Direct I/O needs to fetch a single checksum based on the
extent information instead of page struct content.
Signed-off-by: jim owens <jowens@xxxxxx>
---
fs/btrfs/ctree.h | 2 ++
fs/btrfs/file-item.c | 45 +++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 47 insertions(+), 0 deletions(-)
diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index bf04876..e5926c6 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -2281,6 +2281,8 @@ int btrfs_csum_truncate(struct btrfs_trans_handle *trans,
u64 isize);
int btrfs_lookup_csums_range(struct btrfs_root *root, u64 start,
u64 end, struct list_head *list, u32 *csums);
+int btrfs_lookup_one_csum(struct btrfs_root *root, struct inode *inode,
+ u64 disk_bytenr, u64 fpos, u32 *csum);
/* inode.c */
/* RHEL and EL kernels have a patch that renames PG_checked to FsMisc */
diff --git a/fs/btrfs/file-item.c b/fs/btrfs/file-item.c
index 72c76bd..8482a56 100644
--- a/fs/btrfs/file-item.c
+++ b/fs/btrfs/file-item.c
@@ -244,6 +244,51 @@ found:
return 0;
}
+int btrfs_lookup_one_csum(struct btrfs_root *root, struct inode *inode,
+ u64 disk_bytenr, u64 fpos, u32 *csum)
+{
+ u32 diff;
+ u16 csum_size;
+ int ret;
+ struct btrfs_path *path;
+ struct btrfs_csum_item *item;
+ struct btrfs_key found_key;
+
+ if (!btrfs_find_ordered_sum(inode, fpos, disk_bytenr, csum))
+ return 0;
+
+ *csum = 0;
+ path = btrfs_alloc_path();
+ if (!path)
+ return -ENOMEM;
+
+ item = btrfs_lookup_csum(NULL, root->fs_info->csum_root,
+ path, disk_bytenr, 0);
+ if (IS_ERR(item)) {
+ ret = PTR_ERR(item);
+ printk(KERN_INFO "btrfs no csum found "
+ "for inode %lu start %llu err %d\n",
+ inode->i_ino, (unsigned long long)fpos, ret);
+ goto notfound;
+ }
+
+ btrfs_item_key_to_cpu(path->nodes[0], &found_key, path->slots[0]);
+ item = btrfs_item_ptr(path->nodes[0], path->slots[0],
+ struct btrfs_csum_item);
+ csum_size = btrfs_super_csum_size(&root->fs_info->super_copy);
+
+ diff = disk_bytenr - found_key.offset;
+ diff = diff / root->sectorsize * csum_size;
+
+ read_extent_buffer(path->nodes[0], csum,
+ ((unsigned long)item) + diff, csum_size);
+ ret = 0;
+
+notfound:
+ btrfs_free_path(path);
+ return ret;
+}
+
int btrfs_lookup_csums_range(struct btrfs_root *root, u64 start, u64 end,
struct list_head *list, u32 *csums)
{
--
1.5.6.3
--
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