On 2/18/20 4:01 AM, Qu Wenruo wrote:
Due to the complex nature of btrfs extent tree, when we want to iterate
all backrefs of one extent, it involves quite a lot of work, like
searching the EXTENT_ITEM/METADATA_ITEM, iteration through inline and keyed
backrefs.
Normally this would result pretty complex code, something like:
btrfs_search_slot()
/* Ensure we are at EXTENT_ITEM/METADATA_ITEM */
while (1) { /* Loop for extent tree items */
while (ptr < end) { /* Loop for inlined items */
/* REAL WORK HERE */
}
next:
ret = btrfs_next_item()
/* Ensure we're still at keyed item for specified bytenr */
}
The idea of btrfs_backref_iter is to avoid such complex and hard to
read code structure, but something like the following:
iter = btrfs_backref_iter_alloc();
ret = btrfs_backref_iter_start(iter, bytenr);
if (ret < 0)
goto out;
for (; ; ret = btrfs_backref_iter_next(iter)) {
/* REAL WORK HERE */
}
out:
btrfs_backref_iter_free(iter);
This patch is just the skeleton + btrfs_backref_iter_start() code.
Signed-off-by: Qu Wenruo <wqu@xxxxxxxx>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@xxxxxxx>
Reviewed-by: Josef Bacik <josef@xxxxxxxxxxxxxx>
Thanks,
Josef
