Messages in this thread | | | Date | Thu, 11 Jan 2024 16:11:38 +0000 | Subject | Re: [PATCH v2 00/16] block atomic writes | From | John Garry <> |
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> >>> I think this still needs a check if the fs needs alignment for >>> atomic writes at all. i.e. >>> >>> struct statx statx; >>> struct fsxattr fsxattr; >>> int fd = open('/foofile', O_RDWR | O_DIRECT); >>> >>> ioctl(fd, FS_IOC_GETXATTR, &fsxattr); >>> statx(fd, "", AT_EMPTY_PATH, STATX_ALL | STATX_WRITE_ATOMIC, &statx); >>> if (statx.stx_atomic_write_unit_max < 16384) { >>> bailout(); >>> } >> >> How could this value be >= 16384 initially? Would it be from pre-configured >> FS alignment, like XFS RT extsize? Or is this from some special CoW-based >> atomic write support? Or FS block size of 16384? > > Sorry, this check should not be here at all, we should only check it > later. > >> Incidentally, for consistency only setting FS_XFLAG_WRITE_ATOMIC will lead >> to FMODE_CAN_ATOMIC_WRITE being set. So until FS_XFLAG_WRITE_ATOMIC is set >> would it make sense to have statx return 0 for STATX_WRITE_ATOMIC. > > True. We might need to report the limits even without that, though.
Could we just error the SETXATTR ioctl when FS_XFLAG_FORCEALIGN is not set (and it is required)? The problem is that ioctl reports -EINVAL for any such errors, so hard for the user to know the issue...
Thanks, John
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