Currently, at find_first_extent_bit(), when we are given a cached extent
state that happens to have its end offset match the desired range start,
we find the next extent state using that cached state, with next_state()
calls, and then return it.
We then try to cache that next state by calling cache_state_if_flags(),
but that will not cache the state because we haven't reset *cached_state
to NULL, so we end up with the cached_state unchanged, and if the caller
is iterating over extent states in the io tree, its next call to
find_first_extent_bit() will not use the current cached state as its end
offset does not match the minimum start range offset, therefore the cached
state is reset and we have to search the rbtree to find the next suitable
extent state record.
So fix this by resetting the cached state to NULL (and dropping our ref
on it) when we have a suitable cached state and we found a next state by
using next_state() starting from the cached state. This makes use cases
of calling find_first_extent_bit() to go over all ranges in the io tree
to do a single rbtree full search, only on the first call, and the next
calls will just do next_state() (rb_next() wrapper) calls, which is more
efficient.
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
When freeing a log tree, during a transaction commit, we clear its dirty
log pages io tree by calling clear_extent_bits() using a range from 0 to
(u64)-1. This will iterate the io tree's rbtree and call rb_erase() on
each node before freeing it, which will often trigger rebalance operations
on the rbtree. A better alternative it to use extent_io_tree_release(),
which will not do deletions and trigger rebalances.
So use extent_io_tree_release() instead of clear_extent_bits().
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Currently extent_io_tree_release() is a loop that keeps getting the first
node in the io tree, using rb_first() which is a loop that gets to the
leftmost node of the rbtree, and then for each node it calls rb_erase(),
which often requires rebalancing the rbtree.
We can make this more efficient by using
rbtree_postorder_for_each_entry_safe() to free each node without having
to delete it from the rbtree and without looping to get the first node.
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
The wait_on_state() function is very short and has a single caller, which
is wait_extent_bit(), so remove the function and put its code into the
caller.
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
The memory barrier at extent_io_tree_release() is redundant. Holding
spin_lock here is not enough to drop the barrier completely. We only
change the waitqueue of an extent state record while holding the tree
lock - see wait_on_state().
The update to waitqueue state will not become stale because there will
be an spin_unlock/spin_lock sequence between the change and waiting,
this implies a full memory barrier.
So remove the explicit smp_mb() barrier.
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
[ reword reasoning ]
Signed-off-by: David Sterba <dsterba@suse.com>
The function wait_extent_bit() is not used outside extent-io-tree.c so
make it static. Furthermore the function doesn't have the 'btrfs_' prefix.
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
There's this comment at extent_io_tree_release() that mentions io btrees,
but this function is no longer used only for io btrees. Originally it was
added as a static function named clear_btree_io_tree() at transaction.c,
in commit 663dfbb077 ("Btrfs: deal with convert_extent_bit errors to
avoid fs corruption"), as it was used only for cleaning one of the io
trees that track dirty extent buffers, the dirty_log_pages io tree of a
a root and the dirty_pages io tree of a transaction. Later it was renamed
and exported and now it's used to cleanup other io trees such as the
allocation state io tree of a device or the csums range io tree of a log
root.
So remove that comment and replace it with one at the top of the function
that is more complete, mentioning what the function does and that it's
expected to be called only when a task is sure no one else will need to
use the tree anymore, as well as there should be no locked ranges in the
tree and therefore no waiters on its extent state records. Also add an
assertion to check that there are no locked extent state records in the
tree.
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
When inserting a new extent state record into an io tree that happens to
be mergeable, we currently do the following:
1) Insert the extent state record in the io tree's rbtree. This requires
going down the tree to find where to insert it, and during the
insertion we often need to balance the rbtree;
2) We then check if the previous node is mergeable, so we call rb_prev()
to find it, which requires some looping to find the previous node;
3) If the previous node is mergeable, we adjust our node to include the
range of the previous node and then delete the previous node from the
rbtree, which again may need to balance the rbtree;
4) Then we check if the next node is mergeable with the node we inserted,
so we call rb_next(), which requires some looping too. If the next node
is indeed mergeable, we expand the range of our node to include the
next node's range and then delete the next node from the rbtree, which
again may need to balance the tree.
So these are quite of lot of iterations and looping over the rbtree, and
some of the operations may need to rebalance the rb tree. This can be made
a bit more efficient by:
1) When iterating the rbtree, once we find a node that is mergeable with
the node we want to insert, we can just adjust that node's range with
the range of the node to insert - this avoids continuing iterating
over the tree and deleting a node from the rbtree;
2) If we expand the range of a mergeable node, then we find the next or
the previous node, depending on other we merged a range to the right or
to the left of the node we are currently at during the iteration. This
merging is as before, we find the next or previous node with rb_next()
or rb_prev() and if that other node is mergeable with the current one,
we adjust the range of the current node and remove the other node from
the rbtree;
3) Whenever we need to insert the new extent state record it's because
we don't have any extent state record in the rbtree which can be
merged, so we can remove the call to merge_state() after the insertion,
saving rb_next() and rb_prev() calls, which require some looping.
So update the insertion function insert_state() to have this behaviour.
Running dbench for 120 seconds and capturing the execution times of
set_extent_bit() at pin_down_extent(), resulted in the following data
(time values are in nanoseconds):
Before this change:
Count: 2278299
Range: 0.000 - 4003728.000; Mean: 713.436; Median: 612.000; Stddev: 3606.952
Percentiles: 90th: 1187.000; 95th: 1350.000; 99th: 1724.000
0.000 - 7.534: 5 |
7.534 - 35.418: 36 |
35.418 - 154.403: 273 |
154.403 - 662.138: 1244016 #####################################################
662.138 - 2828.745: 1031335 ############################################
2828.745 - 12074.102: 1395 |
12074.102 - 51525.930: 806 |
51525.930 - 219874.955: 162 |
219874.955 - 938254.688: 22 |
938254.688 - 4003728.000: 3 |
After this change:
Count: 2275862
Range: 0.000 - 1605175.000; Mean: 678.903; Median: 590.000; Stddev: 2149.785
Percentiles: 90th: 1105.000; 95th: 1245.000; 99th: 1590.000
0.000 - 10.219: 10 |
10.219 - 40.957: 36 |
40.957 - 155.907: 262 |
155.907 - 585.789: 1127214 ####################################################
585.789 - 2193.431: 1145134 #####################################################
2193.431 - 8205.578: 1648 |
8205.578 - 30689.378: 1039 |
30689.378 - 114772.699: 362 |
114772.699 - 429221.537: 52 |
429221.537 - 1605175.000: 10 |
Maximum duration (range), average duration, percentiles and standard
deviation are all better.
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
The semantics of test_range_bit() with filled == 0 is now in it's own
helper so test_range_bit will check the whole range unconditionally.
The detection logic is flipped and assumes success by default and
catches exceptions.
Signed-off-by: David Sterba <dsterba@suse.com>
The existing helper test_range_bit works in two ways, checks if the whole
range contains all the bits, or stop on the first occurrence. By adding
a specific helper for the latter case, the inner loop can be simplified
and contains fewer conditionals, making it a bit faster.
There's no caller that uses the cached state pointer so this reduces the
argument count further.
Signed-off-by: David Sterba <dsterba@suse.com>
btrfs_realloc_node() is only used by the defrag code. Nowadays we have a
defrag.c file, so move it, and its helper close_blocks(), into defrag.c.
During the move also do a few minor cosmetic changes:
1) Change the return value of close_blocks() from int to bool;
2) Use SZ_32K instead of 32768 at close_blocks();
3) Make some variables const in btrfs_realloc_node(), 'blocksize' and
'end_slot';
4) Get rid of 'parent_nritems' variable, in both places where it was
used it could be replaced by calling btrfs_header_nritems(parent);
5) Change the type of a couple variables from int to bool;
6) Rename variable 'err' to 'ret', as that's the most common name we
use to track the return value of a function;
7) Move some variables from the top scope to the scope of the for loop
where they are used.
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Export comp_keys() out of ctree.c, as btrfs_comp_keys(), so that in a
later patch we can move out defrag specific code from ctree.c into
defrag.c.
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Rename and export __btrfs_cow_block() as btrfs_force_cow_block(). This is
to allow to move defrag specific code out of ctree.c and into defrag.c in
one of the next patches.
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
At btrfs_cow_block() we can use round_down() to align the extent buffer's
logical offset to the start offset of a metadata block group, instead of
the less easy to read set of bitwise operations (two plus one subtraction).
So replace the bitwise operations with a round_down() call.
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
It's pointless to have the noiline attribute for btrfs_cow_block(), as the
function is exported and widely used. So remove it.
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Previous commit ("btrfs: reject devices with CHANGING_FSID_V2") has
stopped the assembly of devices with the CHANGING_FSID_V2 flag in the
kernel. Such devices can be scanned but will not be registered and can't
be mounted without a manual fix by btrfstune. Remove the related logic
and now unused code.
The original motivation was to allow an interrupted partial conversion
fix itself on next mount, in case the system has to be rebooted. This is
a convenience but brings a lot of complexity the device scanning and
handling the partial states. It's hard to estimate if this was ever
needed in practice, expecting the typical use case like a manual
conversion of an unmounted filesystem where the user can verify the
success and rerun it eventually.
Signed-off-by: Anand Jain <anand.jain@oracle.com>
Reviewed-by: David Sterba <dsterba@suse.com>
[ add historical context ]
Signed-off-by: David Sterba <dsterba@suse.com>
The BTRFS_SUPER_FLAG_CHANGING_FSID_V2 flag indicates a transient state
where the device in the userspace btrfstune -m|-M operation failed to
complete changing the fsid.
This flag makes the kernel to automatically determine the other
partner devices to which a given device can be associated, based on the
fsid, metadata_uuid and generation values.
btrfstune -m|M feature is especially useful in virtual cloud setups, where
compute instances (disk images) are quickly copied, fsid changed, and
launched. Given numerous disk images with the same metadata_uuid but
different fsid, there's no clear way a device can be correctly assembled
with the proper partners when the CHANGING_FSID_V2 flag is set. So, the
disk could be assembled incorrectly, as in the example below:
Before this patch:
Consider the following two filesystems:
/dev/loop[2-3] are raw copies of /dev/loop[0-1] and the btrsftune -m
operation fails.
In this scenario, as the /dev/loop0's fsid change is interrupted, and the
CHANGING_FSID_V2 flag is set as shown below.
$ p="device|devid|^metadata_uuid|^fsid|^incom|^generation|^flags"
$ btrfs inspect dump-super /dev/loop0 | egrep '$p'
superblock: bytenr=65536, device=/dev/loop0
flags 0x1000000001
fsid 7d4b4b93-2b27-4432-b4e4-4be1fbccbd45
metadata_uuid bb040a9f-233a-4de2-ad84-49aa5a28059b
generation 9
num_devices 2
incompat_flags 0x741
dev_item.devid 1
$ btrfs inspect dump-super /dev/loop1 | egrep '$p'
superblock: bytenr=65536, device=/dev/loop1
flags 0x1
fsid 11d2af4d-1b71-45a9-83f6-f2100766939d
metadata_uuid bb040a9f-233a-4de2-ad84-49aa5a28059b
generation 10
num_devices 2
incompat_flags 0x741
dev_item.devid 2
$ btrfs inspect dump-super /dev/loop2 | egrep '$p'
superblock: bytenr=65536, device=/dev/loop2
flags 0x1
fsid 7d4b4b93-2b27-4432-b4e4-4be1fbccbd45
metadata_uuid bb040a9f-233a-4de2-ad84-49aa5a28059b
generation 8
num_devices 2
incompat_flags 0x741
dev_item.devid 1
$ btrfs inspect dump-super /dev/loop3 | egrep '$p'
superblock: bytenr=65536, device=/dev/loop3
flags 0x1
fsid 7d4b4b93-2b27-4432-b4e4-4be1fbccbd45
metadata_uuid bb040a9f-233a-4de2-ad84-49aa5a28059b
generation 8
num_devices 2
incompat_flags 0x741
dev_item.devid 2
It is normal that some devices aren't instantly discovered during
system boot or iSCSI discovery. The controlled scan below demonstrates
this.
$ btrfs device scan --forget
$ btrfs device scan /dev/loop0
Scanning for btrfs filesystems on '/dev/loop0'
$ mount /dev/loop3 /btrfs
$ btrfs filesystem show -m
Label: none uuid: 7d4b4b93-2b27-4432-b4e4-4be1fbccbd45
Total devices 2 FS bytes used 144.00KiB
devid 1 size 300.00MiB used 48.00MiB path /dev/loop0
devid 2 size 300.00MiB used 40.00MiB path /dev/loop3
/dev/loop0 and /dev/loop3 are incorrectly partnered.
This kernel patch removes functions and code connected to the
CHANGING_FSID_V2 flag.
With this patch, now devices with the CHANGING_FSID_V2 flag are rejected.
And its partner will fail to mount with the extra -o degraded option.
The check is removed from open_ctree(), devices are rejected during
scanning which in turn fails the mount.
Signed-off-by: Anand Jain <anand.jain@oracle.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Lots of the functions in relocation.c don't change pointer parameters
but lack the annotations. Add them and reformat according to current
coding style if needed.
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: David Sterba <dsterba@suse.com>
btrfs_should_ignore_reloc_root() is a predicate so it should return
bool.
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
The btrfs_backref_cache::is_reloc is an indicator variable and should
use a bool type.
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
There's only one user of mapping_tree_init, we don't need a helper for
the simple initialization.
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Use bool types for the indicators instead of bitfields. The structure
size slightly grows but the new types are placed within the padding.
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Add an enum type for data relocation stages.
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: David Sterba <dsterba@suse.com>
We don't need to use bitfields for tree_block::level and
tree_block::key_ready, there's enough padding in the structure for
proper types.
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
The btrfs_defrag_root() function does not really belong in the
transaction.{c,h} module and as we have a defrag.{c,h} nowadays,
move it to there instead. This also allows to stop exporting
btrfs_defrag_leaves(), so we can make it static.
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
[ rename info to fs_info for consistency ]
Signed-off-by: David Sterba <dsterba@suse.com>
The root argument for fixup_inode_link_count() always matches the root of
the given inode, so remove the root argument and get it from the inode
argument. This also applies to the helpers count_inode_extrefs() and
count_inode_refs() used by fixup_inode_link_count() - they don't need the
root argument, as it always matches the root of the inode passed to them.
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
The root argument for maybe_insert_hole() always matches the root of the
given inode, so remove the root argument and get it from the inode
argument.
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
The root argument for btrfs_delayed_update_inode() always matches the root
of the given inode, so remove the root argument and get it from the inode
argument.
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
The root argument for btrfs_update_inode_item() always matches the root of
the given inode, so remove the root argument and get it from the inode
argument.
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
The root argument for btrfs_update_inode() always matches the root of the
given inode, so remove the root argument and get it from the inode
argument.
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
The root argument for btrfs_update_inode_fallback() always matches the
root of the given inode, so remove the root argument and get it from the
inode argument.
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
The noinline attribute of btrfs_update_inode() is pointless as the
function is exported and widely used, so remove it.
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
The following condition at btrfs_dirty_inode() is redundant:
if (ret && (ret == -ENOSPC || ret == -EDQUOT))
The first check for a non-zero 'ret' value is pointless, we can simplify
this to simply:
if (ret == -ENOSPC || ret == -EDQUOT)
Not only this makes it easier to read, it also slightly reduces the text
size of the btrfs kernel module:
$ size fs/btrfs/btrfs.ko.before
text data bss dec hex filename
1641400 168265 16864 1826529 1bdee1 fs/btrfs/btrfs.ko.before
$ size fs/btrfs/btrfs.ko.after
text data bss dec hex filename
1641224 168181 16864 1826269 1bdddd fs/btrfs/btrfs.ko.after
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
In open_ctree, we set BTRFS_FS_QUOTA_ENABLED as soon as we see a
quota_root, as opposed to after we are done setting up the qgroup
structures. In the quota_enable path, we wait until after the structures
are set up. Likewise, in disable, we clear the bit before tearing down
the structures. I feel that this organization is less surprising for the
open_ctree path.
I don't believe this fixes any actual bug, but avoids potential
confusion when using btrfs_qgroup_mode in an intermediate state where we
are enabled but haven't yet setup the qgroup status flags. It also
avoids any risk of calling a qgroup function and attempting to use the
qgroup rbtrees before they exist/are setup.
This all occurs before we do rw setup, so I believe it should be mostly
a no-op.
Signed-off-by: Boris Burkov <boris@bur.io>
Signed-off-by: David Sterba <dsterba@suse.com>
Relocation data allocations are quite tricky for simple quotas. The
basic data relocation sequence is (ignoring details that aren't relevant
to this fix):
- create a fake relocation data fs root
- create a fake relocation inode in that root
- for each data extent:
- preallocate a data extent on behalf of the fake inode
- copy over the data
- for each extent
- swap the refs so that the original file extent now refers to the new
extent item
- drop the fake root, dropping its refs on the old extents, which lets
us delete them.
Done naively, this results in storing an extent item in the extent tree
whose owner_ref points at the relocation data root and a no-op squota
recording, since the reloc root is not a legit fstree. So far, that's
OK. The problem comes when you do the swap, and leave an extent item
owned by this bogus root as the real permanent extents of the file. If
the file then drops that ref, we free it and no-op account that against
the fake relocation root. Essentially, this means that relocation is
simple quota "extent laundering", since we re-own the extents into a
fake root.
Simple quotas very intentionally doesn't have a mechanism for
transferring ownership of extents, as that is exactly the complicated
thing we are trying to avoid with the new design. Further, it cannot be
correctly done in this case, since at the time you create the new
"real" refs, there is no way to know which was the original owner before
relocation unless we track it.
Therefore, it makes more sense to trick the preallocation to handle
relocation as a special case and note the proper owner ref from the
beginning. That way, we never write out an extent item without the
correct owner ref that it will eventually have.
This could be done by wiring a special root parameter all the way
through the allocation code path, but to avoid that special case
touching all the code, take advantage of the serial nature of relocation
to store the src root on the relocation root object. Then when we finish
the prealloc, if it happens to be this case, prepare the delayed ref
appropriately.
We must also add logic to handle relocating adjacent extents with
different owning roots. Those cannot be preallocated together in a
cluster as it would lose the separate ownership information.
This is obviously a smelly bit of code, but I think it is the best
solution to the problem, given the relocation implementation.
Signed-off-by: Boris Burkov <boris@bur.io>
Signed-off-by: David Sterba <dsterba@suse.com>
Relocation COWs metadata blocks in two cases for the reloc root:
- copying the subvolume root item when creating the reloc root
- copying a btree node when there is a COW during relocation
In both cases, the resulting btree node hits an abnormal code path with
respect to the owner field in its btrfs_header. It first creates the
root item for the new objectid, which populates the reloc root id, and
it at this point that delayed refs are created.
Later, it fully copies the old node into the new node (including the
original owner field) which overwrites it. This results in a simple
quotas mismatch where we run the delayed ref for the reloc root which
has no simple quota effect (reloc root is not an fstree) but when we
ultimately delete the node, the owner is the real original fstree and we
do free the space.
To work around this without tampering with the behavior of relocation,
add a parameter to btrfs_add_tree_block that lets the relocation code
path specify a different owning root than the "operating" root (in this
case, owning root is the real root and the operating root is the reloc
root). These can naturally be plumbed into delayed refs that have the
same concept.
Note that this is a double count in some sense, but a relatively natural
one, as there are really two extents, and the old one will be deleted
soon. This is consistent with how data relocation extents are accounted
by simple quotas.
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Boris Burkov <boris@bur.io>
Signed-off-by: David Sterba <dsterba@suse.com>
Simple quotas count extents only from the moment the feature is enabled.
Therefore, if we do something like:
1. create subvol S
2. write F in S
3. enable quotas
4. remove F
5. write G in S
then after 3. and 4. we would expect the simple quota usage of S to be 0
(putting aside some metadata extents that might be written) and after
5., it should be the size of G plus metadata. Therefore, we need to be
able to determine whether a particular quota delta we are processing
predates simple quota enablement.
To do this, store the transaction id when quotas were enabled. In
fs_info for immediate use and in the quota status item to make it
recoverable on mount. When we see a delta, check if the generation of
the extent item is less than that of quota enablement. If so, we should
ignore the delta from this extent.
Signed-off-by: Boris Burkov <boris@bur.io>
Signed-off-by: David Sterba <dsterba@suse.com>
Consider the following sequence:
- enable quotas
- create subvol S id 256 at dir outer/
- create a qgroup 1/100
- add 0/256 (S's auto qgroup) to 1/100
- create subvol T id 257 at dir outer/inner/
With full qgroups, there is no relationship between 0/257 and either of
0/256 or 1/100. There is an inherit feature that the creator of inner/
can use to specify it ought to be in 1/100.
Simple quotas are targeted at container isolation, where such automatic
inheritance for not necessarily trusted/controlled nested subvol
creation would be quite helpful. Therefore, add a new default behavior
for simple quotas: when you create a nested subvol, automatically
inherit as parents any parents of the qgroup of the subvol the new inode
is going in.
In our example, 257/0 would also be under 1/100, allowing easy control
of a total quota over an arbitrary hierarchy of subvolumes.
I think this _might_ be a generally useful behavior, so it could be
interesting to put it behind a new inheritance flag that simple quotas
always use while traditional quotas let the user specify, but this is a
minimally intrusive change to start.
Signed-off-by: Boris Burkov <boris@bur.io>
Signed-off-by: David Sterba <dsterba@suse.com>
At the moment that we run delayed refs, we make the final ref-count
based decision on creating/removing extent (and metadata) items.
Therefore, it is exactly the spot to hook up simple quotas.
There are a few important subtleties to the fields we must collect to
accurately track simple quotas, particularly when removing an extent.
When removing a data extent, the ref could be in any tree (due to
reflink, for example) and so we need to recover the owning root id from
the owner ref item. When removing a metadata extent, we know the owning
root from the owner field in the header when we create the delayed ref,
so we can recover it from there.
We must also be careful to handle reservations properly to not leaked
reserved space. The happy path is freeing the reservation when the
simple quota delta runs on a data extent. If that doesn't happen, due to
refs canceling out or some error, the ref head already has the
must_insert_reserved machinery to handle this, so we piggy back on that
and use it to clean up the reserved data.
Signed-off-by: Boris Burkov <boris@bur.io>
Signed-off-by: David Sterba <dsterba@suse.com>
Inline ref parsing is a bit tricky and relies on a decent amount of
implicit information, so I think it is beneficial to have a helper
function for reading the owner ref, if only to "document" the format,
along with the write path.
The main subtlety of note which I was missing by open-coding this was
that it is important to check whether or not inline refs are present
*at all*. i.e., if we are writing out a new extent under squotas, we
will always use a big enough item for the inline ref and have it.
However, it is possible that some random item predating squotas will not
have any inline refs. In that case, trying to read the "type" field of
the first inline ref will just be reading garbage in the form of
whatever is in the next item.
This will be used by the extent free-ing path, which looks up data
extent owners as well as a relocation path which needs to grab the owner
before relocating an extent.
Signed-off-by: Boris Burkov <boris@bur.io>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: David Sterba <dsterba@suse.com>
In order to implement simple quota groups, we need to be able to
associate a data extent with the subvolume that created it. Once you
account for reflink, this information cannot be recovered without
explicitly storing it. Options for storing it are:
- a new key/item
- a new extent inline ref item
The former is backwards compatible, but wastes space, the latter is
incompat, but is efficient in space and reuses the existing inline ref
machinery, while only abusing it a tiny amount -- specifically, the new
item is not a ref, per-se.
Signed-off-by: Boris Burkov <boris@bur.io>
Signed-off-by: David Sterba <dsterba@suse.com>
Simple quotas requires tracking the original creating root of any given
extent. This gets complicated when multiple subvolumes create
overlapping/contradictory refs in the same transaction. For example,
due to modifying or deleting an extent while also snapshotting it.
To resolve this in a general way, take advantage of the fact that we are
essentially already tracking this for handling releasing reservations.
The head ref coalesces the various refs and uses must_insert_reserved to
check if it needs to create an extent/free reservation. Store the ref
that set must_insert_reserved as the owning ref on the head ref.
Note that this can result in writing an extent for the very first time
with an owner different from its only ref, but it will look the same as
if you first created it with the original owning ref, then added the
other ref, then removed the owning ref.
Signed-off-by: Boris Burkov <boris@bur.io>
Signed-off-by: David Sterba <dsterba@suse.com>
While data extents require us to store additional inline refs to track
the original owner on free, this information is available implicitly for
metadata. It is found in the owner field of the header of the tree
block. Even if other trees refer to this block and the original ref goes
away, we will not rewrite that header field, so it will reliably give the
original owner.
In addition, there is a relocation case where a new data extent needs to
have an owning root separate from the referring root wired through
delayed refs.
To use it for recording simple quota deltas, we need to wire this root
id through from when we create the delayed ref until we fully process
it. Store it in the generic btrfs_ref struct of the delayed ref.
Signed-off-by: Boris Burkov <boris@bur.io>
Signed-off-by: David Sterba <dsterba@suse.com>
commit 113479d5b8 ("btrfs: rename root fields in delayed refs structs")
changed these from ref_root to owning_root. However, there are many
circumstances where that name is not really accurate and the root on the
ref struct _is_ the referring root. In general, these are not the owning
root, though it does happen in some ref merging cases involving
overwrites during snapshots and similar.
Simple quotas cares quite a bit about tracking the original owner of an
extent through delayed refs, so rename these back to free up the name
for the real owning root (which will live on the generic btrfs_ref and
the head ref)
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Boris Burkov <boris@bur.io>
Signed-off-by: David Sterba <dsterba@suse.com>
Rather than re-computing shared/exclusive ownership based on backrefs
and walking roots for implicit backrefs, simple quotas does an increment
when creating an extent and a decrement when deleting it. Add the API
for the extent item code to use to track those events.
Signed-off-by: Boris Burkov <boris@bur.io>
Signed-off-by: David Sterba <dsterba@suse.com>
Pull creating the qgroup earlier in the snapshot. This allows simple
quotas qgroups to see all the metadata writes related to the snapshot
being created and to be born with the root node accounted.
Note this has an impact on transaction commit where the qgroup creation
can do a lot of work, allocate memory and take locks. The change is done
for correctness, potential performance issues will be fixed in the
future.
Signed-off-by: Boris Burkov <boris@bur.io>
[ add note ]
Signed-off-by: David Sterba <dsterba@suse.com>
The following sequence:
enable simple quotas
do some writes
reserve space
create ordered_extent
release rsv (store rsv_bytes in OE, mark QGROUP_RESERVED bits)
disable quotas
enable simple quotas
set qgroup rsv to 0 on all subvolumes
ordered_extent finishes
create delayed ref with rsv_bytes from before
run delayed ref
record_simple_quota_delta
free rsv_bytes (0 -> -rsv_delta)
results in us reliably underflowing the subvolume's qgroup rsv counter,
because disabling/re-enabling quotas toggles reservation counters down
to 0, but does not remove other file system state which represents
successful acquisition of qgroup rsv space. Specifically metadata rsv
counters on the root object and rsv_bytes on ordered_extent objects that
have released their reservation as well as the corresponding
QGROUP_RESERVED extent bits.
Normal qgroups gets away with this, I believe because it forces more
work to happen on transaction commit, but I am not certain it is totally
safe from the ordered_extent/leaked extent bit variant. Simple quotas
hits this reliably.
The intent of the fix is to make disable take the time to clear that
external to qgroups state as well: after flipping off the quota bit on
fs_info, flush delalloc and ordered extents, clearing the extent bits
along the way. This makes it so there are no ordered extents or meta
prealloc hanging around from the first enablement period during the second.
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Boris Burkov <boris@bur.io>
Signed-off-by: David Sterba <dsterba@suse.com>
Add an entry in the features directory for the new incompat flag
Signed-off-by: Boris Burkov <boris@bur.io>
Signed-off-by: David Sterba <dsterba@suse.com>
Add a new sysfs file /sys/fs/btrfs/<uuid>/qgroups/mode
which prints out the mode qgroups is running in. The possible modes are
qgroup, and squota.
If quotas are not enabled, then the qgroups directory will not exist,
so don't handle that mode.
Signed-off-by: Boris Burkov <boris@bur.io>
Signed-off-by: David Sterba <dsterba@suse.com>
Add a new quota mode called "simple quotas". It can be enabled by the
existing quota enable ioctl via a new command, and sets an incompat
bit, as the implementation of simple quotas will make backwards
incompatible changes to the disk format of the extent tree.
Signed-off-by: Boris Burkov <boris@bur.io>
Signed-off-by: David Sterba <dsterba@suse.com>
