While resolving backreferences, as part of a logical ino ioctl call or
fiemap, we can end up hitting a BUG_ON() when replaying tree mod log
operations of a root, triggering a stack trace like the following:

  ------------[ cut here ]------------
  kernel BUG at fs/btrfs/ctree.c:1210!
  invalid opcode: 0000 [#1] SMP KASAN PTI
  CPU: 1 PID: 19054 Comm: crawl_335 Tainted: G        W         5.11.0-2d11c0084b02-misc-next+ #89
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.12.0-1 04/01/2014
  RIP: 0010:__tree_mod_log_rewind+0x3b1/0x3c0
  Code: 05 48 8d 74 10 (...)
  RSP: 0018:ffffc90001eb70b8 EFLAGS: 00010297
  RAX: 0000000000000000 RBX: ffff88812344e400 RCX: ffffffffb28933b6
  RDX: 0000000000000007 RSI: dffffc0000000000 RDI: ffff88812344e42c
  RBP: ffffc90001eb7108 R08: 1ffff11020b60a20 R09: ffffed1020b60a20
  R10: ffff888105b050f9 R11: ffffed1020b60a1f R12: 00000000000000ee
  R13: ffff8880195520c0 R14: ffff8881bc958500 R15: ffff88812344e42c
  FS:  00007fd1955e8700(0000) GS:ffff8881f5600000(0000) knlGS:0000000000000000
  CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
  CR2: 00007efdb7928718 CR3: 000000010103a006 CR4: 0000000000170ee0
  Call Trace:
   btrfs_search_old_slot+0x265/0x10d0
   ? lock_acquired+0xbb/0x600
   ? btrfs_search_slot+0x1090/0x1090
   ? free_extent_buffer.part.61+0xd7/0x140
   ? free_extent_buffer+0x13/0x20
   resolve_indirect_refs+0x3e9/0xfc0
   ? lock_downgrade+0x3d0/0x3d0
   ? __kasan_check_read+0x11/0x20
   ? add_prelim_ref.part.11+0x150/0x150
   ? lock_downgrade+0x3d0/0x3d0
   ? __kasan_check_read+0x11/0x20
   ? lock_acquired+0xbb/0x600
   ? __kasan_check_write+0x14/0x20
   ? do_raw_spin_unlock+0xa8/0x140
   ? rb_insert_color+0x30/0x360
   ? prelim_ref_insert+0x12d/0x430
   find_parent_nodes+0x5c3/0x1830
   ? resolve_indirect_refs+0xfc0/0xfc0
   ? lock_release+0xc8/0x620
   ? fs_reclaim_acquire+0x67/0xf0
   ? lock_acquire+0xc7/0x510
   ? lock_downgrade+0x3d0/0x3d0
   ? lockdep_hardirqs_on_prepare+0x160/0x210
   ? lock_release+0xc8/0x620
   ? fs_reclaim_acquire+0x67/0xf0
   ? lock_acquire+0xc7/0x510
   ? poison_range+0x38/0x40
   ? unpoison_range+0x14/0x40
   ? trace_hardirqs_on+0x55/0x120
   btrfs_find_all_roots_safe+0x142/0x1e0
   ? find_parent_nodes+0x1830/0x1830
   ? btrfs_inode_flags_to_xflags+0x50/0x50
   iterate_extent_inodes+0x20e/0x580
   ? tree_backref_for_extent+0x230/0x230
   ? lock_downgrade+0x3d0/0x3d0
   ? read_extent_buffer+0xdd/0x110
   ? lock_downgrade+0x3d0/0x3d0
   ? __kasan_check_read+0x11/0x20
   ? lock_acquired+0xbb/0x600
   ? __kasan_check_write+0x14/0x20
   ? _raw_spin_unlock+0x22/0x30
   ? __kasan_check_write+0x14/0x20
   iterate_inodes_from_logical+0x129/0x170
   ? iterate_inodes_from_logical+0x129/0x170
   ? btrfs_inode_flags_to_xflags+0x50/0x50
   ? iterate_extent_inodes+0x580/0x580
   ? __vmalloc_node+0x92/0xb0
   ? init_data_container+0x34/0xb0
   ? init_data_container+0x34/0xb0
   ? kvmalloc_node+0x60/0x80
   btrfs_ioctl_logical_to_ino+0x158/0x230
   btrfs_ioctl+0x205e/0x4040
   ? __might_sleep+0x71/0xe0
   ? btrfs_ioctl_get_supported_features+0x30/0x30
   ? getrusage+0x4b6/0x9c0
   ? __kasan_check_read+0x11/0x20
   ? lock_release+0xc8/0x620
   ? __might_fault+0x64/0xd0
   ? lock_acquire+0xc7/0x510
   ? lock_downgrade+0x3d0/0x3d0
   ? lockdep_hardirqs_on_prepare+0x210/0x210
   ? lockdep_hardirqs_on_prepare+0x210/0x210
   ? __kasan_check_read+0x11/0x20
   ? do_vfs_ioctl+0xfc/0x9d0
   ? ioctl_file_clone+0xe0/0xe0
   ? lock_downgrade+0x3d0/0x3d0
   ? lockdep_hardirqs_on_prepare+0x210/0x210
   ? __kasan_check_read+0x11/0x20
   ? lock_release+0xc8/0x620
   ? __task_pid_nr_ns+0xd3/0x250
   ? lock_acquire+0xc7/0x510
   ? __fget_files+0x160/0x230
   ? __fget_light+0xf2/0x110
   __x64_sys_ioctl+0xc3/0x100
   do_syscall_64+0x37/0x80
   entry_SYSCALL_64_after_hwframe+0x44/0xa9
  RIP: 0033:0x7fd1976e2427
  Code: 00 00 90 48 8b 05 (...)
  RSP: 002b:00007fd1955e5cf8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
  RAX: ffffffffffffffda RBX: 00007fd1955e5f40 RCX: 00007fd1976e2427
  RDX: 00007fd1955e5f48 RSI: 00000000c038943b RDI: 0000000000000004
  RBP: 0000000001000000 R08: 0000000000000000 R09: 00007fd1955e6120
  R10: 0000557835366b00 R11: 0000000000000246 R12: 0000000000000004
  R13: 00007fd1955e5f48 R14: 00007fd1955e5f40 R15: 00007fd1955e5ef8
  Modules linked in:
  ---[ end trace ec8931a1c36e57be ]---

  (gdb) l *(__tree_mod_log_rewind+0x3b1)
  0xffffffff81893521 is in __tree_mod_log_rewind (fs/btrfs/ctree.c:1210).
  1205                     * the modification. as we're going backwards, we do the
  1206                     * opposite of each operation here.
  1207                     */
  1208                    switch (tm->op) {
  1209                    case MOD_LOG_KEY_REMOVE_WHILE_FREEING:
  1210                            BUG_ON(tm->slot < n);
  1211                            fallthrough;
  1212                    case MOD_LOG_KEY_REMOVE_WHILE_MOVING:
  1213                    case MOD_LOG_KEY_REMOVE:
  1214                            btrfs_set_node_key(eb, &tm->key, tm->slot);

Here's what happens to hit that BUG_ON():

1) We have one tree mod log user (through fiemap or the logical ino ioctl),
   with a sequence number of 1, so we have fs_info->tree_mod_seq == 1;

2) Another task is at ctree.c:balance_level() and we have eb X currently as
   the root of the tree, and we promote its single child, eb Y, as the new
   root.

   Then, at ctree.c:balance_level(), we call:

      tree_mod_log_insert_root(eb X, eb Y, 1);

3) At tree_mod_log_insert_root() we create tree mod log elements for each
   slot of eb X, of operation type MOD_LOG_KEY_REMOVE_WHILE_FREEING each
   with a ->logical pointing to ebX->start. These are placed in an array
   named tm_list.
   Lets assume there are N elements (N pointers in eb X);

4) Then, still at tree_mod_log_insert_root(), we create a tree mod log
   element of operation type MOD_LOG_ROOT_REPLACE, ->logical set to
   ebY->start, ->old_root.logical set to ebX->start, ->old_root.level set
   to the level of eb X and ->generation set to the generation of eb X;

5) Then tree_mod_log_insert_root() calls tree_mod_log_free_eb() with
   tm_list as argument. After that, tree_mod_log_free_eb() calls
   __tree_mod_log_insert() for each member of tm_list in reverse order,
   from highest slot in eb X, slot N - 1, to slot 0 of eb X;

6) __tree_mod_log_insert() sets the sequence number of each given tree mod
   log operation - it increments fs_info->tree_mod_seq and sets
   fs_info->tree_mod_seq as the sequence number of the given tree mod log
   operation.

   This means that for the tm_list created at tree_mod_log_insert_root(),
   the element corresponding to slot 0 of eb X has the highest sequence
   number (1 + N), and the element corresponding to the last slot has the
   lowest sequence number (2);

7) Then, after inserting tm_list's elements into the tree mod log rbtree,
   the MOD_LOG_ROOT_REPLACE element is inserted, which gets the highest
   sequence number, which is N + 2;

8) Back to ctree.c:balance_level(), we free eb X by calling
   btrfs_free_tree_block() on it. Because eb X was created in the current
   transaction, has no other references and writeback did not happen for
   it, we add it back to the free space cache/tree;

9) Later some other task T allocates the metadata extent from eb X, since
   it is marked as free space in the space cache/tree, and uses it as a
   node for some other btree;

10) The tree mod log user task calls btrfs_search_old_slot(), which calls
    get_old_root(), and finally that calls __tree_mod_log_oldest_root()
    with time_seq == 1 and eb_root == eb Y;

11) First iteration of the while loop finds the tree mod log element with
    sequence number N + 2, for the logical address of eb Y and of type
    MOD_LOG_ROOT_REPLACE;

12) Because the operation type is MOD_LOG_ROOT_REPLACE, we don't break out
    of the loop, and set root_logical to point to tm->old_root.logical
    which corresponds to the logical address of eb X;

13) On the next iteration of the while loop, the call to
    tree_mod_log_search_oldest() returns the smallest tree mod log element
    for the logical address of eb X, which has a sequence number of 2, an
    operation type of MOD_LOG_KEY_REMOVE_WHILE_FREEING and corresponds to
    the old slot N - 1 of eb X (eb X had N items in it before being freed);

14) We then break out of the while loop and return the tree mod log operation
    of type MOD_LOG_ROOT_REPLACE (eb Y), and not the one for slot N - 1 of
    eb X, to get_old_root();

15) At get_old_root(), we process the MOD_LOG_ROOT_REPLACE operation
    and set "logical" to the logical address of eb X, which was the old
    root. We then call tree_mod_log_search() passing it the logical
    address of eb X and time_seq == 1;

16) Then before calling tree_mod_log_search(), task T adds a key to eb X,
    which results in adding a tree mod log operation of type
    MOD_LOG_KEY_ADD to the tree mod log - this is done at
    ctree.c:insert_ptr() - but after adding the tree mod log operation
    and before updating the number of items in eb X from 0 to 1...

17) The task at get_old_root() calls tree_mod_log_search() and gets the
    tree mod log operation of type MOD_LOG_KEY_ADD just added by task T.
    Then it enters the following if branch:

    if (old_root && tm && tm->op != MOD_LOG_KEY_REMOVE_WHILE_FREEING) {
       (...)
    } (...)

    Calls read_tree_block() for eb X, which gets a reference on eb X but
    does not lock it - task T has it locked.
    Then it clones eb X while it has nritems set to 0 in its header, before
    task T sets nritems to 1 in eb X's header. From hereupon we use the
    clone of eb X which no other task has access to;

18) Then we call __tree_mod_log_rewind(), passing it the MOD_LOG_KEY_ADD
    mod log operation we just got from tree_mod_log_search() in the
    previous step and the cloned version of eb X;

19) At __tree_mod_log_rewind(), we set the local variable "n" to the number
    of items set in eb X's clone, which is 0. Then we enter the while loop,
    and in its first iteration we process the MOD_LOG_KEY_ADD operation,
    which just decrements "n" from 0 to (u32)-1, since "n" is declared with
    a type of u32. At the end of this iteration we call rb_next() to find the
    next tree mod log operation for eb X, that gives us the mod log operation
    of type MOD_LOG_KEY_REMOVE_WHILE_FREEING, for slot 0, with a sequence
    number of N + 1 (steps 3 to 6);

20) Then we go back to the top of the while loop and trigger the following
    BUG_ON():

        (...)
        switch (tm->op) {
        case MOD_LOG_KEY_REMOVE_WHILE_FREEING:
                 BUG_ON(tm->slot < n);
                 fallthrough;
        (...)

    Because "n" has a value of (u32)-1 (4294967295) and tm->slot is 0.

Fix this by taking a read lock on the extent buffer before cloning it at
ctree.c:get_old_root(). This should be done regardless of the extent
buffer having been freed and reused, as a concurrent task might be
modifying it (while holding a write lock on it).
Reported-by: Zygo Blaxell <ce3g8jdj@umail.furryterror.org>
Link: https://lore.kernel.org/linux-btrfs/20210227155037.GN28049@hungrycats.org/
Fixes: 834328a8 ("Btrfs: tree mod log's old roots could still be part of the tree")
CC: stable@vger.kernel.org # 4.4+
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

The free space tree bitmap slab cache is created with SLAB_RED_ZONE but
that's a debugging flag and not always enabled. Also the other slabs are
created with at least SLAB_MEM_SPREAD that we want as well to average
the memory placement cost.
Reported-by: Vlastimil Babka <vbabka@suse.cz>
Fixes: 3acd4850 ("btrfs: fix allocation of free space cache v1 bitmap pages")
CC: stable@vger.kernel.org # 5.4+
Signed-off-by: David Sterba <dsterba@suse.com>

In readahead infrastructure, we are using a lot of hard coded PAGE_SHIFT
while we're not doing anything specific to PAGE_SIZE.

One of the most affected part is the radix tree operation of
btrfs_fs_info::reada_tree.

If using PAGE_SHIFT, subpage metadata readahead is broken and does no
help reading metadata ahead.

Fix the problem by using btrfs_fs_info::sectorsize_bits so that
readahead could work for subpage.
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

[BUG]
When running fstests for btrfs subpage read-write test, it has a very
high chance to crash at generic/475 with the following stack:

 BTRFS warning (device dm-8): direct IO failed ino 510 rw 1,34817 sector 0xcdf0 len 94208 err no 10
 Unable to handle kernel paging request at virtual address ffff80001157e7c0
 CPU: 2 PID: 687125 Comm: kworker/u12:4 Tainted: G        WC        5.12.0-rc2-custom+ #5
 Hardware name: Khadas VIM3 (DT)
 Workqueue: btrfs-endio-meta btrfs_work_helper [btrfs]
 pc : queued_spin_lock_slowpath+0x1a0/0x390
 lr : do_raw_spin_lock+0xc4/0x11c
 Call trace:
  queued_spin_lock_slowpath+0x1a0/0x390
  _raw_spin_lock+0x68/0x84
  btree_readahead_hook+0x38/0xc0 [btrfs]
  end_bio_extent_readpage+0x504/0x5f4 [btrfs]
  bio_endio+0x170/0x1a4
  end_workqueue_fn+0x3c/0x60 [btrfs]
  btrfs_work_helper+0x1b0/0x1b4 [btrfs]
  process_one_work+0x22c/0x430
  worker_thread+0x70/0x3a0
  kthread+0x13c/0x140
  ret_from_fork+0x10/0x30
 Code: 910020e0 8b0200c2 f861d884 aa0203e1 (f8246827)

[CAUSE]
In end_bio_extent_readpage(), if we hit an error during read, we will
handle the error differently for data and metadata.
For data we queue a repair, while for metadata, we record the error and
let the caller choose what to do.

But the code is still using page->private to grab extent buffer, which
no longer points to extent buffer for subpage metadata pages.

Thus this wild pointer access leads to above crash.

[FIX]
Introduce a helper, find_extent_buffer_readpage(), to grab extent
buffer.

The difference against find_extent_buffer_nospinlock() is:

- Also handles regular sectorsize == PAGE_SIZE case
- No extent buffer refs increase/decrease
  As extent buffer under IO must have non-zero refs, so this is safe
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

When using a zoned filesystem, while syncing the log, if we fail to
allocate the root node for the log root tree, we are not removing the
log context we allocated on stack from the list of log contexts of the
log root tree. This means after the return from btrfs_sync_log() we get
a corrupted linked list.

Fix this by allocating the node before adding our stack allocated context
to the list of log contexts of the log root tree.

Fixes: 3ddebf27 ("btrfs: zoned: reorder log node allocation on zoned filesystem")
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: Naohiro Aota <naohiro.aota@wdc.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

[BUG]
When running fsstress with only falloc workload, and a very low qgroup
limit set, we can get qgroup data rsv leak at unmount time.

 BTRFS warning (device dm-0): qgroup 0/5 has unreleased space, type 0 rsv 20480
 BTRFS error (device dm-0): qgroup reserved space leaked

The minimal reproducer looks like:

  #!/bin/bash
  dev=/dev/test/test
  mnt="/mnt/btrfs"
  fsstress=~/xfstests-dev/ltp/fsstress
  runtime=8

  workload()
  {
          umount $dev &> /dev/null
          umount $mnt &> /dev/null
          mkfs.btrfs -f $dev > /dev/null
          mount $dev $mnt

          btrfs quota en $mnt
          btrfs quota rescan -w $mnt
          btrfs qgroup limit 16m 0/5 $mnt

          $fsstress -w -z -f creat=10 -f fallocate=10 -p 2 -n 100 \
  		-d $mnt -v > /tmp/fsstress

          umount $mnt
          if dmesg | grep leak ; then
		echo "!!! FAILED !!!"
  		exit 1
          fi
  }

  for (( i=0; i < $runtime; i++)); do
          echo "=== $i/$runtime==="
          workload
  done

Normally it would fail before round 4.

[CAUSE]
In function insert_prealloc_file_extent(), we first call
btrfs_qgroup_release_data() to know how many bytes are reserved for
qgroup data rsv.

Then use that @qgroup_released number to continue our work.

But after we call btrfs_qgroup_release_data(), we should either queue
@qgroup_released to delayed ref or free them manually in error path.

Unfortunately, we lack the error handling to free the released bytes,
leaking qgroup data rsv.

All the error handling function outside won't help at all, as we have
released the range, meaning in inode io tree, the EXTENT_QGROUP_RESERVED
bit is already cleared, thus all btrfs_qgroup_free_data() call won't
free any data rsv.

[FIX]
Add free_qgroup tag to manually free the released qgroup data rsv.
Reported-by: Nikolay Borisov <nborisov@suse.com>
Reported-by: David Sterba <dsterba@suse.cz>
Fixes: 9729f10a ("btrfs: inode: move qgroup reserved space release to the callers of insert_reserved_file_extent()")
CC: stable@vger.kernel.org # 5.10+
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

There is a piece of weird code in insert_prealloc_file_extent(), which
looks like:

	ret = btrfs_qgroup_release_data(inode, file_offset, len);
	if (ret < 0)
		return ERR_PTR(ret);
	if (trans) {
		ret = insert_reserved_file_extent(trans, inode,
						  file_offset, &stack_fi,
						  true, ret);
	...
	}
	extent_info.is_new_extent = true;
	extent_info.qgroup_reserved = ret;
	...

Note how the variable @ret is abused here, and if anyone is adding code
just after btrfs_qgroup_release_data() call, it's super easy to
overwrite the @ret and cause tons of qgroup related bugs.

Fix such abuse by introducing new variable @qgroup_released, so that we
won't reuse the existing variable @ret.
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

[BUG]
The test generic/091 fails , with the following output:

  fsx -N 10000 -o 128000 -l 500000 -r PSIZE -t BSIZE -w BSIZE -Z -W
  mapped writes DISABLED
  Seed set to 1
  main: filesystem does not support fallocate mode FALLOC_FL_COLLAPSE_RANGE, disabling!
  main: filesystem does not support fallocate mode FALLOC_FL_INSERT_RANGE, disabling!
  skipping zero size read
  truncating to largest ever: 0xe400
  copying to largest ever: 0x1f400
  cloning to largest ever: 0x70000
  cloning to largest ever: 0x77000
  fallocating to largest ever: 0x7a120
  Mapped Read: non-zero data past EOF (0x3a7ff) page offset 0x800 is 0xf2e1 <<<
  ...

[CAUSE]
In commit c28ea613 ("btrfs: subpage: fix the false data csum mismatch error")
end_bio_extent_readpage() changes to only zero the range inside the bvec
for incoming subpage support.

But that commit is using incorrect offset to calculate the start.

For subpage, we can have a case that the whole bvec is beyond isize,
thus we need to calculate the correct offset.

But the offending commit is using @end (bvec end), other than @start
(bvec start) to calculate the start offset.

This means, we only zero the last byte of the bvec, not from the isize.
This stupid bug makes the range beyond isize is not properly zeroed, and
failed above test.

[FIX]
Use correct @start to calculate the range start.
Reported-by: kernel test robot <oliver.sang@intel.com>
Fixes: c28ea613 ("btrfs: subpage: fix the false data csum mismatch error")
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

We migrate zone unusable bytes to read-only bytes when a block group is
set to read-only, and account all the free region as bytes_readonly.
Thus, we should not increase block_group->zone_unusable when the block
group is read-only.

Fixes: 169e0da9 ("btrfs: zoned: track unusable bytes for zones")
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
Signed-off-by: David Sterba <dsterba@suse.com>

We need to use sector_t for zone_sectors, or it would set the zone size
to zero when the size >= 4GB (= 2^24 sectors) by shifting the
zone_sectors value by SECTOR_SHIFT. We're assuming zones sizes up to
8GiB.

Fixes: 5b316468 ("btrfs: get zone information of zoned block devices")
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

[BUG]
When running fstresss, we can hit strange data csum mismatch where the
on-disk data is in fact correct (passes scrub).

With some extra debug info added, we have the following traces:

  0482us: btrfs_do_readpage: root=5 ino=284 offset=393216, submit force=0 pgoff=0 iosize=8192
  0494us: btrfs_do_readpage: root=5 ino=284 offset=401408, submit force=0 pgoff=8192 iosize=4096
  0498us: btrfs_submit_data_bio: root=5 ino=284 bio first bvec=393216 len=8192
  0591us: btrfs_do_readpage: root=5 ino=284 offset=405504, submit force=0 pgoff=12288 iosize=36864
  0594us: btrfs_submit_data_bio: root=5 ino=284 bio first bvec=401408 len=4096
  0863us: btrfs_submit_data_bio: root=5 ino=284 bio first bvec=405504 len=36864
  0933us: btrfs_verify_data_csum: root=5 ino=284 offset=393216 len=8192
  0967us: btrfs_do_readpage: root=5 ino=284 offset=442368, skip beyond isize pgoff=49152 iosize=16384
  1047us: btrfs_verify_data_csum: root=5 ino=284 offset=401408 len=4096
  1163us: btrfs_verify_data_csum: root=5 ino=284 offset=405504 len=36864
  1290us: check_data_csum: !!! root=5 ino=284 offset=438272 pg_off=45056 !!!
  7387us: end_bio_extent_readpage: root=5 ino=284 before pending_read_bios=0

[CAUSE]
Normally we expect all submitted bio reads to only touch the range we
specified, and under subpage context, it means we should only touch the
range specified in each bvec.

But in data read path, inside end_bio_extent_readpage(), we have page
zeroing which only takes regular page size into consideration.

This means for subpage if we have an inode whose content looks like below:

  0       16K     32K     48K     64K
  |///////|       |///////|       |

  |//| = data needs to be read from disk
  |  | = hole

And i_size is 64K initially.

Then the following race can happen:

		T1		|		T2
--------------------------------+--------------------------------
btrfs_do_readpage()		|
|- isize = 64K;			|
|  At this time, the isize is 	|
|  64K				|
|				|
|- submit_extent_page()		|
|  submit previous assembled bio|
|  assemble bio for [0, 16K)	|
|				|
|- submit_extent_page()		|
   submit read bio for [0, 16K) |
   assemble read bio for	|
   [32K, 48K)			|
 				|
				| btrfs_setsize()
				| |- i_size_write(, 16K);
				|    Now i_size is only 16K
end_io() for [0K, 16K)		|
|- end_bio_extent_readpage()	|
   |- btrfs_verify_data_csum()  |
   |  No csum error		|
   |- i_size = 16K;		|
   |- zero_user_segment(16K,	|
      PAGE_SIZE);		|
      !!! We zeroed range	|
      !!! [32K, 48K)		|
				| end_io for [32K, 48K)
				| |- end_bio_extent_readpage()
				|    |- btrfs_verify_data_csum()
				|       ! CSUM MISMATCH !
				|       ! As the range is zeroed now !

[FIX]
To fix the problem, make end_bio_extent_readpage() to only zero the
range of bvec.

The bug only affects subpage read-write support, as for full read-only
mount we can't change i_size thus won't hit the race condition.
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

When we have smack enabled, during the creation of a directory smack may
attempt to add a "smack transmute" xattr on the inode, which results in
the following warning and trace:

  WARNING: CPU: 3 PID: 2548 at fs/btrfs/transaction.c:537 start_transaction+0x489/0x4f0
  Modules linked in: nft_objref nf_conntrack_netbios_ns (...)
  CPU: 3 PID: 2548 Comm: mkdir Not tainted 5.9.0-rc2smack+ #81
  Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.13.0-2.fc32 04/01/2014
  RIP: 0010:start_transaction+0x489/0x4f0
  Code: e9 be fc ff ff (...)
  RSP: 0018:ffffc90001887d10 EFLAGS: 00010202
  RAX: ffff88816f1e0000 RBX: 0000000000000201 RCX: 0000000000000003
  RDX: 0000000000000201 RSI: 0000000000000002 RDI: ffff888177849000
  RBP: ffff888177849000 R08: 0000000000000001 R09: 0000000000000004
  R10: ffffffff825e8f7a R11: 0000000000000003 R12: ffffffffffffffe2
  R13: 0000000000000000 R14: ffff88803d884270 R15: ffff8881680d8000
  FS:  00007f67317b8440(0000) GS:ffff88817bcc0000(0000) knlGS:0000000000000000
  CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
  CR2: 00007f67247a22a8 CR3: 000000004bfbc002 CR4: 0000000000370ee0
  DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
  DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
  Call Trace:
   ? slab_free_freelist_hook+0xea/0x1b0
   ? trace_hardirqs_on+0x1c/0xe0
   btrfs_setxattr_trans+0x3c/0xf0
   __vfs_setxattr+0x63/0x80
   smack_d_instantiate+0x2d3/0x360
   security_d_instantiate+0x29/0x40
   d_instantiate_new+0x38/0x90
   btrfs_mkdir+0x1cf/0x1e0
   vfs_mkdir+0x14f/0x200
   do_mkdirat+0x6d/0x110
   do_syscall_64+0x2d/0x40
   entry_SYSCALL_64_after_hwframe+0x44/0xa9
  RIP: 0033:0x7f673196ae6b
  Code: 8b 05 11 (...)
  RSP: 002b:00007ffc3c679b18 EFLAGS: 00000246 ORIG_RAX: 0000000000000053
  RAX: ffffffffffffffda RBX: 00000000000001ff RCX: 00007f673196ae6b
  RDX: 0000000000000000 RSI: 00000000000001ff RDI: 00007ffc3c67a30d
  RBP: 00007ffc3c67a30d R08: 00000000000001ff R09: 0000000000000000
  R10: 000055d3e39fe930 R11: 0000000000000246 R12: 0000000000000000
  R13: 00007ffc3c679cd8 R14: 00007ffc3c67a30d R15: 00007ffc3c679ce0
  irq event stamp: 11029
  hardirqs last  enabled at (11037): [<ffffffff81153fe6>] console_unlock+0x486/0x670
  hardirqs last disabled at (11044): [<ffffffff81153c01>] console_unlock+0xa1/0x670
  softirqs last  enabled at (8864): [<ffffffff81e0102f>] asm_call_on_stack+0xf/0x20
  softirqs last disabled at (8851): [<ffffffff81e0102f>] asm_call_on_stack+0xf/0x20

This happens because at btrfs_mkdir() we call d_instantiate_new() while
holding a transaction handle, which results in the following call chain:

  btrfs_mkdir()
     trans = btrfs_start_transaction(root, 5);

     d_instantiate_new()
        smack_d_instantiate()
            __vfs_setxattr()
                btrfs_setxattr_trans()
                   btrfs_start_transaction()
                      start_transaction()
                         WARN_ON()
                           --> a tansaction start has TRANS_EXTWRITERS
                               set in its type
                         h->orig_rsv = h->block_rsv
                         h->block_rsv = NULL

     btrfs_end_transaction(trans)

Besides the warning triggered at start_transaction, we set the handle's
block_rsv to NULL which may cause some surprises later on.

So fix this by making btrfs_setxattr_trans() not start a transaction when
we already have a handle on one, stored in current->journal_info, and use
that handle. We are good to use the handle because at btrfs_mkdir() we did
reserve space for the xattr and the inode item.
Reported-by: Casey Schaufler <casey@schaufler-ca.com>
CC: stable@vger.kernel.org # 5.4+
Acked-by: Casey Schaufler <casey@schaufler-ca.com>
Tested-by: Casey Schaufler <casey@schaufler-ca.com>
Link: https://lore.kernel.org/linux-btrfs/434d856f-bd7b-4889-a6ec-e81aaebfa735@schaufler-ca.com/Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

Calling btrfs_qgroup_reserve_meta_prealloc from
btrfs_delayed_inode_reserve_metadata can result in flushing delalloc
while holding a transaction and delayed node locks. This is deadlock
prone. In the past multiple commits:

 * ae5e070e ("btrfs: qgroup: don't try to wait flushing if we're
already holding a transaction")

 * 6f23277a ("btrfs: qgroup: don't commit transaction when we already
 hold the handle")

Tried to solve various aspects of this but this was always a
whack-a-mole game. Unfortunately those 2 fixes don't solve a deadlock
scenario involving btrfs_delayed_node::mutex. Namely, one thread
can call btrfs_dirty_inode as a result of reading a file and modifying
its atime:

  PID: 6963   TASK: ffff8c7f3f94c000  CPU: 2   COMMAND: "test"
  #0  __schedule at ffffffffa529e07d
  #1  schedule at ffffffffa529e4ff
  #2  schedule_timeout at ffffffffa52a1bdd
  #3  wait_for_completion at ffffffffa529eeea             <-- sleeps with delayed node mutex held
  #4  start_delalloc_inodes at ffffffffc0380db5
  #5  btrfs_start_delalloc_snapshot at ffffffffc0393836
  #6  try_flush_qgroup at ffffffffc03f04b2
  #7  __btrfs_qgroup_reserve_meta at ffffffffc03f5bb6     <-- tries to reserve space and starts delalloc inodes.
  #8  btrfs_delayed_update_inode at ffffffffc03e31aa      <-- acquires delayed node mutex
  #9  btrfs_update_inode at ffffffffc0385ba8
 #10  btrfs_dirty_inode at ffffffffc038627b               <-- TRANSACTIION OPENED
 #11  touch_atime at ffffffffa4cf0000
 #12  generic_file_read_iter at ffffffffa4c1f123
 #13  new_sync_read at ffffffffa4ccdc8a
 #14  vfs_read at ffffffffa4cd0849
 #15  ksys_read at ffffffffa4cd0bd1
 #16  do_syscall_64 at ffffffffa4a052eb
 #17  entry_SYSCALL_64_after_hwframe at ffffffffa540008c

This will cause an asynchronous work to flush the delalloc inodes to
happen which can try to acquire the same delayed_node mutex:

  PID: 455    TASK: ffff8c8085fa4000  CPU: 5   COMMAND: "kworker/u16:30"
  #0  __schedule at ffffffffa529e07d
  #1  schedule at ffffffffa529e4ff
  #2  schedule_preempt_disabled at ffffffffa529e80a
  #3  __mutex_lock at ffffffffa529fdcb                    <-- goes to sleep, never wakes up.
  #4  btrfs_delayed_update_inode at ffffffffc03e3143      <-- tries to acquire the mutex
  #5  btrfs_update_inode at ffffffffc0385ba8              <-- this is the same inode that pid 6963 is holding
  #6  cow_file_range_inline.constprop.78 at ffffffffc0386be7
  #7  cow_file_range at ffffffffc03879c1
  #8  btrfs_run_delalloc_range at ffffffffc038894c
  #9  writepage_delalloc at ffffffffc03a3c8f
 #10  __extent_writepage at ffffffffc03a4c01
 #11  extent_write_cache_pages at ffffffffc03a500b
 #12  extent_writepages at ffffffffc03a6de2
 #13  do_writepages at ffffffffa4c277eb
 #14  __filemap_fdatawrite_range at ffffffffa4c1e5bb
 #15  btrfs_run_delalloc_work at ffffffffc0380987         <-- starts running delayed nodes
 #16  normal_work_helper at ffffffffc03b706c
 #17  process_one_work at ffffffffa4aba4e4
 #18  worker_thread at ffffffffa4aba6fd
 #19  kthread at ffffffffa4ac0a3d
 #20  ret_from_fork at ffffffffa54001ff

To fully address those cases the complete fix is to never issue any
flushing while holding the transaction or the delayed node lock. This
patch achieves it by calling qgroup_reserve_meta directly which will
either succeed without flushing or will fail and return -EDQUOT. In the
latter case that return value is going to be propagated to
btrfs_dirty_inode which will fallback to start a new transaction. That's
fine as the majority of time we expect the inode will have
BTRFS_DELAYED_NODE_INODE_DIRTY flag set which will result in directly
copying the in-memory state.

Fixes: c53e9653 ("btrfs: qgroup: try to flush qgroup space when we get -EDQUOT")
CC: stable@vger.kernel.org # 5.10+
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

Following commit f218ea6c ("btrfs: delayed-inode: Remove wrong
qgroup meta reservation calls") this function now reserves num_bytes,
rather than the fixed amount of nodesize. As such this requires the
same amount to be freed in case of failure. Fix this by adjusting
the amount we are freeing.

Fixes: f218ea6c ("btrfs: delayed-inode: Remove wrong qgroup meta reservation calls")
CC: stable@vger.kernel.org # 4.19+
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

The intended logic of the check is to catch cases where the desired
free_space_tree setting doesn't match the mounted setting, and the
remount is anything but ro->rw. However, it makes the mistake of
checking equality on a masked integer (btrfs_test_opt) against a boolean
(btrfs_fs_compat_ro).

If you run the reproducer:
  $ mount -o space_cache=v2 dev mnt
  $ mount -o remount,ro mnt

you would expect no warning, because the remount is not attempting to
change the free space tree setting, but we do see the warning.

To fix this, add explicit bool type casts to the condition.

I tested a variety of transitions:
sudo mount -o space_cache=v2 /dev/vg0/lv0 mnt/lol
(fst enabled)
mount -o remount,ro mnt/lol
(no warning, no fst change)
sudo mount -o remount,rw,space_cache=v1,clear_cache
(no warning, ro->rw)
sudo mount -o remount,rw,space_cache=v2 mnt
(warning, rw->rw with change)
sudo mount -o remount,ro mnt
(no warning, no fst change)
sudo mount -o remount,rw,space_cache=v2 mnt
(no warning, no fst change)
Reported-by: Chris Murphy <lists@colorremedies.com>
CC: stable@vger.kernel.org # 5.11
Signed-off-by: Boris Burkov <boris@bur.io>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

The problem is we're copying "inherit" from user space but we don't
necessarily know that we're copying enough data for a 64 byte
struct.  Then the next problem is that 'inherit' has a variable size
array at the end, and we have to verify that array is the size we
expected.

Fixes: 6f72c7e2 ("Btrfs: add qgroup inheritance")
CC: stable@vger.kernel.org # 4.4+
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

If btrfs_qgroup_reserve_data returns an error (i.e quota limit reached)
the handling logic directly goes to the 'out' label without first
unlocking the extent range between lockstart, lockend. This results in
deadlocks as other processes try to lock the same extent.

Fixes: a7f8b1c2 ("btrfs: file: reserve qgroup space after the hole punch range is locked")
CC: stable@vger.kernel.org # 5.10+
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

Fix build warnings of function signature when CONFIG_STACKTRACE is not
enabled by reordering the 'inline' and 'void' keywords.

../fs/btrfs/ref-verify.c:221:1: warning: ‘inline’ is not at beginning of declaration [-Wold-style-declaration]
 static void inline __save_stack_trace(struct ref_action *ra)
../fs/btrfs/ref-verify.c:225:1: warning: ‘inline’ is not at beginning of declaration [-Wold-style-declaration]
 static void inline __print_stack_trace(struct btrfs_fs_info *fs_info,
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

Lockdep with fstests test case btrfs/041 detected a unsafe locking
scenario when we allocate the log node on a zoned filesystem.

btrfs/041
 ============================================
 WARNING: possible recursive locking detected
 5.11.0-rc7+ #939 Not tainted
 --------------------------------------------
 xfs_io/698 is trying to acquire lock:
 ffff88810cd673a0 (&root->log_mutex){+.+.}-{3:3}, at: btrfs_sync_log+0x3d1/0xee0 [btrfs]

 but task is already holding lock:
 ffff88810b0fc3a0 (&root->log_mutex){+.+.}-{3:3}, at: btrfs_sync_log+0x313/0xee0 [btrfs]

 other info that might help us debug this:
  Possible unsafe locking scenario:

        CPU0
        ----
   lock(&root->log_mutex);
   lock(&root->log_mutex);

  *** DEADLOCK ***

  May be due to missing lock nesting notation

 2 locks held by xfs_io/698:
  #0: ffff88810cd66620 (sb_internal){.+.+}-{0:0}, at: btrfs_sync_file+0x2c3/0x570 [btrfs]
  #1: ffff88810b0fc3a0 (&root->log_mutex){+.+.}-{3:3}, at: btrfs_sync_log+0x313/0xee0 [btrfs]

 stack backtrace:
 CPU: 0 PID: 698 Comm: xfs_io Not tainted 5.11.0-rc7+ #939
 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.13.0-0-gf21b5a4-rebuilt.opensuse.org 04/01/2014
 Call Trace:
  dump_stack+0x77/0x97
  __lock_acquire.cold+0xb9/0x32a
  lock_acquire+0xb5/0x400
  ? btrfs_sync_log+0x3d1/0xee0 [btrfs]
  __mutex_lock+0x7b/0x8d0
  ? btrfs_sync_log+0x3d1/0xee0 [btrfs]
  ? btrfs_sync_log+0x3d1/0xee0 [btrfs]
  ? find_first_extent_bit+0x9f/0x100 [btrfs]
  ? __mutex_unlock_slowpath+0x35/0x270
  btrfs_sync_log+0x3d1/0xee0 [btrfs]
  btrfs_sync_file+0x3a8/0x570 [btrfs]
  __x64_sys_fsync+0x34/0x60
  do_syscall_64+0x33/0x40
  entry_SYSCALL_64_after_hwframe+0x44/0xa9

This happens, because we are taking the ->log_mutex albeit it has already
been locked.

Also while at it, fix the bogus unlock of the tree_log_mutex in the error
handling.

Fixes: 3ddebf27 ("btrfs: zoned: reorder log node allocation on zoned filesystem")
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

It's wrong calling btrfs_put_block_group in
__btrfs_return_cluster_to_free_space if the block group passed is
different than the block group the cluster represents. As this means the
cluster doesn't have a reference to the passed block group. This results
in double put and a use-after-free bug.

Fix this by simply bailing if the block group we passed in does not
match the block group on the cluster.

Fixes: fa9c0d79 ("Btrfs: rework allocation clustering")
CC: stable@vger.kernel.org # 4.4+
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
[ update changelog ]
Signed-off-by: David Sterba <dsterba@suse.com>

When using the NO_HOLES feature, if we clone a file range that spans only
a hole into a range that is at or beyond the current i_size of the
destination file, we end up not setting the full sync runtime flag on the
inode. As a result, if we then fsync the destination file and have a power
failure, after log replay we can end up exposing stale data instead of
having a hole for that range.

The conditions for this to happen are the following:

1) We have a file with a size of, for example, 1280K;

2) There is a written (non-prealloc) extent for the file range from 1024K
   to 1280K with a length of 256K;

3) This particular file extent layout is durably persisted, so that the
   existing superblock persisted on disk points to a subvolume root where
   the file has that exact file extent layout and state;

4) The file is truncated to a smaller size, to an offset lower than the
   start offset of its last extent, for example to 800K. The truncate sets
   the full sync runtime flag on the inode;

6) Fsync the file to log it and clear the full sync runtime flag;

7) Clone a region that covers only a hole (implicit hole due to NO_HOLES)
   into the file with a destination offset that starts at or beyond the
   256K file extent item we had - for example to offset 1024K;

8) Since the clone operation does not find extents in the source range,
   we end up in the if branch at the bottom of btrfs_clone() where we
   punch a hole for the file range starting at offset 1024K by calling
   btrfs_replace_file_extents(). There we end up not setting the full
   sync flag on the inode, because we don't know we are being called in
   a clone context (and not fallocate's punch hole operation), and
   neither do we create an extent map to represent a hole because the
   requested range is beyond eof;

9) A further fsync to the file will be a fast fsync, since the clone
   operation did not set the full sync flag, and therefore it relies on
   modified extent maps to correctly log the file layout. But since
   it does not find any extent map marking the range from 1024K (the
   previous eof) to the new eof, it does not log a file extent item
   for that range representing the hole;

10) After a power failure no hole for the range starting at 1024K is
   punched and we end up exposing stale data from the old 256K extent.

Turning this into exact steps:

  $ mkfs.btrfs -f -O no-holes /dev/sdi
  $ mount /dev/sdi /mnt

  # Create our test file with 3 extents of 256K and a 256K hole at offset
  # 256K. The file has a size of 1280K.
  $ xfs_io -f -s \
              -c "pwrite -S 0xab -b 256K 0 256K" \
              -c "pwrite -S 0xcd -b 256K 512K 256K" \
              -c "pwrite -S 0xef -b 256K 768K 256K" \
              -c "pwrite -S 0x73 -b 256K 1024K 256K" \
              /mnt/sdi/foobar

  # Make sure it's durably persisted. We want the last committed super
  # block to point to this particular file extent layout.
  sync

  # Now truncate our file to a smaller size, falling within a position of
  # the second extent. This sets the full sync runtime flag on the inode.
  # Then fsync the file to log it and clear the full sync flag from the
  # inode. The third extent is no longer part of the file and therefore
  # it is not logged.
  $ xfs_io -c "truncate 800K" -c "fsync" /mnt/foobar

  # Now do a clone operation that only clones the hole and sets back the
  # file size to match the size it had before the truncate operation
  # (1280K).
  $ xfs_io \
        -c "reflink /mnt/foobar 256K 1024K 256K" \
        -c "fsync" \
        /mnt/foobar

  # File data before power failure:
  $ od -A d -t x1 /mnt/foobar
  0000000 ab ab ab ab ab ab ab ab ab ab ab ab ab ab ab ab
  *
  0262144 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  *
  0524288 cd cd cd cd cd cd cd cd cd cd cd cd cd cd cd cd
  *
  0786432 ef ef ef ef ef ef ef ef ef ef ef ef ef ef ef ef
  *
  0819200 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  *
  1310720

  <power fail>

  # Mount the fs again to replay the log tree.
  $ mount /dev/sdi /mnt

  # File data after power failure:
  $ od -A d -t x1 /mnt/foobar
  0000000 ab ab ab ab ab ab ab ab ab ab ab ab ab ab ab ab
  *
  0262144 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  *
  0524288 cd cd cd cd cd cd cd cd cd cd cd cd cd cd cd cd
  *
  0786432 ef ef ef ef ef ef ef ef ef ef ef ef ef ef ef ef
  *
  0819200 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  *
  1048576 73 73 73 73 73 73 73 73 73 73 73 73 73 73 73 73
  *
  1310720

The range from 1024K to 1280K should correspond to a hole but instead it
points to stale data, to the 256K extent that should not exist after the
truncate operation.

The issue does not exists when not using NO_HOLES, because for that case
we use file extent items to represent holes, these are found and copied
during the loop that iterates over extents at btrfs_clone(), and that
causes btrfs_replace_file_extents() to be called with a non-NULL
extent_info argument and therefore set the full sync runtime flag on the
inode.

So fix this by making the code that deals with a trailing hole during
cloning, at btrfs_clone(), to set the full sync flag on the inode, if the
range starts at or beyond the current i_size.

A test case for fstests will follow soon.

Backporting notes: for kernel 5.4 the change goes to ioctl.c into
btrfs_clone before the last call to btrfs_punch_hole_range.

CC: stable@vger.kernel.org # 5.4+
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

The tree checker checks the extent ref hash at read and write time to
make sure we do not corrupt the file system.  Generally extent
references go inline, but if we have enough of them we need to make an
item, which looks like

key.objectid	= <bytenr>
key.type	= <BTRFS_EXTENT_DATA_REF_KEY|BTRFS_TREE_BLOCK_REF_KEY>
key.offset	= hash(tree, owner, offset)

However if key.offset collide with an unrelated extent reference we'll
simply key.offset++ until we get something that doesn't collide.
Obviously this doesn't match at tree checker time, and thus we error
while writing out the transaction.  This is relatively easy to
reproduce, simply do something like the following

  xfs_io -f -c "pwrite 0 1M" file
  offset=2

  for i in {0..10000}
  do
	  xfs_io -c "reflink file 0 ${offset}M 1M" file
	  offset=$(( offset + 2 ))
  done

  xfs_io -c "reflink file 0 17999258914816 1M" file
  xfs_io -c "reflink file 0 35998517829632 1M" file
  xfs_io -c "reflink file 0 53752752058368 1M" file

  btrfs filesystem sync

And the sync will error out because we'll abort the transaction.  The
magic values above are used because they generate hash collisions with
the first file in the main subvol.

The fix for this is to remove the hash value check from tree checker, as
we have no idea which offset ours should belong to.
Reported-by: Tuomas Lähdekorpi <tuomas.lahdekorpi@gmail.com>
Fixes: 0785a9aa ("btrfs: tree-checker: Add EXTENT_DATA_REF check")
CC: stable@vger.kernel.org # 5.4+
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
[ add comment]
Signed-off-by: David Sterba <dsterba@suse.com>

When creating a snapshot we check if the current number of swap files, in
the root, is non-zero, and if it is, we error out and warn that we can not
create the snapshot because there are active swap files.

However this is racy because when a task started activation of a swap
file, another task might have started already snapshot creation and might
have seen the counter for the number of swap files as zero. This means
that after the swap file is activated we may end up with a snapshot of the
same root successfully created, and therefore when the first write to the
swap file happens it has to fall back into COW mode, which should never
happen for active swap files.

Basically what can happen is:

1) Task A starts snapshot creation and enters ioctl.c:create_snapshot().
   There it sees that root->nr_swapfiles has a value of 0 so it continues;

2) Task B enters btrfs_swap_activate(). It is not aware that another task
   started snapshot creation but it did not finish yet. It increments
   root->nr_swapfiles from 0 to 1;

3) Task B checks that the file meets all requirements to be an active
   swap file - it has NOCOW set, there are no snapshots for the inode's
   root at the moment, no file holes, no reflinked extents, etc;

4) Task B returns success and now the file is an active swap file;

5) Task A commits the transaction to create the snapshot and finishes.
   The swap file's extents are now shared between the original root and
   the snapshot;

6) A write into an extent of the swap file is attempted - there is a
   snapshot of the file's root, so we fall back to COW mode and therefore
   the physical location of the extent changes on disk.

So fix this by taking the snapshot lock during swap file activation before
locking the extent range, as that is the order in which we lock these
during buffered writes.

Fixes: ed46ff3d ("Btrfs: support swap files")
CC: stable@vger.kernel.org # 5.4+
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

When we active a swap file, at btrfs_swap_activate(), we acquire the
exclusive operation lock to prevent the physical location of the swap
file extents to be changed by operations such as balance and device
replace/resize/remove. We also call there can_nocow_extent() which,
among other things, checks if the block group of a swap file extent is
currently RO, and if it is we can not use the extent, since a write
into it would result in COWing the extent.

However we have no protection against a scrub operation running after we
activate the swap file, which can result in the swap file extents to be
COWed while the scrub is running and operating on the respective block
group, because scrub turns a block group into RO before it processes it
and then back again to RW mode after processing it. That means an attempt
to write into a swap file extent while scrub is processing the respective
block group, will result in COWing the extent, changing its physical
location on disk.

Fix this by making sure that block groups that have extents that are used
by active swap files can not be turned into RO mode, therefore making it
not possible for a scrub to turn them into RO mode. When a scrub finds a
block group that can not be turned to RO due to the existence of extents
used by swap files, it proceeds to the next block group and logs a warning
message that mentions the block group was skipped due to active swap
files - this is the same approach we currently use for balance.

Fixes: ed46ff3d ("Btrfs: support swap files")
CC: stable@vger.kernel.org # 5.4+
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

During the nocow writeback path, we currently iterate the rbtree of block
groups twice: once for checking if the target block group is RO with the
call to btrfs_extent_readonly()), and once again for getting a nocow
reference on the block group with a call to btrfs_inc_nocow_writers().

Since btrfs_inc_nocow_writers() already returns false when the target
block group is RO, remove the call to btrfs_extent_readonly(). Not only
we avoid searching the blocks group rbtree twice, it also helps reduce
contention on the lock that protects it (specially since it is a spin
lock and not a read-write lock). That may make a noticeable difference
on very large filesystems, with thousands of allocated block groups.
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

During allocation the allocator will try to allocate an extent using
cluster policy. Once the current cluster is exhausted it will remove the
entry under btrfs_free_cluster::lock and subsequently acquire
btrfs_free_space_ctl::tree_lock to dispose of the already-deleted entry
and adjust btrfs_free_space_ctl::total_bitmap. This poses a problem
because there exists a race condition between removing the entry under
one lock and doing the necessary accounting holding a different lock
since extent freeing only uses the 2nd lock. This can result in the
following situation:

T1:                                    T2:
btrfs_alloc_from_cluster               insert_into_bitmap <holds tree_lock>
 if (entry->bytes == 0)                   if (block_group && !list_empty(&block_group->cluster_list)) {
    rb_erase(entry)

 spin_unlock(&cluster->lock);
   (total_bitmaps is still 4)           spin_lock(&cluster->lock);
                                         <doesn't find entry in cluster->root>
 spin_lock(&ctl->tree_lock);             <goes to new_bitmap label, adds
<blocked since T2 holds tree_lock>       <a new entry and calls add_new_bitmap>
					    recalculate_thresholds  <crashes,
                                              due to total_bitmaps
					      becoming 5 and triggering
					      an ASSERT>

To fix this ensure that once depleted, the cluster entry is deleted when
both cluster lock and tree locks are held in the allocator (T1), this
ensures that even if there is a race with a concurrent
insert_into_bitmap call it will correctly find the entry in the cluster
and add the new space to it.

CC: <stable@vger.kernel.org> # 4.4+
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

Currently check_compressed_csum() completely relies on sectorsize ==
PAGE_SIZE to do checksum verification for compressed extents.

To make it subpage compatible, this patch will:
- Do extra calculation for the csum range
  Since we have multiple sectors inside a page, we need to only hash
  the range we want, not the full page anymore.

- Do sector-by-sector hash inside the page

With this patch and previous conversion on
btrfs_submit_compressed_read(), now we can read subpage compressed
extents properly, and do proper csum verification.
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

For compressed read, we always submit page read using page size.  This
doesn't work well with subpage, as for subpage one page can contain
several sectors.  Such submission will read range out of what we want,
and cause problems.

Thankfully to make it subpage compatible, we only need to change how the
last page of the compressed extent is read.

Instead of always adding a full page to the compressed read bio, if we're
at the last page, calculate the size using compressed length, so that we
only add part of the range into the compressed read bio.

Since we are here, also change the PAGE_SIZE used in
lookup_extent_mapping() to sectorsize.
This modification won't cause any functional change, as
lookup_extent_mapping() can handle the case where the search range is
larger than found extent range.
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

When a qstripe is required an extra page is allocated and mapped.  There
were 3 problems:

1) There is no corresponding call of kunmap() for the qstripe page.
2) There is no reason to map the qstripe page more than once if the
   number of bits set in rbio->dbitmap is greater than one.
3) There is no reason to map the parity page and unmap it each time
   through the loop.

The page memory can continue to be reused with a single mapping on each
iteration by raid6_call.gen_syndrome() without remapping.  So map the
page for the duration of the loop.

Similarly, improve the algorithm by mapping the parity page just 1 time.

Fixes: 5a6ac9ea ("Btrfs, raid56: support parity scrub on raid56")
CC: stable@vger.kernel.org # 4.4.x: c17af965: btrfs: raid56: simplify tracking of Q stripe presence
CC: stable@vger.kernel.org # 4.4.x
Signed-off-by: Ira Weiny <ira.weiny@intel.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

This final patch adds the ZONED incompat flag to the supported flags
and enables to mount ZONED flagged file system.
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

Since the zoned filesystem requires sequential write out of metadata, we
cannot proceed with a hole in tree-log pages. When such a hole exists,
btree_write_cache_pages() will return -EAGAIN. This happens when someone,
e.g., a concurrent transaction commit, writes a dirty extent in this
tree-log commit.

If we are not going to wait for the extents, we can hope the concurrent
writing fills the hole for us. So, we can ignore the error in this case and
hope the next write will succeed.

If we want to wait for them and got the error, we cannot wait for them
because it will cause a deadlock. So, let's bail out to a full commit in
this case.
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
Signed-off-by: David Sterba <dsterba@suse.com>

This is the 3/3 patch to enable tree-log on zoned filesystems.

The allocation order of nodes of "fs_info->log_root_tree" and nodes of
"root->log_root" is not the same as the writing order of them. So, the
writing causes unaligned write errors.

Reorder the allocation of them by delaying allocation of the root node of
"fs_info->log_root_tree," so that the node buffers can go out sequentially
to devices.

Cc: Filipe Manana <fdmanana@gmail.com>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
Signed-off-by: David Sterba <dsterba@suse.com>

This is the 2/3 patch to enable tree-log on zoned filesystems.

Since we can start more than one log transactions per subvolume
simultaneously, nodes from multiple transactions can be allocated
interleaved. Such mixed allocation results in non-sequential writes at
the time of a log transaction commit. The nodes of the global log root
tree (fs_info->log_root_tree), also have the same problem with mixed
allocation.

Serializes log transactions by waiting for a committing transaction when
someone tries to start a new transaction, to avoid the mixed allocation
problem. We must also wait for running log transactions from another
subvolume, but there is no easy way to detect which subvolume root is
running a log transaction. So, this patch forbids starting a new log
transaction when other subvolumes already allocated the global log root
tree.
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
Signed-off-by: David Sterba <dsterba@suse.com>

This is the 1/3 patch to enable tree log on zoned filesystems.

The tree-log feature does not work on a zoned filesystem as is. Blocks for
a tree-log tree are allocated mixed with other metadata blocks and btrfs
writes and syncs the tree-log blocks to devices at the time of fsync(),
which has a different timing than a global transaction commit. As a
result, both writing tree-log blocks and writing other metadata blocks
become non-sequential writes that zoned filesystems must avoid.

Introduce a dedicated block group for tree-log blocks, so that tree-log
blocks and other metadata blocks can be separate write streams.  As a
result, each write stream can now be written to devices separately.
"fs_info->treelog_bg" tracks the dedicated block group and assigns
"treelog_bg" on-demand on tree-log block allocation time.

This commit extends the zoned block allocator to use the block group.
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
Signed-off-by: David Sterba <dsterba@suse.com>

This is a preparation patch for the next patch. Split alloc_log_tree()
into two parts. The first one allocating the tree structure, remains in
alloc_log_tree() and the second part allocating the tree node, which is
moved into btrfs_alloc_log_tree_node().

Also export the latter part is to be used in the next patch.
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

When a bad checksum is found and if the filesystem has a mirror of the
damaged data, we read the correct data from the mirror and writes it to
damaged blocks. This however, violates the sequential write constraints
of a zoned block device.

We can consider three methods to repair an IO failure in zoned filesystems:

(1) Reset and rewrite the damaged zone
(2) Allocate new device extent and replace the damaged device extent to
    the new extent
(3) Relocate the corresponding block group

Method (1) is most similar to a behavior done with regular devices.
However, it also wipes non-damaged data in the same device extent, and
so it unnecessary degrades non-damaged data.

Method (2) is much like device replacing but done in the same device. It
is safe because it keeps the device extent until the replacing finish.
However, extending device replacing is non-trivial. It assumes
"src_dev->physical == dst_dev->physical". Also, the extent mapping
replacing function should be extended to support replacing device extent
position in one device.

Method (3) invokes relocation of the damaged block group and is
straightforward to implement. It relocates all the mirrored device
extents, so it potentially is a more costly operation than method (1) or
(2). But it relocates only used extents which reduce the total IO size.

Let's apply method (3) for now. In the future, we can extend device-replace
and apply method (2).

For protecting a block group gets relocated multiple time with multiple
IO errors, this commit introduces "relocating_repair" bit to show it's
now relocating to repair IO failures. Also it uses a new kthread
"btrfs-relocating-repair", not to block IO path with relocating process.

This commit also supports repairing in the scrub process.
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
Signed-off-by: David Sterba <dsterba@suse.com>

Currently fallocate() is disabled on a zoned filesystem. Since current
relocation process relies on preallocation to move file data extents, it
must be handled differently.

On a zoned filesystem, we just truncate the inode to the size that we
wanted to pre-allocate. Then, we flush dirty pages on the file before
finishing the relocation process. run_delalloc_zoned() will handle all
the allocations and submit IOs to the underlying layers.
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
Signed-off-by: David Sterba <dsterba@suse.com>

This is 4/4 patch to implement device-replace on zoned filesystems.

Even after the copying is done, the write pointers of the source device
and the destination device may not be synchronized. For example, when
the last allocated extent is freed before device-replace process, the
extent is not copied, leaving a hole there.

Synchronize the write pointers by writing zeroes to the destination
device.
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
Signed-off-by: David Sterba <dsterba@suse.com>

This is 3/4 patch to implement device-replace on zoned filesystems.

This commit implements copying. To do this, it tracks the write pointer
during the device replace process. As device-replace's copy process is
smart enough to only copy used extents on the source device, we have to
fill the gap to honor the sequential write requirement in the target
device.

The device-replace process on zoned filesystems must copy or clone all
the extents in the source device exactly once. So, we need to ensure
allocations started just before the dev-replace process to have their
corresponding extent information in the B-trees.
finish_extent_writes_for_zoned() implements that functionality, which
basically is the removed code in the commit 042528f8 ("Btrfs: fix
block group remaining RO forever after error during device replace").
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
Signed-off-by: David Sterba <dsterba@suse.com>