Hi Ted, On 2018/8/25 11:45, Theodore Y. Ts'o wrote: > On Sat, Aug 25, 2018 at 10:29:26AM +0800, Gao Xiang wrote: >> My first question is that 'Is there any way to skip to verify pages in a bio?' >> I am thinking about >> If metadata and data page are mixed in a filesystem of such kind, they could submit together in a bio, but metadata could be unsuitable for such kind of verification. >> >> The second question is related to the first question --- 'Is there any way to verify a partial page?' >> Take scalability into consideration, some files could be totally inlined or partially inlined in metadata. >> Is there any way to deal with them in per-file approach? at least --- support for the interface? > A requirement of both fscrypt and fsverity is that is that block size > == page size, and that all data is stored in blocks. Inline data is > not supported. > > The files that are intended for use with fsverity are large files > (such as APK files), so optimizing for files smaller than a block was > not a design goal. Thanks for your quickly reply. :) I had seen the background of why Google/Android introduces fs-verity before. > But I have some consideration than the current implementation.... (if it is suitable to discuss, thanks...) 1) Since it is the libfs-like library, I think bio-strict is too strict for its future fs users. bios could be already organized in filesystem-specific way, which could include some other pages that is unnecessary to be verified. I could give some example, if some filesystem organizes its bios for decompression, and some data exist in metadata. It could be hard to use this libfs-like fsverity interface. 2) My last question "At last, I hope filesystems could select the on-disk position of hash tree and 'struct fsverity_descriptor' rather than fixed in the end of verity files...I think if fs-verity preparing such support and interfaces could be better....." is also for some files partially or totally encoded (eg. compressed, or whatever ...) I think the hash tree is unnecessary to be compressed...so I think it could be better that it can be selected by users (filesystems of course). Thanks, Gao Xiang. > - Ted
