btrfs: qgroup: pre-allocate btrfs_qgroup to reduce GFP_ATOMIC usage

Browse source

Qgroup is the heaviest user of GFP_ATOMIC, but one call site does not
really need GFP_ATOMIC, that is add_qgroup_rb().

That function only searches the rbtree to find if we already have such
entry.  If not, then it would try to allocate memory for it.

This means we can afford to pre-allocate such structure unconditionally,
then free the memory if it's not needed.

Considering this function is not a hot path, only utilized by the
following functions:

- btrfs_qgroup_inherit()
  For "btrfs subvolume snapshot -i" option.

- btrfs_read_qgroup_config()
  At mount time, and we're ensured there would be no existing rb tree
  entry for each qgroup.

- btrfs_create_qgroup()

Thus we're completely safe to pre-allocate the extra memory for btrfs_qgroup
structure, and reduce unnecessary GFP_ATOMIC usage.

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

...

This commit is contained in:

Qu Wenruo 2023-08-29 19:48:57 +08:00 • committed by David Sterba

parent dce28769a3

commit 8d54518b5e

1 changed files with 61 additions and 26 deletions

Show all changes Ignore whitespace when comparing lines Ignore changes in amount of whitespace Ignore changes in whitespace at EOL

Download patch file Download diff file Expand all files Collapse all files

87

fs/btrfs/qgroup.c

View file