Pull btrfs fixes from David Sterba:

 - fix infinite loop in readdir(), could happen in a big directory when
   files get renamed during enumeration

 - fix extent map handling of skipped pinned ranges

 - fix a corner case when handling ordered extent length

 - fix a potential crash when balance cancel races with pause

 - verify correct uuid when starting scrub or device replace

* tag 'for-6.5-rc6-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux:
  btrfs: fix incorrect splitting in btrfs_drop_extent_map_range
  btrfs: fix BUG_ON condition in btrfs_cancel_balance
  btrfs: only subtract from len_to_oe_boundary when it is tracking an extent
  btrfs: fix replace/scrub failure with metadata_uuid
  btrfs: fix infinite directory reads

In production we were seeing a variety of WARN_ON()'s in the extent_map
code, specifically in btrfs_drop_extent_map_range() when we have to call
add_extent_mapping() for our second split.

Consider the following extent map layout

	PINNED
	[0 16K)  [32K, 48K)

and then we call btrfs_drop_extent_map_range for [0, 36K), with
skip_pinned == true.  The initial loop will have

	start = 0
	end = 36K
	len = 36K

we will find the [0, 16k) extent, but since we are pinned we will skip
it, which has this code

	start = em_end;
	if (end != (u64)-1)
		len = start + len - em_end;

em_end here is 16K, so now the values are

	start = 16K
	len = 16K + 36K - 16K = 36K

len should instead be 20K.  This is a problem when we find the next
extent at [32K, 48K), we need to split this extent to leave [36K, 48k),
however the code for the split looks like this

	split->start = start + len;
	split->len = em_end - (start + len);

In this case we have

	em_end = 48K
	split->start = 16K + 36K       // this should be 16K + 20K
	split->len = 48K - (16K + 36K) // this overflows as 16K + 36K is 52K

and now we have an invalid extent_map in the tree that potentially
overlaps other entries in the extent map.  Even in the non-overlapping
case we will have split->start set improperly, which will cause problems
with any block related calculations.

We don't actually need len in this loop, we can simply use end as our
end point, and only adjust start up when we find a pinned extent we need
to skip.

Adjust the logic to do this, which keeps us from inserting an invalid
extent map.

We only skip_pinned in the relocation case, so this is relatively rare,
except in the case where you are running relocation a lot, which can
happen with auto relocation on.

Fixes: 55ef68990029 ("Btrfs: Fix btrfs_drop_extent_cache for skip pinned case")
CC: stable@vger.kernel.org # 4.14+
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: David Sterba <dsterba@suse.com>

Pausing and canceling balance can race to interrupt balance lead to BUG_ON
panic in btrfs_cancel_balance. The BUG_ON condition in btrfs_cancel_balance
does not take this race scenario into account.

However, the race condition has no other side effects. We can fix that.

Reproducing it with panic trace like this:

  kernel BUG at fs/btrfs/volumes.c:4618!
  RIP: 0010:btrfs_cancel_balance+0x5cf/0x6a0
  Call Trace:
   <TASK>
   ? do_nanosleep+0x60/0x120
   ? hrtimer_nanosleep+0xb7/0x1a0
   ? sched_core_clone_cookie+0x70/0x70
   btrfs_ioctl_balance_ctl+0x55/0x70
   btrfs_ioctl+0xa46/0xd20
   __x64_sys_ioctl+0x7d/0xa0
   do_syscall_64+0x38/0x80
   entry_SYSCALL_64_after_hwframe+0x63/0xcd

  Race scenario as follows:
  > mutex_unlock(&fs_info->balance_mutex);
  > --------------------
  > .......issue pause and cancel req in another thread
  > --------------------
  > ret = __btrfs_balance(fs_info);
  >
  > mutex_lock(&fs_info->balance_mutex);
  > if (ret == -ECANCELED && atomic_read(&fs_info->balance_pause_req)) {
  >         btrfs_info(fs_info, "balance: paused");
  >         btrfs_exclop_balance(fs_info, BTRFS_EXCLOP_BALANCE_PAUSED);
  > }

CC: stable@vger.kernel.org # 4.19+
Signed-off-by: xiaoshoukui <xiaoshoukui@ruijie.com.cn>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

bio_ctrl->len_to_oe_boundary is used to make sure we stay inside a zone
as we submit bios for writes.  Every time we add a page to the bio, we
decrement those bytes from len_to_oe_boundary, and then we submit the
bio if we happen to hit zero.

Most of the time, len_to_oe_boundary gets set to U32_MAX.
submit_extent_page() adds pages into our bio, and the size of the bio
ends up limited by:

- Are we contiguous on disk?
- Does bio_add_page() allow us to stuff more in?
- is len_to_oe_boundary > 0?

The len_to_oe_boundary math starts with U32_MAX, which isn't page or
sector aligned, and subtracts from it until it hits zero.  In the
non-zoned case, the last IO we submit before we hit zero is going to be
unaligned, triggering BUGs.

This is hard to trigger because bio_add_page() isn't going to make a bio
of U32_MAX size unless you give it a perfect set of pages and fully
contiguous extents on disk.  We can hit it pretty reliably while making
large swapfiles during provisioning because the machine is freshly
booted, mostly idle, and the disk is freshly formatted.  It's also
possible to trigger with reads when read_ahead_kb is set to 4GB.

The code has been clean up and shifted around a few times, but this flaw
has been lurking since the counter was added.  I think the commit
24e6c8082208 ("btrfs: simplify main loop in submit_extent_page") ended
up exposing the bug.

The fix used here is to skip doing math on len_to_oe_boundary unless
we've changed it from the default U32_MAX value.  bio_add_page() is the
real limit we want, and there's no reason to do extra math when block
layer is doing it for us.

Sample reproducer, note you'll need to change the path to the bdi and
device:

  SUBVOL=/btrfs/swapvol
  SWAPFILE=$SUBVOL/swapfile
  SZMB=8192

  mkfs.btrfs -f /dev/vdb
  mount /dev/vdb /btrfs

  btrfs subvol create $SUBVOL
  chattr +C $SUBVOL
  dd if=/dev/zero of=$SWAPFILE bs=1M count=$SZMB
  sync

  echo 4 > /proc/sys/vm/drop_caches

  echo 4194304 > /sys/class/bdi/btrfs-2/read_ahead_kb

  while true; do
	  echo 1 > /proc/sys/vm/drop_caches
	  echo 1 > /proc/sys/vm/drop_caches
	  dd of=/dev/zero if=$SWAPFILE bs=4096M count=2 iflag=fullblock
  done

Fixes: 24e6c8082208 ("btrfs: simplify main loop in submit_extent_page")
CC: stable@vger.kernel.org # 6.4+
Reviewed-by: Sweet Tea Dorminy <sweettea-kernel@dorminy.me>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Chris Mason <clm@fb.com>
Signed-off-by: David Sterba <dsterba@suse.com>

Fstests with POST_MKFS_CMD="btrfstune -m" (as in the mailing list)
reported a few of the test cases failing.

The failure scenario can be summarized and simplified as follows:

  $ mkfs.btrfs -fq -draid1 -mraid1 /dev/sdb1 /dev/sdb2 :0
  $ btrfstune -m /dev/sdb1 :0
  $ wipefs -a /dev/sdb1 :0
  $ mount -o degraded /dev/sdb2 /btrfs :0
  $ btrfs replace start -B -f -r 1 /dev/sdb1 /btrfs :1
    STDERR:
    ERROR: ioctl(DEV_REPLACE_START) failed on "/btrfs": Input/output error

  [11290.583502] BTRFS warning (device sdb2): tree block 22036480 mirror 2 has bad fsid, has 99835c32-49f0-4668-9e66-dc277a96b4a6 want da40350c-33ac-4872-92a8-4948ed8c04d0
  [11290.586580] BTRFS error (device sdb2): unable to fix up (regular) error at logical 22020096 on dev /dev/sdb8 physical 1048576

As above, the replace is failing because we are verifying the header with
fs_devices::fsid instead of fs_devices::metadata_uuid, despite the
metadata_uuid actually being present.

To fix this, use fs_devices::metadata_uuid. We copy fsid into
fs_devices::metadata_uuid if there is no metadata_uuid, so its fine.

Fixes: a3ddbaebc7c9 ("btrfs: scrub: introduce a helper to verify one metadata block")
CC: stable@vger.kernel.org # 6.4+
Signed-off-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: David Sterba <dsterba@suse.com>

The readdir implementation currently processes always up to the last index
it finds. This however can result in an infinite loop if the directory has
a large number of entries such that they won't all fit in the given buffer
passed to the readdir callback, that is, dir_emit() returns a non-zero
value. Because in that case readdir() will be called again and if in the
meanwhile new directory entries were added and we still can't put all the
remaining entries in the buffer, we keep repeating this over and over.

The following C program and test script reproduce the problem:

  $ cat /mnt/readdir_prog.c
  #include <sys/types.h>
  #include <dirent.h>
  #include <stdio.h>

  int main(int argc, char *argv[])
  {
    DIR *dir = opendir(".");
    struct dirent *dd;

    while ((dd = readdir(dir))) {
      printf("%s\n", dd->d_name);
      rename(dd->d_name, "TEMPFILE");
      rename("TEMPFILE", dd->d_name);
    }
    closedir(dir);
  }

  $ gcc -o /mnt/readdir_prog /mnt/readdir_prog.c

  $ cat test.sh
  #!/bin/bash

  DEV=/dev/sdi
  MNT=/mnt/sdi

  mkfs.btrfs -f $DEV &> /dev/null
  #mkfs.xfs -f $DEV &> /dev/null
  #mkfs.ext4 -F $DEV &> /dev/null

  mount $DEV $MNT

  mkdir $MNT/testdir
  for ((i = 1; i <= 2000; i++)); do
      echo -n > $MNT/testdir/file_$i
  done

  cd $MNT/testdir
  /mnt/readdir_prog

  cd /mnt

  umount $MNT

This behaviour is surprising to applications and it's unlike ext4, xfs,
tmpfs, vfat and other filesystems, which always finish. In this case where
new entries were added due to renames, some file names may be reported
more than once, but this varies according to each filesystem - for example
ext4 never reported the same file more than once while xfs reports the
first 13 file names twice.

So change our readdir implementation to track the last index number when
opendir() is called and then make readdir() never process beyond that
index number. This gives the same behaviour as ext4.

Reported-by: Rob Landley <rob@landley.net>
Link: https://lore.kernel.org/linux-btrfs/2c8c55ec-04c6-e0dc-9c5c-8c7924778c35@landley.net/
Link: https://bugzilla.kernel.org/show_bug.cgi?id=217681
CC: stable@vger.kernel.org # 6.4+
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

Pull btrfs fixes from David Sterba:
 "More fixes, some of them going back to older releases and there are
  fixes for hangs in stress tests regarding space caching:

   - fixes and progress tracking for hangs in free space caching, found
     by test generic/475

   - writeback fixes, write pages in integrity mode and skip writing
     pages that have been written meanwhile

   - properly clear end of extent range after an error

   - relocation fixes:
      - fix race betwen qgroup tree creation and relocation
      - detect and report invalid reloc roots"

* tag 'for-6.5-rc5-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux:
  btrfs: set cache_block_group_error if we find an error
  btrfs: reject invalid reloc tree root keys with stack dump
  btrfs: exit gracefully if reloc roots don't match
  btrfs: avoid race between qgroup tree creation and relocation
  btrfs: properly clear end of the unreserved range in cow_file_range
  btrfs: don't wait for writeback on clean pages in extent_write_cache_pages
  btrfs: don't stop integrity writeback too early
  btrfs: wait for actual caching progress during allocation

We set cache_block_group_error if btrfs_cache_block_group() returns an
error, this is because we could end up not finding space to allocate and
mistakenly return -ENOSPC, and which could then abort the transaction
with the incorrect errno, and in the case of ENOSPC result in a
WARN_ON() that will trip up tests like generic/475.

However there's the case where multiple threads can be racing, one
thread gets the proper error, and the other thread doesn't actually call
btrfs_cache_block_group(), it instead sees ->cached ==
BTRFS_CACHE_ERROR.  Again the result is the same, we fail to allocate
our space and return -ENOSPC.  Instead we need to set
cache_block_group_error to -EIO in this case to make sure that if we do
not make our allocation we get the appropriate error returned back to
the caller.

CC: stable@vger.kernel.org # 4.14+
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: David Sterba <dsterba@suse.com>

[BUG]
Syzbot reported a crash that an ASSERT() got triggered inside
prepare_to_merge().

That ASSERT() makes sure the reloc tree is properly pointed back by its
subvolume tree.

[CAUSE]
After more debugging output, it turns out we had an invalid reloc tree:

  BTRFS error (device loop1): reloc tree mismatch, root 8 has no reloc root, expect reloc root key (-8, 132, 8) gen 17

Note the above root key is (TREE_RELOC_OBJECTID, ROOT_ITEM,
QUOTA_TREE_OBJECTID), meaning it's a reloc tree for quota tree.

But reloc trees can only exist for subvolumes, as for non-subvolume
trees, we just COW the involved tree block, no need to create a reloc
tree since those tree blocks won't be shared with other trees.

Only subvolumes tree can share tree blocks with other trees (thus they
have BTRFS_ROOT_SHAREABLE flag).

Thus this new debug output proves my previous assumption that corrupted
on-disk data can trigger that ASSERT().

[FIX]
Besides the dedicated fix and the graceful exit, also let tree-checker to
check such root keys, to make sure reloc trees can only exist for subvolumes.

CC: stable@vger.kernel.org # 5.15+
Reported-by: syzbot+ae97a827ae1c3336bbb4@syzkaller.appspotmail.com
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

[BUG]
Syzbot reported a crash that an ASSERT() got triggered inside
prepare_to_merge().

[CAUSE]
The root cause of the triggered ASSERT() is we can have a race between
quota tree creation and relocation.

This leads us to create a duplicated quota tree in the
btrfs_read_fs_root() path, and since it's treated as fs tree, it would
have ROOT_SHAREABLE flag, causing us to create a reloc tree for it.

The bug itself is fixed by a dedicated patch for it, but this already
taught us the ASSERT() is not something straightforward for
developers.

[ENHANCEMENT]
Instead of using an ASSERT(), let's handle it gracefully and output
extra info about the mismatch reloc roots to help debug.

Also with the above ASSERT() removed, we can trigger ASSERT(0)s inside
merge_reloc_roots() later.
Also replace those ASSERT(0)s with WARN_ON()s.

CC: stable@vger.kernel.org # 5.15+
Reported-by: syzbot+ae97a827ae1c3336bbb4@syzkaller.appspotmail.com
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>