On 2018年06月08日 20:47, Nikolay Borisov wrote:
> This commit pulls those portions of the kernel implementation of
> delayed refs which are necessary to have them working in user-space.
> I've done the following modifications:
>
> 1. Replaced all kmem_cache_alloc calls to kmalloc.
>
> 2. Removed all locking-related code, since we are single threaded in
> userspace.
>
> 3. Removed code which deals with data refs - delayed refs in user space
> are going to be used only for cowonly trees.
That's pretty good, although still some data ref related
structures/functions are left.
>
> Signed-off-by: Nikolay Borisov <[email protected]>
> ---
> Makefile | 3 +-
> ctree.h | 3 +
> delayed-ref.c | 608
> ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
> delayed-ref.h | 225 ++++++++++++++++++++++
> extent-tree.c | 228 ++++++++++++++++++++++
> kerncompat.h | 8 +
> transaction.h | 4 +
> 7 files changed, 1078 insertions(+), 1 deletion(-)
> create mode 100644 delayed-ref.c
> create mode 100644 delayed-ref.h
>
> diff --git a/Makefile b/Makefile
> index 544410e6440c..9508ad4f11e6 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -116,7 +116,8 @@ objects = ctree.o disk-io.o kernel-lib/radix-tree.o
> extent-tree.o print-tree.o \
> qgroup.o free-space-cache.o kernel-lib/list_sort.o props.o \
> kernel-shared/ulist.o qgroup-verify.o backref.o string-table.o
> task-utils.o \
> inode.o file.o find-root.o free-space-tree.o help.o send-dump.o \
> - fsfeatures.o kernel-lib/tables.o kernel-lib/raid56.o transaction.o
> + fsfeatures.o kernel-lib/tables.o kernel-lib/raid56.o transaction.o \
> + delayed-ref.o
> cmds_objects = cmds-subvolume.o cmds-filesystem.o cmds-device.o cmds-scrub.o
> \
> cmds-inspect.o cmds-balance.o cmds-send.o cmds-receive.o \
> cmds-quota.o cmds-qgroup.o cmds-replace.o check/main.o \
> diff --git a/ctree.h b/ctree.h
> index b30a946658ce..d1ea45571d1e 100644
> --- a/ctree.h
> +++ b/ctree.h
> @@ -2812,4 +2812,7 @@ int btrfs_punch_hole(struct btrfs_trans_handle *trans,
> int btrfs_read_file(struct btrfs_root *root, u64 ino, u64 start, int len,
> char *dest);
>
> +
> +/* extent-tree.c */
> +int btrfs_run_delayed_refs(struct btrfs_trans_handle *trans, unsigned long
> nr);
> #endif
> diff --git a/delayed-ref.c b/delayed-ref.c
> new file mode 100644
> index 000000000000..f3fa50239380
> --- /dev/null
> +++ b/delayed-ref.c
> @@ -0,0 +1,608 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (C) 2009 Oracle. All rights reserved.
> + */
> +
> +#include "ctree.h"
> +#include "btrfs-list.h"
> +#include "delayed-ref.h"
> +#include "transaction.h"
> +
> +/*
> + * delayed back reference update tracking. For subvolume trees
> + * we queue up extent allocations and backref maintenance for
> + * delayed processing. This avoids deep call chains where we
> + * add extents in the middle of btrfs_search_slot, and it allows
> + * us to buffer up frequently modified backrefs in an rb tree instead
> + * of hammering updates on the extent allocation tree.
> + */
A little more explanation on how delayed ref works will be more appricated.
[snip]
> +struct btrfs_delayed_tree_ref {
> + struct btrfs_delayed_ref_node node;
> + u64 root;
> + u64 parent;
> + int level;
> +};
> +
> +struct btrfs_delayed_data_ref {
> + struct btrfs_delayed_ref_node node;
> + u64 root;
> + u64 parent;
> + u64 objectid;
> + u64 offset;
> +};
Since we don't use this structure and don't support data ref yet, what
about just removing this definiation?
[snip]
> +struct btrfs_delayed_ref_head *
> +btrfs_select_ref_head(struct btrfs_trans_handle *trans);
> +
> +/*
> + * helper functions to cast a node into its container
> + */
> +static inline struct btrfs_delayed_tree_ref *
> +btrfs_delayed_node_to_tree_ref(struct btrfs_delayed_ref_node *node)
> +{
> + return container_of(node, struct btrfs_delayed_tree_ref, node);
> +}
> +
> +static inline struct btrfs_delayed_data_ref *
> +btrfs_delayed_node_to_data_ref(struct btrfs_delayed_ref_node *node)
> +{
> + return container_of(node, struct btrfs_delayed_data_ref, node);
> +}
So is the only user of btrfs_delayed_data_ref structure.
Thanks,
Qu
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