From 453e66a3babf3d8bd4fc0bbf84b7243fc09b016e Mon Sep 17 00:00:00 2001 From: Qu Wenruo Date: Mon, 26 Dec 2016 14:29:28 +0800 Subject: [PATCH] btrfs-progs: csum: Introduce function to read out data csums Introduce a new function: btrfs_read_data_csums(), to read out csums for sectors in range. This is quite useful for read out data csum so we don't need to do it using open code. Signed-off-by: Qu Wenruo Signed-off-by: Su Yue Signed-off-by: Gu Jinxiang --- Makefile | 2 +- csum.c | 130 +++++++++++++++++++++++++++++++++++++++++++++++++++ ctree.h | 4 ++ kerncompat.h | 3 ++ utils.h | 6 +++ 5 files changed, 144 insertions(+), 1 deletion(-) create mode 100644 csum.c diff --git a/Makefile b/Makefile index a114ecac..910209d8 100644 --- a/Makefile +++ b/Makefile @@ -103,7 +103,7 @@ 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 csum.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 cmds-check.o \ diff --git a/csum.c b/csum.c new file mode 100644 index 00000000..a2ce755e --- /dev/null +++ b/csum.c @@ -0,0 +1,130 @@ +/* + * 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. + */ + +#include "kerncompat.h" +#include "kernel-lib/bitops.h" +#include "ctree.h" +#include "utils.h" + +/* + * TODO: + * 1) Add write support for csum + * So we can write new data extents and add csum into csum tree + * + * Get csums of range[@start, @start + len). + * + * @start: Start offset, shall be aligned to sectorsize. + * @len: Length, shall be aligned to sectorsize. + * @csum_ret: The size of csum_ret shall be @len / sectorsize * csum_size. + * @bit_map: Every bit corresponds to the offset have csum or not. + * The size in byte of bit_map should be + * calculate_bitmap_len(csum_ret's size / csum_size). + * + * Returns 0 means success + * Returns >0 means on error + * Returns <0 means on fatal error + */ + +int btrfs_read_data_csums(struct btrfs_fs_info *fs_info, u64 start, u64 len, + void *csum_ret, unsigned long *bitmap_ret) + +{ + struct btrfs_path path; + struct btrfs_key key; + struct btrfs_root *csum_root = fs_info->csum_root; + u32 item_offset; + u32 item_size; + u32 final_offset; + u32 final_len; + u32 i; + u32 sectorsize = fs_info->sectorsize; + u16 csum_size = btrfs_super_csum_size(fs_info->super_copy); + u64 cur_start; + u64 cur_end; + int found = 0; + int ret; + + ASSERT(IS_ALIGNED(start, sectorsize)); + ASSERT(IS_ALIGNED(len, sectorsize)); + ASSERT(csum_ret); + ASSERT(bitmap_ret); + + memset(bitmap_ret, 0, calculate_bitmap_len(len / sectorsize)); + btrfs_init_path(&path); + + key.objectid = BTRFS_EXTENT_CSUM_OBJECTID; + key.type = BTRFS_EXTENT_CSUM_KEY; + key.offset = start; + + ret = btrfs_search_slot(NULL, csum_root, &key, &path, 0, 0); + if (ret < 0) + goto out; + if (ret > 0) { + ret = btrfs_previous_item(csum_root, &path, + BTRFS_EXTENT_CSUM_OBJECTID, + BTRFS_EXTENT_CSUM_KEY); + if (ret < 0) + goto out; + } + /* The csum tree may be empty. */ + if (!btrfs_header_nritems(path.nodes[0])) + goto next; + + while (1) { + btrfs_item_key_to_cpu(path.nodes[0], &key, path.slots[0]); + + if (!IS_ALIGNED(key.offset, sectorsize)) { + error("csum item bytenr %llu is not aligned to %u", + key.offset, sectorsize); + ret = -EIO; + break; + } + /* exceeds end */ + if (key.offset >= start + len) + break; + + item_offset = btrfs_item_ptr_offset(path.nodes[0], + path.slots[0]); + item_size = btrfs_item_size_nr(path.nodes[0], path.slots[0]); + + if (key.offset + item_size / csum_size * sectorsize < start) + goto next; + + /* get start of the extent */ + cur_start = max(start, key.offset); + /* get end of the extent */ + cur_end = min(start + len, key.offset + item_size / csum_size * + sectorsize); + + final_offset = (cur_start - key.offset) / sectorsize * + csum_size + item_offset; + final_len = (cur_end - cur_start) / sectorsize * csum_size; + read_extent_buffer(path.nodes[0], + (csum_ret + (cur_start - start) / + sectorsize * csum_size), + final_offset, final_len); + + for (i = 0; i != final_len / csum_size; i++) + set_bit(i + (cur_start - start) / sectorsize, + bitmap_ret); + + found = 1; +next: + ret = btrfs_next_item(csum_root, &path); + if (ret) + break; + } +out: + if (ret >= 0) + ret = !found; + btrfs_release_path(&path); + return ret; +} diff --git a/ctree.h b/ctree.h index 81c193f1..4684e001 100644 --- a/ctree.h +++ b/ctree.h @@ -2762,4 +2762,8 @@ 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); +/* csum.c */ +int btrfs_read_data_csums(struct btrfs_fs_info *fs_info, u64 start, u64 len, + void *csum_ret, unsigned long *bitmap_ret); + #endif diff --git a/kerncompat.h b/kerncompat.h index fa96715f..4eb62f68 100644 --- a/kerncompat.h +++ b/kerncompat.h @@ -273,6 +273,9 @@ static inline int IS_ERR_OR_NULL(const void *ptr) #define round_up(x, y) ((((x)-1) | __round_mask(x, y))+1) #define round_down(x, y) ((x) & ~__round_mask(x, y)) +#define __KERNEL_DIV_ROUND_UP(n, d) (((n) + (d) - 1) / (d)) +#define DIV_ROUND_UP __KERNEL_DIV_ROUND_UP + /* * printk */ diff --git a/utils.h b/utils.h index d28a05a6..505d3776 100644 --- a/utils.h +++ b/utils.h @@ -28,6 +28,7 @@ #include "btrfs-list.h" #include "sizes.h" #include "messages.h" +#include "kerncompat.h" #define BTRFS_SCAN_MOUNTED (1ULL << 0) #define BTRFS_SCAN_LBLKID (1ULL << 1) @@ -68,6 +69,11 @@ void units_set_base(unsigned *units, unsigned base); #define PREP_DEVICE_DISCARD (1U << 1) #define PREP_DEVICE_VERBOSE (1U << 2) +static inline int calculate_bitmap_len(int nsectors) +{ + return (DIV_ROUND_UP(nsectors, BITS_PER_LONG) * sizeof(long)); +} + int btrfs_make_root_dir(struct btrfs_trans_handle *trans, struct btrfs_root *root, u64 objectid); int btrfs_prepare_device(int fd, const char *file, u64 *block_count_ret,