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d352ac6814
This improves the comments at the top of many functions. It didn't dive into the guts of functions because I was trying to avoid merging problems with the new allocator and back reference work. extent-tree.c and volumes.c were both skipped, and there is definitely more work todo in cleaning and commenting the code. Signed-off-by: Chris Mason <chris.mason@oracle.com>
133 lines
4.6 KiB
C
133 lines
4.6 KiB
C
/*
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* Copyright (C) 2007 Oracle. All rights reserved.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public
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* License v2 as published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*
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* You should have received a copy of the GNU General Public
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* License along with this program; if not, write to the
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* Free Software Foundation, Inc., 59 Temple Place - Suite 330,
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* Boston, MA 021110-1307, USA.
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*/
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#include <linux/highmem.h>
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/* this is some deeply nasty code. ctree.h has a different
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* definition for this BTRFS_SETGET_FUNCS macro, behind a #ifndef
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*
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* The end result is that anyone who #includes ctree.h gets a
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* declaration for the btrfs_set_foo functions and btrfs_foo functions
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*
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* This file declares the macros and then #includes ctree.h, which results
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* in cpp creating the function here based on the template below.
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*
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* These setget functions do all the extent_buffer related mapping
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* required to efficiently read and write specific fields in the extent
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* buffers. Every pointer to metadata items in btrfs is really just
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* an unsigned long offset into the extent buffer which has been
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* cast to a specific type. This gives us all the gcc type checking.
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*
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* The extent buffer api is used to do all the kmapping and page
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* spanning work required to get extent buffers in highmem and have
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* a metadata blocksize different from the page size.
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*/
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#define BTRFS_SETGET_FUNCS(name, type, member, bits) \
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u##bits btrfs_##name(struct extent_buffer *eb, \
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type *s) \
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{ \
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unsigned long part_offset = (unsigned long)s; \
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unsigned long offset = part_offset + offsetof(type, member); \
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type *p; \
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/* ugly, but we want the fast path here */ \
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if (eb->map_token && offset >= eb->map_start && \
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offset + sizeof(((type *)0)->member) <= eb->map_start + \
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eb->map_len) { \
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p = (type *)(eb->kaddr + part_offset - eb->map_start); \
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return le##bits##_to_cpu(p->member); \
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} \
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{ \
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int err; \
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char *map_token; \
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char *kaddr; \
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int unmap_on_exit = (eb->map_token == NULL); \
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unsigned long map_start; \
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unsigned long map_len; \
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__le##bits res; \
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err = map_extent_buffer(eb, offset, \
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sizeof(((type *)0)->member), \
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&map_token, &kaddr, \
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&map_start, &map_len, KM_USER1); \
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if (err) { \
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read_eb_member(eb, s, type, member, &res); \
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return le##bits##_to_cpu(res); \
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} \
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p = (type *)(kaddr + part_offset - map_start); \
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res = le##bits##_to_cpu(p->member); \
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if (unmap_on_exit) \
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unmap_extent_buffer(eb, map_token, KM_USER1); \
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return res; \
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} \
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} \
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void btrfs_set_##name(struct extent_buffer *eb, \
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type *s, u##bits val) \
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{ \
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unsigned long part_offset = (unsigned long)s; \
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unsigned long offset = part_offset + offsetof(type, member); \
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type *p; \
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/* ugly, but we want the fast path here */ \
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if (eb->map_token && offset >= eb->map_start && \
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offset + sizeof(((type *)0)->member) <= eb->map_start + \
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eb->map_len) { \
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p = (type *)(eb->kaddr + part_offset - eb->map_start); \
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p->member = cpu_to_le##bits(val); \
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return; \
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} \
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{ \
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int err; \
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char *map_token; \
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char *kaddr; \
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int unmap_on_exit = (eb->map_token == NULL); \
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unsigned long map_start; \
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unsigned long map_len; \
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err = map_extent_buffer(eb, offset, \
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sizeof(((type *)0)->member), \
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&map_token, &kaddr, \
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&map_start, &map_len, KM_USER1); \
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if (err) { \
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val = cpu_to_le##bits(val); \
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write_eb_member(eb, s, type, member, &val); \
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return; \
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} \
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p = (type *)(kaddr + part_offset - map_start); \
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p->member = cpu_to_le##bits(val); \
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if (unmap_on_exit) \
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unmap_extent_buffer(eb, map_token, KM_USER1); \
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} \
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}
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#include "ctree.h"
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void btrfs_node_key(struct extent_buffer *eb,
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struct btrfs_disk_key *disk_key, int nr)
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{
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unsigned long ptr = btrfs_node_key_ptr_offset(nr);
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if (eb->map_token && ptr >= eb->map_start &&
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ptr + sizeof(*disk_key) <= eb->map_start + eb->map_len) {
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memcpy(disk_key, eb->kaddr + ptr - eb->map_start,
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sizeof(*disk_key));
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return;
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} else if (eb->map_token) {
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unmap_extent_buffer(eb, eb->map_token, KM_USER1);
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eb->map_token = NULL;
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}
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read_eb_member(eb, (struct btrfs_key_ptr *)ptr,
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struct btrfs_key_ptr, key, disk_key);
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}
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