Introduce a new function: btrfs_read_one_data_csum(), to read out a csum
for a sectorsize.
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 <quwenruo@xxxxxxxxxxxxxx>
---
Makefile.in | 2 +-
csum.c | 96 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
ctree.h | 3 ++
3 files changed, 100 insertions(+), 1 deletion(-)
create mode 100644 csum.c
diff --git a/Makefile.in b/Makefile.in
index c3f0eeda..bb619bfe 100644
--- a/Makefile.in
+++ b/Makefile.in
@@ -99,7 +99,7 @@ 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 \
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 \
- kernel-lib/tables.o kernel-lib/raid56.o
+ kernel-lib/tables.o kernel-lib/raid56.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..53195eaf
--- /dev/null
+++ b/csum.c
@@ -0,0 +1,96 @@
+/*
+ * Copyright (C) 2016 Fujitsu. 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 "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
+ * 2) Add csum range search function
+ * So we don't need to search csum tree in a per-sectorsize loop.
+ */
+
+int btrfs_read_one_data_csum(struct btrfs_fs_info *fs_info, u64 bytenr,
+ void *csum_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 sectorsize = fs_info->tree_root->sectorsize;
+ u16 csum_size = btrfs_super_csum_size(fs_info->super_copy);
+ int ret;
+
+ if (!csum_ret) {
+ error("wrong parameter for %s", __func__);
+ return -EINVAL;
+ }
+ path = btrfs_alloc_path();
+ if (!path)
+ return -ENOMEM;
+
+ key.objectid = BTRFS_EXTENT_CSUM_OBJECTID;
+ key.type = BTRFS_EXTENT_CSUM_KEY;
+ key.offset = bytenr;
+
+ ret = btrfs_search_slot(NULL, csum_root, &key, path, 0, 0);
+ if (ret < 0)
+ goto out;
+ if (ret == 0) {
+ 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;
+ goto out;
+ }
+ u32 offset = btrfs_item_ptr_offset(path->nodes[0],
+ path->slots[0]);
+
+ read_extent_buffer(path->nodes[0], csum_ret, offset, csum_size);
+ goto out;
+ }
+ ret = btrfs_previous_item(csum_root, path, BTRFS_EXTENT_CSUM_OBJECTID,
+ BTRFS_EXTENT_CSUM_KEY);
+ if (ret)
+ goto out;
+ 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;
+ goto out;
+ }
+ 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 <= bytenr) {
+ ret = 1;
+ goto out;
+ }
+
+ final_offset = (bytenr - key.offset) / sectorsize * csum_size +
+ item_offset;
+ read_extent_buffer(path->nodes[0], csum_ret, final_offset, csum_size);
+ ret = 0;
+out:
+ btrfs_free_path(path);
+ return ret;
+};
diff --git a/ctree.h b/ctree.h
index dd02ef86..506b107e 100644
--- a/ctree.h
+++ b/ctree.h
@@ -2798,4 +2798,7 @@ int btrfs_get_extent(struct btrfs_trans_handle *trans,
int btrfs_punch_hole(struct btrfs_trans_handle *trans,
struct btrfs_root *root,
u64 ino, u64 offset, u64 len);
+/* csum.c */
+int btrfs_read_one_data_csum(struct btrfs_fs_info *fs_info, u64 bytenr,
+ void *csum_ret);
#endif
--
2.11.0
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