btrfs: track reloc roots based on their commit root bytenr

We always search the commit root of the extent tree for looking up back
references, however we track the reloc roots based on their current

btrfs: track reloc roots based on their commit root bytenr

We always search the commit root of the extent tree for looking up back
references, however we track the reloc roots based on their current
bytenr.

This is wrong, if we commit the transaction between relocating tree
blocks we could end up in this code in build_backref_tree

if (key.objectid == key.offset) {
/*
* Only root blocks of reloc trees use backref
* pointing to itself.
*/
root = find_reloc_root(rc, cur->bytenr);
ASSERT(root);
cur->root = root;
break;
}

find_reloc_root() is looking based on the bytenr we had in the commit
root, but if we've COWed this reloc root we will not find that bytenr,
and we will trip over the ASSERT(root).

Fix this by using the commit_root->start bytenr for indexing the commit
root. Then we change the __update_reloc_root() caller to be used when
we switch the commit root for the reloc root during commit.

This fixes the panic I was seeing when we started throttling relocation
for delayed refs.

Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: David Sterba <dsterba@suse.com>

show more ...

btrfs: restart relocate_tree_blocks properly

There are two bugs here, but fixing them independently would just result
in pain if you happened to bisect between the two patches.

First is how we hand

btrfs: restart relocate_tree_blocks properly

There are two bugs here, but fixing them independently would just result
in pain if you happened to bisect between the two patches.

First is how we handle the -EAGAIN from relocate_tree_block(). We don't
set error, unless we happen to be the first node, which makes no sense,
I have no idea what the code was trying to accomplish here.

We in fact _do_ want err set here so that we know we need to restart in
relocate_block_group(). Also we need finish_pending_nodes() to not
actually call link_to_upper(), because we didn't actually relocate the
block.

And then if we do get -EAGAIN we do not want to set our backref cache
last_trans to the one before ours. This would force us to update our
backref cache if we didn't cross transaction ids, which would mean we'd
have some nodes updated to their new_bytenr, but still able to find
their old bytenr because we're searching the same commit root as the
last time we went through relocate_tree_blocks.

Fixing these two things keeps us from panicing when we start breaking
out of relocate_tree_blocks() either for delayed ref flushing or enospc.

Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: David Sterba <dsterba@suse.com>

show more ...

btrfs: reloc: reorder reservation before root selection

Since we're not only checking for metadata reservations but also if we
need to throttle our delayed ref generation, reorder
reserve_metadata_s

btrfs: reloc: reorder reservation before root selection

Since we're not only checking for metadata reservations but also if we
need to throttle our delayed ref generation, reorder
reserve_metadata_space() above the select_one_root() call in
relocate_tree_block().

The reason we want this is because select_reloc_root() will mess with
the backref cache, and if we're going to bail we want to be able to
cleanly remove this node from the backref cache and come back along to
regenerate it. Move it up so this is the first thing we do to make
restarting cleaner.

Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

show more ...

btrfs: do not readahead in build_backref_tree

Here we are just searching down to the bytenr we're building the backref
tree for, and all of it's paths to the roots. These bytenrs are not
guaranteed

btrfs: do not readahead in build_backref_tree

Here we are just searching down to the bytenr we're building the backref
tree for, and all of it's paths to the roots. These bytenrs are not
guaranteed to be anywhere near each other, so readahead just generates
extra latency.

Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

show more ...

btrfs: move the root freeing stuff into btrfs_put_root

There are a few different ways to free roots, either you allocated them
yourself and you just do

free_extent_buffer(root->node);
free_extent_b

btrfs: move the root freeing stuff into btrfs_put_root

There are a few different ways to free roots, either you allocated them
yourself and you just do

free_extent_buffer(root->node);
free_extent_buffer(root->commit_node);
btrfs_put_root(root);

Which is the pattern for log roots. Or for snapshots/subvolumes that
are being dropped you simply call btrfs_free_fs_root() which does all
the cleanup for you.

Unify this all into btrfs_put_root(), so that we don't free up things
associated with the root until the last reference is dropped. This
makes the root freeing code much more significant.

The only caveat is at close_ctree() time we have to free the extent
buffers for all of our main roots (extent_root, chunk_root, etc) because
we have to drop the btree_inode and we'll run into issues if we hold
onto those nodes until ->kill_sb() time. This will be addressed in the
future when we kill the btree_inode.

Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

show more ...

btrfs: remove a BUG_ON() from merge_reloc_roots()

This was pretty subtle, we default to reloc roots having 0 root refs, so
if we crash in the middle of the relocation they can just be deleted.
If we

btrfs: remove a BUG_ON() from merge_reloc_roots()

This was pretty subtle, we default to reloc roots having 0 root refs, so
if we crash in the middle of the relocation they can just be deleted.
If we successfully complete the relocation operations we'll set our root
refs to 1 in prepare_to_merge() and then go on to merge_reloc_roots().

At prepare_to_merge() time if any of the reloc roots have a 0 reference
still, we will remove that reloc root from our reloc root rb tree, and
then clean it up later.

However this only happens if we successfully start a transaction. If
we've aborted previously we will skip this step completely, and only
have reloc roots with a reference count of 0, but were never properly
removed from the reloc control's rb tree.

This isn't a problem per-se, our references are held by the list the
reloc roots are on, and by the original root the reloc root belongs to.
If we end up in this situation all the reloc roots will be added to the
dirty_reloc_list, and then properly dropped at that point. The reloc
control will be free'd and the rb tree is no longer used.

There were two options when fixing this, one was to remove the BUG_ON(),
the other was to make prepare_to_merge() handle the case where we
couldn't start a trans handle.

IMO this is the cleaner solution. I started with handling the error in
prepare_to_merge(), but it turned out super ugly. And in the end this
BUG_ON() simply doesn't matter, the cleanup was happening properly, we
were just panicing because this BUG_ON() only matters in the success
case. So I've opted to just remove it and add a comment where it was.

Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: David Sterba <dsterba@suse.com>

show more ...

btrfs: hold a ref on the root->reloc_root

We previously were relying on root->reloc_root to be cleaned up by the
drop snapshot, or the error handling. However if btrfs_drop_snapshot()
failed it wou

btrfs: hold a ref on the root->reloc_root

We previously were relying on root->reloc_root to be cleaned up by the
drop snapshot, or the error handling. However if btrfs_drop_snapshot()
failed it wouldn't drop the ref for the root. Also we sort of depend on
the right thing to happen with moving reloc roots between lists and the
fs root they belong to, which makes it hard to figure out who owns the
reference.

Fix this by explicitly holding a reference on the reloc root for
roo->reloc_root. This means that we hold two references on reloc roots,
one for whichever reloc_roots list it's attached to, and the
root->reloc_root we're on.

This makes it easier to reason out who owns a reference on the root, and
when it needs to be dropped.

Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

show more ...

btrfs: clear DEAD_RELOC_TREE before dropping the reloc root

The DEAD_RELOC_TREE flag is in place in order to avoid a use after free
in init_reloc_root, tracking the presence of reloc_root. However

btrfs: clear DEAD_RELOC_TREE before dropping the reloc root

The DEAD_RELOC_TREE flag is in place in order to avoid a use after free
in init_reloc_root, tracking the presence of reloc_root. However adding
the explicit tree references in previous patches makes the use after
free impossible because at this point we no longer have a reloc_control
set on the fs_info and thus cannot enter the function.

So move this to be coupled with clearing the root->reloc_root so we're
consistent with all other operations of the reloc root.

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>

show more ...

btrfs: free the reloc_control in a consistent way

If we have an error while processing the reloc roots we could leak roots
that were added to rc->reloc_roots before we hit the error. We could
have

btrfs: free the reloc_control in a consistent way

If we have an error while processing the reloc roots we could leak roots
that were added to rc->reloc_roots before we hit the error. We could
have also not removed the reloc tree mapping from our rb_tree, so clean
up any remaining nodes in the reloc root rb_tree.

Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
[ use rbtree_postorder_for_each_entry_safe ]
Signed-off-by: David Sterba <dsterba@suse.com>

show more ...

btrfs: do not init a reloc root if we aren't relocating

We previously were checking if the root had a dead root before accessing
root->reloc_root in order to avoid a use-after-free type bug. Howeve

btrfs: do not init a reloc root if we aren't relocating

We previously were checking if the root had a dead root before accessing
root->reloc_root in order to avoid a use-after-free type bug. However
this scenario happens after we've unset the reloc control, so we would
have been saved if we'd simply checked for fs_info->reloc_control. At
this point during relocation we no longer need to be creating new reloc
roots, so simply move this check above the reloc_root checks to avoid
any future races and confusion.

Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

show more ...

btrfs: reloc: clean dirty subvols if we fail to start a transaction

If we do merge_reloc_roots() we could insert a few roots onto the dirty
subvol roots list, where we hold a ref on them. If we fai

btrfs: reloc: clean dirty subvols if we fail to start a transaction

If we do merge_reloc_roots() we could insert a few roots onto the dirty
subvol roots list, where we hold a ref on them. If we fail to start the
transaction we need to run clean_dirty_subvols() in order to cleanup the
refs.

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

show more ...

btrfs: unset reloc control if we fail to recover

If we fail to load an fs root, or fail to start a transaction we can
bail without unsetting the reloc control, which leads to problems later
when we

btrfs: unset reloc control if we fail to recover

If we fail to load an fs root, or fail to start a transaction we can
bail without unsetting the reloc control, which leads to problems later
when we free the reloc control but still have it attached to the file
system.

In the normal path we'll end up calling unset_reloc_control() twice, but
all it does is set fs_info->reloc_control = NULL, and we can only have
one balance at a time so it's not racey.

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

show more ...

btrfs: drop block from cache on error in relocation

If we have an error while building the backref tree in relocation we'll
process all the pending edges and then free the node. However if we
integ

btrfs: drop block from cache on error in relocation

If we have an error while building the backref tree in relocation we'll
process all the pending edges and then free the node. However if we
integrated some edges into the cache we'll lose our link to those edges
by simply freeing this node, which means we'll leak memory and
references to any roots that we've found.

Instead we need to use remove_backref_node(), which walks through all of
the edges that are still linked to this node and free's them up and
drops any root references we may be holding.

CC: stable@vger.kernel.org # 4.9+
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

show more ...

btrfs: relocation: Use btrfs_find_all_leafs to locate data extent parent tree leaves

In relocation, we need to locate all parent tree leaves referring to one
data extent, thus we have a complex mech

btrfs: relocation: Use btrfs_find_all_leafs to locate data extent parent tree leaves

In relocation, we need to locate all parent tree leaves referring to one
data extent, thus we have a complex mechanism to iterate throught extent
tree and subvolume trees to locate the related leaves.

However this is already done in backref.c, we have
btrfs_find_all_leafs(), which can return a ulist containing all leaves
referring to that data extent.

Use btrfs_find_all_leafs() to replace find_data_references().

There is a special handling for v1 space cache data extents, where we
need to delete the v1 space cache data extents, to avoid those data
extents to hang the data relocation.

In this patch, the special handling is done by re-iterating the root
tree leaf. Although it's a little less efficient than the old handling,
considering we can reuse a lot of code, it should be acceptable.

Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

show more ...

btrfs: Remove block_rsv parameter from btrfs_drop_snapshot

It's no longer used following 30d40577e322 ("btrfs: reloc: Also queue
orphan reloc tree for cleanup to avoid BUG_ON()"), so just remove it.

btrfs: Remove block_rsv parameter from btrfs_drop_snapshot

It's no longer used following 30d40577e322 ("btrfs: reloc: Also queue
orphan reloc tree for cleanup to avoid BUG_ON()"), so just remove it.

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

show more ...

btrfs: Remove __ prefix from btrfs_block_rsv_release

Currently the non-prefixed version is a simple wrapper used to hide
the 4th argument of the prefixed version. This doesn't bring much value
in pr

btrfs: Remove __ prefix from btrfs_block_rsv_release

Currently the non-prefixed version is a simple wrapper used to hide
the 4th argument of the prefixed version. This doesn't bring much value
in practice and only makes the code harder to follow by adding another
level of indirection. Rectify this by removing the __ prefix and
have only one public function to release bytes from a block reservation.
No semantic changes.

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

show more ...

btrfs: relocation: Check cancel request after each extent found

When relocating data block groups with tons of small extents, or large
metadata block groups, there can be over 200,000 extents.

We w

btrfs: relocation: Check cancel request after each extent found

When relocating data block groups with tons of small extents, or large
metadata block groups, there can be over 200,000 extents.

We will iterate all extents of such block group in relocate_block_group(),
where iteration itself can be kinda time-consuming.

So when user want to cancel the balance, the extent iteration loop can
be another target.

This patch will add the cancelling check in the extent iteration loop of
relocate_block_group() to make balance cancelling faster.

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>

show more ...

btrfs: relocation: Check cancel request after each data page read

When relocating a data extents with large large data extents, we spend
most of our time in relocate_file_extent_cluster() at stage "

btrfs: relocation: Check cancel request after each data page read

When relocating a data extents with large large data extents, we spend
most of our time in relocate_file_extent_cluster() at stage "moving data
extents":

1) | btrfs_relocate_block_group [btrfs]() {
1) | relocate_file_extent_cluster [btrfs]() {
1) $ 6586769 us | }
1) + 18.260 us | relocate_file_extent_cluster [btrfs]();
1) + 15.770 us | relocate_file_extent_cluster [btrfs]();
1) $ 8916340 us | }
1) | btrfs_relocate_block_group [btrfs]() {
1) | relocate_file_extent_cluster [btrfs]() {
1) $ 11611586 us | }
1) + 16.930 us | relocate_file_extent_cluster [btrfs]();
1) + 15.870 us | relocate_file_extent_cluster [btrfs]();
1) $ 14986130 us | }

To make data relocation cancelling quicker, add extra balance cancelling
check after each page read in relocate_file_extent_cluster().

Cleanup and error handling uses the same mechanism as if the whole
process finished

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>

show more ...

btrfs: relocation: add error injection points for cancelling balance

Introduce a new error injection point, should_cancel_balance().

It's just a wrapper of atomic_read(&fs_info->balance_cancel_req)

btrfs: relocation: add error injection points for cancelling balance

Introduce a new error injection point, should_cancel_balance().

It's just a wrapper of atomic_read(&fs_info->balance_cancel_req), but
allows us to override the return value.

Currently there are only one locations using this function:

- btrfs_balance()
It checks cancel before each block group.

There are other locations checking fs_info->balance_cancel_req, but they
are not used as an indicator to exit, so there is no need to use the
wrapper.

But there will be more locations coming, and some locations can cause
kernel panic if not handled properly. So introduce this error injection
to provide better test interface.

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>

show more ...

btrfs: Remove impossible BUG_ON in get_tree_block_key

relocate_tree_blocks calls get_tree_block_key for a block iff that block
has its ->key_ready equal false. Thus the BUG_ON in the latter function

btrfs: Remove impossible BUG_ON in get_tree_block_key

relocate_tree_blocks calls get_tree_block_key for a block iff that block
has its ->key_ready equal false. Thus the BUG_ON in the latter function
cannot ever be triggered so remove it.

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

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btrfs: relocation: Remove is_cowonly_root()

This function is only used in read_fs_root(), which is just a wrapper of
btrfs_get_fs_root().

For all the mentioned essential roots except log root tree,

btrfs: relocation: Remove is_cowonly_root()

This function is only used in read_fs_root(), which is just a wrapper of
btrfs_get_fs_root().

For all the mentioned essential roots except log root tree,
btrfs_get_fs_root() has its own quick path to grab them from fs_info
directly, thus no need for key.offset modification.

For subvolume trees, btrfs_get_fs_root() with key.offset == -1 is
completely fine.

For log trees and log root tree, it's impossible to hit them, as for
relocation all backrefs are fetched from commit root, which never
records log tree blocks.

Log tree blocks either get freed in regular transaction commit, or
replayed at mount time. At runtime we should never hit an backref for
log tree in extent tree.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

show more ...

btrfs: rename btrfs_put_fs_root and btrfs_grab_fs_root

We are now using these for all roots, rename them to btrfs_put_root()
and btrfs_grab_root();

Reviewed-by: Nikolay Borisov <nborisov@suse.com>

btrfs: rename btrfs_put_fs_root and btrfs_grab_fs_root

We are now using these for all roots, rename them to btrfs_put_root()
and btrfs_grab_root();

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

show more ...

btrfs: push btrfs_grab_fs_root into btrfs_get_fs_root

Now that all callers of btrfs_get_fs_root are subsequently calling
btrfs_grab_fs_root and handling dropping the ref when they are done
appropria

btrfs: push btrfs_grab_fs_root into btrfs_get_fs_root

Now that all callers of btrfs_get_fs_root are subsequently calling
btrfs_grab_fs_root and handling dropping the ref when they are done
appropriately, go ahead and push btrfs_grab_fs_root up into
btrfs_get_fs_root.

Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

show more ...

btrfs: push grab_fs_root into read_fs_root

All of relocation uses read_fs_root to lookup fs roots, so push the
btrfs_grab_fs_root() up into that helper and remove the individual
calls.

Signed-off-b

btrfs: push grab_fs_root into read_fs_root

All of relocation uses read_fs_root to lookup fs roots, so push the
btrfs_grab_fs_root() up into that helper and remove the individual
calls.

Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

show more ...

btrfs: hold a ref on the root in btrfs_recover_relocation

We look up the fs root in various places in here when recovering from a
crashed relcoation. Make sure we hold a ref on the root whenever we

btrfs: hold a ref on the root in btrfs_recover_relocation

We look up the fs root in various places in here when recovering from a
crashed relcoation. Make sure we hold a ref on the root whenever we
look them up.

Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

show more ...