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Qu Wenruo
8d54518b5e
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>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.