Re: [PATCH RFC 4/4] btrfs-progs: convert: support ext2 unwritten file data extents

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在 2024/5/3 21:55, Anand Jain 写道:
+int find_prealloc(struct blk_iterate_data *data, int index, bool *prealloc)

This function is called for every file extent we're going to create.
I'm not a big fan of doing so many lookup.

My question is, is this the only way to determine the flag of the data extent?

My instinct says there should be a straight forward way to determine if a file extent is preallocated or not, just like what we do in our file extent items.

Thus during the ext2fs_block_iterate2(), there should be some way to tell if a block is preallocated or not.

Unfortunately, the callback doesn't provide the extent flags. Unless,  I miss something?

You're right, the iterator interface does not provide any extra info.

And I also checked the kernel implementation, they have extra ext4_map_blocks() to do the resolve, and then ext4_es_lookup_extent() to determine if it's unwritten.

So I'm afraid we have to go this solution.

Meanwhile related to the implementation, can we put the prealloc flat into blk_iterate_data? So that we can handle different fses' preallocated extents in a more common way.


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