Randy Dunlap [Wed, 20 Dec 2023 06:44:09 +0000 (22:44 -0800)]
bcachefs: mean and variance: fix kernel-doc for function params
Add missing function parameter descriptions in mean_and_variance.c.
The also eliminates the "Excess function parameter" warnings.
Prevents these kernel-doc warnings:
mean_and_variance.c:67: warning: Function parameter or member 's' not described in 'mean_and_variance_get_mean'
mean_and_variance.c:78: warning: Function parameter or member 's1' not described in 'mean_and_variance_get_variance'
mean_and_variance.c:94: warning: Function parameter or member 's' not described in 'mean_and_variance_get_stddev'
mean_and_variance.c:108: warning: Function parameter or member 's' not described in 'mean_and_variance_weighted_update'
mean_and_variance.c:108: warning: Function parameter or member 'x' not described in 'mean_and_variance_weighted_update'
mean_and_variance.c:108: warning: Excess function parameter 's1' description in 'mean_and_variance_weighted_update'
mean_and_variance.c:108: warning: Excess function parameter 's2' description in 'mean_and_variance_weighted_update'
mean_and_variance.c:134: warning: Function parameter or member 's' not described in 'mean_and_variance_weighted_get_mean'
mean_and_variance.c:143: warning: Function parameter or member 's' not described in 'mean_and_variance_weighted_get_variance'
mean_and_variance.c:153: warning: Function parameter or member 's' not described in 'mean_and_variance_weighted_get_stddev'
Kent Overstreet [Sat, 23 Dec 2023 02:58:43 +0000 (21:58 -0500)]
bcachefs: check for failure to downgrade
With the upcoming member seq patch, it's now critical that we don't ever
write to a superblock that hasn't been version downgraded - failure to
update member seq fields will cause split brain detection to fire
erroniously.
Brian Foster [Tue, 19 Dec 2023 14:02:15 +0000 (09:02 -0500)]
bcachefs: clean up some dead fallocate code
The have_reservation local variable in bch2_extent_fallocate() is
initialized to false and set to true further down in the function.
Between this two points, one branch of code checks for negative
value and one for positive, and nothing ever checks the variable
after it is set to true. Clean up some of the unnecessary logic and
code.
Kent Overstreet [Tue, 19 Dec 2023 23:08:19 +0000 (18:08 -0500)]
bcachefs: Make sure allocation failure errors are logged
The previous patch fixed a bug in allocation path error handling, and it
would've been noticed sooner had it been logged properly.
Generally speaking, errors that shouldn't happen in normal operation and
are being returned up the stack should be logged: the write path was
already logging IO errors, but non IO errors were missed.
bcachefs: Replace zero-length array with flex-array member and use __counted_by
Fake flexible arrays (zero-length and one-element arrays) are
deprecated, and should be replaced by flexible-array members.
So, replace zero-length array with a flexible-array member in
`struct bch_ioctl_fsck_offline`.
Also annotate array `devs` with `__counted_by()` to prepare for the
coming implementation by GCC and Clang of the `__counted_by` attribute.
Flexible array members annotated with `__counted_by` can have their
accesses bounds-checked at run-time via `CONFIG_UBSAN_BOUNDS` (for
array indexing) and `CONFIG_FORTIFY_SOURCE` (for strcpy/memcpy-family
functions).
This fixes the following -Warray-bounds warnings:
fs/bcachefs/chardev.c: In function 'bch2_ioctl_fsck_offline':
fs/bcachefs/chardev.c:363:34: warning: array subscript 0 is outside array bounds of '__u64[0]' {aka 'long long unsigned int[]'} [-Warray-bounds=]
363 | if (copy_from_user(devs, &user_arg->devs[0], sizeof(user_arg->devs[0]) * arg.nr_devs)) {
| ^~~~~~~~~~~~~~~~~~
In file included from fs/bcachefs/chardev.c:5:
fs/bcachefs/bcachefs_ioctl.h:400:33: note: while referencing 'devs'
400 | __u64 devs[0];
Kent Overstreet [Mon, 11 Dec 2023 07:13:33 +0000 (02:13 -0500)]
bcachefs: Drop journal entry compaction
Previously, we dropped empty journal entries and coalesced entries that
could be - but it's not worth the overhead; we very rarely leave unused
journal entries after getting a journal reservation.
Kent Overstreet [Sat, 4 Nov 2023 04:06:56 +0000 (00:06 -0400)]
bcachefs: Inline btree write buffer sort
The sort in the btree write buffer flush path is a very hot path, and
it's particularly performance sensitive since it's single threaded and
can block every other thread on a multithreaded write workload.
It's well worth doing a sort with inlined cmp and swap functions.
Kent Overstreet [Thu, 2 Nov 2023 22:57:19 +0000 (18:57 -0400)]
bcachefs: btree write buffer now slurps keys from journal
Previosuly, the transaction commit path would have to add keys to the
btree write buffer as a separate operation, requiring additional global
synchronization.
This patch introduces a new journal entry type, which indicates that the
keys need to be copied into the btree write buffer prior to being
written out. We switch the journal entry type back to
JSET_ENTRY_btree_keys prior to write, so this is not an on disk format
change.
Flushing the btree write buffer may require pulling keys out of journal
entries yet to be written, and quiescing outstanding journal
reservations; we previously added journal->buf_lock for synchronization
with the journal write path.
We also can't put strict bounds on the number of keys in the journal
destined for the write buffer, which means we might overflow the size of
the preallocated buffer and have to reallocate - this introduces a
potentially fatal memory allocation failure. This is something we'll
have to watch for, if it becomes an issue in practice we can do
additional mitigation.
The transaction commit path no longer has to explicitly check if the
write buffer is full and wait on flushing; this is another performance
optimization. Instead, when the btree write buffer is close to full we
change the journal watermark, so that only reservations for journal
reclaim are allowed.
Kent Overstreet [Sun, 10 Dec 2023 22:44:04 +0000 (17:44 -0500)]
bcachefs: bch2_trans_node_add no longer uses trans_for_each_path()
In the future we'll be making trans->paths resizable and potentially
having _many_ more paths (for fsck); we need to start fixing algorithms
that walk each path in a transaction where possible.
Kent Overstreet [Sun, 10 Dec 2023 21:48:22 +0000 (16:48 -0500)]
bcachefs: Improve trans->extra_journal_entries
Instead of using a darray, we now allocate journal entries for the
transaction commit path with our normal bump allocator - with an inlined
fastpath, and using btree_transaction_stats to remember how much to
initially allocate so as to avoid transaction restarts.
This is prep work for converting write buffer updates to use this
mechanism.
Kent Overstreet [Fri, 8 Dec 2023 04:28:26 +0000 (23:28 -0500)]
bcachefs: Kill for_each_btree_key()
for_each_btree_key() handles transaction restarts, like
for_each_btree_key2(), but only calls bch2_trans_begin() after a
transaction restart - for_each_btree_key2() wraps every loop iteration
in a transaction.
The for_each_btree_key() behaviour is problematic when it leads to
holding the SRCU lock that prevents key cache reclaim for an unbounded
amount of time - there's no real need to keep it around.
Kent Overstreet [Fri, 8 Dec 2023 04:50:38 +0000 (23:50 -0500)]
bcachefs: Fix bch2_read_btree()
In the debugfs code, we had an incorrect use of drop_locks_do(); on
transaction restart we don't want to restart the current loop iteration,
since we've already emitted the current key to the buffer for userspace.
Kent Overstreet [Mon, 4 Dec 2023 18:45:33 +0000 (13:45 -0500)]
bcachefs: BCH_IOCTL_FSCK_ONLINE
This adds a new ioctl for running fsck on a mounted, in use filesystem.
This reuses the fsck_thread code from the previous patch for running
fsck on an offline, unmounted filesystem, so that log messages for the
fsck thread are redirected to userspace.
Only one running fsck instance is allowed at a time; a new semaphore
(since the lock will be taken by one thread and released by another) is
added for this.
Kent Overstreet [Wed, 12 Jul 2023 03:23:40 +0000 (23:23 -0400)]
bcachefs: BCH_IOCTL_FSCK_OFFLINE
This adds a new ioctl for running fsck on a list of devices.
Normally, if we wish to use the kernel's implementation of fsck we'd run
it at mount time with -o fsck. This ioctl lets us run fsck without
mounting, so that userspace bcachefs-tools can transparently switch to
the kernel's implementation of fsck when appropriate - primarily if the
kernel version of bcachefs better matches the filesystem on disk.
Kent Overstreet [Wed, 6 Dec 2023 19:36:18 +0000 (14:36 -0500)]
bcachefs: bch2_run_online_recovery_passes()
Add a new helper for running online recovery passes - i.e. online fsck.
This is a subset of our normal recovery passes, and does not - for now -
use or follow c->curr_recovery_pass.
Kent Overstreet [Tue, 5 Dec 2023 01:15:23 +0000 (20:15 -0500)]
bcachefs: Add ability to redirect log output
Upcoming patches are going to add two new ioctls for running fsck in the
kernel, but pretending that we're running our normal userspace fsck.
This patch adds some plumbing for redirecting our normal log messages
away from the dmesg log to a thread_with_file file descriptor - via a
struct log_output, which will be consumed by the fsck f_op's read method.
The new ioctls will allow for running fsck in the kernel against an
offline filesystem (without mounting it), and an online filesystem. For
an offline filesystem we need a way to pass in a pointer to the
log_output, which is done via a new hidden opts.h option.
For online fsck, we can set c->output directly, but only want to
redirect log messages from the thread running fsck - hence the new
c->output_filter method.
Kent Overstreet [Tue, 5 Dec 2023 20:22:25 +0000 (15:22 -0500)]
bcachefs: Improve error message when finding wrong btree node
single_device.merge_torture_flakey is, very rarely, finding a btree node
that doesn't match the key that points to it: this patch improves the
error message to print out more fields from the btree node header, so
that we can see what else does or does not match the key.
Brian Foster [Tue, 5 Dec 2023 13:24:39 +0000 (08:24 -0500)]
bcachefs: return from fsync on writeback error to avoid early shutdown
When investigating transient failures of generic/441 on bcachefs, it
was determined that the cause of the failure was a combination of
unconditional emergency shutdown and racing between background
journal activity and the test switchover from a working device
mapper table to an error injecting table.
Part of the reason for this sequence of events is that bcachefs
aggressively flushes as much as possible during fsync(), regardless
of errors. While this is reasonable behavior, it is technically
unnecessary because once an error is returned from fsync(), the
caller cannot make any assumptions about the resilience of data.
Tweak the bch2_fsync() logic to return an error on failure of any of
the steps involved in the flush. Note that this change alone does
not prevent generic/441 failure, but in combination with a test
tweak to avoid racing during the dm-error table switchover it avoids
the unnecessary shutdowns and allows the test to pass reliably on
bcachefs.
Brian Foster [Thu, 30 Nov 2023 19:17:11 +0000 (14:17 -0500)]
bcachefs: remove sb lock and flags update on explicit shutdown
bcachefs grabs s_umount and sets SB_RDONLY when the fs is shutdown
via the ioctl() interface. This has a couple issues related to
interactions between shutdown and freeze:
1. The flags == FSOP_GOING_FLAGS_DEFAULT case is a deadlock vector
because freeze_bdev() calls into freeze_super(), which also
acquires s_umount.
2. If an explicit shutdown occurs while the sb is frozen, SB_RDONLY
alters the thaw path as if the sb was read-only at freeze time.
This effectively leaks the frozen state and leaves the sb frozen
indefinitely.
The usage of SB_RDONLY here goes back to the initial bcachefs commit
and AFAICT is simply historical behavior. This behavior is unique to
bcachefs relative to the handful of other filesystems that support
the shutdown ioctl(). Typically, SB_RDONLY is reserved for the
proper remount path, which itself is restricted from modifying
frozen superblocks in reconfigure_super(). Drop the unnecessary sb
lock and flags update bch2_ioc_goingdown() to address both of these
issues.
Kent Overstreet [Thu, 30 Nov 2023 07:16:19 +0000 (02:16 -0500)]
bcachefs: Make backpointer fsck wb flush check more rigorous
backpointers fsck now always runs in rw mode - the btree is being
modified while it runs, by e.g. copygc, rebalance, the discard worker,
the invalidate worker.
We could find a missing backpointer, flush the btree write buffer, and
then on the next iteration find a new key at the exact same position -
which will most likely need another write buffer flush.
Hence, we have to check for an exact match on last_flushed, not just the
pos.
Kent Overstreet [Thu, 2 Nov 2023 23:37:15 +0000 (19:37 -0400)]
bcachefs: Clean up btree write buffer write ref handling
__bch2_btree_write_buffer_flush() now assumes a write ref is already
held (as called by the transaction commit path); and the wrappers
bch2_write_buffer_flush() and flush_sync() take an explicit write ref.
This means internally the write buffer code can always use
BTREE_INSERT_NOCHECK_RW, instead of in the previous code passing flags
around and hoping the NOCHECK_RW flag was always carried around
correctly.
Kent Overstreet [Sat, 25 Nov 2023 20:46:02 +0000 (15:46 -0500)]
bcachefs: Refactor bch2_check_alloc_to_lru_ref()
This code was somewhat convoluted - because originally bch2_lru_set()
could modify the LRU index if there was a collision.
That's no longer the case, so the "create LRU entry" path has no reason
to update the alloc key, so we can separate the handling of the two fsck
errors.
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