Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
It is unused everywhere now, it can be removed.
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
It is completely unused now, remove it.
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
We no longer use recursion, so
__btrfs_tree_read_lock(BTRFS_NESTING_NORMAL) == btrfs_tree_read_lock.
Replace this call with the simple helper.
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
We no longer have recursive locking and there's no need for separate
helpers that allowed the transition to rwsem with minimal code changes.
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Now that we're no longer using recursion, rip out all of the supporting
code. Follow up patches will clean up the callers of these functions.
The extent_buffer::lock_owner is still retained as it allows safety
checks in btrfs_init_new_buffer for the case that the free space cache
is corrupted and we try to allocate a block that we are currently using
and have locked in the path.
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
With my async free space cache loading patches ("btrfs: load free space
cache asynchronously") we no longer have a user of path->recurse and can
remove it.
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Filipe reported the following lockdep splat
======================================================
WARNING: possible circular locking dependency detected
5.10.0-rc2-btrfs-next-71 #1 Not tainted
------------------------------------------------------
find/324157 is trying to acquire lock:
ffff8ebc48d293a0 (btrfs-tree-01#2/3){++++}-{3:3}, at: __btrfs_tree_read_lock+0x32/0x1a0 [btrfs]
but task is already holding lock:
ffff8eb9932c5088 (btrfs-tree-00){++++}-{3:3}, at: __btrfs_tree_read_lock+0x32/0x1a0 [btrfs]
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #1 (btrfs-tree-00){++++}-{3:3}:
lock_acquire+0xd8/0x490
down_write_nested+0x44/0x120
__btrfs_tree_lock+0x27/0x120 [btrfs]
btrfs_search_slot+0x2a3/0xc50 [btrfs]
btrfs_insert_empty_items+0x58/0xa0 [btrfs]
insert_with_overflow+0x44/0x110 [btrfs]
btrfs_insert_xattr_item+0xb8/0x1d0 [btrfs]
btrfs_setxattr+0xd6/0x4c0 [btrfs]
btrfs_setxattr_trans+0x68/0x100 [btrfs]
__vfs_setxattr+0x66/0x80
__vfs_setxattr_noperm+0x70/0x200
vfs_setxattr+0x6b/0x120
setxattr+0x125/0x240
path_setxattr+0xba/0xd0
__x64_sys_setxattr+0x27/0x30
do_syscall_64+0x33/0x80
entry_SYSCALL_64_after_hwframe+0x44/0xa9
-> #0 (btrfs-tree-01#2/3){++++}-{3:3}:
check_prev_add+0x91/0xc60
__lock_acquire+0x1689/0x3130
lock_acquire+0xd8/0x490
down_read_nested+0x45/0x220
__btrfs_tree_read_lock+0x32/0x1a0 [btrfs]
btrfs_next_old_leaf+0x27d/0x580 [btrfs]
btrfs_real_readdir+0x1e3/0x4b0 [btrfs]
iterate_dir+0x170/0x1c0
__x64_sys_getdents64+0x83/0x140
do_syscall_64+0x33/0x80
entry_SYSCALL_64_after_hwframe+0x44/0xa9
other info that might help us debug this:
Possible unsafe locking scenario:
CPU0 CPU1
---- ----
lock(btrfs-tree-00);
lock(btrfs-tree-01#2/3);
lock(btrfs-tree-00);
lock(btrfs-tree-01#2/3);
*** DEADLOCK ***
5 locks held by find/324157:
#0: ffff8ebc502c6e00 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0x4d/0x60
#1: ffff8eb97f689980 (&type->i_mutex_dir_key#10){++++}-{3:3}, at: iterate_dir+0x52/0x1c0
#2: ffff8ebaec00ca58 (btrfs-tree-02#2){++++}-{3:3}, at: __btrfs_tree_read_lock+0x32/0x1a0 [btrfs]
#3: ffff8eb98f986f78 (btrfs-tree-01#2){++++}-{3:3}, at: __btrfs_tree_read_lock+0x32/0x1a0 [btrfs]
#4: ffff8eb9932c5088 (btrfs-tree-00){++++}-{3:3}, at: __btrfs_tree_read_lock+0x32/0x1a0 [btrfs]
stack backtrace:
CPU: 2 PID: 324157 Comm: find Not tainted 5.10.0-rc2-btrfs-next-71 #1
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014
Call Trace:
dump_stack+0x8d/0xb5
check_noncircular+0xff/0x110
? mark_lock.part.0+0x468/0xe90
check_prev_add+0x91/0xc60
__lock_acquire+0x1689/0x3130
? kvm_clock_read+0x14/0x30
? kvm_sched_clock_read+0x5/0x10
lock_acquire+0xd8/0x490
? __btrfs_tree_read_lock+0x32/0x1a0 [btrfs]
down_read_nested+0x45/0x220
? __btrfs_tree_read_lock+0x32/0x1a0 [btrfs]
__btrfs_tree_read_lock+0x32/0x1a0 [btrfs]
btrfs_next_old_leaf+0x27d/0x580 [btrfs]
btrfs_real_readdir+0x1e3/0x4b0 [btrfs]
iterate_dir+0x170/0x1c0
__x64_sys_getdents64+0x83/0x140
? filldir+0x1d0/0x1d0
do_syscall_64+0x33/0x80
entry_SYSCALL_64_after_hwframe+0x44/0xa9
This happens because btrfs_next_old_leaf searches down to our current
key, and then walks up the path until we can move to the next slot, and
then reads back down the path so we get the next leaf.
However it doesn't unlock any lower levels until it replaces them with
the new extent buffer. This is technically fine, but of course causes
lockdep to complain, because we could be holding locks on lower levels
while locking upper levels.
Fix this by dropping all nodes below the level that we use as our new
starting point before we start reading back down the path. This also
allows us to drop the nested/recursive locking magic, because we're no
longer locking two nodes at the same level anymore.
Reported-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
We are carrying around this next_rw_lock from when we would do spinning
vs blocking read locks. Now that we have the rwsem locking we can
simply use the read lock flag unconditionally and the read lock helpers.
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Commit 343694eee8d8 ("btrfs: switch seed device to list api"), missed to
check if the parameter seed is true in the function btrfs_find_device().
This tells it whether to traverse the seed device list or not.
After this commit, the argument is unused and can be removed.
In device_list_add() it's not necessary because fs_devices always points
to the device's fs_devices. So with the devid+uuid matching, it will
find the right device and return, thus not needing to traverse seed
devices.
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Anand Jain <anand.jain@oracle.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Drop the condition in verify_one_dev_extent,
btrfs_device::disk_total_bytes is set even for a seed device. The
comment is wrong, the size is properly set when cloning the device.
Commit 1b3922a8bc ("btrfs: Use real device structure to verify
dev extent") introduced it but it's unclear why the total_disk_bytes
was 0.
Theoretically, all devices (including missing and seed) marked with the
BTRFS_DEV_STATE_IN_FS_METADATA flag gets the total_disk_bytes updated at
fill_device_from_item():
open_ctree()
btrfs_read_chunk_tree()
read_one_dev()
open_seed_device()
fill_device_from_item()
Even if verify_one_dev_extent() reports total_disk_bytes == 0, then its
a bug to be fixed somewhere else and not in verify_one_dev_extent() as
it's just a messenger. It is never expected that a total_disk_bytes
shall be zero.
The function fill_device_from_item() does the job of reading it from the
item and updating btrfs_device::disk_total_bytes. So both the missing
device and the seed devices do have their disk_total_bytes updated.
btrfs_find_device can also return a device from fs_info->seed_list
because it searches it as well.
Furthermore, while removing the device if there is a power loss, we
could have a device with its total_bytes = 0, that's still valid.
Instead, introduce a check against maximum block device size in
read_one_dev().
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Anand Jain <anand.jain@oracle.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Commit cf89af146b ("btrfs: dev-replace: fail mount if we don't have
replace item with target device") dropped the multi stage operation of
btrfs_free_extra_devids() that does not need to check replace target
anymore and we can remove the 'step' argument.
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Anand Jain <anand.jain@oracle.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
There are several occasions where we do not update the inode's number of
used bytes atomically, resulting in a concurrent stat(2) syscall to report
a value of used blocks that does not correspond to a valid value, that is,
a value that does not match neither what we had before the operation nor
what we get after the operation completes.
In extreme cases it can result in stat(2) reporting zero used blocks, which
can cause problems for some userspace tools where they can consider a file
with a non-zero size and zero used blocks as completely sparse and skip
reading data, as reported/discussed a long time ago in some threads like
the following:
https://lists.gnu.org/archive/html/bug-tar/2016-07/msg00001.html
The cases where this can happen are the following:
-> Case 1
If we do a write (buffered or direct IO) against a file region for which
there is already an allocated extent (or multiple extents), then we have a
short time window where we can report a number of used blocks to stat(2)
that does not take into account the file region being overwritten. This
short time window happens when completing the ordered extent(s).
This happens because when we drop the extents in the write range we
decrement the inode's number of bytes and later on when we insert the new
extent(s) we increment the number of bytes in the inode, resulting in a
short time window where a stat(2) syscall can get an incorrect number of
used blocks.
If we do writes that overwrite an entire file, then we have a short time
window where we report 0 used blocks to stat(2).
Example reproducer:
$ cat reproducer-1.sh
#!/bin/bash
MNT=/mnt/sdi
DEV=/dev/sdi
stat_loop()
{
trap "wait; exit" SIGTERM
local filepath=$1
local expected=$2
local got
while :; do
got=$(stat -c %b $filepath)
if [ $got -ne $expected ]; then
echo -n "ERROR: unexpected used blocks"
echo " (got: $got expected: $expected)"
fi
done
}
mkfs.btrfs -f $DEV > /dev/null
# mkfs.xfs -f $DEV > /dev/null
# mkfs.ext4 -F $DEV > /dev/null
# mkfs.f2fs -f $DEV > /dev/null
# mkfs.reiserfs -f $DEV > /dev/null
mount $DEV $MNT
xfs_io -f -s -c "pwrite -b 64K 0 64K" $MNT/foobar >/dev/null
expected=$(stat -c %b $MNT/foobar)
# Create a process to keep calling stat(2) on the file and see if the
# reported number of blocks used (disk space used) changes, it should
# not because we are not increasing the file size nor punching holes.
stat_loop $MNT/foobar $expected &
loop_pid=$!
for ((i = 0; i < 50000; i++)); do
xfs_io -s -c "pwrite -b 64K 0 64K" $MNT/foobar >/dev/null
done
kill $loop_pid &> /dev/null
wait
umount $DEV
$ ./reproducer-1.sh
ERROR: unexpected used blocks (got: 0 expected: 128)
ERROR: unexpected used blocks (got: 0 expected: 128)
(...)
Note that since this is a short time window where the race can happen, the
reproducer may not be able to always trigger the bug in one run, or it may
trigger it multiple times.
-> Case 2
If we do a buffered write against a file region that does not have any
allocated extents, like a hole or beyond EOF, then during ordered extent
completion we have a short time window where a concurrent stat(2) syscall
can report a number of used blocks that does not correspond to the value
before or after the write operation, a value that is actually larger than
the value after the write completes.
This happens because once we start a buffered write into an unallocated
file range we increment the inode's 'new_delalloc_bytes', to make sure
any stat(2) call gets a correct used blocks value before delalloc is
flushed and completes. However at ordered extent completion, after we
inserted the new extent, we increment the inode's number of bytes used
with the size of the new extent, and only later, when clearing the range
in the inode's iotree, we decrement the inode's 'new_delalloc_bytes'
counter with the size of the extent. So this results in a short time
window where a concurrent stat(2) syscall can report a number of used
blocks that accounts for the new extent twice.
Example reproducer:
$ cat reproducer-2.sh
#!/bin/bash
MNT=/mnt/sdi
DEV=/dev/sdi
stat_loop()
{
trap "wait; exit" SIGTERM
local filepath=$1
local expected=$2
local got
while :; do
got=$(stat -c %b $filepath)
if [ $got -ne $expected ]; then
echo -n "ERROR: unexpected used blocks"
echo " (got: $got expected: $expected)"
fi
done
}
mkfs.btrfs -f $DEV > /dev/null
# mkfs.xfs -f $DEV > /dev/null
# mkfs.ext4 -F $DEV > /dev/null
# mkfs.f2fs -f $DEV > /dev/null
# mkfs.reiserfs -f $DEV > /dev/null
mount $DEV $MNT
touch $MNT/foobar
write_size=$((64 * 1024))
for ((i = 0; i < 16384; i++)); do
offset=$(($i * $write_size))
xfs_io -c "pwrite -S 0xab $offset $write_size" $MNT/foobar >/dev/null
blocks_used=$(stat -c %b $MNT/foobar)
# Fsync the file to trigger writeback and keep calling stat(2) on it
# to see if the number of blocks used changes.
stat_loop $MNT/foobar $blocks_used &
loop_pid=$!
xfs_io -c "fsync" $MNT/foobar
kill $loop_pid &> /dev/null
wait $loop_pid
done
umount $DEV
$ ./reproducer-2.sh
ERROR: unexpected used blocks (got: 265472 expected: 265344)
ERROR: unexpected used blocks (got: 284032 expected: 283904)
(...)
Note that since this is a short time window where the race can happen, the
reproducer may not be able to always trigger the bug in one run, or it may
trigger it multiple times.
-> Case 3
Another case where such problems happen is during other operations that
replace extents in a file range with other extents. Those operations are
extent cloning, deduplication and fallocate's zero range operation.
The cause of the problem is similar to the first case. When we drop the
extents from a range, we decrement the inode's number of bytes, and later
on, after inserting the new extents we increment it. Since this is not
done atomically, a concurrent stat(2) call can see and return a number of
used blocks that is smaller than it should be, does not match the number
of used blocks before or after the clone/deduplication/zero operation.
Like for the first case, when doing a clone, deduplication or zero range
operation against an entire file, we end up having a time window where we
can report 0 used blocks to a stat(2) call.
Example reproducer:
$ cat reproducer-3.sh
#!/bin/bash
MNT=/mnt/sdi
DEV=/dev/sdi
mkfs.btrfs -f $DEV > /dev/null
# mkfs.xfs -f -m reflink=1 $DEV > /dev/null
mount $DEV $MNT
extent_size=$((64 * 1024))
num_extents=16384
file_size=$(($extent_size * $num_extents))
# File foo has many small extents.
xfs_io -f -s -c "pwrite -S 0xab -b $extent_size 0 $file_size" $MNT/foo \
> /dev/null
# File bar has much less extents and has exactly the same data as foo.
xfs_io -f -c "pwrite -S 0xab 0 $file_size" $MNT/bar > /dev/null
expected=$(stat -c %b $MNT/foo)
# Now deduplicate bar into foo. While the deduplication is in progres,
# the number of used blocks/file size reported by stat should not change
xfs_io -c "dedupe $MNT/bar 0 0 $file_size" $MNT/foo > /dev/null &
dedupe_pid=$!
while [ -n "$(ps -p $dedupe_pid -o pid=)" ]; do
used=$(stat -c %b $MNT/foo)
if [ $used -ne $expected ]; then
echo "Unexpected blocks used: $used (expected: $expected)"
fi
done
umount $DEV
$ ./reproducer-3.sh
Unexpected blocks used: 2076800 (expected: 2097152)
Unexpected blocks used: 2097024 (expected: 2097152)
Unexpected blocks used: 2079872 (expected: 2097152)
(...)
Note that since this is a short time window where the race can happen, the
reproducer may not be able to always trigger the bug in one run, or it may
trigger it multiple times.
So fix this by:
1) Making btrfs_drop_extents() not decrement the VFS inode's number of
bytes, and instead return the number of bytes;
2) Making any code that drops extents and adds new extents update the
inode's number of bytes atomically, while holding the btrfs inode's
spinlock, which is also used by the stat(2) callback to get the inode's
number of bytes;
3) For ranges in the inode's iotree that are marked as 'delalloc new',
corresponding to previously unallocated ranges, increment the inode's
number of bytes when clearing the 'delalloc new' bit from the range,
in the same critical section that decrements the inode's
'new_delalloc_bytes' counter, delimited by the btrfs inode's spinlock.
An alternative would be to have btrfs_getattr() wait for any IO (ordered
extents in progress) and locking the whole range (0 to (u64)-1) while it
it computes the number of blocks used. But that would mean blocking
stat(2), which is a very used syscall and expected to be fast, waiting
for writes, clone/dedupe, fallocate, page reads, fiemap, etc.
CC: stable@vger.kernel.org # 5.4+
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
When defragmenting we skip ranges that have holes or inline extents, so that
we don't do unnecessary IO and waste space. We do this check when calling
should_defrag_range() at btrfs_defrag_file(). However we do it without
holding the inode's lock. The reason we do it like this is to avoid
blocking other tasks for too long, that possibly want to operate on other
file ranges, since after the call to should_defrag_range() and before
locking the inode, we trigger a synchronous page cache readahead. However
before we were able to lock the inode, some other task might have punched
a hole in our range, or we may now have an inline extent there, in which
case we should not set the range for defrag anymore since that would cause
unnecessary IO and make us waste space (i.e. allocating extents to contain
zeros for a hole).
So after we locked the inode and the range in the iotree, check again if
we have holes or an inline extent, and if we do, just skip the range.
I hit this while testing my next patch that fixes races when updating an
inode's number of bytes (subject "btrfs: update the number of bytes used
by an inode atomically"), and it depends on this change in order to work
correctly. Alternatively I could rework that other patch to detect holes
and flag their range with the 'new delalloc' bit, but this itself fixes
an efficiency problem due a race that from a functional point of view is
not harmful (it could be triggered with btrfs/062 from fstests).
CC: stable@vger.kernel.org # 5.4+
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
There are many arguments for __btrfs_drop_extents() and its wrapper
btrfs_drop_extents(), which makes it hard to add more arguments to it and
requires changing every caller. I have added a couple myself back in 2014
commit 1acae57b16 ("Btrfs: faster file extent item replace operations")
and therefore know firsthand that it is a bit cumbersome to add additional
arguments to these functions.
Since I will need to add more arguments in a subsequent bug fix, this
change is preparatory work and adds a data structure that holds all the
arguments, for both input and output, that are passed to this function,
with some comments in the structure's definition mentioning what each
field is and how it relates to other fields.
Callers of this function need only to zero out the content of the
structure and setup only the fields they need. This also removes the
need to have both __btrfs_drop_extents() and btrfs_drop_extents(), so
now we have a single function named btrfs_drop_extents() that takes a
pointer to this new data structure (struct btrfs_drop_extents_args).
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Both Filipe and Fedora QA recently hit the following lockdep splat:
WARNING: possible recursive locking detected
5.10.0-0.rc1.20201028gited8780e3f2ec.57.fc34.x86_64 #1 Not tainted
--------------------------------------------
rsync/2610 is trying to acquire lock:
ffff89617ed48f20 (&eb->lock){++++}-{2:2}, at: btrfs_tree_read_lock_atomic+0x34/0x140
but task is already holding lock:
ffff8961757b1130 (&eb->lock){++++}-{2:2}, at: btrfs_tree_read_lock_atomic+0x34/0x140
other info that might help us debug this:
Possible unsafe locking scenario:
CPU0
----
lock(&eb->lock);
lock(&eb->lock);
*** DEADLOCK ***
May be due to missing lock nesting notation
2 locks held by rsync/2610:
#0: ffff896107212b90 (&type->i_mutex_dir_key#10){++++}-{3:3}, at: walk_component+0x10c/0x190
#1: ffff8961757b1130 (&eb->lock){++++}-{2:2}, at: btrfs_tree_read_lock_atomic+0x34/0x140
stack backtrace:
CPU: 1 PID: 2610 Comm: rsync Not tainted 5.10.0-0.rc1.20201028gited8780e3f2ec.57.fc34.x86_64 #1
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 0.0.0 02/06/2015
Call Trace:
dump_stack+0x8b/0xb0
__lock_acquire.cold+0x12d/0x2a4
? kvm_sched_clock_read+0x14/0x30
? sched_clock+0x5/0x10
lock_acquire+0xc8/0x400
? btrfs_tree_read_lock_atomic+0x34/0x140
? read_block_for_search.isra.0+0xdd/0x320
_raw_read_lock+0x3d/0xa0
? btrfs_tree_read_lock_atomic+0x34/0x140
btrfs_tree_read_lock_atomic+0x34/0x140
btrfs_search_slot+0x616/0x9a0
btrfs_lookup_dir_item+0x6c/0xb0
btrfs_lookup_dentry+0xa8/0x520
? lockdep_init_map_waits+0x4c/0x210
btrfs_lookup+0xe/0x30
__lookup_slow+0x10f/0x1e0
walk_component+0x11b/0x190
path_lookupat+0x72/0x1c0
filename_lookup+0x97/0x180
? strncpy_from_user+0x96/0x1e0
? getname_flags.part.0+0x45/0x1a0
vfs_statx+0x64/0x100
? lockdep_hardirqs_on_prepare+0xff/0x180
? _raw_spin_unlock_irqrestore+0x41/0x50
__do_sys_newlstat+0x26/0x40
? lockdep_hardirqs_on_prepare+0xff/0x180
? syscall_enter_from_user_mode+0x27/0x80
? syscall_enter_from_user_mode+0x27/0x80
do_syscall_64+0x33/0x40
entry_SYSCALL_64_after_hwframe+0x44/0xa9
I have also seen a report of lockdep complaining about the lock class
that was looked up being the same as the lock class on the lock we were
using, but I can't find the report.
These are problems that occur because we do not have the lockdep class
set on the extent buffer until _after_ we read the eb in properly. This
is problematic for concurrent readers, because we will create the extent
buffer, lock it, and then attempt to read the extent buffer.
If a second thread comes in and tries to do a search down the same path
they'll get the above lockdep splat because the class isn't set properly
on the extent buffer.
There was a good reason for this, we generally didn't know the real
owner of the eb until we read it, specifically in refcounted roots.
However now all refcounted roots have the same class name, so we no
longer need to worry about this. For non-refcounted trees we know
which root we're on based on the parent.
Fix this by setting the lockdep class on the eb at creation time instead
of read time. This will fix the splat and the weirdness where the class
changes in the middle of locking the block.
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Now that we've plumbed all of the callers to have the owner root and the
level, plumb it down into alloc_extent_buffer().
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
The readahead infrastructure does raw reads of extent buffers, but we're
going to need to know their owner and level in order to set the lockdep
key properly, so plumb in the infrastructure that we'll need to have
this information when we start allocating extent buffers.
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
In order to properly set the lockdep class of a newly allocated block we
need to know the owner of the block. For non-refcounted trees this is
straightforward, we always know in advance what tree we're reading from.
For refcounted trees we don't necessarily know, however all refcounted
trees share the same lockdep class name, tree-<level>.
Fix all the callers of read_tree_block() to pass in the root objectid
we're using. In places like relocation and backref we could probably
unconditionally use 0, but just in case use the root when we have it,
otherwise use 0 in the cases we don't have the root as it's going to be
a refcounted tree anyway.
This is a preparation patch for further changes.
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
We're open-coding btrfs_read_node_slot() here, replace with the helper.
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
We're open-coding btrfs_read_node_slot() here, replace with the helper.
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
We're open-coding btrfs_read_node_slot() here, replace with the helper.
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
We're open-coding btrfs_read_node_slot() here, replace with the helper.
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
We're open-coding btrfs_read_node_slot() here, replace with the helper.
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
We're open coding btrfs_read_node_slot in do_relocation, replace this
with the proper helper.
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
We do not need to call read_tree_block() here, simply use the
btrfs_read_node_slot helper.
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
We have this open-coded nightmare in btrfs_realloc_node that does
the same thing that the normal read path does, which is to see if we
have the eb in memory already, and if not read it, and verify the eb is
uptodate. Delete this open coding and simply use btrfs_read_node_slot.
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
We're going to pass around more information when we allocate extent
buffers, in order to make that cleaner how we do readahead. Most of the
callers have the parent node that we're getting our blockptr from, with
the sole exception of relocation which simply has the bytenr it wants to
read.
Add a helper that takes the current arguments that we need (bytenr and
gen), and add another helper for simply reading the slot out of a node.
In followup patches the helper that takes all the extra arguments will
be expanded, and the simpler helper won't need to have it's arguments
adjusted.
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
We have this weird problem where our lockdep class is set after we
read a tree block, which can race with concurrent readers and result in
erroneous lockdep errors. We want to set the lockdep class at
allocation time if possible, but in certain cases we may not have the
actual root owner, such as with relocation or any backref lookups. This
is only really a problem for reference counted trees, because all other
trees have their root reference set in their extent reference. Remove
the fs tree specific lock class. We need to still keep the reloc tree
one, it's still reference counted, because replace_path will lock the
reloc tree and the destination tree, and if they're both set to
tree-<level> we'll have issues.
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
After sysfs updates discard's iops_limit or kbps_limit it also needs to
adjust current timer through rescheduling, otherwise the discard work
may wait for a long time for the previous timer to expire or bumped by
someone else.
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
If btrfs_discard_schedule_work() is called with override=true, it sets
delay anew regardless how much time is left until the timer should have
fired. If delays are long (that can happen, for example, with low
kbps_limit), they might get constantly overridden without having a
chance to run the discard work.
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Most delay calculations are done in ns or ms, so store
discard_ctl->delay in ms and convert the final delay to jiffies only at
the end.
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Instead of using iops_limit only for cutting off extremes, calculate the
discard delay directly from it, so it closely follows iops_limit and
doesn't under-discard even though quotas are not saturated.
The iops limit could be hit more often in some cases and could increase
the discard rate.
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Function scrub_find_csum() is to locate the csum for bytenr @logical
from sctx->csum_list.
However it lacks a lot of comments to explain things like how the
csum_list is organized and why we need to drop csum range which is
before us.
Refactor the function by:
- Add more comments explaining the behavior
- Add comment explaining why we need to drop the csum range
- Put the csum copy in the main loop
This is mostly for the incoming patches to make scrub_find_csum() able
to find multiple checksums.
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
The @force parameter for scrub_pages() is to indicate whether we want to
force bio submission. Currently it's only used for the super block,
and it can be easily determined by the @flags, so we can remove the
parameter.
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
There are several call sites where we declare something like
"struct scrub_page *page".
This is confusing as we also use regular page in this code,
rename it to 'spage' where applicable.
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Currently csum_dirty_buffer() uses page to grab extent buffer, but that
only works for sector size == PAGE_SIZE case.
For subpage we need page + page_offset to grab extent buffer.
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Currently btrfs_validate_metadata_buffer() only needs to handle one
extent buffer as currently one page maps to at most one extent buffer.
For incoming subpage support, we need to extend the support where one
page could contain multiple extent buffers.
Split the function so we can call validate_extent_buffer on extent
buffers independently.
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
For subpage size support, metadata blocks of nodesize are smaller than
one page and this needs to be handled when calculating the checksum.
The checksummed start and length need to be adjusted but only for the
first page:
- start is simply offset in the page
- length is nodesize (subpage) or PAGE_SIZE for all other cases
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Since commit f28491e0a6 ("Btrfs: move the extent buffer radix tree into
the fs_info"), fs_info can be grabbed from extent_buffer directly.
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
For subpage sector size support, one page can contain multiple tree
blocks. The entries cannot be based on page size and index must be
derived from the sectorsize. No change for page size == sector size.
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
When calling attach_extent_buffer_page(), either we're attaching
anonymous pages, called from btrfs_clone_extent_buffer(),
or we're attaching btree inode pages, called from alloc_extent_buffer().
For the latter case, we should hold page->mapping->private_lock to avoid
parallel changes to page->private.
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Nikolay Borisov