If a file is unlinked but still open, we don't want online fsck to
delete it - or fun inconsistencies will happen.

https://github.com/koverstreet/bcachefs/issues/727

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>

bch2_bkey_drop_ptrs() had a some complicated machinery for avoiding
O(n^2) when dropping multiple pointers - but when n is only going to be
~4, it's not worth it.

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

Without this, we'd potentially sort multiple times without a
cond_resched(), leading to hung task warnings on larger systems.

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

ca->io_ref does not protect against the filesystem going way,
c->write_ref does. Much like

0b50b7313ef2 bcachefs: Fix refcounting in discard path

the other async paths need fixing.

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

Create a sentinal value for "invalid device".

This is needed for removing devices that have stripes on them (force
removing, without evacuating); we need a sentinal value for the stripe
pointers to the device being removed.

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

Fixes: 49aa7830396b ("bcachefs: Fix rebalance_work accounting")
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

errors that are known to always be safe to fix should be autofix: this
should be most errors even at this point, but that will need some
thorough review.

note that errors are still logged in the superblock, so we'll still know
that they happened.

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

We had a report of data corruption on nixos when building installer
images.

https://github.com/NixOS/nixpkgs/pull/321055#issuecomment-2184131334

It seems that writes are being dropped, but only when issued by QEMU,
and possibly only in snapshot mode. It's undetermined if it's write
calls are being dropped or dirty folios.

Further testing, via minimizing the original patch to just the change
that skips the inode lock on non appends/truncates, reveals that it
really is just not taking the inode lock that causes the corruption: it
has nothing to do with the other logic changes for preserving write
atomicity in corner cases.

It's also kernel config dependent: it doesn't reproduce with the minimal
kernel config that ktest uses, but it does reproduce with nixos's distro
config. Bisection the kernel config initially pointer the finger at page
migration or compaction, but it appears that was erroneous; we haven't
yet determined what kernel config option actually triggers it.

Sadly it appears this will have to be reverted since we're getting too
close to release and my plate is full, but we'd _really_ like to fully
debug it.

My suspicion is that this patch is exposing a preexisting bug - the
inode lock actually covers very little in IO paths, and we have a
different lock (the pagecache add lock) that guards against races with
truncate here.

Fixes: 7e64c86cdc6c ("bcachefs: Buffered write path now can avoid the inode lock")
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>