We set cache_block_group_error if btrfs_cache_block_group() returns an
error, this is because we could end up not finding space to allocate and
mistakenly return -ENOSPC, and which could then abort the transaction
with the incorrect errno, and in the case of ENOSPC result in a
WARN_ON() that will trip up tests like generic/475.
However there's the case where multiple threads can be racing, one
thread gets the proper error, and the other thread doesn't actually call
btrfs_cache_block_group(), it instead sees ->cached ==
BTRFS_CACHE_ERROR. Again the result is the same, we fail to allocate
our space and return -ENOSPC. Instead we need to set
cache_block_group_error to -EIO in this case to make sure that if we do
not make our allocation we get the appropriate error returned back to
the caller.
CC: stable@vger.kernel.org # 4.14+
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: David Sterba <dsterba@suse.com>
There's no point in have several fields defined as 1 bit unsigned int in
struct btrfs_delayed_ref_head, we can instead use a bool type, it makes
the code a bit more readable and it doesn't change the structure size.
So switch them to proper booleans.
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
The 'in_tree' field is really not needed in struct btrfs_delayed_ref_node,
as we can check whether a reference is in the tree or not simply by
checking its red black tree node member with RB_EMPTY_NODE(), as when we
remove it from the tree we always call RB_CLEAR_NODE(). So remove that
field and use RB_EMPTY_NODE().
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Now that all extent state bit helpers effectively take the GFP_NOFS mask
(and GFP_NOWAIT is encoded in the bits) we can remove the parameter.
This reduces stack consumption in many functions and simplifies a lot of
code.
Net effect on module on a release build:
text data bss dec hex filename
1250432 20985 16088 1287505 13a551 pre/btrfs.ko
1247074 20985 16088 1284147 139833 post/btrfs.ko
DELTA: -3358
Signed-off-by: David Sterba <dsterba@suse.com>
The __GFP_NOFAIL passed to set_extent_bit first appeared in 2010
(commit f0486c68e4 ("Btrfs: Introduce contexts for metadata
reservation")), without any explanation why it would be needed.
Meanwhile we've updated the semantics of set_extent_bit to handle failed
allocations and do unlock, sleep and retry if needed. The use of the
NOFAIL flag is also an outlier, we never want any of the set/clear
extent bit helpers to fail, they're used for many critical changes like
extent locking, besides the extent state bit changes.
Signed-off-by: David Sterba <dsterba@suse.com>
This helper calls set_extent_bit with two more parameters set to default
values, but otherwise it's purpose is not clear.
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
The helper is used a few times, that it's setting the DIRTY extent bit
is still clear.
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
The helper is used only once.
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
There's a comment at btrfs_init_new_buffer() that refers to a function
named btrfs_clean_tree_block(), however the function was renamed to
btrfs_clear_buffer_dirty() in commit 190a83391b ("btrfs: rename
btrfs_clean_tree_block to btrfs_clear_buffer_dirty"). So update the
comment to refer to the current name.
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
We just pass in btrfs_header_level(eb) for the level, and we're passing
in the eb already, so simply get the level from the eb inside of
btrfs_set_block_flags.
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Using SECTOR_SHIFT to convert LBA to physical address makes it more
readable.
Signed-off-by: Anand Jain <anand.jain@oracle.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Use SECTOR_SHIFT while converting a physical address to an LBA, makes
it more readable.
Signed-off-by: Anand Jain <anand.jain@oracle.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Improve the leaf dump behavior by:
- Always dump the leaf first, then the error message
- Output the slot number if possible
Especially in __btrfs_free_extent() the leaf dump of extent tree can
be pretty large.
With an extra slot number it's much easier to locate the problem.
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Since print-tree infrastructure only prints the content of a tree block,
we can make them to accept const extent buffer pointer.
This removes a forced type convert in extent-tree, where we convert a
const extent buffer pointer to regular one, just to avoid compiler
warning.
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
We have this logic encapsulated in btrfs_should_throttle_delayed_refs()
where we try to estimate if running the current amount of delayed
references we have will take more than half a second, and if so, the
caller btrfs_should_throttle_delayed_refs() should do something to
prevent more and more delayed refs from being accumulated.
This logic was added in commit 0a2b2a844a ("Btrfs: throttle delayed
refs better") and then further refined in commit a79b7d4b3e ("Btrfs:
async delayed refs"). The idea back then was that the caller of
btrfs_should_throttle_delayed_refs() would release its transaction
handle (by calling btrfs_end_transaction()) when that function returned
true, then btrfs_end_transaction() would trigger an async job to run
delayed references in a workqueue, and later start/join a transaction
again and do more work.
However we don't run delayed references asynchronously anymore, that
was removed in commit db2462a6ad ("btrfs: don't run delayed refs in
the end transaction logic"). That makes the logic that tries to estimate
how long we will take to run our current delayed references, at
btrfs_should_throttle_delayed_refs(), pointless as we don't take any
action to run delayed references anymore. We do have other type of
throttling, which consists of checking the size and reserved space of
the delayed and global block reserves, as well as if fluhsing delayed
references for the current transaction was already started, etc - this
is all done by btrfs_should_end_transaction(), and the only user of
btrfs_should_throttle_delayed_refs() does periodically call
btrfs_should_end_transaction().
So remove btrfs_should_throttle_delayed_refs() and the infrastructure
that keeps track of the average time used for running delayed references,
as well as adapting btrfs_truncate_inode_items() to call
btrfs_check_space_for_delayed_refs() instead.
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>
We were seeing weird errors when we were testing our btrfs backports
before we had the incorrect level check fix. These errors appeared to
be improper error handling, but error injection testing uncovered that
the errors were a result of corruption that occurred from improper error
handling during snapshot delete.
With snapshot delete if we encounter any errors during walk_down or
walk_up we'll simply return an error, we won't abort the transaction.
This is problematic because we will be dropping references for nodes and
leaves along the way, and if we fail in the middle we will leave the
file system corrupt because we don't know where we left off in the drop.
Fix this by making sure we abort if we hit any errors during the walk
down or walk up operations, as we have no idea what operations could
have been left half done at this point.
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
We can get errors in walk_down_proc as we try and lookup extent info for
the snapshot dropping to act on. However if we get an error we simply
return 1 which indicates we're done with walking down, which will lead
us to improperly continue with the snapshot drop with the incorrect
information. Instead break if we get any error from walk_down_proc or
do_walk_down, and handle the case of ret == 1 by returning 0, otherwise
return the ret value that we have.
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
btrfs_clean_tree_block is a misnomer, it's just
clear_extent_buffer_dirty with some extra accounting around it. Rename
this to btrfs_clear_buffer_dirty to make it more clear it belongs with
it's setter, btrfs_mark_buffer_dirty.
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
We check the header generation in the extent buffer against the current
running transaction id to see if it's safe to clear DIRTY on this
buffer. Generally speaking if we're clearing the buffer dirty we're
holding the transaction open, but in the case of cleaning up an aborted
transaction we don't, so we have extra checks in that path to check the
transid. To allow for a future cleanup go ahead and pass in the trans
handle so we don't have to rely on ->running_transaction being set.
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
We want to clean up the dirty handling for extent buffers so it's a
little more consistent, so skip the check for generation == transid and
simply always lock the extent buffer before calling btrfs_clean_tree_block.
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: David Sterba <dsterba@suse.com>
extent-tree.h is included more than once, added in a0231804af ("btrfs:
move extent-tree helpers into their own header file").
Signed-off-by: ye xingchen <ye.xingchen@zte.com.cn>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
When a file system has ZNS devices which are constrained by a maximum
number of active block groups, then not being able to use all the block
groups for every allocation is not ideal, and could cause us to loop a
ton with mixed size allocations.
In general, since zoned doesn't write into gaps behind where block
groups are writing, it is not susceptible to the same sort of
fragmentation that size classes are designed to solve, so we can skip
size classes for zoned file systems in general, even though there would
probably be no harm for SMR devices.
Signed-off-by: Boris Burkov <boris@bur.io>
Signed-off-by: David Sterba <dsterba@suse.com>
The aim of this patch is to reduce the fragmentation of block groups
under certain unhappy workloads. It is particularly effective when the
size of extents correlates with their lifetime, which is something we
have observed causing fragmentation in the fleet at Meta.
This patch categorizes extents into size classes:
- x < 128KiB: "small"
- 128KiB < x < 8MiB: "medium"
- x > 8MiB: "large"
and as much as possible reduces allocations of extents into block groups
that don't match the size class. This takes advantage of any (possible)
correlation between size and lifetime and also leaves behind predictable
re-usable gaps when extents are freed; small writes don't gum up bigger
holes.
Size classes are implemented in the following way:
- Mark each new block group with a size class of the first allocation
that goes into it.
- Add two new passes to ffe: "unset size class" and "wrong size class".
First, try only matching block groups, then try unset ones, then allow
allocation of new ones, and finally allow mismatched block groups.
- Filtering is done just by skipping inappropriate ones, there is no
special size class indexing.
Other solutions I considered were:
- A best fit allocator with an rb-tree. This worked well, as small
writes didn't leak big holes from large freed extents, but led to
regressions in ffe and write performance due to lock contention on
the rb-tree with every allocation possibly updating it in parallel.
Perhaps something clever could be done to do the updates in the
background while being "right enough".
- A fixed size "working set". This prevents freeing an extent
drastically changing where writes currently land, and seems like a
good option too. Doesn't take advantage of size in any way.
- The same size class idea, but implemented with xarray marks. This
turned out to be slower than looping the linked list and skipping
wrong block groups, and is also less flexible since we must have only
3 size classes (max #marks). With the current approach we can have as
many as we like.
Performance testing was done via: https://github.com/josefbacik/fsperf
Of particular relevance are the new fragmentation specific tests.
A brief summary of the testing results:
- Neutral results on existing tests. There are some minor regressions
and improvements here and there, but nothing that truly stands out as
notable.
- Improvement on new tests where size class and extent lifetime are
correlated. Fragmentation in these cases is completely eliminated
and write performance is generally a little better. There is also
significant improvement where extent sizes are just a bit larger than
the size class boundaries.
- Regression on one new tests: where the allocations are sized
intentionally a hair under the borders of the size classes. Results
are neutral on the test that intentionally attacks this new scheme by
mixing extent size and lifetime.
The full dump of the performance results can be found here:
https://bur.io/fsperf/size-class-2022-11-15.txt
(there are ANSI escape codes, so best to curl and view in terminal)
Here is a snippet from the full results for a new test which mixes
buffered writes appending to a long lived set of files and large short
lived fallocates:
bufferedappendvsfallocate results
metric baseline current stdev diff
======================================================================================
avg_commit_ms 31.13 29.20 2.67 -6.22%
bg_count 14 15.60 0 11.43%
commits 11.10 12.20 0.32 9.91%
elapsed 27.30 26.40 2.98 -3.30%
end_state_mount_ns 11122551.90 10635118.90 851143.04 -4.38%
end_state_umount_ns 1.36e+09 1.35e+09 12248056.65 -1.07%
find_free_extent_calls 116244.30 114354.30 964.56 -1.63%
find_free_extent_ns_max 599507.20 1047168.20 103337.08 74.67%
find_free_extent_ns_mean 3607.19 3672.11 101.20 1.80%
find_free_extent_ns_min 500 512 6.67 2.40%
find_free_extent_ns_p50 2848 2876 37.65 0.98%
find_free_extent_ns_p95 4916 5000 75.45 1.71%
find_free_extent_ns_p99 20734.49 20920.48 1670.93 0.90%
frag_pct_max 61.67 0 8.05 -100.00%
frag_pct_mean 43.59 0 6.10 -100.00%
frag_pct_min 25.91 0 16.60 -100.00%
frag_pct_p50 42.53 0 7.25 -100.00%
frag_pct_p95 61.67 0 8.05 -100.00%
frag_pct_p99 61.67 0 8.05 -100.00%
fragmented_bg_count 6.10 0 1.45 -100.00%
max_commit_ms 49.80 46 5.37 -7.63%
sys_cpu 2.59 2.62 0.29 1.39%
write_bw_bytes 1.62e+08 1.68e+08 17975843.50 3.23%
write_clat_ns_mean 57426.39 54475.95 2292.72 -5.14%
write_clat_ns_p50 46950.40 42905.60 2101.35 -8.62%
write_clat_ns_p99 148070.40 143769.60 2115.17 -2.90%
write_io_kbytes 4194304 4194304 0 0.00%
write_iops 2476.15 2556.10 274.29 3.23%
write_lat_ns_max 2101667.60 2251129.50 370556.59 7.11%
write_lat_ns_mean 59374.91 55682.00 2523.09 -6.22%
write_lat_ns_min 17353.10 16250 1646.08 -6.36%
There are some mixed improvements/regressions in most metrics along with
an elimination of fragmentation in this workload.
On the balance, the drastic 1->0 improvement in the happy cases seems
worth the mix of regressions and improvements we do observe.
Some considerations for future work:
- Experimenting with more size classes
- More hinting/search ordering work to approximate a best-fit allocator
Signed-off-by: Boris Burkov <boris@bur.io>
Signed-off-by: David Sterba <dsterba@suse.com>
find_free_extent is a complicated function. It consists (at least) of:
- a hint that jumps into the middle of a for loop macro
- a middle loop trying every raid level
- an outer loop ascending through ffe loop levels
- complicated logic for skipping some of those ffe loop levels
- multiple underlying in-bg allocators (zoned, cluster, no cluster)
Which is all to say that more tracing is helpful for debugging its
behavior. Add two new tracepoints: at the entrance to the block_groups
loop (hit for every raid level and every ffe_ctl loop) and at the point
we seriously consider a block_group for allocation. This way we can see
the whole path through the algorithm, including hints, multiple loops,
etc.
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Boris Burkov <boris@bur.io>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
The allocator tracepoints currently have a pile of values from ffe_ctl.
In modifying the allocator and adding more tracepoints, I found myself
adding to the already long argument list of the tracepoints. It makes it
a lot simpler to just send in the ffe_ctl itself.
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: Boris Burkov <boris@bur.io>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Now that none of the functions called by btrfs_merge_delayed_refs() needs
a btrfs_trans_handle, directly pass in a btrfs_fs_info to
btrfs_merge_delayed_refs().
Reviewed-by: Qu Wenruo <wqu@suse.com>
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>
Currently we have a btrfs_debug() for run_one_delayed_ref() failure, but
if end users hit such problem, there will be no chance that
btrfs_debug() is enabled. This can lead to very little useful info for
debugging.
This patch will:
- Add extra info for error reporting
Including:
* logical bytenr
* num_bytes
* type
* action
* ref_mod
- Replace the btrfs_debug() with btrfs_err()
- Move the error reporting into run_one_delayed_ref()
This is to avoid use-after-free, the @node can be freed in the caller.
This error should only be triggered at most once.
As if run_one_delayed_ref() failed, we trigger the error message, then
causing the call chain to error out:
btrfs_run_delayed_refs()
`- btrfs_run_delayed_refs()
`- btrfs_run_delayed_refs_for_head()
`- run_one_delayed_ref()
And we will abort the current transaction in btrfs_run_delayed_refs().
If we have to run delayed refs for the abort transaction,
run_one_delayed_ref() will just cleanup the refs and do nothing, thus no
new error messages would be output.
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
The code used by btrfs_submit_bio only interacts with the rest of
volumes.c through __btrfs_map_block (which itself is a more generic
version of two exported helpers) and does not really have anything
to do with volumes.c. Create a new bio.c file and a bio.h header
going along with it for the btrfs_bio-based storage layer, which
will grow even more going forward.
Also update the file with my copyright notice given that a large
part of the moved code was written or rewritten by me.
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
[BUG]
If dev-replace failed to re-construct its data/metadata, the kernel
message would be incorrect for the missing device:
BTRFS info (device dm-1): dev_replace from <missing disk> (devid 2) to /dev/mapper/test-scratch2 started
BTRFS error (device dm-1): failed to rebuild valid logical 38862848 for dev (efault)
Note the above "dev (efault)" of the second line.
While the first line is properly reporting "<missing disk>".
[CAUSE]
Although dev-replace is using btrfs_dev_name(), the heavy lifting work
is still done by scrub (scrub is reused by both dev-replace and regular
scrub).
Unfortunately scrub code never uses btrfs_dev_name() helper, as it's
only declared locally inside dev-replace.c.
[FIX]
Fix the output by:
- Move the btrfs_dev_name() helper to volumes.h
- Use btrfs_dev_name() to replace open-coded rcu_str_deref() calls
Only zoned code is not touched, as I'm not familiar with degraded
zoned code.
- Constify return value and parameter
Now the output looks pretty sane:
BTRFS info (device dm-1): dev_replace from <missing disk> (devid 2) to /dev/mapper/test-scratch2 started
BTRFS error (device dm-1): failed to rebuild valid logical 38862848 for dev <missing disk>
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
There are several different tree block parentness check parameters used
across several helpers:
- level
Mandatory
- transid
Under most cases it's mandatory, but there are several backref cases
which skips this check.
- owner_root
- first_key
Utilized by most top-down tree search routine. Otherwise can be
skipped.
Those four members are not always mandatory checks, and some of them are
the same u64, which means if some arguments got swapped compiler will
not catch it.
Furthermore if we're going to further expand the parentness check, we
need to modify quite some helpers just to add one more parameter.
This patch will concentrate all these members into a structure called
btrfs_tree_parent_check, and pass that structure for the following
helpers:
- btrfs_read_extent_buffer()
- read_tree_block()
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Move these out of ctree.h into orphan.h to cut down on code in ctree.h.
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Move these prototypes out of ctree.h and into file-item.h.
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Move all the root-tree.c prototypes to root-tree.h, and then update all
the necessary files to include the new header.
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Move all the extent tree related prototypes to extent-tree.h out of
ctree.h, and then go include it everywhere needed so everything
compiles.
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This was prototyped in ctree.h and the code existed in extent-tree.c,
but it's space-info related so move it into space-info.c.
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 a large patch, but because they're all macros it's impossible to
split up. Simply copy all of the item accessors in ctree.h and paste
them in accessors.h, and then update any files to include the header so
everything compiles.
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
[ reformat comments, style fixups ]
Signed-off-by: David Sterba <dsterba@suse.com>
We have several fs wide related helpers in ctree.h. The bulk of these
are the incompat flag test helpers, but there are things such as
btrfs_fs_closing() and the read only helpers that also aren't directly
related to the ctree code. Move these into a fs.h header, which will
serve as the location for file system wide related helpers.
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: Anand Jain <anand.jain@oracle.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 been seeing the following panic in production
kernel BUG at fs/btrfs/tree-mod-log.c:677!
invalid opcode: 0000 [#1] SMP
RIP: 0010:tree_mod_log_rewind+0x1b4/0x200
RSP: 0000:ffffc9002c02f890 EFLAGS: 00010293
RAX: 0000000000000003 RBX: ffff8882b448c700 RCX: 0000000000000000
RDX: 0000000000008000 RSI: 00000000000000a7 RDI: ffff88877d831c00
RBP: 0000000000000002 R08: 000000000000009f R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000100c40 R12: 0000000000000001
R13: ffff8886c26d6a00 R14: ffff88829f5424f8 R15: ffff88877d831a00
FS: 00007fee1d80c780(0000) GS:ffff8890400c0000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fee1963a020 CR3: 0000000434f33002 CR4: 00000000007706e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
PKRU: 55555554
Call Trace:
btrfs_get_old_root+0x12b/0x420
btrfs_search_old_slot+0x64/0x2f0
? tree_mod_log_oldest_root+0x3d/0xf0
resolve_indirect_ref+0xfd/0x660
? ulist_alloc+0x31/0x60
? kmem_cache_alloc_trace+0x114/0x2c0
find_parent_nodes+0x97a/0x17e0
? ulist_alloc+0x30/0x60
btrfs_find_all_roots_safe+0x97/0x150
iterate_extent_inodes+0x154/0x370
? btrfs_search_path_in_tree+0x240/0x240
iterate_inodes_from_logical+0x98/0xd0
? btrfs_search_path_in_tree+0x240/0x240
btrfs_ioctl_logical_to_ino+0xd9/0x180
btrfs_ioctl+0xe2/0x2ec0
? __mod_memcg_lruvec_state+0x3d/0x280
? do_sys_openat2+0x6d/0x140
? kretprobe_dispatcher+0x47/0x70
? kretprobe_rethook_handler+0x38/0x50
? rethook_trampoline_handler+0x82/0x140
? arch_rethook_trampoline_callback+0x3b/0x50
? kmem_cache_free+0xfb/0x270
? do_sys_openat2+0xd5/0x140
__x64_sys_ioctl+0x71/0xb0
do_syscall_64+0x2d/0x40
Which is this code in tree_mod_log_rewind()
switch (tm->op) {
case BTRFS_MOD_LOG_KEY_REMOVE_WHILE_FREEING:
BUG_ON(tm->slot < n);
This occurs because we replay the nodes in order that they happened, and
when we do a REPLACE we will log a REMOVE_WHILE_FREEING for every slot,
starting at 0. 'n' here is the number of items in this block, which in
this case was 1, but we had 2 REMOVE_WHILE_FREEING operations.
The actual root cause of this was that we were replaying operations for
a block that shouldn't have been replayed. Consider the following
sequence of events
1. We have an already modified root, and we do a btrfs_get_tree_mod_seq().
2. We begin removing items from this root, triggering KEY_REPLACE for
it's child slots.
3. We remove one of the 2 children this root node points to, thus triggering
the root node promotion of the remaining child, and freeing this node.
4. We modify a new root, and re-allocate the above node to the root node of
this other root.
The tree mod log looks something like this
logical 0 op KEY_REPLACE (slot 1) seq 2
logical 0 op KEY_REMOVE (slot 1) seq 3
logical 0 op KEY_REMOVE_WHILE_FREEING (slot 0) seq 4
logical 4096 op LOG_ROOT_REPLACE (old logical 0) seq 5
logical 8192 op KEY_REMOVE_WHILE_FREEING (slot 1) seq 6
logical 8192 op KEY_REMOVE_WHILE_FREEING (slot 0) seq 7
logical 0 op LOG_ROOT_REPLACE (old logical 8192) seq 8
>From here the bug is triggered by the following steps
1. Call btrfs_get_old_root() on the new_root.
2. We call tree_mod_log_oldest_root(btrfs_root_node(new_root)), which is
currently logical 0.
3. tree_mod_log_oldest_root() calls tree_mod_log_search_oldest(), which
gives us the KEY_REPLACE seq 2, and since that's not a
LOG_ROOT_REPLACE we incorrectly believe that we don't have an old
root, because we expect that the most recent change should be a
LOG_ROOT_REPLACE.
4. Back in tree_mod_log_oldest_root() we don't have a LOG_ROOT_REPLACE,
so we don't set old_root, we simply use our existing extent buffer.
5. Since we're using our existing extent buffer (logical 0) we call
tree_mod_log_search(0) in order to get the newest change to start the
rewind from, which ends up being the LOG_ROOT_REPLACE at seq 8.
6. Again since we didn't find an old_root we simply clone logical 0 at
it's current state.
7. We call tree_mod_log_rewind() with the cloned extent buffer.
8. Set n = btrfs_header_nritems(logical 0), which would be whatever the
original nritems was when we COWed the original root, say for this
example it's 2.
9. We start from the newest operation and work our way forward, so we
see LOG_ROOT_REPLACE which we ignore.
10. Next we see KEY_REMOVE_WHILE_FREEING for slot 0, which triggers the
BUG_ON(tm->slot < n), because it expects if we've done this we have a
completely empty extent buffer to replay completely.
The correct thing would be to find the first LOG_ROOT_REPLACE, and then
get the old_root set to logical 8192. In fact making that change fixes
this particular problem.
However consider the much more complicated case. We have a child node
in this tree and the above situation. In the above case we freed one
of the child blocks at the seq 3 operation. If this block was also
re-allocated and got new tree mod log operations we would have a
different problem. btrfs_search_old_slot(orig root) would get down to
the logical 0 root that still pointed at that node. However in
btrfs_search_old_slot() we call tree_mod_log_rewind(buf) directly. This
is not context aware enough to know which operations we should be
replaying. If the block was re-allocated multiple times we may only
want to replay a range of operations, and determining what that range is
isn't possible to determine.
We could maybe solve this by keeping track of which root the node
belonged to at every tree mod log operation, and then passing this
around to make sure we're only replaying operations that relate to the
root we're trying to rewind.
However there's a simpler way to solve this problem, simply disallow
reallocations if we have currently running tree mod log users. We
already do this for leaf's, so we're simply expanding this to nodes as
well. This is a relatively uncommon occurrence, and the problem is
complicated enough I'm worried that we will still have corner cases in
the reallocation case. So fix this in the most straightforward way
possible.
Fixes: bd989ba359 ("Btrfs: add tree modification log functions")
CC: stable@vger.kernel.org # 3.3+
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: David Sterba <dsterba@suse.com>
syzbot is reporting uninit-value in btrfs_clean_tree_block() [1], for
commit bc877d285c ("btrfs: Deduplicate extent_buffer init code")
missed that btrfs_set_header_generation() in btrfs_init_new_buffer() must
not be moved to after clean_tree_block() because clean_tree_block() is
calling btrfs_header_generation() since commit 55c69072d6 ("Btrfs:
Fix extent_buffer usage when nodesize != leafsize").
Since memzero_extent_buffer() will reset "struct btrfs_header" part, we
can't move btrfs_set_header_generation() to before memzero_extent_buffer().
Just re-add btrfs_set_header_generation() before btrfs_clean_tree_block().
Link: https://syzkaller.appspot.com/bug?extid=fba8e2116a12609b6c59 [1]
Reported-by: syzbot <syzbot+fba8e2116a12609b6c59@syzkaller.appspotmail.com>
Fixes: bc877d285c ("btrfs: Deduplicate extent_buffer init code")
CC: stable@vger.kernel.org # 4.19+
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Signed-off-by: David Sterba <dsterba@suse.com>
If we have NOWAIT specified on our IOCB and we're writing into a
PREALLOC or NOCOW extent then we need to be able to tell
can_nocow_extent that we don't want to wait on any locks or metadata IO.
Fix can_nocow_extent to allow for NOWAIT.
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Stefan Roesch <shr@fb.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
One of the most expensive tasks performed during fiemap is to check if
an extent is shared. This task has two major steps:
1) Check if the data extent is shared. This implies checking the extent
item in the extent tree, checking delayed references, etc. If we
find the data extent is directly shared, we terminate immediately;
2) If the data extent is not directly shared (its extent item has a
refcount of 1), then it may be shared if we have snapshots that share
subtrees of the inode's subvolume b+tree. So we check if the leaf
containing the file extent item is shared, then its parent node, then
the parent node of the parent node, etc, until we reach the root node
or we find one of them is shared - in which case we stop immediately.
During fiemap we process the extents of a file from left to right, from
file offset 0 to EOF. This means that we iterate b+tree leaves from left
to right, and has the implication that we keep repeating that second step
above several times for the same b+tree path of the inode's subvolume
b+tree.
For example, if we have two file extent items in leaf X, and the path to
leaf X is A -> B -> C -> X, then when we try to determine if the data
extent referenced by the first extent item is shared, we check if the data
extent is shared - if it's not, then we check if leaf X is shared, if not,
then we check if node C is shared, if not, then check if node B is shared,
if not than check if node A is shared. When we move to the next file
extent item, after determining the data extent is not shared, we repeat
the checks for X, C, B and A - doing all the expensive searches in the
extent tree, delayed refs, etc. If we have thousands of tile extents, then
we keep repeating the sharedness checks for the same paths over and over.
On a file that has no shared extents or only a small portion, it's easy
to see that this scales terribly with the number of extents in the file
and the sizes of the extent and subvolume b+trees.
This change eliminates the repeated sharedness check on extent buffers
by caching the results of the last path used. The results can be used as
long as no snapshots were created since they were cached (for not shared
extent buffers) or no roots were dropped since they were cached (for
shared extent buffers). This greatly reduces the time spent by fiemap for
files with thousands of extents and/or large extent and subvolume b+trees.
Example performance test:
$ cat fiemap-perf-test.sh
#!/bin/bash
DEV=/dev/sdi
MNT=/mnt/sdi
mkfs.btrfs -f $DEV
mount -o compress=lzo $DEV $MNT
# 40G gives 327680 128K file extents (due to compression).
xfs_io -f -c "pwrite -S 0xab -b 1M 0 40G" $MNT/foobar
umount $MNT
mount -o compress=lzo $DEV $MNT
start=$(date +%s%N)
filefrag $MNT/foobar
end=$(date +%s%N)
dur=$(( (end - start) / 1000000 ))
echo "fiemap took $dur milliseconds (metadata not cached)"
start=$(date +%s%N)
filefrag $MNT/foobar
end=$(date +%s%N)
dur=$(( (end - start) / 1000000 ))
echo "fiemap took $dur milliseconds (metadata cached)"
umount $MNT
Before this patch:
$ ./fiemap-perf-test.sh
(...)
/mnt/sdi/foobar: 327680 extents found
fiemap took 3597 milliseconds (metadata not cached)
/mnt/sdi/foobar: 327680 extents found
fiemap took 2107 milliseconds (metadata cached)
After this patch:
$ ./fiemap-perf-test.sh
(...)
/mnt/sdi/foobar: 327680 extents found
fiemap took 1646 milliseconds (metadata not cached)
/mnt/sdi/foobar: 327680 extents found
fiemap took 698 milliseconds (metadata cached)
That's about 2.2x faster when no metadata is cached, and about 3x faster
when all metadata is cached. On a real filesystem with many other files,
data, directories, etc, the b+trees will be 2 or 3 levels higher,
therefore this optimization will have a higher impact.
Several reports of a slow fiemap show up often, the two Link tags below
refer to two recent reports of such slowness. This patch, together with
the next ones in the series, is meant to address that.
Link: https://lore.kernel.org/linux-btrfs/21dd32c6-f1f9-f44a-466a-e18fdc6788a7@virtuozzo.com/
Link: https://lore.kernel.org/linux-btrfs/Ysace25wh5BbLd5f@atmark-techno.com/
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
struct btrfs_caching_ctl::progress and struct
btrfs_block_group::last_byte_to_unpin were previously needed to ensure
that unpin_extent_range() didn't return a range to the free space cache
before the caching thread had a chance to cache that range. However, the
commit "btrfs: fix space cache corruption and potential double
allocations" made it so that we always synchronously cache the block
group at the time that we pin the extent, so this machinery is no longer
necessary.
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: David Sterba <dsterba@suse.com>
We use a bit field in the btrfs_block_group for different flags, however
this is awkward because we have to hold the block_group->lock for any
modification of any of these fields, and makes the code clunky for a few
of these flags. Convert these to a properly flags setup so we can
utilize the bit helpers.
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
When testing space_cache v2 on a large set of machines, we encountered a
few symptoms:
1. "unable to add free space :-17" (EEXIST) errors.
2. Missing free space info items, sometimes caught with a "missing free
space info for X" error.
3. Double-accounted space: ranges that were allocated in the extent tree
and also marked as free in the free space tree, ranges that were
marked as allocated twice in the extent tree, or ranges that were
marked as free twice in the free space tree. If the latter made it
onto disk, the next reboot would hit the BUG_ON() in
add_new_free_space().
4. On some hosts with no on-disk corruption or error messages, the
in-memory space cache (dumped with drgn) disagreed with the free
space tree.
All of these symptoms have the same underlying cause: a race between
caching the free space for a block group and returning free space to the
in-memory space cache for pinned extents causes us to double-add a free
range to the space cache. This race exists when free space is cached
from the free space tree (space_cache=v2) or the extent tree
(nospace_cache, or space_cache=v1 if the cache needs to be regenerated).
struct btrfs_block_group::last_byte_to_unpin and struct
btrfs_block_group::progress are supposed to protect against this race,
but commit d0c2f4fa55 ("btrfs: make concurrent fsyncs wait less when
waiting for a transaction commit") subtly broke this by allowing
multiple transactions to be unpinning extents at the same time.
Specifically, the race is as follows:
1. An extent is deleted from an uncached block group in transaction A.
2. btrfs_commit_transaction() is called for transaction A.
3. btrfs_run_delayed_refs() -> __btrfs_free_extent() runs the delayed
ref for the deleted extent.
4. __btrfs_free_extent() -> do_free_extent_accounting() ->
add_to_free_space_tree() adds the deleted extent back to the free
space tree.
5. do_free_extent_accounting() -> btrfs_update_block_group() ->
btrfs_cache_block_group() queues up the block group to get cached.
block_group->progress is set to block_group->start.
6. btrfs_commit_transaction() for transaction A calls
switch_commit_roots(). It sets block_group->last_byte_to_unpin to
block_group->progress, which is block_group->start because the block
group hasn't been cached yet.
7. The caching thread gets to our block group. Since the commit roots
were already switched, load_free_space_tree() sees the deleted extent
as free and adds it to the space cache. It finishes caching and sets
block_group->progress to U64_MAX.
8. btrfs_commit_transaction() advances transaction A to
TRANS_STATE_SUPER_COMMITTED.
9. fsync calls btrfs_commit_transaction() for transaction B. Since
transaction A is already in TRANS_STATE_SUPER_COMMITTED and the
commit is for fsync, it advances.
10. btrfs_commit_transaction() for transaction B calls
switch_commit_roots(). This time, the block group has already been
cached, so it sets block_group->last_byte_to_unpin to U64_MAX.
11. btrfs_commit_transaction() for transaction A calls
btrfs_finish_extent_commit(), which calls unpin_extent_range() for
the deleted extent. It sees last_byte_to_unpin set to U64_MAX (by
transaction B!), so it adds the deleted extent to the space cache
again!
This explains all of our symptoms above:
* If the sequence of events is exactly as described above, when the free
space is re-added in step 11, it will fail with EEXIST.
* If another thread reallocates the deleted extent in between steps 7
and 11, then step 11 will silently re-add that space to the space
cache as free even though it is actually allocated. Then, if that
space is allocated *again*, the free space tree will be corrupted
(namely, the wrong item will be deleted).
* If we don't catch this free space tree corruption, it will continue
to get worse as extents are deleted and reallocated.
The v1 space_cache is synchronously loaded when an extent is deleted
(btrfs_update_block_group() with alloc=0 calls btrfs_cache_block_group()
with load_cache_only=1), so it is not normally affected by this bug.
However, as noted above, if we fail to load the space cache, we will
fall back to caching from the extent tree and may hit this bug.
The easiest fix for this race is to also make caching from the free
space tree or extent tree synchronous. Josef tested this and found no
performance regressions.
A few extra changes fall out of this change. Namely, this fix does the
following, with step 2 being the crucial fix:
1. Factor btrfs_caching_ctl_wait_done() out of
btrfs_wait_block_group_cache_done() to allow waiting on a caching_ctl
that we already hold a reference to.
2. Change the call in btrfs_cache_block_group() of
btrfs_wait_space_cache_v1_finished() to
btrfs_caching_ctl_wait_done(), which makes us wait regardless of the
space_cache option.
3. Delete the now unused btrfs_wait_space_cache_v1_finished() and
space_cache_v1_done().
4. Change btrfs_cache_block_group()'s `int load_cache_only` parameter to
`bool wait` to more accurately describe its new meaning.
5. Change a few callers which had a separate call to
btrfs_wait_block_group_cache_done() to use wait = true instead.
6. Make btrfs_wait_block_group_cache_done() static now that it's not
used outside of block-group.c anymore.
Fixes: d0c2f4fa55 ("btrfs: make concurrent fsyncs wait less when waiting for a transaction commit")
CC: stable@vger.kernel.org # 5.12+
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: David Sterba <dsterba@suse.com>
We have been hitting the following lockdep splat with btrfs/187 recently
WARNING: possible circular locking dependency detected
5.19.0-rc8+ #775 Not tainted
------------------------------------------------------
btrfs/752500 is trying to acquire lock:
ffff97e1875a97b8 (btrfs-treloc-02#2){+.+.}-{3:3}, at: __btrfs_tree_lock+0x24/0x110
but task is already holding lock:
ffff97e1875a9278 (btrfs-tree-01/1){+.+.}-{3:3}, at: __btrfs_tree_lock+0x24/0x110
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #2 (btrfs-tree-01/1){+.+.}-{3:3}:
down_write_nested+0x41/0x80
__btrfs_tree_lock+0x24/0x110
btrfs_init_new_buffer+0x7d/0x2c0
btrfs_alloc_tree_block+0x120/0x3b0
__btrfs_cow_block+0x136/0x600
btrfs_cow_block+0x10b/0x230
btrfs_search_slot+0x53b/0xb70
btrfs_lookup_inode+0x2a/0xa0
__btrfs_update_delayed_inode+0x5f/0x280
btrfs_async_run_delayed_root+0x24c/0x290
btrfs_work_helper+0xf2/0x3e0
process_one_work+0x271/0x590
worker_thread+0x52/0x3b0
kthread+0xf0/0x120
ret_from_fork+0x1f/0x30
-> #1 (btrfs-tree-01){++++}-{3:3}:
down_write_nested+0x41/0x80
__btrfs_tree_lock+0x24/0x110
btrfs_search_slot+0x3c3/0xb70
do_relocation+0x10c/0x6b0
relocate_tree_blocks+0x317/0x6d0
relocate_block_group+0x1f1/0x560
btrfs_relocate_block_group+0x23e/0x400
btrfs_relocate_chunk+0x4c/0x140
btrfs_balance+0x755/0xe40
btrfs_ioctl+0x1ea2/0x2c90
__x64_sys_ioctl+0x88/0xc0
do_syscall_64+0x38/0x90
entry_SYSCALL_64_after_hwframe+0x63/0xcd
-> #0 (btrfs-treloc-02#2){+.+.}-{3:3}:
__lock_acquire+0x1122/0x1e10
lock_acquire+0xc2/0x2d0
down_write_nested+0x41/0x80
__btrfs_tree_lock+0x24/0x110
btrfs_lock_root_node+0x31/0x50
btrfs_search_slot+0x1cb/0xb70
replace_path+0x541/0x9f0
merge_reloc_root+0x1d6/0x610
merge_reloc_roots+0xe2/0x260
relocate_block_group+0x2c8/0x560
btrfs_relocate_block_group+0x23e/0x400
btrfs_relocate_chunk+0x4c/0x140
btrfs_balance+0x755/0xe40
btrfs_ioctl+0x1ea2/0x2c90
__x64_sys_ioctl+0x88/0xc0
do_syscall_64+0x38/0x90
entry_SYSCALL_64_after_hwframe+0x63/0xcd
other info that might help us debug this:
Chain exists of:
btrfs-treloc-02#2 --> btrfs-tree-01 --> btrfs-tree-01/1
Possible unsafe locking scenario:
CPU0 CPU1
---- ----
lock(btrfs-tree-01/1);
lock(btrfs-tree-01);
lock(btrfs-tree-01/1);
lock(btrfs-treloc-02#2);
*** DEADLOCK ***
7 locks held by btrfs/752500:
#0: ffff97e292fdf460 (sb_writers#12){.+.+}-{0:0}, at: btrfs_ioctl+0x208/0x2c90
#1: ffff97e284c02050 (&fs_info->reclaim_bgs_lock){+.+.}-{3:3}, at: btrfs_balance+0x55f/0xe40
#2: ffff97e284c00878 (&fs_info->cleaner_mutex){+.+.}-{3:3}, at: btrfs_relocate_block_group+0x236/0x400
#3: ffff97e292fdf650 (sb_internal#2){.+.+}-{0:0}, at: merge_reloc_root+0xef/0x610
#4: ffff97e284c02378 (btrfs_trans_num_writers){++++}-{0:0}, at: join_transaction+0x1a8/0x5a0
#5: ffff97e284c023a0 (btrfs_trans_num_extwriters){++++}-{0:0}, at: join_transaction+0x1a8/0x5a0
#6: ffff97e1875a9278 (btrfs-tree-01/1){+.+.}-{3:3}, at: __btrfs_tree_lock+0x24/0x110
stack backtrace:
CPU: 1 PID: 752500 Comm: btrfs Not tainted 5.19.0-rc8+ #775
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.13.0-2.fc32 04/01/2014
Call Trace:
dump_stack_lvl+0x56/0x73
check_noncircular+0xd6/0x100
? lock_is_held_type+0xe2/0x140
__lock_acquire+0x1122/0x1e10
lock_acquire+0xc2/0x2d0
? __btrfs_tree_lock+0x24/0x110
down_write_nested+0x41/0x80
? __btrfs_tree_lock+0x24/0x110
__btrfs_tree_lock+0x24/0x110
btrfs_lock_root_node+0x31/0x50
btrfs_search_slot+0x1cb/0xb70
? lock_release+0x137/0x2d0
? _raw_spin_unlock+0x29/0x50
? release_extent_buffer+0x128/0x180
replace_path+0x541/0x9f0
merge_reloc_root+0x1d6/0x610
merge_reloc_roots+0xe2/0x260
relocate_block_group+0x2c8/0x560
btrfs_relocate_block_group+0x23e/0x400
btrfs_relocate_chunk+0x4c/0x140
btrfs_balance+0x755/0xe40
btrfs_ioctl+0x1ea2/0x2c90
? lock_is_held_type+0xe2/0x140
? lock_is_held_type+0xe2/0x140
? __x64_sys_ioctl+0x88/0xc0
__x64_sys_ioctl+0x88/0xc0
do_syscall_64+0x38/0x90
entry_SYSCALL_64_after_hwframe+0x63/0xcd
This isn't necessarily new, it's just tricky to hit in practice. There
are two competing things going on here. With relocation we create a
snapshot of every fs tree with a reloc tree. Any extent buffers that
get initialized here are initialized with the reloc root lockdep key.
However since it is a snapshot, any blocks that are currently in cache
that originally belonged to the fs tree will have the normal tree
lockdep key set. This creates the lock dependency of
reloc tree -> normal tree
for the extent buffer locking during the first phase of the relocation
as we walk down the reloc root to relocate blocks.
However this is problematic because the final phase of the relocation is
merging the reloc root into the original fs root. This involves
searching down to any keys that exist in the original fs root and then
swapping the relocated block and the original fs root block. We have to
search down to the fs root first, and then go search the reloc root for
the block we need to replace. This creates the dependency of
normal tree -> reloc tree
which is why lockdep complains.
Additionally even if we were to fix this particular mismatch with a
different nesting for the merge case, we're still slotting in a block
that has a owner of the reloc root objectid into a normal tree, so that
block will have its lockdep key set to the tree reloc root, and create a
lockdep splat later on when we wander into that block from the fs root.
Unfortunately the only solution here is to make sure we do not set the
lockdep key to the reloc tree lockdep key normally, and then reset any
blocks we wander into from the reloc root when we're doing the merged.
This solves the problem of having mixed tree reloc keys intermixed with
normal tree keys, and then allows us to make sure in the merge case we
maintain the lock order of
normal tree -> reloc tree
We handle this by setting a bit on the reloc root when we do the search
for the block we want to relocate, and any block we search into or COW
at that point gets set to the reloc tree key. This works correctly
because we only ever COW down to the parent node, so we aren't resetting
the key for the block we're linking into the fs root.
With this patch we no longer have the lockdep splat in btrfs/187.
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
cow_file_range() works in an all-or-nothing way: if it fails to allocate an
extent for a part of the given region, it gives up all the region including
the successfully allocated parts. On cow_file_range(), run_delalloc_zoned()
writes data for the region only when it successfully allocate all the
region.
This all-or-nothing allocation and write-out are problematic when available
space in all the block groups are get tight with the active zone
restriction. btrfs_reserve_extent() try hard to utilize the left space in
the active block groups and gives up finally and fails with
-ENOSPC. However, if we send IOs for the successfully allocated region, we
can finish a zone and can continue on the rest of the allocation on a newly
allocated block group.
This patch implements the partial write-out for run_delalloc_zoned(). With
this patch applied, cow_file_range() returns -EAGAIN to tell the caller to
do something to progress the further allocation, and tells the successfully
allocated region with done_offset. Furthermore, the zoned extent allocator
returns -EAGAIN to tell cow_file_range() going back to the caller side.
Actually, we still need to wait for an IO to complete to continue the
allocation. The next patch implements that part.
CC: stable@vger.kernel.org # 5.16+
Fixes: afba2bc036 ("btrfs: zoned: implement active zone tracking")
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
Signed-off-by: David Sterba <dsterba@suse.com>
When we run out of active zones and no sufficient space is left in any
block groups, we need to finish one block group to make room to activate a
new block group.
However, we cannot do this for metadata block groups because we can cause a
deadlock by waiting for a running transaction commit. So, do that only for
a data block group.
Furthermore, the block group to be finished has two requirements. First,
the block group must not have reserved bytes left. Having reserved bytes
means we have an allocated region but did not yet send bios for it. If that
region is allocated by the thread calling btrfs_zone_finish(), it results
in a deadlock.
Second, the block group to be finished must not be a SYSTEM block
group. Finishing a SYSTEM block group easily breaks further chunk
allocation by nullifying the SYSTEM free space.
In a certain case, we cannot find any zone finish candidate or
btrfs_zone_finish() may fail. In that case, we fall back to split the
allocation bytes and fill the last spaces left in the block groups.
CC: stable@vger.kernel.org # 5.16+
Fixes: afba2bc036 ("btrfs: zoned: implement active zone tracking")
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
Signed-off-by: David Sterba <dsterba@suse.com>
For the later patch, convert the return type from bool to int and return
errors. No functional changes.
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
Signed-off-by: David Sterba <dsterba@suse.com>
There's a reserved space on each device of size 1MiB that can be used by
bootloaders or to avoid accidental overwrite. Use a symbolic constant
with the explaining comment instead of hard coding the value and
multiple comments.
Note: since btrfs-progs v4.1, mkfs.btrfs will reserve the first 1MiB for
the primary super block (at offset 64KiB), until then the range could
have been used by mistake. Kernel has been always respecting the 1MiB
range for writes.
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
[ update changelog ]
Signed-off-by: David Sterba <dsterba@suse.com>
Mapping block for discard doesn't really share any code with the regular
block mapping case. Split it out into an entirely separate helper
that just returns an array of btrfs_discard_stripe structures and the
number of stripes.
This removes the need for the length field in the btrfs_io_context
structure, so remove tht.
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
