gc lock must be held while invalidating buckets - fixes
"1f7a95698e bcachefs: Invalidate buckets when writing to alloc btree"
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

was returning wrong value
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

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

Also improve error reporting - only return an error from
bch2_journal_flush_seq() if we had an error writing that entry (i.e. not
if there was an error with a newer entry).
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>

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

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

Prep work for persistent alloc information. Refactoring also lets us
make free_inc much smaller, which means a lot fewer buckets stranded on
freelists.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

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

journal_buf_switch is called from the foreground when getting a journal
reservation and thus is somewhat latency sensitive;
bch2_bucket_seq_cleanup has to run infrequently but is a bit expensive
when it does run.

Call it from the journal write path instead, and punt the journal write
to worqueue context.
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>

This is prep work for using deferred btree updates for inode updates -
the way inodes are done now we're relying on btree locking for ei_inode
and ei_update_lock could probably be removed, but it'll actually be
needed when we switch to deferred updates.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

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

Also make inode flags consistent with how the rest of the inode is
updated
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

ei_update_lock isn't currently needed for write inode (but it will be
needed again when deferred btree updates are used for inode updates)
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>

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

exceptionally crappy "tracing", but it's a start at documenting the
places restarts can be triggered
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

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

Now that all filesystem operatinos that manipulate the filesystem
heirachy and i_nlink are fully atomic, we can add a feature bit to
indicate i_nlink doesn't need to be checked.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

Initially forked from drivers/md/bcache, bcachefs is a new copy-on-write
filesystem with every feature you could possibly want.

Website: https://bcachefs.orgSigned-off-by: Kent Overstreet <kent.overstreet@linux.dev>

bcachefs is a new copy-on-write filesystem; add a MAINTAINERS entry for
it.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

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

This patch adds genradix_peek_prev(), genradix_iter_rewind(), and
genradix_for_each_reverse(), for iterating backwards over a generic
radix tree.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

When we started spreading new inode numbers throughout most of the 64
bit inode space, that triggered some corner case bugs, in particular
some integer overflows related to the radix tree code. Oops.
Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>

lib/generic-radix-tree.c is a simple radix tree that supports storing
arbitrary types. Add a maintainers entry for it.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

Fixes building in userspace.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

Factor out a new helper, which returns the number of events outstanding.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

Like wait_event() - except, because it uses closures and closure
waitlists it doesn't have the restriction on modifying task state inside
the condition check, like wait_event() does.
Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
Acked-by: Coly Li <colyli@suse.de>

closures, from bcache, are async widgets with a variety of uses.
bcachefs also uses them, so they're being moved to lib/; mark them as
maintained.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
Acked-by: Coly Li <colyli@suse.de>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

Prep work for bcachefs - being a fork of bcache it also uses closures
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
Acked-by: Coly Li <colyli@suse.de>
Reviewed-by: Randy Dunlap <rdunlap@infradead.org>

The bcachefs implementation of six locks is intended to land in
generic locking code in the long term, but has been pulled into the
bcachefs subsystem for internal use for the time being. This code
lift breaks the bcachefs module build as six locks depend a couple
of the generic locking tracepoints. Export these tracepoint symbols
for bcachefs.
Signed-off-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

errname() returns the name of an errcode; this functionality is
otherwise only available for error pointers via %pE - bcachefs uses this
for better error messages.
Signed-off-by: Christopher James Halse Rogers <raof@ubuntu.com>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

printbuf now needs to know the number of characters that would have been
written if the buffer was too small, like snprintf(); this changes
string_get_size() to return the the return value of snprintf().
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

The bcachefs module wants it, and there doesn't seem to be any
reason it shouldn't be exported like the other functions.
Signed-off-by: Christopher James Halse Rogers <raof@ubuntu.com>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

New helper for bcachefs - bcachefs doesn't want the
inode_dec_link_count() call that d_tmpfile does, it handles i_nlink on
its own atomically with other btree updates
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Christian Brauner <brauner@kernel.org>
Cc: linux-fsdevel@vger.kernel.org
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christian Brauner <brauner@kernel.org>

There has been a long standing page cache coherence bug with direct IO.
This provides part of a mechanism to fix it, currently just used by
bcachefs but potentially worth promoting to the VFS.

Direct IO evicts the range of the pagecache being read or written to.

For reads, we need dirty pages to be written to disk, so that the read
doesn't return stale data. For writes, we need to evict that range of
the pagecache so that it's not stale after the write completes.

However, without a locking mechanism to prevent those pages from being
re-added to the pagecache - by a buffered read or page fault - page
cache inconsistency is still possible.

This isn't necessarily just an issue for userspace when they're playing
games; filesystems may hang arbitrary state off the pagecache, and so
page cache inconsistency may cause real filesystem bugs, depending on
the filesystem. This is less of an issue for iomap based filesystems,
but e.g. buffer heads caches disk block mappings (!) and attaches them
to the pagecache, and bcachefs attaches disk reservations to pagecache
pages.

This issue has been hard to fix, because
 - we need to add a lock (henceforth called pagecache_add_lock), which
   would be held for the duration of the direct IO
 - page faults add pages to the page cache, thus need to take the same
   lock
 - dio -> gup -> page fault thus can deadlock

And we cannot enforce a lock ordering with this lock, since userspace
will be controlling the lock ordering (via the fd and buffer arguments
to direct IOs), so we need a different method of deadlock avoidance.

We need to tell the page fault handler that we're already holding a
pagecache_add_lock, and since plumbing it through the entire gup() path
would be highly impractical this adds a field to task_struct.

Then the full method is:
 - in the dio path, when we first take the pagecache_add_lock, note the
   mapping in the current task_struct
 - in the page fault handler, if faults_disabled_mapping is set, we
   check if it's the same mapping as the one we're taking a page fault
   for, and if so return an error.

   Then we check lock ordering: if there's a lock ordering violation and
   trylock fails, we'll have to cycle the locks and return an error that
   tells the DIO path to retry: faults_disabled_mapping is also used for
   signalling "locks were dropped, please retry".

Also relevant to this patch: mapping->invalidate_lock.
mapping->invalidate_lock provides most of the required semantics - it's
used by truncate/fallocate to block pages being added to the pagecache.
However, since it's a rwsem, direct IOs would need to take the write
side in order to block page cache adds, and would then be exclusive with
each other - we'll need a new type of lock to pair with this approach.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
Cc: Jan Kara <jack@suse.cz>
Cc: Darrick J. Wong <djwong@kernel.org>
Cc: linux-fsdevel@vger.kernel.org
Cc: Andreas Grünbacher <andreas.gruenbacher@gmail.com>