Currently scrub can race with the cleaner kthread when the later attempts
to delete an unused block group, and the result is preventing the cleaner
kthread from ever deleting later the block group - unless the block group
becomes used and unused again. The following diagram illustrates that
race:
CPU 1 CPU 2
cleaner kthread
btrfs_delete_unused_bgs()
gets block group X from
fs_info->unused_bgs and
removes it from that list
scrub_enumerate_chunks()
searches device tree using
its commit root
finds device extent for
block group X
gets block group X from the tree
fs_info->block_group_cache_tree
(via btrfs_lookup_block_group())
sets bg X to RO
sees the block group is
already RO and therefore
doesn't delete it nor adds
it back to unused list
So fix this by making scrub add the block group again to the list of
unused block groups if the block group is still unused when it finished
scrubbing it and it hasn't been removed already.
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Chris Mason <clm@fb.com>
Scrub can race with the cleaner kthread deleting block groups that are
unused (and with relocation too) leading to a failure with error -EINVAL
that gets returned to user space.
The following diagram illustrates how it happens:
CPU 1 CPU 2
cleaner kthread
btrfs_delete_unused_bgs()
gets block group X from
fs_info->unused_bgs
sets block group to RO
btrfs_remove_chunk(bg X)
deletes device extents
scrub_enumerate_chunks()
searches device tree using
its commit root
finds device extent for
block group X
gets block group X from the tree
fs_info->block_group_cache_tree
(via btrfs_lookup_block_group())
sets bg X to RO (again)
btrfs_remove_block_group(bg X)
deletes block group from
fs_info->block_group_cache_tree
removes extent map from
fs_info->mapping_tree
scrub_chunk(offset X)
searches fs_info->mapping_tree
for extent map starting at
offset X
--> doesn't find any such
extent map
--> returns -EINVAL and scrub
errors out to userspace
with -EINVAL
Fix this by dealing with an extent map lookup failure as an indicator of
block group deletion.
Issue reproduced with fstest btrfs/071.
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Chris Mason <clm@fb.com>
The test btrfs/011 triggers a rcu warning
Reviewed-by: Anand Jain <anand.jain@oracle.com>
===============================
[ INFO: suspicious RCU usage. ]
4.4.0-rc1-default+ #286 Tainted: G W
-------------------------------
fs/btrfs/volumes.c:1977 suspicious rcu_dereference_check() usage!
other info that might help us debug this:
rcu_scheduler_active = 1, debug_locks = 0
4 locks held by btrfs/28786:
0: (&fs_info->dev_replace.lock_finishing_cancel_unmount){+.+...}, at: [<ffffffffa00bc785>] btrfs_dev_replace_finishing+0x45/0xa00 [btrfs]
1: (uuid_mutex){+.+.+.}, at: [<ffffffffa00bc84f>] btrfs_dev_replace_finishing+0x10f/0xa00 [btrfs]
2: (&fs_devs->device_list_mutex){+.+.+.}, at: [<ffffffffa00bc868>] btrfs_dev_replace_finishing+0x128/0xa00 [btrfs]
3: (&fs_info->chunk_mutex){+.+...}, at: [<ffffffffa00bc87d>] btrfs_dev_replace_finishing+0x13d/0xa00 [btrfs]
stack backtrace:
CPU: 0 PID: 28786 Comm: btrfs Tainted: G W 4.4.0-rc1-default+ #286
Hardware name: Intel Corporation SandyBridge Platform/To be filled by O.E.M., BIOS ASNBCPT1.86C.0031.B00.1006301607 06/30/2010
0000000000000001 ffff8800a07dfb48 ffffffff8141d47b 0000000000000001
0000000000000001 0000000000000000 ffff8801464a4f00 ffff8800a07dfb78
ffffffff810cd883 ffff880146eb9400 ffff8800a3698600 ffff8800a33fe220
Call Trace:
[<ffffffff8141d47b>] dump_stack+0x4f/0x74
[<ffffffff810cd883>] lockdep_rcu_suspicious+0x103/0x140
[<ffffffffa0071261>] btrfs_rm_dev_replace_remove_srcdev+0x111/0x130 [btrfs]
[<ffffffff810d354d>] ? trace_hardirqs_on+0xd/0x10
[<ffffffff81449536>] ? __percpu_counter_sum+0x66/0x80
[<ffffffffa00bcc15>] btrfs_dev_replace_finishing+0x4d5/0xa00 [btrfs]
[<ffffffffa00bc96e>] ? btrfs_dev_replace_finishing+0x22e/0xa00 [btrfs]
[<ffffffffa00a8795>] ? btrfs_scrub_dev+0x415/0x6d0 [btrfs]
[<ffffffffa003ea69>] ? btrfs_start_transaction+0x9/0x20 [btrfs]
[<ffffffffa00bda79>] btrfs_dev_replace_start+0x339/0x590 [btrfs]
[<ffffffff81196aa5>] ? __might_fault+0x95/0xa0
[<ffffffffa0078638>] btrfs_ioctl_dev_replace+0x118/0x160 [btrfs]
[<ffffffff811409c6>] ? stack_trace_call+0x46/0x70
[<ffffffffa007c914>] ? btrfs_ioctl+0x24/0x1770 [btrfs]
[<ffffffffa007ce43>] btrfs_ioctl+0x553/0x1770 [btrfs]
[<ffffffff811409c6>] ? stack_trace_call+0x46/0x70
[<ffffffff811d6eb1>] ? do_vfs_ioctl+0x21/0x5a0
[<ffffffff811d6f1c>] do_vfs_ioctl+0x8c/0x5a0
[<ffffffff811e3336>] ? __fget_light+0x86/0xb0
[<ffffffff811e3369>] ? __fdget+0x9/0x20
[<ffffffff811d7451>] ? SyS_ioctl+0x21/0x80
[<ffffffff811d7483>] SyS_ioctl+0x53/0x80
[<ffffffff81b1efd7>] entry_SYSCALL_64_fastpath+0x12/0x6f
This is because of unprotected use of rcu_dereference in
btrfs_scratch_superblocks. We can't add rcu locks around the whole
function because we read the superblock.
The fix will use the rcu string buffer directly without the rcu locking.
Thi is safe as the device will not go away in the meantime. We're
holding the device list mutexes.
Restructuring the code to narrow down the rcu section turned out to be
impossible, we need to call filp_open (through update_dev_time) on the
buffer and this could call kmalloc/__might_sleep. We could call kstrdup
with GFP_ATOMIC but it's not absolutely necessary.
Fixes: 12b1c2637b (Btrfs: enhance btrfs_scratch_superblock to scratch all superblocks)
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Chris Mason <clm@fb.com>
xfstests/011 failed in node with small_size filesystem.
Can be reproduced by following script:
DEV_LIST="/dev/vdd /dev/vde"
DEV_REPLACE="/dev/vdf"
do_test()
{
local mkfs_opt="$1"
local size="$2"
dmesg -c >/dev/null
umount $SCRATCH_MNT &>/dev/null
echo mkfs.btrfs -f $mkfs_opt "${DEV_LIST[*]}"
mkfs.btrfs -f $mkfs_opt "${DEV_LIST[@]}" || return 1
mount "${DEV_LIST[0]}" $SCRATCH_MNT
echo -n "Writing big files"
dd if=/dev/urandom of=$SCRATCH_MNT/t0 bs=1M count=1 >/dev/null 2>&1
for ((i = 1; i <= size; i++)); do
echo -n .
/bin/cp $SCRATCH_MNT/t0 $SCRATCH_MNT/t$i || return 1
done
echo
echo Start replace
btrfs replace start -Bf "${DEV_LIST[0]}" "$DEV_REPLACE" $SCRATCH_MNT || {
dmesg
return 1
}
return 0
}
# Set size to value near fs size
# for example, 1897 can trigger this bug in 2.6G device.
#
./do_test "-d raid1 -m raid1" 1897
System will report replace fail with following warning in dmesg:
[ 134.710853] BTRFS: dev_replace from /dev/vdd (devid 1) to /dev/vdf started
[ 135.542390] BTRFS: btrfs_scrub_dev(/dev/vdd, 1, /dev/vdf) failed -28
[ 135.543505] ------------[ cut here ]------------
[ 135.544127] WARNING: CPU: 0 PID: 4080 at fs/btrfs/dev-replace.c:428 btrfs_dev_replace_start+0x398/0x440()
[ 135.545276] Modules linked in:
[ 135.545681] CPU: 0 PID: 4080 Comm: btrfs Not tainted 4.3.0 #256
[ 135.546439] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.8.2-0-g33fbe13 by qemu-project.org 04/01/2014
[ 135.547798] ffffffff81c5bfcf ffff88003cbb3d28 ffffffff817fe7b5 0000000000000000
[ 135.548774] ffff88003cbb3d60 ffffffff810a88f1 ffff88002b030000 00000000ffffffe4
[ 135.549774] ffff88003c080000 ffff88003c082588 ffff88003c28ab60 ffff88003cbb3d70
[ 135.550758] Call Trace:
[ 135.551086] [<ffffffff817fe7b5>] dump_stack+0x44/0x55
[ 135.551737] [<ffffffff810a88f1>] warn_slowpath_common+0x81/0xc0
[ 135.552487] [<ffffffff810a89e5>] warn_slowpath_null+0x15/0x20
[ 135.553211] [<ffffffff81448c88>] btrfs_dev_replace_start+0x398/0x440
[ 135.554051] [<ffffffff81412c3e>] btrfs_ioctl+0x1d2e/0x25c0
[ 135.554722] [<ffffffff8114c7ba>] ? __audit_syscall_entry+0xaa/0xf0
[ 135.555506] [<ffffffff8111ab36>] ? current_kernel_time64+0x56/0xa0
[ 135.556304] [<ffffffff81201e3d>] do_vfs_ioctl+0x30d/0x580
[ 135.557009] [<ffffffff8114c7ba>] ? __audit_syscall_entry+0xaa/0xf0
[ 135.557855] [<ffffffff810011d1>] ? do_audit_syscall_entry+0x61/0x70
[ 135.558669] [<ffffffff8120d1c1>] ? __fget_light+0x61/0x90
[ 135.559374] [<ffffffff81202124>] SyS_ioctl+0x74/0x80
[ 135.559987] [<ffffffff81809857>] entry_SYSCALL_64_fastpath+0x12/0x6f
[ 135.560842] ---[ end trace 2a5c1fc3205abbdd ]---
Reason:
When big data writen to fs, the whole free space will be allocated
for data chunk.
And operation as scrub need to set_block_ro(), and when there is
only one metadata chunk in system(or other metadata chunks
are all full), the function will try to allocate a new chunk,
and failed because no space in device.
Fix:
When set_block_ro failed for metadata chunk, it is not a problem
because scrub_lock paused commit_trancaction in same time, and
metadata are always cowed, so the on-the-fly writepages will not
write data into same place with scrub/replace.
Let replace continue in this case is no problem.
Tested by above script, and xfstests/011, plus 100 times xfstests/070.
Changelog v1->v2:
1: Add detail comments in source and commit-message.
2: Add dmesg detail into commit-message.
3: Limit return value of -ENOSPC to be passed.
All suggested by: Filipe Manana <fdmanana@gmail.com>
Suggested-by: Filipe Manana <fdmanana@gmail.com>
Signed-off-by: Zhao Lei <zhaolei@cn.fujitsu.com>
Signed-off-by: Chris Mason <clm@fb.com>
I've accidentally picked an already used number for the enhanced usage
filter represented by BTRFS_BALANCE_ARGS_USAGE_RANGE, clashing with
BTRFS_BALANCE_ARGS_CONVERT. Introduced during the development phase,
no backward compatibility issues.
Reported-by: Holger Hoffstätte <holger.hoffstaette@googlemail.com>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Fixes: bc3094673f ("btrfs: extend balance filter usage to take minimum and maximum")
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Chris Mason <clm@fb.com>
We were using only 1 transaction unit when attempting to delete an unused
block group but in reality we need 3 + N units, where N corresponds to the
number of stripes. We were accounting only for the addition of the orphan
item (for the block group's free space cache inode) but we were not
accounting that we need to delete one block group item from the extent
tree, one free space item from the tree of tree roots and N device extent
items from the device tree.
While one unit is not enough, it worked most of the time because for each
single unit we are too pessimistic and assume an entire tree path, with
the highest possible heigth (8), needs to be COWed with eventual node
splits at every possible level in the tree, so there was usually enough
reserved space for removing all the items and adding the orphan item.
However after adding the orphan item, writepages() can by called by the VM
subsystem against the btree inode when we are under memory pressure, which
causes writeback to start for the nodes we COWed before, this forces the
operation to remove the free space item to COW again some (or all of) the
same nodes (in the tree of tree roots). Even without writepages() being
called, we could fail with ENOSPC because these items are located in
multiple trees and one of them might have a higher heigth and require
node/leaf splits at many levels, exhausting all the reserved space before
removing all the items and adding the orphan.
In the kernel 4.0 release, commit 3d84be7991 ("Btrfs: fix BUG_ON in
btrfs_orphan_add() when delete unused block group"), we attempted to fix
a BUG_ON due to ENOSPC when trying to add the orphan item by making the
cleaner kthread reserve one transaction unit before attempting to remove
the block group, but this was not enough. We had a couple user reports
still hitting the same BUG_ON after 4.0, like Stefan Priebe's report on
a 4.2-rc6 kernel for example:
http://www.spinics.net/lists/linux-btrfs/msg46070.html
So fix this by reserving all the necessary units of metadata.
Reported-by: Stefan Priebe <s.priebe@profihost.ag>
Fixes: 3d84be7991 ("Btrfs: fix BUG_ON in btrfs_orphan_add() when delete unused block group")
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Chris Mason <clm@fb.com>
It's possible to reach a state where the cleaner kthread isn't able to
start a transaction to delete an unused block group due to lack of enough
free metadata space and due to lack of unallocated device space to allocate
a new metadata block group as well. If this happens try to use space from
the global block group reserve just like we do for unlink operations, so
that we don't reach a permanent state where starting a transaction for
filesystem operations (file creation, renames, etc) keeps failing with
-ENOSPC. Such an unfortunate state was observed on a machine where over
a dozen unused data block groups existed and the cleaner kthread was
failing to delete them due to ENOSPC error when attempting to start a
transaction, and even running balance with a -dusage=0 filter failed with
ENOSPC as well. Also unmounting and mounting again the filesystem didn't
help. Allowing the cleaner kthread to use the global block reserve to
delete the unused data block groups fixed the problem.
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Jeff Mahoney <jeffm@suse.com>
Signed-off-by: Chris Mason <clm@fb.com>
btrfs_alloc_dummy_root() return an error pointer on failure, it never
returns NULL.
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: Chris Mason <clm@fb.com>
The calculation of range length in btrfs_sync_file leads to signed
overflow. This was caught by PaX gcc SIZE_OVERFLOW plugin.
https://forums.grsecurity.net/viewtopic.php?f=1&t=4284
The fsync call passes 0 and LLONG_MAX, the range length does not fit to
loff_t and overflows, but the value is converted to u64 so it silently
works as expected.
The minimal fix is a typecast to u64, switching functions to take
(start, end) instead of (start, len) would be more intrusive.
Coccinelle script found that there's one more opencoded calculation of
the length.
<smpl>
@@
loff_t start, end;
@@
* end - start
</smpl>
CC: stable@vger.kernel.org
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Chris Mason <clm@fb.com>
No need to use root->fs_info in btrfs_delete_unused_bgs(),
use fs_info directly instead.
Signed-off-by: Zhao Lei <zhaolei@cn.fujitsu.com>
Signed-off-by: Chris Mason <clm@fb.com>
Reproduce:
(In integration-4.3 branch)
TEST_DEV=(/dev/vdg /dev/vdh)
TEST_DIR=/mnt/tmp
umount "$TEST_DEV" >/dev/null
mkfs.btrfs -f -d raid1 "${TEST_DEV[@]}"
mount -o nospace_cache "$TEST_DEV" "$TEST_DIR"
btrfs balance start -dusage=0 $TEST_DIR
btrfs filesystem usage $TEST_DIR
dd if=/dev/zero of="$TEST_DIR"/file count=100
btrfs filesystem usage $TEST_DIR
Result:
We can see "no data chunk" in first "btrfs filesystem usage":
# btrfs filesystem usage $TEST_DIR
Overall:
...
Metadata,single: Size:8.00MiB, Used:0.00B
/dev/vdg 8.00MiB
Metadata,RAID1: Size:122.88MiB, Used:112.00KiB
/dev/vdg 122.88MiB
/dev/vdh 122.88MiB
System,single: Size:4.00MiB, Used:0.00B
/dev/vdg 4.00MiB
System,RAID1: Size:8.00MiB, Used:16.00KiB
/dev/vdg 8.00MiB
/dev/vdh 8.00MiB
Unallocated:
/dev/vdg 1.06GiB
/dev/vdh 1.07GiB
And "data chunks changed from raid1 to single" in second
"btrfs filesystem usage":
# btrfs filesystem usage $TEST_DIR
Overall:
...
Data,single: Size:256.00MiB, Used:0.00B
/dev/vdh 256.00MiB
Metadata,single: Size:8.00MiB, Used:0.00B
/dev/vdg 8.00MiB
Metadata,RAID1: Size:122.88MiB, Used:112.00KiB
/dev/vdg 122.88MiB
/dev/vdh 122.88MiB
System,single: Size:4.00MiB, Used:0.00B
/dev/vdg 4.00MiB
System,RAID1: Size:8.00MiB, Used:16.00KiB
/dev/vdg 8.00MiB
/dev/vdh 8.00MiB
Unallocated:
/dev/vdg 1.06GiB
/dev/vdh 841.92MiB
Reason:
btrfs balance delete last data chunk in case of no data in
the filesystem, then we can see "no data chunk" by "fi usage"
command.
And when we do write operation to fs, the only available data
profile is 0x0, result is all new chunks are allocated single type.
Fix:
Allocate a data chunk explicitly to ensure we don't lose the
raid profile for data.
Test:
Test by above script, and confirmed the logic by debug output.
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Zhao Lei <zhaolei@cn.fujitsu.com>
Signed-off-by: Chris Mason <clm@fb.com>
Reproduce:
(In integration-4.3 branch)
TEST_DEV=(/dev/vdg /dev/vdh)
TEST_DIR=/mnt/tmp
umount "$TEST_DEV" >/dev/null
mkfs.btrfs -f -d raid1 "${TEST_DEV[@]}"
mount -o nospace_cache "$TEST_DEV" "$TEST_DIR"
umount "$TEST_DEV"
mount -o nospace_cache "$TEST_DEV" "$TEST_DIR"
btrfs filesystem usage $TEST_DIR
We can see the data chunk changed from raid1 to single:
# btrfs filesystem usage $TEST_DIR
Data,single: Size:8.00MiB, Used:0.00B
/dev/vdg 8.00MiB
#
Reason:
When a empty filesystem mount with -o nospace_cache, the last
data blockgroup will be auto-removed in umount.
Then if we mount it again, there is no data chunk in the
filesystem, so the only available data profile is 0x0, result
is all new chunks are created as single type.
Fix:
Don't auto-delete last blockgroup for a raid type.
Test:
Test by above script, and confirmed the logic by debug output.
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Zhao Lei <zhaolei@cn.fujitsu.com>
Signed-off-by: Chris Mason <clm@fb.com>
We don't need pass so many arguments for recheck sblock now,
this patch cleans them.
Signed-off-by: Zhao Lei <zhaolei@cn.fujitsu.com>
Signed-off-by: Chris Mason <clm@fb.com>
We can use existing scrub_checksum_data() and scrub_checksum_tree_block()
for scrub_recheck_block_checksum(), instead of write duplicated code.
Signed-off-by: Zhao Lei <zhaolei@cn.fujitsu.com>
Signed-off-by: Chris Mason <clm@fb.com>
We should reset sblock->xxx_error stats before calling
scrub_recheck_block_checksum().
Current code run correctly because all sblock are allocated by
k[cz]alloc(), and the error stats are not got changed.
Signed-off-by: Zhao Lei <zhaolei@cn.fujitsu.com>
Signed-off-by: Chris Mason <clm@fb.com>
scrub_setup_recheck_block() isn't setup all necessary fields for
sblock_to_check because history reason.
So current code need more arguments in severial functions,
and more local variables, just to passing these lacked values to
necessary place.
This patch setup above fields to sblock_to_check in
scrub_setup_recheck_block(), for:
1: more cleanup for function arg, local variable
2: to make sblock_to_check complete, then we can use sblock_to_check
without concern about some uninitialized member.
Signed-off-by: Zhao Lei <zhaolei@cn.fujitsu.com>
Signed-off-by: Chris Mason <clm@fb.com>
It is better to show error stats to user when we found tree block
spanning stripes.
On a btrfs created by old version of btrfs-convert:
Before patch:
# btrfs scrub start -B /dev/vdh
scrub done for 8b342d35-2904-41ab-b3cb-2f929709cf47
scrub started at Tue Aug 25 21:19:09 2015 and finished after 00:00:00
total bytes scrubbed: 53.54MiB with 0 errors
# dmesg
...
[ 128.711434] BTRFS error (device vdh): scrub: tree block 27054080 spanning stripes, ignored. logical=27000832
[ 128.712744] BTRFS error (device vdh): scrub: tree block 27054080 spanning stripes, ignored. logical=27066368
...
After patch:
# btrfs scrub start -B /dev/vdh
scrub done for ff7f844b-7a4e-4b1a-88a9-8252ab25be1b
scrub started at Tue Aug 25 21:42:29 2015 and finished after 00:00:00
total bytes scrubbed: 53.60MiB with 2 errors
error details:
corrected errors: 0, uncorrectable errors: 2, unverified errors: 0
ERROR: There are uncorrectable errors.
# dmesg
...omit...
#
Signed-off-by: Zhao Lei <zhaolei@cn.fujitsu.com>
Signed-off-by: Chris Mason <clm@fb.com>
When listing a inode's xattrs we have a time window where we race against
a concurrent operation for adding a new hard link for our inode that makes
us not return any xattr to user space. In order for this to happen, the
first xattr of our inode needs to be at slot 0 of a leaf and the previous
leaf must still have room for an inode ref (or extref) item, and this can
happen because an inode's listxattrs callback does not lock the inode's
i_mutex (nor does the VFS does it for us), but adding a hard link to an
inode makes the VFS lock the inode's i_mutex before calling the inode's
link callback.
If we have the following leafs:
Leaf X (has N items) Leaf Y
[ ... (257 INODE_ITEM 0) (257 INODE_REF 256) ] [ (257 XATTR_ITEM 12345), ... ]
slot N - 2 slot N - 1 slot 0
The race illustrated by the following sequence diagram is possible:
CPU 1 CPU 2
btrfs_listxattr()
searches for key (257 XATTR_ITEM 0)
gets path with path->nodes[0] == leaf X
and path->slots[0] == N
because path->slots[0] is >=
btrfs_header_nritems(leaf X), it calls
btrfs_next_leaf()
btrfs_next_leaf()
releases the path
adds key (257 INODE_REF 666)
to the end of leaf X (slot N),
and leaf X now has N + 1 items
searches for the key (257 INODE_REF 256),
with path->keep_locks == 1, because that
is the last key it saw in leaf X before
releasing the path
ends up at leaf X again and it verifies
that the key (257 INODE_REF 256) is no
longer the last key in leaf X, so it
returns with path->nodes[0] == leaf X
and path->slots[0] == N, pointing to
the new item with key (257 INODE_REF 666)
btrfs_listxattr's loop iteration sees that
the type of the key pointed by the path is
different from the type BTRFS_XATTR_ITEM_KEY
and so it breaks the loop and stops looking
for more xattr items
--> the application doesn't get any xattr
listed for our inode
So fix this by breaking the loop only if the key's type is greater than
BTRFS_XATTR_ITEM_KEY and skip the current key if its type is smaller.
Cc: stable@vger.kernel.org
Signed-off-by: Filipe Manana <fdmanana@suse.com>
If we are using the NO_HOLES feature, we have a tiny time window when
running delalloc for a nodatacow inode where we can race with a concurrent
link or xattr add operation leading to a BUG_ON.
This happens because at run_delalloc_nocow() we end up casting a leaf item
of type BTRFS_INODE_[REF|EXTREF]_KEY or of type BTRFS_XATTR_ITEM_KEY to a
file extent item (struct btrfs_file_extent_item) and then analyse its
extent type field, which won't match any of the expected extent types
(values BTRFS_FILE_EXTENT_[REG|PREALLOC|INLINE]) and therefore trigger an
explicit BUG_ON(1).
The following sequence diagram shows how the race happens when running a
no-cow dellaloc range [4K, 8K[ for inode 257 and we have the following
neighbour leafs:
Leaf X (has N items) Leaf Y
[ ... (257 INODE_ITEM 0) (257 INODE_REF 256) ] [ (257 EXTENT_DATA 8192), ... ]
slot N - 2 slot N - 1 slot 0
(Note the implicit hole for inode 257 regarding the [0, 8K[ range)
CPU 1 CPU 2
run_dealloc_nocow()
btrfs_lookup_file_extent()
--> searches for a key with value
(257 EXTENT_DATA 4096) in the
fs/subvol tree
--> returns us a path with
path->nodes[0] == leaf X and
path->slots[0] == N
because path->slots[0] is >=
btrfs_header_nritems(leaf X), it
calls btrfs_next_leaf()
btrfs_next_leaf()
--> releases the path
hard link added to our inode,
with key (257 INODE_REF 500)
added to the end of leaf X,
so leaf X now has N + 1 keys
--> searches for the key
(257 INODE_REF 256), because
it was the last key in leaf X
before it released the path,
with path->keep_locks set to 1
--> ends up at leaf X again and
it verifies that the key
(257 INODE_REF 256) is no longer
the last key in the leaf, so it
returns with path->nodes[0] ==
leaf X and path->slots[0] == N,
pointing to the new item with
key (257 INODE_REF 500)
the loop iteration of run_dealloc_nocow()
does not break out the loop and continues
because the key referenced in the path
at path->nodes[0] and path->slots[0] is
for inode 257, its type is < BTRFS_EXTENT_DATA_KEY
and its offset (500) is less then our delalloc
range's end (8192)
the item pointed by the path, an inode reference item,
is (incorrectly) interpreted as a file extent item and
we get an invalid extent type, leading to the BUG_ON(1):
if (extent_type == BTRFS_FILE_EXTENT_REG ||
extent_type == BTRFS_FILE_EXTENT_PREALLOC) {
(...)
} else if (extent_type == BTRFS_FILE_EXTENT_INLINE) {
(...)
} else {
BUG_ON(1)
}
The same can happen if a xattr is added concurrently and ends up having
a key with an offset smaller then the delalloc's range end.
So fix this by skipping keys with a type smaller than
BTRFS_EXTENT_DATA_KEY.
Cc: stable@vger.kernel.org
Signed-off-by: Filipe Manana <fdmanana@suse.com>
While running a stress test I got the following warning triggered:
[191627.672810] ------------[ cut here ]------------
[191627.673949] WARNING: CPU: 8 PID: 8447 at fs/btrfs/file.c:779 __btrfs_drop_extents+0x391/0xa50 [btrfs]()
(...)
[191627.701485] Call Trace:
[191627.702037] [<ffffffff8145f077>] dump_stack+0x4f/0x7b
[191627.702992] [<ffffffff81095de5>] ? console_unlock+0x356/0x3a2
[191627.704091] [<ffffffff8104b3b0>] warn_slowpath_common+0xa1/0xbb
[191627.705380] [<ffffffffa0664499>] ? __btrfs_drop_extents+0x391/0xa50 [btrfs]
[191627.706637] [<ffffffff8104b46d>] warn_slowpath_null+0x1a/0x1c
[191627.707789] [<ffffffffa0664499>] __btrfs_drop_extents+0x391/0xa50 [btrfs]
[191627.709155] [<ffffffff8115663c>] ? cache_alloc_debugcheck_after.isra.32+0x171/0x1d0
[191627.712444] [<ffffffff81155007>] ? kmemleak_alloc_recursive.constprop.40+0x16/0x18
[191627.714162] [<ffffffffa06570c9>] insert_reserved_file_extent.constprop.40+0x83/0x24e [btrfs]
[191627.715887] [<ffffffffa065422b>] ? start_transaction+0x3bb/0x610 [btrfs]
[191627.717287] [<ffffffffa065b604>] btrfs_finish_ordered_io+0x273/0x4e2 [btrfs]
[191627.728865] [<ffffffffa065b888>] finish_ordered_fn+0x15/0x17 [btrfs]
[191627.730045] [<ffffffffa067d688>] normal_work_helper+0x14c/0x32c [btrfs]
[191627.731256] [<ffffffffa067d96a>] btrfs_endio_write_helper+0x12/0x14 [btrfs]
[191627.732661] [<ffffffff81061119>] process_one_work+0x24c/0x4ae
[191627.733822] [<ffffffff810615b0>] worker_thread+0x206/0x2c2
[191627.734857] [<ffffffff810613aa>] ? process_scheduled_works+0x2f/0x2f
[191627.736052] [<ffffffff810613aa>] ? process_scheduled_works+0x2f/0x2f
[191627.737349] [<ffffffff810669a6>] kthread+0xef/0xf7
[191627.738267] [<ffffffff810f3b3a>] ? time_hardirqs_on+0x15/0x28
[191627.739330] [<ffffffff810668b7>] ? __kthread_parkme+0xad/0xad
[191627.741976] [<ffffffff81465592>] ret_from_fork+0x42/0x70
[191627.743080] [<ffffffff810668b7>] ? __kthread_parkme+0xad/0xad
[191627.744206] ---[ end trace bbfddacb7aaada8d ]---
$ cat -n fs/btrfs/file.c
691 int __btrfs_drop_extents(struct btrfs_trans_handle *trans,
(...)
758 btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
759 if (key.objectid > ino ||
760 key.type > BTRFS_EXTENT_DATA_KEY || key.offset >= end)
761 break;
762
763 fi = btrfs_item_ptr(leaf, path->slots[0],
764 struct btrfs_file_extent_item);
765 extent_type = btrfs_file_extent_type(leaf, fi);
766
767 if (extent_type == BTRFS_FILE_EXTENT_REG ||
768 extent_type == BTRFS_FILE_EXTENT_PREALLOC) {
(...)
774 } else if (extent_type == BTRFS_FILE_EXTENT_INLINE) {
(...)
778 } else {
779 WARN_ON(1);
780 extent_end = search_start;
781 }
(...)
This happened because the item we were processing did not match a file
extent item (its key type != BTRFS_EXTENT_DATA_KEY), and even on this
case we cast the item to a struct btrfs_file_extent_item pointer and
then find a type field value that does not match any of the expected
values (BTRFS_FILE_EXTENT_[REG|PREALLOC|INLINE]). This scenario happens
due to a tiny time window where a race can happen as exemplified below.
For example, consider the following scenario where we're using the
NO_HOLES feature and we have the following two neighbour leafs:
Leaf X (has N items) Leaf Y
[ ... (257 INODE_ITEM 0) (257 INODE_REF 256) ] [ (257 EXTENT_DATA 8192), ... ]
slot N - 2 slot N - 1 slot 0
Our inode 257 has an implicit hole in the range [0, 8K[ (implicit rather
than explicit because NO_HOLES is enabled). Now if our inode has an
ordered extent for the range [4K, 8K[ that is finishing, the following
can happen:
CPU 1 CPU 2
btrfs_finish_ordered_io()
insert_reserved_file_extent()
__btrfs_drop_extents()
Searches for the key
(257 EXTENT_DATA 4096) through
btrfs_lookup_file_extent()
Key not found and we get a path where
path->nodes[0] == leaf X and
path->slots[0] == N
Because path->slots[0] is >=
btrfs_header_nritems(leaf X), we call
btrfs_next_leaf()
btrfs_next_leaf() releases the path
inserts key
(257 INODE_REF 4096)
at the end of leaf X,
leaf X now has N + 1 keys,
and the new key is at
slot N
btrfs_next_leaf() searches for
key (257 INODE_REF 256), with
path->keep_locks set to 1,
because it was the last key it
saw in leaf X
finds it in leaf X again and
notices it's no longer the last
key of the leaf, so it returns 0
with path->nodes[0] == leaf X and
path->slots[0] == N (which is now
< btrfs_header_nritems(leaf X)),
pointing to the new key
(257 INODE_REF 4096)
__btrfs_drop_extents() casts the
item at path->nodes[0], slot
path->slots[0], to a struct
btrfs_file_extent_item - it does
not skip keys for the target
inode with a type less than
BTRFS_EXTENT_DATA_KEY
(BTRFS_INODE_REF_KEY < BTRFS_EXTENT_DATA_KEY)
sees a bogus value for the type
field triggering the WARN_ON in
the trace shown above, and sets
extent_end = search_start (4096)
does the if-then-else logic to
fixup 0 length extent items created
by a past bug from hole punching:
if (extent_end == key.offset &&
extent_end >= search_start)
goto delete_extent_item;
that evaluates to true and it ends
up deleting the key pointed to by
path->slots[0], (257 INODE_REF 4096),
from leaf X
The same could happen for example for a xattr that ends up having a key
with an offset value that matches search_start (very unlikely but not
impossible).
So fix this by ensuring that keys smaller than BTRFS_EXTENT_DATA_KEY are
skipped, never casted to struct btrfs_file_extent_item and never deleted
by accident. Also protect against the unexpected case of getting a key
for a lower inode number by skipping that key and issuing a warning.
Cc: stable@vger.kernel.org
Signed-off-by: Filipe Manana <fdmanana@suse.com>
We were initializing the completion (fs_info->qgroup_rescan_completion)
object after releasing the qgroup rescan lock, which gives a small time
window for a rescan waiter to not actually wait for the rescan worker
to finish. Example:
CPU 1 CPU 2
fs_info->qgroup_rescan_completion->done is 0
btrfs_qgroup_rescan_worker()
complete_all(&fs_info->qgroup_rescan_completion)
sets fs_info->qgroup_rescan_completion->done
to UINT_MAX / 2
... do some other stuff ....
qgroup_rescan_init()
mutex_lock(&fs_info->qgroup_rescan_lock)
set flag BTRFS_QGROUP_STATUS_FLAG_RESCAN
in fs_info->qgroup_flags
mutex_unlock(&fs_info->qgroup_rescan_lock)
btrfs_qgroup_wait_for_completion()
mutex_lock(&fs_info->qgroup_rescan_lock)
sees flag BTRFS_QGROUP_STATUS_FLAG_RESCAN
in fs_info->qgroup_flags
mutex_unlock(&fs_info->qgroup_rescan_lock)
wait_for_completion_interruptible(
&fs_info->qgroup_rescan_completion)
fs_info->qgroup_rescan_completion->done
is > 0 so it returns immediately
init_completion(&fs_info->qgroup_rescan_completion)
sets fs_info->qgroup_rescan_completion->done to 0
So fix this by initializing the completion object while holding the mutex
fs_info->qgroup_rescan_lock.
Signed-off-by: Filipe Manana <fdmanana@suse.com>
I was hitting a consistent NULL pointer dereference during shutdown that
showed the trace running through end_workqueue_bio(). I traced it back to
the endio_meta_workers workqueue being poked after it had already been
destroyed.
Eventually I found that the root cause was a qgroup rescan that was still
in progress while we were stopping all the btrfs workers.
Currently we explicitly pause balance and scrub operations in
close_ctree(), but we do nothing to stop the qgroup rescan. We should
probably be doing the same for qgroup rescan, but that's a much larger
change. This small change is good enough to allow me to unmount without
crashing.
Signed-off-by: Justin Maggard <jmaggard@netgear.com>
Reviewed-by: Filipe Manana <fdmanana@suse.com>
When doing a write using direct IO we can end up not doing the whole write
operation using the direct IO path, in that case we fallback to a buffered
write to do the remaining IO. This happens for example if the range we are
writing to contains a compressed extent.
When we do a partial write and fallback to buffered IO, due to the
existence of a compressed extent for example, we end up not adjusting the
outstanding extents counter of our inode which ends up getting decremented
twice, once by the DIO ordered extent for the partial write and once again
by btrfs_direct_IO(), resulting in an arithmetic underflow at
extent-tree.c:drop_outstanding_extent(). For example if we have:
extents [ prealloc extent ] [ compressed extent ]
offsets A B C D E
and at the moment our inode's outstanding extents counter is 0, if we do a
direct IO write against the range [B, D[ (which has a length smaller than
128Mb), we end up bumping our inode's outstanding extents counter to 1, we
create a DIO ordered extent for the range [B, C[ and then fallback to a
buffered write for the range [C, D[. The direct IO handler
(inode.c:btrfs_direct_IO()) decrements the outstanding extents counter by
1, leaving it with a value of 0, through a call to
btrfs_delalloc_release_space() and then shortly after the DIO ordered
extent finishes and calls btrfs_delalloc_release_metadata() which ends
up to attempt to decrement the inode's outstanding extents counter by 1,
resulting in an assertion failure at drop_outstanding_extent() because
the operation would result in an arithmetic underflow (0 - 1). This
produces the following trace:
[125471.336838] BTRFS: assertion failed: BTRFS_I(inode)->outstanding_extents >= num_extents, file: fs/btrfs/extent-tree.c, line: 5526
[125471.338844] ------------[ cut here ]------------
[125471.340745] kernel BUG at fs/btrfs/ctree.h:4173!
[125471.340745] invalid opcode: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC
[125471.340745] Modules linked in: btrfs f2fs xfs libcrc32c dm_flakey dm_mod crc32c_generic xor raid6_pq nfsd auth_rpcgss oid_registry nfs_acl nfs lockd grace fscache sunrpc loop fuse parport_pc acpi_cpufreq psmouse i2c_piix4 parport pcspkr serio_raw microcode processor evdev i2c_core button ext4 crc16 jbd2 mbcache sd_mod sg sr_mod cdrom ata_generic virtio_scsi ata_piix virtio_pci virtio_ring floppy libata virtio e1000 scsi_mod [last unloaded: btrfs]
[125471.340745] CPU: 10 PID: 23649 Comm: kworker/u32:1 Tainted: G W 4.3.0-rc5-btrfs-next-17+ #1
[125471.340745] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.8.1-0-g4adadbd-20150316_085822-nilsson.home.kraxel.org 04/01/2014
[125471.340745] Workqueue: btrfs-endio-write btrfs_endio_write_helper [btrfs]
[125471.340745] task: ffff8804244fcf80 ti: ffff88040a118000 task.ti: ffff88040a118000
[125471.340745] RIP: 0010:[<ffffffffa0550da1>] [<ffffffffa0550da1>] assfail.constprop.46+0x1e/0x20 [btrfs]
[125471.340745] RSP: 0018:ffff88040a11bc78 EFLAGS: 00010296
[125471.340745] RAX: 0000000000000075 RBX: 0000000000005000 RCX: 0000000000000000
[125471.340745] RDX: ffffffff81098f93 RSI: ffffffff8147c619 RDI: 00000000ffffffff
[125471.340745] RBP: ffff88040a11bc78 R08: 0000000000000001 R09: 0000000000000000
[125471.340745] R10: ffff88040a11bc08 R11: ffffffff81651000 R12: ffff8803efb4a000
[125471.340745] R13: ffff8803efb4a000 R14: 0000000000000000 R15: ffff8802f8e33c88
[125471.340745] FS: 0000000000000000(0000) GS:ffff88043dd40000(0000) knlGS:0000000000000000
[125471.340745] CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b
[125471.340745] CR2: 00007fae7ca86095 CR3: 0000000001a0b000 CR4: 00000000000006e0
[125471.340745] Stack:
[125471.340745] ffff88040a11bc88 ffffffffa04ca0cd ffff88040a11bcc8 ffffffffa04ceeb1
[125471.340745] ffff8802f8e33940 ffff8802c93eadb0 ffff8802f8e0bf50 ffff8803efb4a000
[125471.340745] 0000000000000000 ffff8802f8e33c88 ffff88040a11bd38 ffffffffa04eccfa
[125471.340745] Call Trace:
[125471.340745] [<ffffffffa04ca0cd>] drop_outstanding_extent+0x3d/0x6d [btrfs]
[125471.340745] [<ffffffffa04ceeb1>] btrfs_delalloc_release_metadata+0x51/0xdd [btrfs]
[125471.340745] [<ffffffffa04eccfa>] btrfs_finish_ordered_io+0x420/0x4eb [btrfs]
[125471.340745] [<ffffffffa04ecdda>] finish_ordered_fn+0x15/0x17 [btrfs]
[125471.340745] [<ffffffffa050e6e8>] normal_work_helper+0x14c/0x32a [btrfs]
[125471.340745] [<ffffffffa050e9c8>] btrfs_endio_write_helper+0x12/0x14 [btrfs]
[125471.340745] [<ffffffff81063b23>] process_one_work+0x24a/0x4ac
[125471.340745] [<ffffffff81064285>] worker_thread+0x206/0x2c2
[125471.340745] [<ffffffff8106407f>] ? rescuer_thread+0x2cb/0x2cb
[125471.340745] [<ffffffff8106407f>] ? rescuer_thread+0x2cb/0x2cb
[125471.340745] [<ffffffff8106904d>] kthread+0xef/0xf7
[125471.340745] [<ffffffff81068f5e>] ? kthread_parkme+0x24/0x24
[125471.340745] [<ffffffff8147d10f>] ret_from_fork+0x3f/0x70
[125471.340745] [<ffffffff81068f5e>] ? kthread_parkme+0x24/0x24
[125471.340745] Code: a5 55 a0 48 89 e5 e8 42 50 bc e0 0f 0b 55 89 f1 48 c7 c2 f0 a8 55 a0 48 89 fe 31 c0 48 c7 c7 14 aa 55 a0 48 89 e5 e8 22 50 bc e0 <0f> 0b 0f 1f 44 00 00 55 31 c9 ba 18 00 00 00 48 89 e5 41 56 41
[125471.340745] RIP [<ffffffffa0550da1>] assfail.constprop.46+0x1e/0x20 [btrfs]
[125471.340745] RSP <ffff88040a11bc78>
[125471.539620] ---[ end trace 144259f7838b4aa4 ]---
So fix this by ensuring we adjust the outstanding extents counter when we
do the fallback just like we do for the case where the whole write can be
done through the direct IO path.
We were also adjusting the outstanding extents counter by a constant value
of 1, which is incorrect because we were ignorning that we account extents
in BTRFS_MAX_EXTENT_SIZE units, o fix that as well.
The following test case for fstests reproduces this issue:
seq=`basename $0`
seqres=$RESULT_DIR/$seq
echo "QA output created by $seq"
tmp=/tmp/$$
status=1 # failure is the default!
trap "_cleanup; exit \$status" 0 1 2 3 15
_cleanup()
{
rm -f $tmp.*
}
# get standard environment, filters and checks
. ./common/rc
. ./common/filter
# real QA test starts here
_need_to_be_root
_supported_fs btrfs
_supported_os Linux
_require_scratch
_require_xfs_io_command "falloc"
rm -f $seqres.full
_scratch_mkfs >>$seqres.full 2>&1
_scratch_mount "-o compress"
# Create a compressed extent covering the range [700K, 800K[.
$XFS_IO_PROG -f -s -c "pwrite -S 0xaa -b 100K 700K 100K" \
$SCRATCH_MNT/foo | _filter_xfs_io
# Create prealloc extent covering the range [600K, 700K[.
$XFS_IO_PROG -c "falloc 600K 100K" $SCRATCH_MNT/foo
# Write 80K of data to the range [640K, 720K[ using direct IO. This
# range covers both the prealloc extent and the compressed extent.
# Because there's a compressed extent in the range we are writing to,
# the DIO write code path ends up only writing the first 60k of data,
# which goes to the prealloc extent, and then falls back to buffered IO
# for writing the remaining 20K of data - because that remaining data
# maps to a file range containing a compressed extent.
# When falling back to buffered IO, we used to trigger an assertion when
# releasing reserved space due to bad accounting of the inode's
# outstanding extents counter, which was set to 1 but we ended up
# decrementing it by 1 twice, once through the ordered extent for the
# 60K of data we wrote using direct IO, and once through the main direct
# IO handler (inode.cbtrfs_direct_IO()) because the direct IO write
# wrote less than 80K of data (60K).
$XFS_IO_PROG -d -c "pwrite -S 0xbb -b 80K 640K 80K" \
$SCRATCH_MNT/foo | _filter_xfs_io
# Now similar test as above but for very large write operations. This
# triggers special cases for an inode's outstanding extents accounting,
# as internally btrfs logically splits extents into 128Mb units.
$XFS_IO_PROG -f -s \
-c "pwrite -S 0xaa -b 128M 258M 128M" \
-c "falloc 0 258M" \
$SCRATCH_MNT/bar | _filter_xfs_io
$XFS_IO_PROG -d -c "pwrite -S 0xbb -b 256M 3M 256M" $SCRATCH_MNT/bar \
| _filter_xfs_io
# Now verify the file contents are correct and that they are the same
# even after unmounting and mounting the fs again (or evicting the page
# cache).
#
# For file foo, all bytes in the range [0, 640K[ must have a value of
# 0x00, all bytes in the range [640K, 720K[ must have a value of 0xbb
# and all bytes in the range [720K, 800K[ must have a value of 0xaa.
#
# For file bar, all bytes in the range [0, 3M[ must havea value of 0x00,
# all bytes in the range [3M, 259M[ must have a value of 0xbb and all
# bytes in the range [259M, 386M[ must have a value of 0xaa.
#
echo "File digests before remounting the file system:"
md5sum $SCRATCH_MNT/foo | _filter_scratch
md5sum $SCRATCH_MNT/bar | _filter_scratch
_scratch_remount
echo "File digests after remounting the file system:"
md5sum $SCRATCH_MNT/foo | _filter_scratch
md5sum $SCRATCH_MNT/bar | _filter_scratch
status=0
exit
Fixes: e1cbbfa5f5 ("Btrfs: fix outstanding_extents accounting in DIO")
Fixes: 3e05bde8c3 ("Btrfs: only adjust outstanding_extents when we do a short write")
Signed-off-by: Filipe Manana <fdmanana@suse.com>
When we are using the no-holes feature, if we punch a hole into a file
range that already contains a hole which overlaps the range we are passing
to fallocate(), we end up removing the extent map that represents the
existing hole without adding a new one. This happens because with the
no-holes feature we do not have explicit extent items to represent holes
and therefore the call to __btrfs_drop_extents(), made from
btrfs_punch_hole(), returns an end offset to the variable drop_end that
is smaller than the end of the range passed to fallocate(), while it
drops all existing extent maps in that range.
Normally having a missing extent map is not a problem, for example for
a readpages() operation we just end up building the extent map by
looking at the fs/subvol tree for a matching extent item (or a lack of
one for implicit holes). However for an fsync that uses the fast path,
which needs to look at the list of modified extent maps, this means
the fsync will not record information about the complete hole we had
before the fallocate() call into the log tree, resulting in a file with
content/layout that does not match what we had neither before nor after
the hole punch operation.
The following test case for fstests reproduces the issue. It fails without
this change because we get a file with a different digest after the fsync
log replay and also with a different extent/hole layout.
seq=`basename $0`
seqres=$RESULT_DIR/$seq
echo "QA output created by $seq"
tmp=/tmp/$$
status=1 # failure is the default!
trap "_cleanup; exit \$status" 0 1 2 3 15
_cleanup()
{
_cleanup_flakey
rm -f $tmp.*
}
# get standard environment, filters and checks
. ./common/rc
. ./common/filter
. ./common/punch
. ./common/dmflakey
# real QA test starts here
_need_to_be_root
_supported_fs generic
_supported_os Linux
_require_scratch
_require_xfs_io_command "fpunch"
_require_xfs_io_command "fiemap"
_require_dm_target flakey
_require_metadata_journaling $SCRATCH_DEV
# This test was motivated by an issue found in btrfs when the btrfs
# no-holes feature is enabled (introduced in kernel 3.14). So enable
# the feature if the fs being tested is btrfs.
if [ $FSTYP == "btrfs" ]; then
_require_btrfs_fs_feature "no_holes"
_require_btrfs_mkfs_feature "no-holes"
MKFS_OPTIONS="$MKFS_OPTIONS -O no-holes"
fi
rm -f $seqres.full
_scratch_mkfs >>$seqres.full 2>&1
_init_flakey
_mount_flakey
# Create out test file with some data and then fsync it.
# We do the fsync only to make sure the last fsync we do in this test
# triggers the fast code path of btrfs' fsync implementation, a
# condition necessary to trigger the bug btrfs had.
$XFS_IO_PROG -f -c "pwrite -S 0xaa 0K 128K" \
-c "fsync" \
$SCRATCH_MNT/foobar | _filter_xfs_io
# Now punch a hole against the range [96K, 128K[.
$XFS_IO_PROG -c "fpunch 96K 32K" $SCRATCH_MNT/foobar
# Punch another hole against a range that overlaps the previous range
# and ends beyond eof.
$XFS_IO_PROG -c "fpunch 64K 128K" $SCRATCH_MNT/foobar
# Punch another hole against a range that overlaps the first range
# ([96K, 128K[) and ends at eof.
$XFS_IO_PROG -c "fpunch 32K 96K" $SCRATCH_MNT/foobar
# Fsync our file. We want to verify that, after a power failure and
# mounting the filesystem again, the file content reflects all the hole
# punch operations.
$XFS_IO_PROG -c "fsync" $SCRATCH_MNT/foobar
echo "File digest before power failure:"
md5sum $SCRATCH_MNT/foobar | _filter_scratch
echo "Fiemap before power failure:"
$XFS_IO_PROG -c "fiemap -v" $SCRATCH_MNT/foobar | _filter_fiemap
# Silently drop all writes and umount to simulate a crash/power failure.
_load_flakey_table $FLAKEY_DROP_WRITES
_unmount_flakey
# Allow writes again, mount to trigger log replay and validate file
# contents.
_load_flakey_table $FLAKEY_ALLOW_WRITES
_mount_flakey
echo "File digest after log replay:"
# Must match the same digest we got before the power failure.
md5sum $SCRATCH_MNT/foobar | _filter_scratch
echo "Fiemap after log replay:"
# Must match the same extent listing we got before the power failure.
$XFS_IO_PROG -c "fiemap -v" $SCRATCH_MNT/foobar | _filter_fiemap
_unmount_flakey
status=0
exit
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Chris Mason <clm@fb.com>
When executing generic/001 in a loop on a ppc64 machine (with both sectorsize
and nodesize set to 64k), the following call trace is observed,
WARNING: at /root/repos/linux/fs/btrfs/locking.c:253
Modules linked in:
CPU: 2 PID: 8353 Comm: umount Not tainted 4.3.0-rc5-13676-ga5e681d #54
task: c0000000f2b1f560 ti: c0000000f6008000 task.ti: c0000000f6008000
NIP: c000000000520c88 LR: c0000000004a3b34 CTR: 0000000000000000
REGS: c0000000f600a820 TRAP: 0700 Not tainted (4.3.0-rc5-13676-ga5e681d)
MSR: 8000000102029032 <SF,VEC,EE,ME,IR,DR,RI> CR: 24444884 XER: 00000000
CFAR: c0000000004a3b30 SOFTE: 1
GPR00: c0000000004a3b34 c0000000f600aaa0 c00000000108ac00 c0000000f5a808c0
GPR04: 0000000000000000 c0000000f600ae60 0000000000000000 0000000000000005
GPR08: 00000000000020a1 0000000000000001 c0000000f2b1f560 0000000000000030
GPR12: 0000000084842882 c00000000fdc0900 c0000000f600ae60 c0000000f070b800
GPR16: 0000000000000000 c0000000f3c8a000 0000000000000000 0000000000000049
GPR20: 0000000000000001 0000000000000001 c0000000f5aa01f8 0000000000000000
GPR24: 0f83e0f83e0f83e1 c0000000f5a808c0 c0000000f3c8d000 c000000000000000
GPR28: c0000000f600ae74 0000000000000001 c0000000f3c8d000 c0000000f5a808c0
NIP [c000000000520c88] .btrfs_tree_lock+0x48/0x2a0
LR [c0000000004a3b34] .btrfs_lock_root_node+0x44/0x80
Call Trace:
[c0000000f600aaa0] [c0000000f600ab80] 0xc0000000f600ab80 (unreliable)
[c0000000f600ab80] [c0000000004a3b34] .btrfs_lock_root_node+0x44/0x80
[c0000000f600ac00] [c0000000004a99dc] .btrfs_search_slot+0xa8c/0xc00
[c0000000f600ad40] [c0000000004ab878] .btrfs_insert_empty_items+0x98/0x120
[c0000000f600adf0] [c00000000050da44] .btrfs_finish_chunk_alloc+0x1d4/0x620
[c0000000f600af20] [c0000000004be854] .btrfs_create_pending_block_groups+0x1d4/0x2c0
[c0000000f600b020] [c0000000004bf188] .do_chunk_alloc+0x3c8/0x420
[c0000000f600b100] [c0000000004c27cc] .find_free_extent+0xbfc/0x1030
[c0000000f600b260] [c0000000004c2ce8] .btrfs_reserve_extent+0xe8/0x250
[c0000000f600b330] [c0000000004c2f90] .btrfs_alloc_tree_block+0x140/0x590
[c0000000f600b440] [c0000000004a47b4] .__btrfs_cow_block+0x124/0x780
[c0000000f600b530] [c0000000004a4fc0] .btrfs_cow_block+0xf0/0x250
[c0000000f600b5e0] [c0000000004a917c] .btrfs_search_slot+0x22c/0xc00
[c0000000f600b720] [c00000000050aa40] .btrfs_remove_chunk+0x1b0/0x9f0
[c0000000f600b850] [c0000000004c4e04] .btrfs_delete_unused_bgs+0x434/0x570
[c0000000f600b950] [c0000000004d3cb8] .close_ctree+0x2e8/0x3b0
[c0000000f600ba20] [c00000000049d178] .btrfs_put_super+0x18/0x30
[c0000000f600ba90] [c000000000243cd4] .generic_shutdown_super+0xa4/0x1a0
[c0000000f600bb10] [c0000000002441d8] .kill_anon_super+0x18/0x30
[c0000000f600bb90] [c00000000049c898] .btrfs_kill_super+0x18/0xc0
[c0000000f600bc10] [c0000000002444f8] .deactivate_locked_super+0x98/0xe0
[c0000000f600bc90] [c000000000269f94] .cleanup_mnt+0x54/0xa0
[c0000000f600bd10] [c0000000000bd744] .task_work_run+0xc4/0x100
[c0000000f600bdb0] [c000000000016334] .do_notify_resume+0x74/0x80
[c0000000f600be30] [c0000000000098b8] .ret_from_except_lite+0x64/0x68
Instruction dump:
fba1ffe8 fbc1fff0 fbe1fff8 7c791b78 f8010010 f821ff21 e94d0290 81030040
812a04e8 7d094a78 7d290034 5529d97e <0b090000> 3b400000 3be30050 3bc3004c
The above call trace is seen even on x86_64; albeit very rarely and that too
with nodesize set to 64k and with nospace_cache mount option being used.
The reason for the above call trace is,
btrfs_remove_chunk
check_system_chunk
Allocate chunk if required
For each physical stripe on underlying device,
btrfs_free_dev_extent
...
Take lock on Device tree's root node
btrfs_cow_block("dev tree's root node");
btrfs_reserve_extent
find_free_extent
index = BTRFS_RAID_DUP;
have_caching_bg = false;
When in LOOP_CACHING_NOWAIT state, Assume we find a block group
which is being cached; Hence have_caching_bg is set to true
When repeating the search for the next RAID index, we set
have_caching_bg to false.
Hence right after completing the LOOP_CACHING_NOWAIT state, we incorrectly
skip LOOP_CACHING_WAIT state and move to LOOP_ALLOC_CHUNK state where we
allocate a chunk and try to add entries corresponding to the chunk's physical
stripe into the device tree. When doing so the task deadlocks itself waiting
for the blocking lock on the root node of the device tree.
This commit fixes the issue by introducing a new local variable to help
indicate as to whether a block group of any RAID type is being cached.
Signed-off-by: Chandan Rajendra <chandan@linux.vnet.ibm.com>
Reviewed-by: Josef Bacik <jbacik@fb.com>
Signed-off-by: Chris Mason <clm@fb.com>
Even with quota disabled, generic/127 will trigger a kernel warning by
underflow data space info.
The bug is caused by buffered write, which in case of short copy, the
start parameter for btrfs_delalloc_release_space() is wrong, and
round_up/down() in btrfs_delalloc_release() extents the range to page
aligned, decreasing one more page than expected.
This patch will fix it by passing correct start.
Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
Signed-off-by: Chris Mason <clm@fb.com>
When rebasing my patchset, I forgot to pick up a cleanup patch to remove
old hotfix in 4.2 release.
Witouth the cleanup, it will screw up new qgroup reserve framework and
always cause minus reserved number.
Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
Signed-off-by: Chris Mason <clm@fb.com>
Between btrfs_allocerved_file_extent() and
btrfs_add_delayed_qgroup_reserve(), there is a window that delayed_refs
are run and delayed ref head maybe freed before
btrfs_add_delayed_qgroup_reserve().
This will cause btrfs_dad_delayed_qgroup_reserve() to return -ENOENT,
and cause transaction to be aborted.
This patch will record qgroup reserve space info into delayed_ref_head
at btrfs_add_delayed_ref(), to eliminate the race window.
Reported-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
Signed-off-by: Chris Mason <clm@fb.com>
cleaner_kthread() kthread calls try_to_freeze() at the beginning of every
cleanup attempt. This operation can't ever succeed though, as the kthread
hasn't marked itself as freezable.
Before (hopefully eventually) kthread freezing gets converted to fileystem
freezing, we'd rather mark cleaner_kthread() freezable (as my
understanding is that it can generate filesystem I/O during suspend).
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Chris Mason <clm@fb.com>
Ancient qgroup code call memcpy() on a extent buffer and use it for leaf
iteration.
As extent buffer contains lock, pointers to pages, it's never sane to do
such copy.
The following bug may be caused by this insane operation:
[92098.841309] general protection fault: 0000 [#1] SMP
[92098.841338] Modules linked in: ...
[92098.841814] CPU: 1 PID: 24655 Comm: kworker/u4:12 Not tainted
4.3.0-rc1 #1
[92098.841868] Workqueue: btrfs-qgroup-rescan btrfs_qgroup_rescan_helper
[btrfs]
[92098.842261] Call Trace:
[92098.842277] [<ffffffffc035a5d8>] ? read_extent_buffer+0xb8/0x110
[btrfs]
[92098.842304] [<ffffffffc0396d00>] ? btrfs_find_all_roots+0x60/0x70
[btrfs]
[92098.842329] [<ffffffffc039af3d>]
btrfs_qgroup_rescan_worker+0x28d/0x5a0 [btrfs]
Where btrfs_qgroup_rescan_worker+0x28d is btrfs_disk_key_to_cpu(),
called in reading key from the copied extent_buffer.
This patch will use btrfs_clone_extent_buffer() to a better copy of
extent buffer to deal such case.
Reported-by: Stephane Lesimple <stephane_btrfs@lesimple.fr>
Suggested-by: Filipe Manana <fdmanana@kernel.org>
Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Chris Mason <clm@fb.com>
Enable the extended 'limit' syntax (a range), the new 'stripes' and
extended 'usage' syntax (a range) filters in the filters mask. The patch
comes separate and not within the series that introduced the new filters
because the patch adding the mask was merged in a late rc. The
integration branch was based on an older rc and could not merge the
patch due to the missing changes.
Prerequisities:
* btrfs: check unsupported filters in balance arguments
* btrfs: extend balance filter limit to take minimum and maximum
* btrfs: add balance filter for stripes
* btrfs: extend balance filter usage to take minimum and maximum
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Chris Mason <clm@fb.com>
Similar to the 'limit' filter, we can enhance the 'usage' filter to
accept a range. The change is backward compatible, the range is applied
only in connection with the BTRFS_BALANCE_ARGS_USAGE_RANGE flag.
We don't have a usecase yet, the current syntax has been sufficient. The
enhancement should provide parity with other range-like filters.
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Chris Mason <clm@fb.com>
Balance block groups which have the given number of stripes, defined by
a range min..max. This is useful to selectively rebalance only chunks
that do not span enough devices, applies to RAID0/10/5/6.
Signed-off-by: Gabríel Arthúr Pétursson <gabriel@system.is>
[ renamed bargs members, added to the UAPI, wrote the changelog ]
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Chris Mason <clm@fb.com>
The 'limit' filter is underdesigned, it should have been a range for
[min,max], with some relaxed semantics when one of the bounds is
missing. Besides that, using a full u64 for a single value is a waste of
bytes.
Let's fix both by extending the use of the u64 bytes for the [min,max]
range. This can be done in a backward compatible way, the range will be
interpreted only if the appropriate flag is set
(BTRFS_BALANCE_ARGS_LIMIT_RANGE).
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Chris Mason <clm@fb.com>
The code for btrfs inode-resolve has never worked properly for
files with enough hard links to trigger extrefs. It was trying to
get the leaf out of a path after freeing the path:
btrfs_release_path(path);
leaf = path->nodes[0];
item_size = btrfs_item_size_nr(leaf, slot);
The fix here is to use the extent buffer we cloned just a little higher
up to avoid deadlocks caused by using the leaf in the path.
Signed-off-by: Chris Mason <clm@fb.com>
cc: stable@vger.kernel.org # v3.7+
cc: Mark Fasheh <mfasheh@suse.de>
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: Mark Fasheh <mfasheh@suse.de>
Signed-off-by: Chris Mason <clm@fb.com>
We don't verify that all the balance filter arguments supplemented by
the flags are actually known to the kernel. Thus we let it silently pass
and do nothing.
At the moment this means only the 'limit' filter, but we're going to add
a few more soon so it's better to have that fixed. Also in older stable
kernels so that it works with newer userspace tools.
Cc: stable@vger.kernel.org # 3.16+
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Chris Mason <clm@fb.com>
In the kernel 4.2 merge window we had a big changes to the implementation
of delayed references and qgroups which made the no_quota field of delayed
references not used anymore. More specifically the no_quota field is not
used anymore as of:
commit 0ed4792af0 ("btrfs: qgroup: Switch to new extent-oriented qgroup mechanism.")
Leaving the no_quota field actually prevents delayed references from
getting merged, which in turn cause the following BUG_ON(), at
fs/btrfs/extent-tree.c, to be hit when qgroups are enabled:
static int run_delayed_tree_ref(...)
{
(...)
BUG_ON(node->ref_mod != 1);
(...)
}
This happens on a scenario like the following:
1) Ref1 bytenr X, action = BTRFS_ADD_DELAYED_REF, no_quota = 1, added.
2) Ref2 bytenr X, action = BTRFS_DROP_DELAYED_REF, no_quota = 0, added.
It's not merged with Ref1 because Ref1->no_quota != Ref2->no_quota.
3) Ref3 bytenr X, action = BTRFS_ADD_DELAYED_REF, no_quota = 1, added.
It's not merged with the reference at the tail of the list of refs
for bytenr X because the reference at the tail, Ref2 is incompatible
due to Ref2->no_quota != Ref3->no_quota.
4) Ref4 bytenr X, action = BTRFS_DROP_DELAYED_REF, no_quota = 0, added.
It's not merged with the reference at the tail of the list of refs
for bytenr X because the reference at the tail, Ref3 is incompatible
due to Ref3->no_quota != Ref4->no_quota.
5) We run delayed references, trigger merging of delayed references,
through __btrfs_run_delayed_refs() -> btrfs_merge_delayed_refs().
6) Ref1 and Ref3 are merged as Ref1->no_quota = Ref3->no_quota and
all other conditions are satisfied too. So Ref1 gets a ref_mod
value of 2.
7) Ref2 and Ref4 are merged as Ref2->no_quota = Ref4->no_quota and
all other conditions are satisfied too. So Ref2 gets a ref_mod
value of 2.
8) Ref1 and Ref2 aren't merged, because they have different values
for their no_quota field.
9) Delayed reference Ref1 is picked for running (select_delayed_ref()
always prefers references with an action == BTRFS_ADD_DELAYED_REF).
So run_delayed_tree_ref() is called for Ref1 which triggers the
BUG_ON because Ref1->red_mod != 1 (equals 2).
So fix this by removing the no_quota field, as it's not used anymore as
of commit 0ed4792af0 ("btrfs: qgroup: Switch to new extent-oriented
qgroup mechanism.").
The use of no_quota was also buggy in at least two places:
1) At delayed-refs.c:btrfs_add_delayed_tree_ref() - we were setting
no_quota to 0 instead of 1 when the following condition was true:
is_fstree(ref_root) || !fs_info->quota_enabled
2) At extent-tree.c:__btrfs_inc_extent_ref() - we were attempting to
reset a node's no_quota when the condition "!is_fstree(root_objectid)
|| !root->fs_info->quota_enabled" was true but we did it only in
an unused local stack variable, that is, we never reset the no_quota
value in the node itself.
This fixes the remainder of problems several people have been having when
running delayed references, mostly while a balance is running in parallel,
on a 4.2+ kernel.
Very special thanks to Stéphane Lesimple for helping debugging this issue
and testing this fix on his multi terabyte filesystem (which took more
than one day to balance alone, plus fsck, etc).
Also, this fixes deadlock issue when using the clone ioctl with qgroups
enabled, as reported by Elias Probst in the mailing list. The deadlock
happens because after calling btrfs_insert_empty_item we have our path
holding a write lock on a leaf of the fs/subvol tree and then before
releasing the path we called check_ref() which did backref walking, when
qgroups are enabled, and tried to read lock the same leaf. The trace for
this case is the following:
INFO: task systemd-nspawn:6095 blocked for more than 120 seconds.
(...)
Call Trace:
[<ffffffff86999201>] schedule+0x74/0x83
[<ffffffff863ef64c>] btrfs_tree_read_lock+0xc0/0xea
[<ffffffff86137ed7>] ? wait_woken+0x74/0x74
[<ffffffff8639f0a7>] btrfs_search_old_slot+0x51a/0x810
[<ffffffff863a129b>] btrfs_next_old_leaf+0xdf/0x3ce
[<ffffffff86413a00>] ? ulist_add_merge+0x1b/0x127
[<ffffffff86411688>] __resolve_indirect_refs+0x62a/0x667
[<ffffffff863ef546>] ? btrfs_clear_lock_blocking_rw+0x78/0xbe
[<ffffffff864122d3>] find_parent_nodes+0xaf3/0xfc6
[<ffffffff86412838>] __btrfs_find_all_roots+0x92/0xf0
[<ffffffff864128f2>] btrfs_find_all_roots+0x45/0x65
[<ffffffff8639a75b>] ? btrfs_get_tree_mod_seq+0x2b/0x88
[<ffffffff863e852e>] check_ref+0x64/0xc4
[<ffffffff863e9e01>] btrfs_clone+0x66e/0xb5d
[<ffffffff863ea77f>] btrfs_ioctl_clone+0x48f/0x5bb
[<ffffffff86048a68>] ? native_sched_clock+0x28/0x77
[<ffffffff863ed9b0>] btrfs_ioctl+0xabc/0x25cb
(...)
The problem goes away by eleminating check_ref(), which no longer is
needed as its purpose was to get a value for the no_quota field of
a delayed reference (this patch removes the no_quota field as mentioned
earlier).
Reported-by: Stéphane Lesimple <stephane_btrfs@lesimple.fr>
Tested-by: Stéphane Lesimple <stephane_btrfs@lesimple.fr>
Reported-by: Elias Probst <mail@eliasprobst.eu>
Reported-by: Peter Becker <floyd.net@gmail.com>
Reported-by: Malte Schröder <malte@tnxip.de>
Reported-by: Derek Dongray <derek@valedon.co.uk>
Reported-by: Erkki Seppala <flux-btrfs@inside.org>
Cc: stable@vger.kernel.org # 4.2+
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
In the kernel 4.2 merge window we had a refactoring/rework of the delayed
references implementation in order to fix certain problems with qgroups.
However that rework introduced one more regression that leads to the
following trace when running delayed references for metadata:
[35908.064664] kernel BUG at fs/btrfs/extent-tree.c:1832!
[35908.065201] invalid opcode: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC
[35908.065201] Modules linked in: dm_flakey dm_mod btrfs crc32c_generic xor raid6_pq nfsd auth_rpcgss oid_registry nfs_acl nfs lockd grace fscache sunrpc loop fuse parport_pc psmouse i2
[35908.065201] CPU: 14 PID: 15014 Comm: kworker/u32:9 Tainted: G W 4.3.0-rc5-btrfs-next-17+ #1
[35908.065201] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.8.1-0-g4adadbd-20150316_085822-nilsson.home.kraxel.org 04/01/2014
[35908.065201] Workqueue: btrfs-extent-refs btrfs_extent_refs_helper [btrfs]
[35908.065201] task: ffff880114b7d780 ti: ffff88010c4c8000 task.ti: ffff88010c4c8000
[35908.065201] RIP: 0010:[<ffffffffa04928b5>] [<ffffffffa04928b5>] insert_inline_extent_backref+0x52/0xb1 [btrfs]
[35908.065201] RSP: 0018:ffff88010c4cbb08 EFLAGS: 00010293
[35908.065201] RAX: 0000000000000000 RBX: ffff88008a661000 RCX: 0000000000000000
[35908.065201] RDX: ffffffffa04dd58f RSI: 0000000000000001 RDI: 0000000000000000
[35908.065201] RBP: ffff88010c4cbb40 R08: 0000000000001000 R09: ffff88010c4cb9f8
[35908.065201] R10: 0000000000000000 R11: 000000000000002c R12: 0000000000000000
[35908.065201] R13: ffff88020a74c578 R14: 0000000000000000 R15: 0000000000000000
[35908.065201] FS: 0000000000000000(0000) GS:ffff88023edc0000(0000) knlGS:0000000000000000
[35908.065201] CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b
[35908.065201] CR2: 00000000015e8708 CR3: 0000000102185000 CR4: 00000000000006e0
[35908.065201] Stack:
[35908.065201] ffff88010c4cbb18 0000000000000f37 ffff88020a74c578 ffff88015a408000
[35908.065201] ffff880154a44000 0000000000000000 0000000000000005 ffff88010c4cbbd8
[35908.065201] ffffffffa0492b9a 0000000000000005 0000000000000000 0000000000000000
[35908.065201] Call Trace:
[35908.065201] [<ffffffffa0492b9a>] __btrfs_inc_extent_ref+0x8b/0x208 [btrfs]
[35908.065201] [<ffffffffa0497117>] ? __btrfs_run_delayed_refs+0x4d4/0xd33 [btrfs]
[35908.065201] [<ffffffffa049773d>] __btrfs_run_delayed_refs+0xafa/0xd33 [btrfs]
[35908.065201] [<ffffffffa04a976a>] ? join_transaction.isra.10+0x25/0x41f [btrfs]
[35908.065201] [<ffffffffa04a97ed>] ? join_transaction.isra.10+0xa8/0x41f [btrfs]
[35908.065201] [<ffffffffa049914d>] btrfs_run_delayed_refs+0x75/0x1dd [btrfs]
[35908.065201] [<ffffffffa04992f1>] delayed_ref_async_start+0x3c/0x7b [btrfs]
[35908.065201] [<ffffffffa04d4b4f>] normal_work_helper+0x14c/0x32a [btrfs]
[35908.065201] [<ffffffffa04d4e93>] btrfs_extent_refs_helper+0x12/0x14 [btrfs]
[35908.065201] [<ffffffff81063b23>] process_one_work+0x24a/0x4ac
[35908.065201] [<ffffffff81064285>] worker_thread+0x206/0x2c2
[35908.065201] [<ffffffff8106407f>] ? rescuer_thread+0x2cb/0x2cb
[35908.065201] [<ffffffff8106407f>] ? rescuer_thread+0x2cb/0x2cb
[35908.065201] [<ffffffff8106904d>] kthread+0xef/0xf7
[35908.065201] [<ffffffff81068f5e>] ? kthread_parkme+0x24/0x24
[35908.065201] [<ffffffff8147d10f>] ret_from_fork+0x3f/0x70
[35908.065201] [<ffffffff81068f5e>] ? kthread_parkme+0x24/0x24
[35908.065201] Code: 6a 01 41 56 41 54 ff 75 10 41 51 4d 89 c1 49 89 c8 48 8d 4d d0 e8 f6 f1 ff ff 48 83 c4 28 85 c0 75 2c 49 81 fc ff 00 00 00 77 02 <0f> 0b 4c 8b 45 30 8b 4d 28 45 31
[35908.065201] RIP [<ffffffffa04928b5>] insert_inline_extent_backref+0x52/0xb1 [btrfs]
[35908.065201] RSP <ffff88010c4cbb08>
[35908.310885] ---[ end trace fe4299baf0666457 ]---
This happens because the new delayed references code no longer merges
delayed references that have different sequence values. The following
steps are an example sequence leading to this issue:
1) Transaction N starts, fs_info->tree_mod_seq has value 0;
2) Extent buffer (btree node) A is allocated, delayed reference Ref1 for
bytenr A is created, with a value of 1 and a seq value of 0;
3) fs_info->tree_mod_seq is incremented to 1;
4) Extent buffer A is deleted through btrfs_del_items(), which calls
btrfs_del_leaf(), which in turn calls btrfs_free_tree_block(). The
later returns the metadata extent associated to extent buffer A to
the free space cache (the range is not pinned), because the extent
buffer was created in the current transaction (N) and writeback never
happened for the extent buffer (flag BTRFS_HEADER_FLAG_WRITTEN not set
in the extent buffer).
This creates the delayed reference Ref2 for bytenr A, with a value
of -1 and a seq value of 1;
5) Delayed reference Ref2 is not merged with Ref1 when we create it,
because they have different sequence numbers (decided at
add_delayed_ref_tail_merge());
6) fs_info->tree_mod_seq is incremented to 2;
7) Some task attempts to allocate a new extent buffer (done at
extent-tree.c:find_free_extent()), but due to heavy fragmentation
and running low on metadata space the clustered allocation fails
and we fall back to unclustered allocation, which finds the
extent at offset A, so a new extent buffer at offset A is allocated.
This creates delayed reference Ref3 for bytenr A, with a value of 1
and a seq value of 2;
8) Ref3 is not merged neither with Ref2 nor Ref1, again because they
all have different seq values;
9) We start running the delayed references (__btrfs_run_delayed_refs());
10) The delayed Ref1 is the first one being applied, which ends up
creating an inline extent backref in the extent tree;
10) Next the delayed reference Ref3 is selected for execution, and not
Ref2, because select_delayed_ref() always gives a preference for
positive references (that have an action of BTRFS_ADD_DELAYED_REF);
11) When running Ref3 we encounter alreay the inline extent backref
in the extent tree at insert_inline_extent_backref(), which makes
us hit the following BUG_ON:
BUG_ON(owner < BTRFS_FIRST_FREE_OBJECTID);
This is always true because owner corresponds to the level of the
extent buffer/btree node in the btree.
For the scenario described above we hit the BUG_ON because we never merge
references that have different seq values.
We used to do the merging before the 4.2 kernel, more specifically, before
the commmits:
c6fc245499 ("btrfs: delayed-ref: Use list to replace the ref_root in ref_head.")
c43d160fcd ("btrfs: delayed-ref: Cleanup the unneeded functions.")
This issue became more exposed after the following change that was added
to 4.2 as well:
cffc3374e5 ("Btrfs: fix order by which delayed references are run")
Which in turn fixed another regression by the two commits previously
mentioned.
So fix this by bringing back the delayed reference merge code, with the
proper adaptations so that it operates against the new data structure
(linked list vs old red black tree implementation).
This issue was hit running fstest btrfs/063 in a loop. Several people have
reported this issue in the mailing list when running on kernels 4.2+.
Very special thanks to Stéphane Lesimple for helping debugging this issue
and testing this fix on his multi terabyte filesystem (which took more
than one day to balance alone, plus fsck, etc).
Fixes: c6fc245499 ("btrfs: delayed-ref: Use list to replace the ref_root in ref_head.")
Reported-by: Peter Becker <floyd.net@gmail.com>
Reported-by: Stéphane Lesimple <stephane_btrfs@lesimple.fr>
Tested-by: Stéphane Lesimple <stephane_btrfs@lesimple.fr>
Reported-by: Malte Schröder <malte@tnxip.de>
Reported-by: Derek Dongray <derek@valedon.co.uk>
Reported-by: Erkki Seppala <flux-btrfs@inside.org>
Cc: stable@vger.kernel.org # 4.2+
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: Liu Bo <bo.li.liu@oracle.com>
When we make ctl->unit allocations from a bitmap there is no point in searching
for the next 0 in the bitmap. If we've found a bit we're done and can just exit
the loop. Thanks,
Signed-off-by: Josef Bacik <jbacik@fb.com>
Signed-off-by: Chris Mason <clm@fb.com>
We can waste a lot of time searching through bitmaps when we are heavily
fragmented trying to find large contiguous areas that don't exist in the bitmap.
So keep track of the max extent size when we do a full search of a bitmap so
that next time around we can just skip the expensive searching if our max size
is less than what we are looking for. Thanks,
Signed-off-by: Josef Bacik <jbacik@fb.com>
Signed-off-by: Chris Mason <clm@fb.com>
If we are extremely fragmented then we won't be able to create a free_cluster.
So if this happens set last_ptr->fragmented so that all future allcations will
give up trying to create a cluster. When we unpin extents we will unset
->fragmented if we free up a sufficient amount of space in a block group.
Thanks,
Signed-off-by: Josef Bacik <jbacik@fb.com>
Signed-off-by: Chris Mason <clm@fb.com>
We try really really hard to make allocations, but sometimes it is just not
going to happen, especially when free space is extremely fragmented. So add a
few short cuts through the looping states. For example if we couldn't allocate
a chunk, just go straight to the NO_EMPTY_SIZE loop. If there are no uncached
block groups and we've done a full search, go straight to the ALLOC_CHUNK stage.
And finally if we already have empty_size and empty_cluster set to 0 go ahead
and return -ENOSPC. Thanks,
Signed-off-by: Josef Bacik <jbacik@fb.com>
Signed-off-by: Chris Mason <clm@fb.com>
If we hit ENOSPC when setting up a space cache don't bother setting up any of
the other space cache's in this transaction, it'll just induce unnecessary
latency. Thanks,
Signed-off-by: Josef Bacik <jbacik@fb.com>
Signed-off-by: Chris Mason <clm@fb.com>
When we are heavily fragmented we can induce a lot of latency trying to make an
allocation happen that is simply not going to happen. Thankfully we keep track
of our max_extent_size when going through the allocator, so if we get to the
point where we are exiting find_free_extent with ENOSPC then set our
space_info->max_extent_size so we can keep future allocations from having to pay
this cost. We reset the max_extent_size whenever we release pinned bytes back
into this space info so we can redo all the work. Thanks,
Signed-off-by: Josef Bacik <jbacik@fb.com>
Signed-off-by: Chris Mason <clm@fb.com>
The space cache needs to have contiguous allocations, and the allocator tries to
make allocations by reducing the amount of bytes requested and re-searching.
But this just makes us waste time when we are very fragmented, so if we can't
find our space just exit, don't bother trying to search again. Thanks,
Signed-off-by: Josef Bacik <jbacik@fb.com>
Signed-off-by: Chris Mason <clm@fb.com>
I want to set some per transaction flags, so instead of adding yet another int
lets just convert the current two int indicators to flags and add a flags field
for future use. Thanks,
Signed-off-by: Josef Bacik <jbacik@fb.com>
Signed-off-by: Chris Mason <clm@fb.com>
If we are heavily fragmented we will continually try to prealloc the largest
extent size we can every time we call btrfs_reserve_extent. This can be very
expensive when we are heavily fragmented, burning lots of CPU cycles and loops
through the allocator. So instead notice when we get a smaller chunk from the
allocator than what we specified and use this as the new maximum size we try to
allocate. Thanks,
Signed-off-by: Josef Bacik <jbacik@fb.com>
Signed-off-by: Chris Mason <clm@fb.com>
Filipe Manana
David Sterba
Zhaolei
Dan Carpenter
Justin Maggard
chandan
Qu Wenruo
Jiri Kosina
Gabríel Arthúr Pétursson
Chris Mason
Josef Bacik