I'm trying to implement statx for fuse and ran into the following issues: - Need a STATX_ATTRIBUTES bit, so that userspace can explicitly ask for stx_attribute; otherwise if querying has non-zero cost, then filesystem cannot do it without regressing performance. - STATX_ALL definition is unclear, can this change, or is it fixed? If it's the former, than that's a backward compatibility nightmare. If it's the latter, then what's the point? - STATX_ATIME is cleared from stx_mask on SB_RDONLY, and on NFS it is also cleared on MNT_NOATIME, but not on MNT_RDONLY. We need some sort of guideline in the documentation about what constitutes "unsupported": does atime become unsupported because filesystem is remounted r/o? If so, why isn't this case handled consistently in the VFS and filesystems? - What about fields that are not cached when statx() is called with AT_STATX_DONT_SYNC? E.g. stx_btime is supported by the filesystem, but getting it requires a roundtrip to the server. Requesting STATX_BTIME in the mask and adding AT_STATX_DONT_SYNC to the flags means the filesystem has to decide which it will honor. My feeling is that it should honor AT_STATX_DONT_SYNC and clear STATX_BTIME in stx_mask. Documentation has no word about this case. Thanks, Miklos
