diff options
Diffstat (limited to 'fs/btrfs/struct-funcs.c')
| -rw-r--r-- | fs/btrfs/struct-funcs.c | 142 |
1 files changed, 142 insertions, 0 deletions
diff --git a/fs/btrfs/struct-funcs.c b/fs/btrfs/struct-funcs.c new file mode 100644 index 000000000..b976597b0 --- /dev/null +++ b/fs/btrfs/struct-funcs.c @@ -0,0 +1,142 @@ +/* + * Copyright (C) 2007 Oracle. All rights reserved. + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public + * License v2 as published by the Free Software Foundation. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + * General Public License for more details. + * + * You should have received a copy of the GNU General Public + * License along with this program; if not, write to the + * Free Software Foundation, Inc., 59 Temple Place - Suite 330, + * Boston, MA 021110-1307, USA. + */ + +#include <linux/highmem.h> +#include <asm/unaligned.h> + +#include "ctree.h" + +static inline u8 get_unaligned_le8(const void *p) +{ + return *(u8 *)p; +} + +static inline void put_unaligned_le8(u8 val, void *p) +{ + *(u8 *)p = val; +} + +/* + * this is some deeply nasty code. + * + * The end result is that anyone who #includes ctree.h gets a + * declaration for the btrfs_set_foo functions and btrfs_foo functions, + * which are wappers of btrfs_set_token_#bits functions and + * btrfs_get_token_#bits functions, which are defined in this file. + * + * These setget functions do all the extent_buffer related mapping + * required to efficiently read and write specific fields in the extent + * buffers. Every pointer to metadata items in btrfs is really just + * an unsigned long offset into the extent buffer which has been + * cast to a specific type. This gives us all the gcc type checking. + * + * The extent buffer api is used to do the page spanning work required to + * have a metadata blocksize different from the page size. + */ + +#define DEFINE_BTRFS_SETGET_BITS(bits) \ +u##bits btrfs_get_token_##bits(struct extent_buffer *eb, void *ptr, \ + unsigned long off, \ + struct btrfs_map_token *token) \ +{ \ + unsigned long part_offset = (unsigned long)ptr; \ + unsigned long offset = part_offset + off; \ + void *p; \ + int err; \ + char *kaddr; \ + unsigned long map_start; \ + unsigned long map_len; \ + int size = sizeof(u##bits); \ + u##bits res; \ + \ + if (token && token->kaddr && token->offset <= offset && \ + token->eb == eb && \ + (token->offset + PAGE_CACHE_SIZE >= offset + size)) { \ + kaddr = token->kaddr; \ + p = kaddr + part_offset - token->offset; \ + res = get_unaligned_le##bits(p + off); \ + return res; \ + } \ + err = map_private_extent_buffer(eb, offset, size, \ + &kaddr, &map_start, &map_len); \ + if (err) { \ + __le##bits leres; \ + \ + read_extent_buffer(eb, &leres, offset, size); \ + return le##bits##_to_cpu(leres); \ + } \ + p = kaddr + part_offset - map_start; \ + res = get_unaligned_le##bits(p + off); \ + if (token) { \ + token->kaddr = kaddr; \ + token->offset = map_start; \ + token->eb = eb; \ + } \ + return res; \ +} \ +void btrfs_set_token_##bits(struct extent_buffer *eb, \ + void *ptr, unsigned long off, u##bits val, \ + struct btrfs_map_token *token) \ +{ \ + unsigned long part_offset = (unsigned long)ptr; \ + unsigned long offset = part_offset + off; \ + void *p; \ + int err; \ + char *kaddr; \ + unsigned long map_start; \ + unsigned long map_len; \ + int size = sizeof(u##bits); \ + \ + if (token && token->kaddr && token->offset <= offset && \ + token->eb == eb && \ + (token->offset + PAGE_CACHE_SIZE >= offset + size)) { \ + kaddr = token->kaddr; \ + p = kaddr + part_offset - token->offset; \ + put_unaligned_le##bits(val, p + off); \ + return; \ + } \ + err = map_private_extent_buffer(eb, offset, size, \ + &kaddr, &map_start, &map_len); \ + if (err) { \ + __le##bits val2; \ + \ + val2 = cpu_to_le##bits(val); \ + write_extent_buffer(eb, &val2, offset, size); \ + return; \ + } \ + p = kaddr + part_offset - map_start; \ + put_unaligned_le##bits(val, p + off); \ + if (token) { \ + token->kaddr = kaddr; \ + token->offset = map_start; \ + token->eb = eb; \ + } \ +} + +DEFINE_BTRFS_SETGET_BITS(8) +DEFINE_BTRFS_SETGET_BITS(16) +DEFINE_BTRFS_SETGET_BITS(32) +DEFINE_BTRFS_SETGET_BITS(64) + +void btrfs_node_key(struct extent_buffer *eb, + struct btrfs_disk_key *disk_key, int nr) +{ + unsigned long ptr = btrfs_node_key_ptr_offset(nr); + read_eb_member(eb, (struct btrfs_key_ptr *)ptr, + struct btrfs_key_ptr, key, disk_key); +} |