- backpointer_not_found() checks backpointers_no_use_write_buffer, no
   need to do it inbackpointer_get_key().

 - always use backpointer_get_node() for pointers to nodes:
   backpointer_get_key() was sometimes returning the key from the root
   node unlocked.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

This can be calculated locally.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

We're not supposed to have more than one btree_trans at a time in a
given thread - that causes recursive locking deadlocks.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

Small performance optimization, and a bit of a code cleanup too.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

Split up bch2_journal_write() to simplify locking:
 - bch2_journal_write_pick_flush(), which needs j->lock
 - bch2_journal_write_prep, which operates on the journal buffer to be
   written and will need the upcoming buf_lock for synchronization with
   the btree write buffer flush path
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

We avoid using standard error codes: private, per-callsite error codes
make debugging easier.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

This lets us use bch2_prt_bitflags to print them out.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

Open coded dynamic arrays are deprecated.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

Improved, better named version of pr_time().
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

BCACHEFS_DEBUG_TRANSACTIONS is useful, but it's too expensive to have on
by default - and it hasn't been coming up in bug reports.

Turn it off by default until we figure out a way to make it cheaper.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

BTREE_INSERT_NOJOURNAL is primarily used for a performance optimization
related to inode updates and fsync - document it.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

rebalance_work entries may refer to entries in the extents btree, which
is a snapshots btree, or they may also refer to entries in the reflink
btree, which is not.

Hence rebalance_work keys may use the snapshot field but it's not
required to be nonzero - add a new btree flag to reflect this.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

This was causing error messages in -tools to not get printed.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

When we didn't find anything in the journal that we'd like to use, and
we're forced to use whatever we can find - that entry will have been a
JSET_NO_FLUSH entry with a garbage last_seq value, since it's not
normally used.

Initialize it to something sane, for bch2_fs_journal_start().
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

Delete the useless check for inum == 0; we'll return -ENOENT without it,
which is what we want.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

 - the fsck_err() check for the filesystem being clean was incorrect,
   causing us to always fail to delete unlinked inodes
 - if a snapshot had been taken, the unlinked inode needs to be
   propagated to snapshot leaves so the unlink can happen there - fixed.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

The bucket_offset field of bch_backpointer is a 40-bit bitfield, but the
bch2_backpointer_swab() helper uses swab32. This leads to inconsistency
when an on-disk fs is accessed from an opposite endian machine.

As it turns out, we already have an internal swab40() helper that is
used from the bch_alloc_v4 swab callback. Lift it into the backpointers
header file and use it consistently in both places.
Signed-off-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

A simple test to populate a filesystem on one CPU architecture and
fsck on an arch of the opposite byte order produces errors related
to the fragmentation LRU. This occurs because the 64-bit
fragmentation_lru field is not byte-order swapped when reads detect
that the on-disk/bset key values were written in opposite byte-order
of the current CPU.

Update the bch2_alloc_v4 swab callback to handle fragmentation_lru
as is done for other multi-byte fields. This doesn't affect existing
filesystems when accessed by CPUs of the same endianness because the
->swab() callback is only called when the bset flags indicate an
endianness mismatch between the CPU and on-disk data.
Signed-off-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

The bcachefs folio writeback code includes a bio full check as well
as a fixed size check to determine when to split off and submit
writeback I/O. The inclusive check of the latter against the limit
means that writeback can submit slightly prematurely. This is not a
functional problem, but results in unnecessarily split I/Os and
extent merging.

This can be observed with a buffered write sized exactly to the
current maximum value (1MB) and with key_merging_disabled=1. The
latter prevents the merge from the second write such that a
subsequent check of the extent list shows a 1020k extent followed by
a contiguous 4k extent.

The purpose for the fixed size check is also undocumented and
somewhat obscure. Lift this check into a new helper that wraps the
bio check, fix the comparison logic, and add a comment to document
the purpose and how we might improve on this in the future.
Signed-off-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

Guenter Roeck reports a lockdep splat and DEBUG_OBJECTS_WORK related
warning when bch2_copygc_thread() initializes its rhashtable. The
lockdep splat relates to a warning print caused by the fact that the
rhashtable exists on the stack but is not annotated as so. This is
something that could be addressed by INIT_WORK_ONSTACK(), but
rhashtable doesn't expose that control and probably isnt worth the
churn for just one user. Instead, dynamically allocate the
buckets_in_flight structure and avoid the splat that way.
Reported-by: Guenter Roeck <linux@roeck-us.net>
Tested-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

A recent bug report uncovered a scenario where a filesystem never
runs with freespace_initialized, and therefore the user observes
significantly degraded write performance by virtue of running the
early bucket allocator. The associated bug aside, the primary cause
of the performance drop in this particular instance is that the
early bucket allocator does not update the allocation cursor. This
means that every allocation walks the alloc btree from the first
bucket of the associated device looking for a bucket marked as free
space.

Update the early allocator code to set the alloc cursor to the last
processed position in the tree, similar to how the freelist
allocator behaves. With the alloc_cursor being updated, the retry
logic also needs to be updated to restart from the beginning of the
device when a free bucket is not available between the cursor and
the end of the device. Track the restart position in a first_bucket
variable to make the code a bit more easily readable and consistent
with the freelist allocator.
Signed-off-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

bcachefs had a transient bug where freespace_initialized was not
properly being set, which lead to unexpected use of the early bucket
allocator at runtime. This issue has been fixed, but the existence
of it uncovered a coherency issue in the early bucket allocation
code that is somewhat related to how uncached iterators deal with
the key cache.

The problem itself manifests as occasional failure of generic/113
due to corruption, often seen as a duplicate backpointer or multiple
data types per-bucket error. The immediate cause of the error is a
racing bucket allocation along the lines of the following sequence:

- Task 1 selects key A in bch2_bucket_alloc_early() and schedules.
- Task 2 selects the same key A, but proceeds to complete the
  allocation and associated I/O, after which it releases the
  open_bucket.
- Task 1 resumes with key A, but does not recognize the bucket is
  now allocated because the open_bucket has been removed
  from the hash when it was released in the previous step.

This generally shouldn't happen because the allocating task updates
the alloc btree key before releasing the bucket. This is not
sufficient in this particular instance, however, because an uncached
iterator for a cached btree doesn't actually lock the key cache slot
when no key exists for a given slot in the cache. Thus the fact that
the allocation side updates the cached key means that multiple
uncached iters can stumble across the same alloc key and duplicate
the bucket allocation as described above.

This is something that probably needs a longer term fix in the
iterator code. As a short term fix, close the race through explicit
use of a cached iterator for likely allocation candidates. We don't
want to scan the btree with a cached iterator because that would
unnecessarily pollute the cache. This mitigates cache pollution by
primarily scanning the tree with an uncached iterator, but closes
the race by creating a key cache entry for any prospective slot
prior to the bucket allocation attempt (also similar to how
_alloc_freelist() works via try_alloc_bucket()). This survives many
iterations of generic/113 on a kernel hacked to always use the early
bucket allocator.
Signed-off-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

The SRCU read lock that btree_trans takes exists to make it safe for
bch2_trans_relock() to deref pointers to btree nodes/key cache items we
don't have locked, but as a side effect it blocks reclaim from freeing
those items.

Thus, it's important to not hold it for too long: we need to
differentiate between bch2_trans_unlock() calls that will be only for a
short duration, and ones that will be for an unbounded duration.

This introduces bch2_trans_unlock_long(), to be used mainly by the data
move paths.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

gcc 10 seems to complain about array bounds in situations where gcc 11
does not - curious.

This unfortunately requires adding some casts for now; we may
investigate getting rid of our __u64 _data[] VLA in a future patch so
that our start[0] members can be VLAs.
Reported-by: John Stoffel <john@stoffel.org>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

Fixes:

https://lore.kernel.org/linux-bcachefs/CAMuHMdXpwMdLuoWsNGa8qacT_5Wv-vSTz0xoBR5n_fnD9cNOuQ@mail.gmail.com/Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

If copygc does no work - finds no fragmented buckets - wait for a bit of
IO to happen.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

This fixes show-super output - we shouldn't be printing members that
have been deleted.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

Fixes:

bcachefs (e7fdc10e-54a3-49d9-bd0c-390370889d84): disk usage increased 4294967296 more than 2823707312 sectors reserved)
transaction updates for __bchfs_fallocate journal seq 467859
  update: btree=extents cached=0 bch2_trans_update+0x4e8/0x540
    old u64s 5 type deleted 536925940:3559337304:4294967283 len 0 ver 0
    new u64s 6 type reservation 536925940:3559337304:4294967283 len 3559337304 ver 0: generation 0 replicas 2
  update: btree=inodes cached=1 bch2_extent_update_i_size_sectors+0x305/0x3b0
    old u64s 19 type inode_v3 0:536925940:4294967283 len 0 ver 0: mode 100600 flags 15300000 journal_seq 467859 bi_size 0 bi_sectors 0 bi_version 0 bi_atime 40905301656446 bi_ctime 40905301656446 bi_mtime 40905301656446 bi_otime 40905301656446 bi_uid 0 bi_gid 0 bi_nlink 0 bi_generation 0 bi_dev 0 bi_data_checksum 0 bi_compression 0 bi_project 0 bi_background_compression 0 bi_data_replicas 0 bi_promote_target 0 bi_foreground_target 0 bi_background_target 0 bi_erasure_code 0 bi_fields_set 0 bi_dir 1879048193 bi_dir_offset 3384856038735393365 bi_subvol 0 bi_parent_subvol 0 bi_nocow 0
    new u64s 19 type inode_v3 0:536925940:4294967283 len 0 ver 0: mode 100600 flags 15300000 journal_seq 467859 bi_size 0 bi_sectors 3559337304 bi_version 0 bi_atime 40905301656446 bi_ctime 40905301656446 bi_mtime 40905301656446 bi_otime 40905301656446 bi_uid 0 bi_gid 0 bi_nlink 0 bi_generation 0 bi_dev 0 bi_data_checksum 0 bi_compression 0 bi_project 0 bi_background_compression 0 bi_data_replicas 0 bi_promote_target 0 bi_foreground_target 0 bi_background_target 0 bi_erasure_code 0 bi_fields_set 0 bi_dir 1879048193 bi_dir_offset 3384856038735393365 bi_subvol 0 bi_parent_subvol 0 bi_nocow 0

Kernel panic - not syncing: bcachefs (e7fdc10e-54a3-49d9-bd0c-390370889d84): panic after error
CPU: 4 PID: 5154 Comm: rsync Not tainted 6.5.9-gateway-gca1614174cc0-dirty #1
Hardware name: To Be Filled By O.E.M. To Be Filled By O.E.M./X570 Phantom Gaming 4, BIOS P4.20 08/02/2021
Call Trace:
 <TASK>
 dump_stack_lvl+0x5a/0x90
 panic+0x105/0x300
 ? console_unlock+0xf1/0x130
 ? bch2_printbuf_exit+0x16/0x30
 ? srso_return_thunk+0x5/0x10
 bch2_inconsistent_error+0x6f/0x80
 bch2_trans_fs_usage_apply+0x279/0x3d0
 __bch2_trans_commit+0x112a/0x1df0
 ? bch2_extent_update+0x13a/0x1d0
 bch2_extent_update+0x13a/0x1d0
 bch2_extent_fallocate+0x58e/0x740
 bch2_fallocate_dispatch+0xb7c/0x1030
 ? do_filp_open+0xa0/0x140
 vfs_fallocate+0x18e/0x1d0
 __x64_sys_fallocate+0x46/0x70
 do_syscall_64+0x48/0xa0
 ? exit_to_user_mode_prepare+0x4d/0xa0
 entry_SYSCALL_64_after_hwframe+0x6e/0xd8
RIP: 0033:0x7fc85d91bbb3
Code: 64 89 02 b8 ff ff ff ff eb bd 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 00 80 3d 31 da 0d 00 00 49 89 ca 74 14 b8 1d 01 00 00 0f 05 <48> 3d 00 f0 ff ff 77 5d c3 0f 1f 40 00 48 83 ec 28 48 89 54 24 10
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

We should only be downgrading locks on success - otherwise, our
transaction restarts won't be getting the correct locks and we'll
livelock.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

We were dropping a lock we hadn't taken when entering with an error.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

This patch adds a superblock error counter for every distinct fsck
error; this means that when analyzing filesystems out in the wild we'll
be able to see what sorts of inconsistencies are being found and repair,
and hence what bugs to look for.

Errors validating bkeys are not yet considered distinct fsck errors, but
this patch adds a new helper, bkey_fsck_err(), in order to add distinct
error types for them as well.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

Add a new superblock section to keep counts of errors seen since
filesystem creation: we'll be addingcounters for every distinct fsck
error.

The new superblock section has entries of the for [ id, count,
time_of_last_error ]; this is intended to let us see what errors are
occuring - and getting fixed - via show-super output.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

We now track IO errors per device since filesystem creation.

IO error counts can be viewed in sysfs, or with the 'bcachefs
show-super' command.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

This fixes a use after free - mi is dangling after the resize call.

Additionally, resizing the device's member info section was useless - we
were attempting to preallocate the space required before adding it to
the filesystem superblock, but there's other sections that we should
have been preallocating as well for that to work.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>