On Mon, Oct 7, 2024 at 8:09 PM Chuck Lever III <chuck.lever@xxxxxxxxxx> wrote:
>
>
>
> > On Oct 7, 2024, at 11:26 AM, Amir Goldstein <amir73il@xxxxxxxxx> wrote:
> >
> > On Wed, Sep 25, 2024 at 11:14 AM Christian Brauner <brauner@xxxxxxxxxx> wrote:
> >>
> >>> open_by_handle_at(2) does not have AT_ flags argument, but also, I find
> >>> it more useful API that encoding a connectable file handle can mandate
> >>> the resolving of a connected fd, without having to opt-in for a
> >>> connected fd independently.
> >>
> >> This seems the best option to me too if this api is to be added.
> >
> > Thanks.
> >
> > Jeff, Chuck,
> >
> > Any thoughts on this?
>
> I don't have anything clever to add.
>
Sometimes that's a good thing ;)
FYI, I wrote a draft for the would be man page update to go with the
proposed flag:
name_to_handle_at()
The name_to_handle_at() system call returns a file handle and a mount ID
corresponding to the file specified by the dirfd and pathname arguments.
...
When flags contain the AT_HANDLE_FID (since Linux 6.5) flag,
the caller indicates that the returned file_handle is needed to
identify the filesystem object,
and not for opening the file later,
so it should be expected that a subsequent call to open_by_handle_at()
with the returned file_handle may fail.
+ When flags contain the AT_HANDLE_CONNECTABLE (since Linux 6.x) flag,
+ the caller indicates that the returned file_handle is needed to
open a file with known path later,
+ so it should be expected that a subsequent call to open_by_handle_at()
+ with the returned file_handle may fail if the file was moved,
but otherwise,
+ the path of the opened file is expected to be visible from the
/proc/pid/fd/* magic link.
+ This flag can not be used in combination with the flags
AT_HANDLE_FID, and AT_EMPTY_PATH.
...
ESTALE The specified handle is not valid for opening a file.
This error will occur if, for example, the file has been deleted.
This error can also occur if the handle was acquired
using the AT_HANDLE_FID flag
and the filesystem does not support open_by_handle_at().
+ This error can also occur if the handle was acquired
using the AT_HANDLE_CONNECTABLE
+ flag and the file was moved to a different parent.
--
Apropos man page,
Aleksa,
Are you planning to post a man page patch for AT_HANDLE_MNT_ID_UNIQUE?
I realize that there is no man page maintainer at the moment, but I myself
would love to have this patch in my man-page updates queue,
until a man-page maintainer shows up, because, well, my update to
AT_HANDLE_CONNECTABLE depends on it and so will my changes to
fanotify to support mount/unmount events if/when I will get to them.
Thanks,
Amir.
