From: Qu Wenruo wqu@suse.com
This implements lookup_data_extent() function for the incoming new implementation of btrfs_file_read().
Signed-off-by: Qu Wenruo wqu@suse.com Reviewed-by: Marek Behún marek.behun@nic.cz --- fs/btrfs/inode.c | 101 +++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 101 insertions(+)
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c index ab45db87a6..11eb30c27a 100644 --- a/fs/btrfs/inode.c +++ b/fs/btrfs/inode.c @@ -825,3 +825,104 @@ out: free(dbuf); return ret; } + +/* + * Get the first file extent that covers bytenr @file_offset. + * + * @file_offset must be aligned to sectorsize. + * + * return 0 for found, and path points to the file extent. + * return >0 for not found, and fill @next_offset. + * @next_offset can be 0 if there is no next file extent. + * return <0 for error. + */ +static int lookup_data_extent(struct btrfs_root *root, struct btrfs_path *path, + u64 ino, u64 file_offset, u64 *next_offset) +{ + struct btrfs_key key; + struct btrfs_file_extent_item *fi; + u8 extent_type; + int ret = 0; + + ASSERT(IS_ALIGNED(file_offset, root->fs_info->sectorsize)); + key.objectid = ino; + key.type = BTRFS_EXTENT_DATA_KEY; + key.offset = file_offset; + + ret = btrfs_search_slot(NULL, root, &key, path, 0, 0); + /* Error or we're already at the file extent */ + if (ret <= 0) + return ret; + if (ret > 0) { + /* Check previous file extent */ + ret = btrfs_previous_item(root, path, ino, + BTRFS_EXTENT_DATA_KEY); + if (ret < 0) + return ret; + if (ret > 0) + goto check_next; + } + /* Now the key.offset must be smaller than @file_offset */ + btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]); + if (key.objectid != ino || + key.type != BTRFS_EXTENT_DATA_KEY) + goto check_next; + + fi = btrfs_item_ptr(path->nodes[0], path->slots[0], + struct btrfs_file_extent_item); + extent_type = btrfs_file_extent_type(path->nodes[0], fi); + if (extent_type == BTRFS_FILE_EXTENT_INLINE) { + if (file_offset == 0) + return 0; + /* Inline extent should be the only extent, no next extent. */ + *next_offset = 0; + return 1; + } + + /* This file extent covers @file_offset */ + if (key.offset <= file_offset && key.offset + + btrfs_file_extent_num_bytes(path->nodes[0], fi) > file_offset) + return 0; +check_next: + ret = btrfs_next_item(root, path); + if (ret < 0) + return ret; + if (ret > 0) { + *next_offset = 0; + return 1; + } + + btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]); + fi = btrfs_item_ptr(path->nodes[0], path->slots[0], + struct btrfs_file_extent_item); + /* Next next data extent */ + if (key.objectid != ino || + key.type != BTRFS_EXTENT_DATA_KEY) { + *next_offset = 0; + return 1; + } + /* Current file extent already beyond @file_offset */ + if (key.offset > file_offset) { + *next_offset = key.offset; + return 1; + } + /* This file extent covers @file_offset */ + if (key.offset <= file_offset && key.offset + + btrfs_file_extent_num_bytes(path->nodes[0], fi) > file_offset) + return 0; + /* This file extent ends before @file_offset, check next */ + ret = btrfs_next_item(root, path); + if (ret < 0) + return ret; + if (ret > 0) { + *next_offset = 0; + return 1; + } + btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]); + if (key.type != BTRFS_EXTENT_DATA_KEY || key.objectid != ino) { + *next_offset = 0; + return 1; + } + *next_offset = key.offset; + return 1; +}