commit 3c17916510428dbccdf657de050c34e208347089 upstream.
During allocation the allocator will try to allocate an extent using
cluster policy. Once the current cluster is exhausted it will remove the
entry under btrfs_free_cluster::lock and subsequently acquire
btrfs_free_space_ctl::tree_lock to dispose of the already-deleted entry
and adjust btrfs_free_space_ctl::total_bitmap. This poses a problem
because there exists a race condition between removing the entry under
one lock and doing the necessary accounting holding a different lock
since extent freeing only uses the 2nd lock. This can result in the
following situation:
T1: T2:
btrfs_alloc_from_cluster insert_into_bitmap <holds tree_lock>
if (entry->bytes == 0) if (block_group && !list_empty(&block_group->cluster_list)) {
rb_erase(entry)
spin_unlock(&cluster->lock);
(total_bitmaps is still 4) spin_lock(&cluster->lock);
<doesn't find entry in cluster->root>
spin_lock(&ctl->tree_lock); <goes to new_bitmap label, adds
<blocked since T2 holds tree_lock> <a new entry and calls add_new_bitmap>
recalculate_thresholds <crashes,
due to total_bitmaps
becoming 5 and triggering
an ASSERT>
To fix this ensure that once depleted, the cluster entry is deleted when
both cluster lock and tree locks are held in the allocator (T1), this
ensures that even if there is a race with a concurrent
insert_into_bitmap call it will correctly find the entry in the cluster
and add the new space to it.
CC: <stable@vger.kernel.org> # 4.4+
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
commit 95c85fba1f64c3249c67f0078a29f8a125078189 upstream.
It's wrong calling btrfs_put_block_group in
__btrfs_return_cluster_to_free_space if the block group passed is
different than the block group the cluster represents. As this means the
cluster doesn't have a reference to the passed block group. This results
in double put and a use-after-free bug.
Fix this by simply bailing if the block group we passed in does not
match the block group on the cluster.
Fixes: fa9c0d795f ("Btrfs: rework allocation clustering")
CC: stable@vger.kernel.org # 4.4+
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
[ update changelog ]
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[ Upstream commit 3cc64e7ebfb0d7faaba2438334c43466955a96e8 ]
Return value in __load_free_space_cache is not properly set after
(unlikely) memory allocation failures and 0 is returned instead.
This is not a problem for the caller load_free_space_cache because only
value 1 is considered as 'cache loaded' but for clarity it's better
to set the errors accordingly.
Fixes: a67509c300 ("Btrfs: add a io_ctl struct and helpers for dealing with the space cache")
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Zhihao Cheng <chengzhihao1@huawei.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
The free space inode stores the tracking data, checksums etc, using the
io_ctl structure and moving the pointers. The data are generally aligned
to at least 4 bytes (u32 for CRC) so it's not completely unaligned but
for clarity we should use the proper helpers whenever a struct is
initialized from io_ctl->cur pointer.
Signed-off-by: David Sterba <dsterba@suse.com>
Delete repeated words in fs/btrfs/.
{to, the, a, and old}
and change "into 2 part" to "into 2 parts".
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
If a transaction aborts it can cause a memory leak of the pages array of
a block group's io_ctl structure. The following steps explain how that can
happen:
1) Transaction N is committing, currently in state TRANS_STATE_UNBLOCKED
and it's about to start writing out dirty extent buffers;
2) Transaction N + 1 already started and another task, task A, just called
btrfs_commit_transaction() on it;
3) Block group B was dirtied (extents allocated from it) by transaction
N + 1, so when task A calls btrfs_start_dirty_block_groups(), at the
very beginning of the transaction commit, it starts writeback for the
block group's space cache by calling btrfs_write_out_cache(), which
allocates the pages array for the block group's io_ctl with a call to
io_ctl_init(). Block group A is added to the io_list of transaction
N + 1 by btrfs_start_dirty_block_groups();
4) While transaction N's commit is writing out the extent buffers, it gets
an IO error and aborts transaction N, also setting the file system to
RO mode;
5) Task A has already returned from btrfs_start_dirty_block_groups(), is at
btrfs_commit_transaction() and has set transaction N + 1 state to
TRANS_STATE_COMMIT_START. Immediately after that it checks that the
filesystem was turned to RO mode, due to transaction N's abort, and
jumps to the "cleanup_transaction" label. After that we end up at
btrfs_cleanup_one_transaction() which calls btrfs_cleanup_dirty_bgs().
That helper finds block group B in the transaction's io_list but it
never releases the pages array of the block group's io_ctl, resulting in
a memory leak.
In fact at the point when we are at btrfs_cleanup_dirty_bgs(), the pages
array points to pages that were already released by us at
__btrfs_write_out_cache() through the call to io_ctl_drop_pages(). We end
up freeing the pages array only after waiting for the ordered extent to
complete through btrfs_wait_cache_io(), which calls io_ctl_free() to do
that. But in the transaction abort case we don't wait for the space cache's
ordered extent to complete through a call to btrfs_wait_cache_io(), so
that's why we end up with a memory leak - we wait for the ordered extent
to complete indirectly by shutting down the work queues and waiting for
any jobs in them to complete before returning from close_ctree().
We can solve the leak simply by freeing the pages array right after
releasing the pages (with the call to io_ctl_drop_pages()) at
__btrfs_write_out_cache(), since we will never use it anymore after that
and the pages array points to already released pages at that point, which
is currently not a problem since no one will use it after that, but not a
good practice anyway since it can easily lead to use-after-free issues.
So fix this by freeing the pages array right after releasing the pages at
__btrfs_write_out_cache().
This issue can often be reproduced with test case generic/475 from fstests
and kmemleak can detect it and reports it with the following trace:
unreferenced object 0xffff9bbf009fa600 (size 512):
comm "fsstress", pid 38807, jiffies 4298504428 (age 22.028s)
hex dump (first 32 bytes):
00 a0 7c 4d 3d ed ff ff 40 a0 7c 4d 3d ed ff ff ..|M=...@.|M=...
80 a0 7c 4d 3d ed ff ff c0 a0 7c 4d 3d ed ff ff ..|M=.....|M=...
backtrace:
[<00000000f4b5cfe2>] __kmalloc+0x1a8/0x3e0
[<0000000028665e7f>] io_ctl_init+0xa7/0x120 [btrfs]
[<00000000a1f95b2d>] __btrfs_write_out_cache+0x86/0x4a0 [btrfs]
[<00000000207ea1b0>] btrfs_write_out_cache+0x7f/0xf0 [btrfs]
[<00000000af21f534>] btrfs_start_dirty_block_groups+0x27b/0x580 [btrfs]
[<00000000c3c23d44>] btrfs_commit_transaction+0xa6f/0xe70 [btrfs]
[<000000009588930c>] create_subvol+0x581/0x9a0 [btrfs]
[<000000009ef2fd7f>] btrfs_mksubvol+0x3fb/0x4a0 [btrfs]
[<00000000474e5187>] __btrfs_ioctl_snap_create+0x119/0x1a0 [btrfs]
[<00000000708ee349>] btrfs_ioctl_snap_create_v2+0xb0/0xf0 [btrfs]
[<00000000ea60106f>] btrfs_ioctl+0x12c/0x3130 [btrfs]
[<000000005c923d6d>] __x64_sys_ioctl+0x83/0xb0
[<0000000043ace2c9>] do_syscall_64+0x33/0x80
[<00000000904efbce>] entry_SYSCALL_64_after_hwframe+0x44/0xa9
CC: stable@vger.kernel.org # 4.9+
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
In try_to_merge_free_space we attempt to find entries to the left and
right of the entry we are adding to see if they can be merged. We
search for an entry past our current info (saved into right_info), and
then if right_info exists and it has a rb_prev() we save the rb_prev()
into left_info.
However there's a slight problem in the case that we have a right_info,
but no entry previous to that entry. At that point we will search for
an entry just before the info we're attempting to insert. This will
simply find right_info again, and assign it to left_info, making them
both the same pointer.
Now if right_info _can_ be merged with the range we're inserting, we'll
add it to the info and free right_info. However further down we'll
access left_info, which was right_info, and thus get a use-after-free.
Fix this by only searching for the left entry if we don't find a right
entry at all.
The CVE referenced had a specially crafted file system that could
trigger this use-after-free. However with the tree checker improvements
we no longer trigger the conditions for the UAF. But the original
conditions still apply, hence this fix.
Reference: CVE-2019-19448
Fixes: 9630308170 ("Btrfs: use hybrid extents+bitmap rb tree for free space")
CC: stable@vger.kernel.org # 4.4+
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: David Sterba <dsterba@suse.com>
There is a single use of the generic vfs_inode so let's take btrfs_inode
as a parameter and remove couple of redundant BTRFS_I() calls.
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Use the helper function where it is open coded to increment the
block_group reference count As btrfs_get_block_group() is a one-liner we
could have open-coded it, but its partner function
btrfs_put_block_group() isn't one-liner which does the free part in it.
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.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>
__btrfs_return_cluster_to_free_space() returns only 0. And all its
parent functions don't need the return value either so make this a void
function.
Further, as none of the callers of btrfs_return_cluster_to_free_space()
is actually using the return from this function, make this function also
return void.
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.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>
Since commit 1afb648e94 ("btrfs: use standard debug config option to
enable free-space-cache debug prints"), we started to log error messages
that were never logged before since there was no DEBUG macro defined
anywhere. This started to make test case btrfs/187 to fail very often,
as it greps for any btrfs error messages in dmesg/syslog and fails if
any is found:
(...)
btrfs/186 1s ... 2s
btrfs/187 - output mismatch (see .../results//btrfs/187.out.bad)
\--- tests/btrfs/187.out 2019-05-17 12:48:32.537340749 +0100
\+++ /home/fdmanana/git/hub/xfstests/results//btrfs/187.out.bad ...
\@@ -1,3 +1,8 @@
QA output created by 187
Create a readonly snapshot of 'SCRATCH_MNT' in 'SCRATCH_MNT/snap1'
Create a readonly snapshot of 'SCRATCH_MNT' in 'SCRATCH_MNT/snap2'
+[268364.139958] BTRFS error (device sdc): failed to write free space cache for block group 30408704
+[268380.156503] BTRFS error (device sdc): failed to write free space cache for block group 30408704
+[268380.161703] BTRFS error (device sdc): failed to write free space cache for block group 30408704
+[268380.253180] BTRFS error (device sdc): failed to write free space cache for block group 30408704
...
(Run 'diff -u /home/fdmanana/git/hub/xfstests/tests/btrfs/187.out ...
btrfs/188 4s ... 2s
(...)
The space cache write failures happen due to ENOSPC when attempting to
update the free space cache items in the root tree. This happens because
when starting or joining a transaction we don't know how many block
groups we will end up changing (due to extent allocation or release) and
therefore never reserve space for updating free space cache items.
More often than not, the free space cache writeout succeeds since the
metadata space info is not yet full nor very close to being full, but
when it is, the space cache writeout fails with ENOSPC.
Occasional failures to write space caches are not considered critical
since they can be rebuilt when mounting the filesystem or the next
attempt to write a free space cache in the next transaction commit might
succeed, so we used to hide those error messages with a preprocessor
check for the existence of the DEBUG macro that was never enabled
anywhere.
A few other generic test cases also trigger the error messages due to
ENOSPC failure when writing free space caches as well, however they don't
fail since they don't grep dmesg/syslog for any btrfs specific error
messages.
So change the messages from 'error' level to 'debug' level, as it doesn't
make much sense to have error messages triggered only if the debug macro
is enabled plus, more importantly, the error is not serious nor highly
unexpected.
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Currently the error messages logged when we fail to write a free space
cache or an inode cache are not very useful as they don't mention what
was the error. So include the error number in the messages.
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
The inode lookup starting at btrfs_iget takes the full location key,
while only the objectid is used to match the inode, because the lookup
happens inside the given root thus the inode number is unique.
The entire location key is properly set up in btrfs_init_locked_inode.
Simplify the helpers and pass only inode number, renaming it to 'ino'
instead of 'objectid'. This allows to remove temporary variables key,
saving some stack space.
Signed-off-by: David Sterba <dsterba@suse.com>
The helpers btrfs_freeze_block_group() and btrfs_unfreeze_block_group()
used to be named btrfs_get_block_group_trimming() and
btrfs_put_block_group_trimming() respectively.
At the time they were added to free-space-cache.c, by commit e33e17ee10
("btrfs: add missing discards when unpinning extents with -o discard")
because all the trimming related functions were in free-space-cache.c.
Now that the helpers were renamed and are used in scrub context as well,
move them to block-group.c, a much more logical location for them.
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Back in 2014, commit 04216820fe ("Btrfs: fix race between fs trimming
and block group remove/allocation"), I added the 'trimming' member to the
block group structure. Its purpose was to prevent races between trimming
and block group deletion/allocation by pinning the block group in a way
that prevents its logical address and device extents from being reused
while trimming is in progress for a block group, so that if another task
deletes the block group and then another task allocates a new block group
that gets the same logical address and device extents while the trimming
task is still in progress.
After the previous fix for scrub (patch "btrfs: fix a race between scrub
and block group removal/allocation"), scrub now also has the same needs that
trimming has, so the member name 'trimming' no longer makes sense.
Since there is already a 'pinned' member in the block group that refers
to space reservations (pinned bytes), rename the member to 'frozen',
add a comment on top of it to describe its general purpose and rename
the helpers to increment and decrement the counter as well, to match
the new member name.
The next patch in the series will move the helpers into a more suitable
file (from free-space-cache.c to block-group.c).
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
The error cleanup gotos in __btrfs_write_out_cache() needlessly jump
back making the code less readable then needed. Flatten them out so no
back-jump is necessary and the read flow is uninterrupted.
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
free-space-cache.c has it's own set of DEBUG ifdefs which need to be
turned on instead of the global CONFIG_BTRFS_DEBUG to print debug
messages about failed block-group writes.
Switch this over to CONFIG_BTRFS_DEBUG so we always see these messages
when running a debug kernel.
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Make the uptodate argument of io_ctl_add_pages() boolean.
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
io_ctl_prepare_pages() gets a 'struct btrfs_io_ctl' as well as a 'struct
inode', but btrfs_io_ctl::inode points to the same struct inode as this is
assgined in io_ctl_init().
Use the inode form io_ctl to reduce the arguments of io_ctl_prepare_pages.
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit flips the switch to start tracking/processing pinned extents
on a per-transaction basis. It mostly replaces all references from
btrfs_fs_info::(pinned_extents|freed_extents[]) to
btrfs_transaction::pinned_extents.
Two notable modifications that warrant explicit mention are changing
clean_pinned_extents to get a reference to the previously running
transaction. The other one is removal of call to
btrfs_destroy_pinned_extent since transactions are going to be cleaned
in btrfs_cleanup_one_transaction.
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Preparation for refactoring pinned extents tracking.
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Most callers of free_bitmap() only call it if bitmap_info->bytes is 0.
However, there are certain cases where we may free the free space cache
via __btrfs_remove_free_space_cache(). This exposes a path where
free_bitmap() is called regardless. This may result in a bad accounting
situation for discardable_bytes and discardable_extents. So, remove the
stats and call btrfs_discard_update_discardable().
Signed-off-by: Dennis Zhou <dennis@kernel.org>
Signed-off-by: David Sterba <dsterba@suse.com>
It's less than ideal for small extents to eat into our extent budget, so
force extents <= 32KB into the bitmaps save for the first handful.
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Dennis Zhou <dennis@kernel.org>
Signed-off-by: David Sterba <dsterba@suse.com>
Currently, there is no way for the free space cache to recover from
being serviced by purely bitmaps because the extent threshold is set to
0 in recalculate_thresholds() when we surpass the metadata allowance.
This adds a recovery mechanism by keeping large extents out of the
bitmaps and increases the metadata upper bound to 64KB. The recovery
mechanism bypasses this upper bound, thus making it a soft upper bound.
But, with the bypass being 1MB or greater, it shouldn't add unbounded
overhead.
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Dennis Zhou <dennis@kernel.org>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Keep track of how much we are discarding and how often we are reusing
with async discard. The discard_*_bytes values don't need any special
protection because the work item provides the single threaded access.
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Dennis Zhou <dennis@kernel.org>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Non-block group destruction discarding currently only had a single list
with no minimum discard length. This can lead to caravaning more
meaningful discards behind a heavily fragmented block group.
This adds support for multiple lists with minimum discard lengths to
prevent the caravan effect. We promote block groups back up when we
exceed the BTRFS_ASYNC_DISCARD_MAX_FILTER size, currently we support
only 2 lists with filters of 1MB and 32KB respectively.
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Dennis Zhou <dennis@kernel.org>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Expose max_discard_size as a tunable via sysfs and switch the current
fixed maximum to the default value.
Signed-off-by: Dennis Zhou <dennis@kernel.org>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Throttle the maximum size of a discard so that we can provide an upper
bound for the rate of async discard. While the block layer is able to
split discards into the appropriate sized discards, we want to be able
to account more accurately the rate at which we are consuming NCQ slots
as well as limit the upper bound of work for a discard.
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Dennis Zhou <dennis@kernel.org>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Keep track of this metric so that we can understand how ahead or behind
we are in discarding rate. This uses the same accounting method as
discardable_extents, deltas between previous/current values and
propagating them up.
Signed-off-by: Dennis Zhou <dennis@kernel.org>
Reviewed-by: David Sterba <dsterba@suse.com>
[ update changelog ]
Signed-off-by: David Sterba <dsterba@suse.com>
The number of discardable extents will serve as the rate limiting metric
for how often we should discard. This keeps track of discardable extents
in the free space caches by maintaining deltas and propagating them to
the global count.
The deltas are calculated from 2 values stored in PREV and CURR entries,
then propagated up to the global discard ctl. The current counter value
becomes the previous counter value after update.
Signed-off-by: Dennis Zhou <dennis@kernel.org>
Reviewed-by: David Sterba <dsterba@suse.com>
[ update changelog ]
Signed-off-by: David Sterba <dsterba@suse.com>
The prior two patches added discarding via a background workqueue. This
just piggybacked off of the fstrim code to trim the whole block at once.
Well inevitably this is worse performance wise and will aggressively
overtrim. But it was nice to plumb the other infrastructure to keep the
patches easier to review.
This adds the real goal of this series which is discarding slowly (ie. a
slow long running fstrim). The discarding is split into two phases,
extents and then bitmaps. The reason for this is two fold. First, the
bitmap regions overlap the extent regions. Second, discarding the
extents first will let the newly trimmed bitmaps have the highest chance
of coalescing when being readded to the free space cache.
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Dennis Zhou <dennis@kernel.org>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
block_group removal is a little tricky. It can race with the extent
allocator, the cleaner thread, and balancing. The current path is for a
block_group to be added to the unused_bgs list. Then, when the cleaner
thread comes around, it starts a transaction and then proceeds with
removing the block_group. Extents that are pinned are subsequently
removed from the pinned trees and then eventually a discard is issued
for the entire block_group.
Async discard introduces another player into the game, the discard
workqueue. While it has none of the racing issues, the new problem is
ensuring we don't leave free space untrimmed prior to forgetting the
block_group. This is handled by placing fully free block_groups on a
separate discard queue. This is necessary to maintain discarding order
as in the future we will slowly trim even fully free block_groups. The
ordering helps us make progress on the same block_group rather than say
the last fully freed block_group or needing to search through the fully
freed block groups at the beginning of a list and insert after.
The new order of events is a fully freed block group gets placed on the
unused discard queue first. Once it's processed, it will be placed on
the unusued_bgs list and then the original sequence of events will
happen, just without the final whole block_group discard.
The mount flags can change when processing unused_bgs, so when flipping
from DISCARD to DISCARD_ASYNC, the unused_bgs must be punted to the
discard_list to be trimmed. If we flip off DISCARD_ASYNC, we punt
free block groups on the discard_list to the unused_bg queue which will
do the final discard for us.
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Dennis Zhou <dennis@kernel.org>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
When discard is enabled, everytime a pinned extent is released back to
the block_group's free space cache, a discard is issued for the extent.
This is an overeager approach when it comes to discarding and helping
the SSD maintain enough free space to prevent severe garbage collection
situations.
This adds the beginning of async discard. Instead of issuing a discard
prior to returning it to the free space, it is just marked as untrimmed.
The block_group is then added to a LRU which then feeds into a workqueue
to issue discards at a much slower rate. Full discarding of unused block
groups is still done and will be addressed in a future patch of the
series.
For now, we don't persist the discard state of extents and bitmaps.
Therefore, our failure recovery mode will be to consider extents
untrimmed. This lets us handle failure and unmounting as one in the
same.
On a number of Facebook webservers, I collected data every minute
accounting the time we spent in btrfs_finish_extent_commit() (col. 1)
and in btrfs_commit_transaction() (col. 2). btrfs_finish_extent_commit()
is where we discard extents synchronously before returning them to the
free space cache.
discard=sync:
p99 total per minute p99 total per minute
Drive | extent_commit() (ms) | commit_trans() (ms)
---------------------------------------------------------------
Drive A | 434 | 1170
Drive B | 880 | 2330
Drive C | 2943 | 3920
Drive D | 4763 | 5701
discard=async:
p99 total per minute p99 total per minute
Drive | extent_commit() (ms) | commit_trans() (ms)
--------------------------------------------------------------
Drive A | 134 | 956
Drive B | 64 | 1972
Drive C | 59 | 1032
Drive D | 62 | 1200
While it's not great that the stats are cumulative over 1m, all of these
servers are running the same workload and and the delta between the two
are substantial. We are spending significantly less time in
btrfs_finish_extent_commit() which is responsible for discarding.
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Dennis Zhou <dennis@kernel.org>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
There is a cap in btrfs in the amount of free extents that a block group
can have. When it surpasses that threshold, future extents are placed
into bitmaps. Instead of keeping track of if a certain bit is trimmed or
not in a second bitmap, keep track of the relative state of the bitmap.
With async discard, trimming bitmaps becomes a more frequent operation.
As a trade off with simplicity, we keep track of if discarding a bitmap
is in progress. If we fully scan a bitmap and trim as necessary, the
bitmap is marked clean. This has some caveats as the min block size may
skip over regions deemed too small. But this should be a reasonable
trade off rather than keeping a second bitmap and making allocation
paths more complex. The downside is we may overtrim, but ideally the min
block size should prevent us from doing that too often and getting stuck
trimming pathological cases.
BTRFS_TRIM_STATE_TRIMMING is added to indicate a bitmap is in the
process of being trimmed. If additional free space is added to that
bitmap, the bit is cleared. A bitmap will be marked
BTRFS_TRIM_STATE_TRIMMED if the trimming code was able to reach the end
of it and the former is still set.
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Dennis Zhou <dennis@kernel.org>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Async discard will use the free space cache as backing knowledge for
which extents to discard. This patch plumbs knowledge about which
extents need to be discarded into the free space cache from
unpin_extent_range().
An untrimmed extent can merge with everything as this is a new region.
Absorbing trimmed extents is a tradeoff to for greater coalescing which
makes life better for find_free_extent(). Additionally, it seems the
size of a trim isn't as problematic as the trim io itself.
When reading in the free space cache from disk, if sync is set, mark all
extents as trimmed. The current code ensures at transaction commit that
all free space is trimmed when sync is set, so this reflects that.
Signed-off-by: Dennis Zhou <dennis@kernel.org>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
The type name is misleading, a single entry is named 'cache' while this
normally means a collection of objects. Rename that everywhere. Also the
identifier was quite long, making function prototypes harder to format.
Suggested-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
The on-disk format of block group item makes use of the key that stores
the offset and length. This is further used in the code, although this
makes thing harder to understand. The key is also packed so the
offset/length is not properly aligned as u64.
Add start (key.objectid) and length (key.offset) members to block group
and remove the embedded key. When the item is searched or written, a
local variable for key is used.
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
For unknown reasons, the member 'used' in the block group struct is
stored in the b-tree item and accessed everywhere using the special
accessor helper. Let's unify it and make it a regular member and only
update the item before writing it to the tree.
The item is still being used for flags and chunk_objectid, there's some
duplication until the item is removed in following patches.
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
While testing 5.2 we ran into the following panic
[52238.017028] BUG: kernel NULL pointer dereference, address: 0000000000000001
[52238.105608] RIP: 0010:drop_buffers+0x3d/0x150
[52238.304051] Call Trace:
[52238.308958] try_to_free_buffers+0x15b/0x1b0
[52238.317503] shrink_page_list+0x1164/0x1780
[52238.325877] shrink_inactive_list+0x18f/0x3b0
[52238.334596] shrink_node_memcg+0x23e/0x7d0
[52238.342790] ? do_shrink_slab+0x4f/0x290
[52238.350648] shrink_node+0xce/0x4a0
[52238.357628] balance_pgdat+0x2c7/0x510
[52238.365135] kswapd+0x216/0x3e0
[52238.371425] ? wait_woken+0x80/0x80
[52238.378412] ? balance_pgdat+0x510/0x510
[52238.386265] kthread+0x111/0x130
[52238.392727] ? kthread_create_on_node+0x60/0x60
[52238.401782] ret_from_fork+0x1f/0x30
The page we were trying to drop had a page->private, but had no
page->mapping and so called drop_buffers, assuming that we had a
buffer_head on the page, and then panic'ed trying to deref 1, which is
our page->private for data pages.
This is happening because we're truncating the free space cache while
we're trying to load the free space cache. This isn't supposed to
happen, and I'll fix that in a followup patch. However we still
shouldn't allow those sort of mistakes to result in messing with pages
that do not belong to us. So add the page->mapping check to verify that
we still own this page after dropping and re-acquiring the page lock.
This page being unlocked as:
btrfs_readpage
extent_read_full_page
__extent_read_full_page
__do_readpage
if (!nr)
unlock_page <-- nr can be 0 only if submit_extent_page
returns an error
CC: stable@vger.kernel.org # 4.4+
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
[ add callchain ]
Signed-off-by: David Sterba <dsterba@suse.com>
The parameter is now always set to NULL and could be dropped. The last
user was get_default_root but that got reworked in 05dbe6837b ("Btrfs:
unify subvol= and subvolid= mounting") and the parameter became unused.
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Since commit fee187d9d9 ("Btrfs: do not set EXTENT_DIRTY along with
EXTENT_DELALLOC"), we never set EXTENT_DIRTY in inode->io_tree, so we
can simplify and stop trying to clear it.
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Omar Sandoval <osandov@fb.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Various notifications of type "BUG kmalloc-4096 () : Redzone
overwritten" have been observed recently in various parts of the kernel.
After some time, it has been made a relation with the use of BTRFS
filesystem and with SLUB_DEBUG turned on.
[ 22.809700] BUG kmalloc-4096 (Tainted: G W ): Redzone overwritten
[ 22.810286] INFO: 0xbe1a5921-0xfbfc06cd. First byte 0x0 instead of 0xcc
[ 22.810866] INFO: Allocated in __load_free_space_cache+0x588/0x780 [btrfs] age=22 cpu=0 pid=224
[ 22.811193] __slab_alloc.constprop.26+0x44/0x70
[ 22.811345] kmem_cache_alloc_trace+0xf0/0x2ec
[ 22.811588] __load_free_space_cache+0x588/0x780 [btrfs]
[ 22.811848] load_free_space_cache+0xf4/0x1b0 [btrfs]
[ 22.812090] cache_block_group+0x1d0/0x3d0 [btrfs]
[ 22.812321] find_free_extent+0x680/0x12a4 [btrfs]
[ 22.812549] btrfs_reserve_extent+0xec/0x220 [btrfs]
[ 22.812785] btrfs_alloc_tree_block+0x178/0x5f4 [btrfs]
[ 22.813032] __btrfs_cow_block+0x150/0x5d4 [btrfs]
[ 22.813262] btrfs_cow_block+0x194/0x298 [btrfs]
[ 22.813484] commit_cowonly_roots+0x44/0x294 [btrfs]
[ 22.813718] btrfs_commit_transaction+0x63c/0xc0c [btrfs]
[ 22.813973] close_ctree+0xf8/0x2a4 [btrfs]
[ 22.814107] generic_shutdown_super+0x80/0x110
[ 22.814250] kill_anon_super+0x18/0x30
[ 22.814437] btrfs_kill_super+0x18/0x90 [btrfs]
[ 22.814590] INFO: Freed in proc_cgroup_show+0xc0/0x248 age=41 cpu=0 pid=83
[ 22.814841] proc_cgroup_show+0xc0/0x248
[ 22.814967] proc_single_show+0x54/0x98
[ 22.815086] seq_read+0x278/0x45c
[ 22.815190] __vfs_read+0x28/0x17c
[ 22.815289] vfs_read+0xa8/0x14c
[ 22.815381] ksys_read+0x50/0x94
[ 22.815475] ret_from_syscall+0x0/0x38
Commit 69d2480456 ("btrfs: use copy_page for copying pages instead of
memcpy") changed the way bitmap blocks are copied. But allthough bitmaps
have the size of a page, they were allocated with kzalloc().
Most of the time, kzalloc() allocates aligned blocks of memory, so
copy_page() can be used. But when some debug options like SLAB_DEBUG are
activated, kzalloc() may return unaligned pointer.
On powerpc, memcpy(), copy_page() and other copying functions use
'dcbz' instruction which provides an entire zeroed cacheline to avoid
memory read when the intention is to overwrite a full line. Functions
like memcpy() are writen to care about partial cachelines at the start
and end of the destination, but copy_page() assumes it gets pages. As
pages are naturally cache aligned, copy_page() doesn't care about
partial lines. This means that when copy_page() is called with a
misaligned pointer, a few leading bytes are zeroed.
To fix it, allocate bitmaps through kmem_cache instead of using kzalloc()
The cache pool is created with PAGE_SIZE alignment constraint.
Reported-by: Erhard F. <erhard_f@mailbox.org>
Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=204371
Fixes: 69d2480456 ("btrfs: use copy_page for copying pages instead of memcpy")
Cc: stable@vger.kernel.org # 4.19+
Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Reviewed-by: David Sterba <dsterba@suse.com>
[ rename to btrfs_free_space_bitmap ]
Signed-off-by: David Sterba <dsterba@suse.com>
btrfs_calc_trunc_metadata_size differs from trans_metadata_size in that
it doesn't take into account any splitting at the levels, because
truncate will never split nodes. However truncate _and_ changing will
never split nodes, so rename btrfs_calc_trunc_metadata_size to
btrfs_calc_metadata_size. Also btrfs_calc_trans_metadata_size is purely
for inserting items, so rename this to btrfs_calc_insert_metadata_size.
Making these clearer will help when I start using them differently in
upcoming patches.
Reviewed-by: Nikolay Borisov <nborisov@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>
This is prep work for moving all of the block group cache code into its
own file.
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
[ minor comment updates ]
Signed-off-by: David Sterba <dsterba@suse.com>
This is prep work for moving block_group_cache around. Having this in
the header file makes the header file include need to be in a certain
order, which is awkward, so just move it into free-space-cache.c and
then we can re-arrange later.
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 code for data and metadata reservations for delalloc. There's
quite a bit of code here, and it's used in a lot of places so I've
separated it out to it's own file. inode.c and file.c are already
pretty large, and this code is complicated enough to live in its own
space.
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Migrate the struct definition and the one helper that's in ctree.h into
space-info.h
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: David Sterba <dsterba@suse.com>
The CRC checksum in the free space cache is not dependant on the super
block's csum_type field but always a CRC32C.
So use btrfs_crc32c() and btrfs_crc32c_final() instead of
btrfs_csum_data() and btrfs_csum_final() for computing these checksums.
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Johannes Thumshirn <jthumshirn@suse.de>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
fs_info::mapping_tree is the physical<->logical mapping tree and uses
the same underlying structure as extents, but is embedded to another
structure. There are no other members and this indirection is useless.
No functional change.
Signed-off-by: David Sterba <dsterba@suse.com>
In function do_trimming(), block_group->lock should be unlocked first,
as the locks should be released in the reverse order. This does not
cause problems but should follow the best practices.
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Su Yue <suy.fnst@cn.fujitsu.com>
Reviewed-by: David Sterba <dsterba@suse.com>
[ update changelog ]
Signed-off-by: David Sterba <dsterba@suse.com>
