
[  588.965892]  [] ? cpuacct_charge+0x86/0xa0
[  588.965900]  [] btrfs_run_delayed_refs+0x9f/0x2c0 [btrfs]
[  588.965908]  [] delayed_ref_async_start+0x94/0xb0 [btrfs]
[  588.965918]  [] btrfs_scrubparity_helper+0xca/0x350 [btrfs]
[  588.965928]  [] btrfs_extent_refs_helper+0xe/0x10 [btrfs]
[  588.965930]  [] process_one_work+0x1f3/0x4e0
[  588.965931]  [] worker_thread+0x48/0x4e0
[  588.965932]  [] ? process_one_work+0x4e0/0x4e0
[  588.965934]  [] kthread+0xc9/0xe0
[  588.965936]  [] ret_from_fork+0x1f/0x40
[  588.965937]  [] ? kthread_worker_fn+0x170/0x170
[  588.965938] ---[ end trace 34e5232c933a1749 ]---
[  588.966187] ------------[ cut here ]------------
[  588.966196] WARNING: CPU: 2 PID: 2479 at fs/btrfs/extent-tree.c:2966 btrfs_run_delayed_refs+0x28c/0x2c0 [btrfs]
[  588.966196] BTRFS: Transaction aborted (error -5)
[  588.966197] Modules linked in: af_packet iscsi_ibft iscsi_boot_sysfs xfs libcrc32c ppdev acpi_cpufreq button tpm_tis e1000 i2c_piix4 pcspkr parport_pc
parport tpm qemu_fw_cfg joydev btrfs xor raid6_pq sr_mod cdrom ata_generic virtio_scsi ata_piix virtio_pci bochs_drm virtio_ring drm_kms_helper syscopyarea
sysfillrect sysimgblt fb_sys_fops virtio ttm serio_raw drm floppy sg
[  588.966206] CPU: 2 PID: 2479 Comm: kworker/u8:7 Tainted: G        W       4.7.3-3-default-fdm+ #1
[  588.966207] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.9.1-0-gb3ef39f-prebuilt.qemu-project.org 04/01/2014
[  588.966217] Workqueue: btrfs-extent-refs btrfs_extent_refs_helper [btrfs]
[  588.966217]  0000000000000000 ffff8802263bfc98 ffffffff813af542 ffff8802263bfce8
[  588.966219]  0000000000000000 ffff8802263bfcd8 ffffffff81081e8b 00000b96345ee000
[  588.966220]  ffffffffa021ae1c ffff880215703b48 00000000000005fe ffff8802345ee000
[  588.966221] Call Trace:
[  588.966223]  [] dump_stack+0x63/0x81
[  588.966224]  [] __warn+0xcb/0xf0
[  588.966225]  [] warn_slowpath_fmt+0x4f/0x60
[  588.966233]  [] btrfs_run_delayed_refs+0x28c/0x2c0 [btrfs]
[  588.966241]  [] delayed_ref_async_start+0x94/0xb0 [btrfs]
[  588.966250]  [] btrfs_scrubparity_helper+0xca/0x350 [btrfs]
[  588.966259]  [] btrfs_extent_refs_helper+0xe/0x10 [btrfs]
[  588.966260]  [] process_one_work+0x1f3/0x4e0
[  588.966261]  [] worker_thread+0x48/0x4e0
[  588.966263]  [] ? process_one_work+0x4e0/0x4e0
[  588.966264]  [] kthread+0xc9/0xe0
[  588.966265]  [] ret_from_fork+0x1f/0x40
[  588.966267]  [] ? kthread_worker_fn+0x170/0x170
[  588.966268] ---[ end trace 34e5232c933a174a ]---
[  588.966269] BTRFS: error (device sda2) in btrfs_run_delayed_refs:2966: errno=-5 IO failure
[  588.966270] BTRFS info (device sda2): forced readonly

This was happening often on openSUSE and SLE systems using btrfs as the
root filesystem (with its default layout where multiple subvolumes are
used) where balance happens in the background triggered by a cron job and
snapshots are automatically created before/after package installations,
upgrades and removals. The issue could be triggered simply by running the
following loop on the first system boot post installation:

  while true; do
     zypper -n in nfs-kernel-server
     zypper -n rm nfs-kernel-server
  done

(If we were fast enough and made that loop before the cron job triggered
a balance operation and the balance finished)

So fix by setting the last_snapshot field of the root to the value of the
generation of its commit root. Like this btrfs_block_can_be_shared()
behaves correctly for the case where the relocation root is created during
a transaction commit and for the case where it's created before a
transaction commit.

Fixes: 6426c7ad697d (btrfs: qgroup: Fix qgroup accounting when creating snapshot)
Signed-off-by: Filipe Manana 
Reviewed-by: Josef Bacik 
Signed-off-by: Greg Kroah-Hartman

Btrfs: kill BUG_ON in do_relocation

2016-10-17T13:48:40+00:00

While updating btree, we try to push items between sibling
nodes/leaves in order to keep height as low as possible.
But we don't memset the original places with zero when
pushing items so that we could end up leaving stale content
in nodes/leaves.  One may read the above stale content by
increasing btree blocks' @nritems.

One case I've come across is that in fs tree, a leaf has two
parent nodes, hence running balance ends up with processing
this leaf with two parent nodes, but it can only reach the
valid parent node through btrfs_search_slot, so it'd be like,

do_relocation
    for P in all parent nodes of block A:
        if !P->eb:
            btrfs_search_slot(key);   --> get path from P to A.
        if lowest:
            BUG_ON(A->bytenr != bytenr of A recorded in P);
        btrfs_cow_block(P, A);   --> change A's bytenr in P.

After btrfs_cow_block, P has the new bytenr of A, but with the
same @key, we get the same path again, and get panic by BUG_ON.

Note that this is only happening in a corrupted fs, for a
regular fs in which we have correct @nritems so that we won't
read stale content in any case.

Reviewed-by: Josef Bacik 
Signed-off-by: Liu Bo 
Signed-off-by: David Sterba

btrfs: unsplit printed strings

2016-09-26T16:08:44+00:00

CodingStyle chapter 2:
"[...] never break user-visible strings such as printk messages,
because that breaks the ability to grep for them."

This patch unsplits user-visible strings.

Signed-off-by: Jeff Mahoney 
Signed-off-by: David Sterba

Btrfs: don't leak reloc root nodes on error

2016-09-26T16:08:44+00:00

We don't track the reloc roots in any sort of normal way, so the only way the
root/commit_root nodes get free'd is if the relocation finishes successfully and
the reloc root is deleted.  Fix this by free'ing them in free_reloc_roots.
Thanks,

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

Btrfs: return gracefully from balance if fs tree is corrupted

2016-09-26T15:59:49+00:00

When relocating tree blocks, we firstly get block information from
back references in the extent tree, we then search fs tree to try to
find all parents of a block.

However, if fs tree is corrupted, eg. if there're some missing
items, we could come across these WARN_ONs and BUG_ONs.

This makes us print some error messages and return gracefully
from balance.

Signed-off-by: Liu Bo 
Reviewed-by: Josef Bacik 
Signed-off-by: David Sterba

Btrfs: add a flags field to btrfs_fs_info

2016-09-26T15:59:49+00:00

We have a lot of random ints in btrfs_fs_info that can be put into flags.  This
is mostly equivalent with the exception of how we deal with quota going on or
off, now instead we set a flag when we are turning it on or off and deal with
that appropriately, rather than just having a pending state that the current
quota_enabled gets set to.  Thanks,

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

btrfs: extend btrfs_set_extent_delalloc and its friends to support in-band dedupe and subpage size patchset

2016-09-26T15:59:49+00:00

Extend btrfs_set_extent_delalloc() and extent_clear_unlock_delalloc()
parameters for both in-band dedupe and subpage sector size patchset.

This should reduce conflict of both patchset and the effort to rebase
them.

Cc: Chandan Rajendra 
Cc: David Sterba 
Signed-off-by: Qu Wenruo 
Signed-off-by: David Sterba

Btrfs: fix endless loop in balancing block groups

2016-09-01T15:16:47+00:00

Qgroup function may overwrite the saved error 'err' with 0
in case quota is not enabled, and this ends up with a
endless loop in balance because we keep going back to balance
the same block group.

It really should use 'ret' instead.

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

btrfs: update btrfs_space_info's bytes_may_use timely

2016-08-25T10:58:26+00:00

This patch can fix some false ENOSPC errors, below test script can
reproduce one false ENOSPC error:
	#!/bin/bash
	dd if=/dev/zero of=fs.img bs=$((1024*1024)) count=128
	dev=$(losetup --show -f fs.img)
	mkfs.btrfs -f -M $dev
	mkdir /tmp/mntpoint
	mount $dev /tmp/mntpoint
	cd /tmp/mntpoint
	xfs_io -f -c "falloc 0 $((64*1024*1024))" testfile

Above script will fail for ENOSPC reason, but indeed fs still has free
space to satisfy this request. Please see call graph:
btrfs_fallocate()
|-> btrfs_alloc_data_chunk_ondemand()
|   bytes_may_use += 64M
|-> btrfs_prealloc_file_range()
    |-> btrfs_reserve_extent()
        |-> btrfs_add_reserved_bytes()
        |   alloc_type is RESERVE_ALLOC_NO_ACCOUNT, so it does not
        |   change bytes_may_use, and bytes_reserved += 64M. Now
        |   bytes_may_use + bytes_reserved == 128M, which is greater
        |   than btrfs_space_info's total_bytes, false enospc occurs.
        |   Note, the bytes_may_use decrease operation will be done in
        |   end of btrfs_fallocate(), which is too late.

Here is another simple case for buffered write:
                    CPU 1              |              CPU 2
                                       |
|-> cow_file_range()                   |-> __btrfs_buffered_write()
    |-> btrfs_reserve_extent()         |   |
    |                                  |   |
    |                                  |   |
    |    .....                         |   |-> btrfs_check_data_free_space()
    |                                  |
    |                                  |
    |-> extent_clear_unlock_delalloc() |

In CPU 1, btrfs_reserve_extent()->find_free_extent()->
btrfs_add_reserved_bytes() do not decrease bytes_may_use, the decrease
operation will be delayed to be done in extent_clear_unlock_delalloc().
Assume in this case, btrfs_reserve_extent() reserved 128MB data, CPU2's
btrfs_check_data_free_space() tries to reserve 100MB data space.
If
	100MB > data_sinfo->total_bytes - data_sinfo->bytes_used -
		data_sinfo->bytes_reserved - data_sinfo->bytes_pinned -
		data_sinfo->bytes_readonly - data_sinfo->bytes_may_use
btrfs_check_data_free_space() will try to allcate new data chunk or call
btrfs_start_delalloc_roots(), or commit current transaction in order to
reserve some free space, obviously a lot of work. But indeed it's not
necessary as long as decreasing bytes_may_use timely, we still have
free space, decreasing 128M from bytes_may_use.

To fix this issue, this patch chooses to update bytes_may_use for both
data and metadata in btrfs_add_reserved_bytes(). For compress path, real
extent length may not be equal to file content length, so introduce a
ram_bytes argument for btrfs_reserve_extent(), find_free_extent() and
btrfs_add_reserved_bytes(), it's becasue bytes_may_use is increased by
file content length. Then compress path can update bytes_may_use
correctly. Also now we can discard RESERVE_ALLOC_NO_ACCOUNT, RESERVE_ALLOC
and RESERVE_FREE.

As we know, usually EXTENT_DO_ACCOUNTING is used for error path. In
run_delalloc_nocow(), for inode marked as NODATACOW or extent marked as
PREALLOC, we also need to update bytes_may_use, but can not pass
EXTENT_DO_ACCOUNTING, because it also clears metadata reservation, so
here we introduce EXTENT_CLEAR_DATA_RESV flag to indicate btrfs_clear_bit_hook()
to update btrfs_space_info's bytes_may_use.

Meanwhile __btrfs_prealloc_file_range() will call
btrfs_free_reserved_data_space() internally for both sucessful and failed
path, btrfs_prealloc_file_range()'s callers does not need to call
btrfs_free_reserved_data_space() any more.

Signed-off-by: Wang Xiaoguang 
Reviewed-by: Josef Bacik 
Signed-off-by: David Sterba 
Signed-off-by: Chris Mason