From mboxrd@z Thu Jan 1 00:00:00 1970 From: jim owens Subject: [RFC 11/12 PATCH] Btrfs: add direct I/O helper btrfs_lookup_one_csum(). Date: Mon, 04 Jan 2010 16:14:21 -0500 Message-ID: <4B425A2D.5030207@hp.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 To: linux-btrfs Return-path: List-ID: Direct I/O needs to fetch a single checksum based on the extent information instead of page struct content. Signed-off-by: jim owens --- 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