We can't be holding btree_trans_lock while copying to user space, which
might incur a page fault. To fix this, convert it to a seqmutex so we
can unlock/relock.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

This fixes a deadlock:

01305 WARNING: possible circular locking dependency detected
01305 6.3.0-ktest-gf4de9bee61af #5305 Tainted: G        W
01305 ------------------------------------------------------
01305 cat/14658 is trying to acquire lock:
01305 ffffffc00982f460 (fs_reclaim){+.+.}-{0:0}, at: __kmem_cache_alloc_node+0x48/0x278
01305
01305 but task is already holding lock:
01305 ffffff8011aaf040 (&lock->wait_lock){+.+.}-{2:2}, at: bch2_check_for_deadlock+0x4b8/0xa58
01305
01305 which lock already depends on the new lock.
01305
01305
01305 the existing dependency chain (in reverse order) is:
01305
01305 -> #2 (&lock->wait_lock){+.+.}-{2:2}:
01305        _raw_spin_lock+0x54/0x70
01305        __six_lock_wakeup+0x40/0x1b0
01305        six_unlock_ip+0xe8/0x248
01305        bch2_btree_key_cache_scan+0x720/0x940
01305        shrink_slab.constprop.0+0x284/0x770
01305        shrink_node+0x390/0x828
01305        balance_pgdat+0x390/0x6d0
01305        kswapd+0x2e4/0x718
01305        kthread+0x184/0x1a8
01305        ret_from_fork+0x10/0x20
01305
01305 -> #1 (&c->lock#2){+.+.}-{3:3}:
01305        __mutex_lock+0x104/0x14a0
01305        mutex_lock_nested+0x30/0x40
01305        bch2_btree_key_cache_scan+0x5c/0x940
01305        shrink_slab.constprop.0+0x284/0x770
01305        shrink_node+0x390/0x828
01305        balance_pgdat+0x390/0x6d0
01305        kswapd+0x2e4/0x718
01305        kthread+0x184/0x1a8
01305        ret_from_fork+0x10/0x20
01305
01305 -> #0 (fs_reclaim){+.+.}-{0:0}:
01305        __lock_acquire+0x19d0/0x2930
01305        lock_acquire+0x1dc/0x458
01305        fs_reclaim_acquire+0x9c/0xe0
01305        __kmem_cache_alloc_node+0x48/0x278
01305        __kmalloc_node_track_caller+0x5c/0x278
01305        krealloc+0x94/0x180
01305        bch2_printbuf_make_room.part.0+0xac/0x118
01305        bch2_prt_printf+0x150/0x1e8
01305        bch2_btree_bkey_cached_common_to_text+0x170/0x298
01305        bch2_btree_trans_to_text+0x244/0x348
01305        print_cycle+0x7c/0xb0
01305        break_cycle+0x254/0x528
01305        bch2_check_for_deadlock+0x59c/0xa58
01305        bch2_btree_deadlock_read+0x174/0x200
01305        full_proxy_read+0x94/0xf0
01305        vfs_read+0x15c/0x3a8
01305        ksys_read+0xb8/0x148
01305        __arm64_sys_read+0x48/0x60
01305        invoke_syscall.constprop.0+0x64/0x138
01305        do_el0_svc+0x84/0x138
01305        el0_svc+0x34/0x80
01305        el0t_64_sync_handler+0xb0/0xb8
01305        el0t_64_sync+0x14c/0x150
01305
01305 other info that might help us debug this:
01305
01305 Chain exists of:
01305   fs_reclaim --> &c->lock#2 --> &lock->wait_lock
01305
01305  Possible unsafe locking scenario:
01305
01305        CPU0                    CPU1
01305        ----                    ----
01305   lock(&lock->wait_lock);
01305                                lock(&c->lock#2);
01305                                lock(&lock->wait_lock);
01305   lock(fs_reclaim);
01305
01305  *** DEADLOCK ***
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

We weren't correctly checking the freespace btree - it's an extents
btree, which means we need to iterate over each bucket in a freespace
extent.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

This fixes a spurious assert in the btree node read path.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

The calculation for number of nodes to allocate in
bch2_btree_update_start() was incorrect - this fixes a BUG_ON() on the
small nodes test.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

This adds a new helper for getting a pointer's durability irrespective
of the device state, and uses it in the the data update path.

This fixes a bug where we do a data update but request 0 replicas to be
allocated, because the replica being rewritten is on a device marked as
failed.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

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

 - We may need to drop btree locks before taking the writepoint_lock, as
   is done in other places.
 - We should be using open_bucket_free_unused(), so that we don't waste
   space.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

since we currently don't have a good fault injection library,
bch2_btree_insert_node() was randomly injecting faults based on
local_clock().

At the very least this should have been a debug mode only thing, but
this is a brittle method so let's just delete it.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

btree write buffer flush is only invoked from contexts that already hold
a write ref, and checking if we're still RW could cause us to fail to
completely flush the write buffer when shutting down.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

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

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

On Mon, 29 May 2023, Mikulas Patocka wrote:

> The oops happens in set_btree_iter_dontneed and it is caused by the fact
> that iter->path is NULL. The code in try_alloc_bucket is buggy because it
> sets "struct btree_iter iter = { NULL };" and then jumps to the "err"
> label that tries to dereference values in "iter".

Here I'm sending a patch for it.

From: Mikulas Patocka <mpatocka@redhat.com>

The function try_alloc_bucket sets the variable "iter" to NULL and then
(on various error conditions) jumps to the label "err". On the "err"
label, it calls "set_btree_iter_dontneed" that tries to dereference
"iter->trans" and "iter->path".

So, we get an oops on error condition.

This patch fixes the crash by testing that iter.trans and iter.path is
non-zero before calling set_btree_iter_dontneed.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

d_prune_aliases() may call bch2_evict_inode(), which needs
c->vfs_inodes_list_lock.

Fix this by always calling igrab() before putting the inodes onto our
disposal list, and then calling d_prune_aliases() with
c->vfs_inodes_lock dropped.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

If a bcachefs filesystem is configured with a background device
(disk group), rebalance will relocate data to this device in the
background by checking extent keys for whether they currently reside
in the specified target. For keys that do not, rebalance performs a
read/write cycle to allow the write path to properly relocate data.

If the background target is not usable (read-only, for example),
however, the write path doesn't actually move data to another
device. Instead, rebalance spins indefinitely reading and rewriting
the same data over and over to the same device. If the background
target is made available again, the rebalance picks this up,
relocates the data, and eventually terminates.

To avoid this spinning behavior, update the rebalance background
target logic to not only check whether the extent is not in the
target, but whether the target is actually usable as well. If not,
then don't mark the key for rewrite.
Signed-off-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

We have one caller that cycles the rcu lock solely for this call
(via target_rw_devs()), and we'd like to add another. Simplify
things by pushing the rcu lock down into bch2_target_to_mask(),
similar to how bch2_dev_in_target() works.
Signed-off-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

We have bch2_sb_disk_groups_to_text() to dump disk group labels, but
no good information on device group membership at runtime. Add
bch2_disk_groups_to_text() and an associated 'disk_groups' sysfs
file to print group and device relationships.
Signed-off-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

 - delete redundant error messages
 - convert various code to bch2_trans_run
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

the error message here dated from when backpointers could be stored in
alloc keys; now, we should always print the full key.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

Using drop_locks_do() ensures that every unlock() is paired with a
relock(), with proper error checking.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

It's possible to see a -BCH_ERR_ENOSPC_disk_reservation here, and that's
fine.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

 - getline() output includes a newline, without stripping that we were
   just looping

 - Make the prompt clearer
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

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

More work to avoid allocating memory with btree locks held.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

Add two new helpers for allocating memory with btree locks held: The
idea is to first try the allocation with GFP_NOWAIT|__GFP_NOWARN, then
if that fails - unlock, retry with GFP_KERNEL, and then call
trans_relock().
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

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

The promote path had a BUG_ON() for unknown error type, which we're now
seeing: change it to a WARN_ON() - because we're curious what this is -
and otherwise handle it in the normal error path.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

GFP_NOFS doesn't ever make sense. If we're allocatingc memory it should
be GFP_NOWAIT if btree locks are held, GFP_KERNEL otherwise.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

When allocating memory, gfp flags should generally be

 - GFP_NOWAIT|__GFP_NOWARN if btree locks are held
 - GFP_NOFS if in the IO path or otherwise holding resources needed for
   IO submission
 - GFP_KERNEL otherwise
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

Add a new helper for the common pattern of:
 - trans_unlock()
 - do something
 - trans_relock()
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

GFP_NOIO dates from the bcache days, when we operated under the block
layer. Now, GFP_NOFS is more appropriate, so switch all GFP_NOIO uses to
GFP_NOFS.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

Fix a bug where bch2_btree_node_get() might call bch2_trans_unlock() (in
fill) without calling bch2_trans_relock(); this is a bug when it's done
in the core btree code.

Also, twea bch2_btree_node_mem_alloc() to drop btree locks before doing
a blocking memory allocation.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

We've been using __GFP_NOFAIL for allocating struct bch_folio, our
private per-folio state.

However, that struct is variable size - it holds state for each sector
in the folio, and folios can be quite large now, which means it's
possible for bch_folio to be larger than PAGE_SIZE now.

__GFP_NOFAIL allocations are undesirable in normal circumstances, but
particularly so at >= PAGE_SIZE, and warnings are emitted for that.

So, this patch adds proper error paths and eliminates most uses of
__GFP_NOFAIL. Also, do some more cleanup of gfp flags w.r.t. btree node
locks: we can use GFP_KERNEL, but only if we're not holding btree locks,
and if we are holding btree locks we should be using GFP_NOWAIT.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

When partially overwriting an extent in an older snapshot, the existing
extent has to be split.

If the existing extent was overwritten in a different (sibling)
snapshot, we have to ensure that the split won't be visible in the
sibling snapshot.

data_update.c already has code for this,
bch2_insert_snapshot_writeouts() - we just need to move it into
btree_update_leaf.c and change bch2_trans_update_extent() to use it as
well.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

As with previous conversions, replace -ENOENT uses with more informative
private error codes.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

bch2_btree_trans_to_text() is used on btree_trans objects that are owned
by different threads - when printing out deadlock cycles - so we need a
safe version of trans_for_each_path(), else we race with seeing a
btree_path that was just allocated and not fully initialized:
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

bch2_fs_quota_read() could see an inode that's been deleted
(KEY_TYPE_inode_generation) - bch2_fs_quota_read_inode() needs to check
for that instead of erroring.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fail counters need to be events, not numbers of sectors - or the
calculations the tests use for determining if we've had too many
slowpath events don't work.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

We've been seeing difficult to debug "missing indirect extent" bugs,
that fsck doesn't seem to find.

One possibility is that there was a missing indirect extent, but then a
new indirect extent was created at the location of the previous indirect
extent.

This patch eliminates that possibility by always creating new indirect
extents right after the last one, at the end of the reflink btree.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

abs() is in math.h
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>