Remove incorrect comments.

[markj]

Summary

(ufs|ext2)_getlbns() will return the logical block numbers of indirect
blocks needed to address a block.

[kib]

sys/ufs/ufs/ufs_bmap.c

104

Can you replace it by description what the function returns, de-facto ?

[markj]

• Readd a comment explaining the return value.

[kib]

sys/ufs/ufs/ufs_bmap.c

101–106

to a physical block number,

102

nbp must be provided when mapping extattr block, and is the buffer for that block.
runb and runp, if provided, store the contiguous block runs before and after the *bnp block.

[markj]

• Describe nbp, runb and runp parameters per kib's suggestion.

[mckusick]

I would preface the actual condition "The nbp parameter is non-NULL when the mapping is for a block that contains data, one of an external data block, a direct block, or the final block in a chain of indirect blocks." before the correct clarification "If mapping an extended attribute block, nbp must point to a buffer for that block."

[markj]

• Update based on Kirk's comment.

[markj]

In D19598#419790, @mckusick wrote:

I would preface the actual condition "The nbp parameter is non-NULL when the mapping is for a block that contains data, one of an external data block, a direct block, or the final block in a chain of indirect blocks." before the correct clarification "If mapping an extended attribute block, nbp must point to a buffer for that block."

@kib pointed out that this doesn't make much sense given that nbp is only actually used when mapping an extended attribute block. In practice, ufs_strategy() will specify the buffer when reading data blocks, but it doesn't have to. Is this what you were referring to?