Messages in this thread | | | Date | Wed, 19 Mar 2014 15:13:49 +1100 | From | NeilBrown <> | Subject | Re: For review: open_by_name_at(2) man page [v2] |
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On Tue, 18 Mar 2014 13:55:15 +0100 "Michael Kerrisk (man-pages)" <mtk.manpages@gmail.com> wrote:
> Hi Aneesh, (and others) > > After integrating review comments from NeilBown and Christoph Hellwig, > here is draft 2 of a man page I've written for name_to_handle_at(2) and > open_by_name_at(2). Especially thanks to Neil's comments, several parts > of the page underwent a substantial rewrite. Would you be willing to > review it please, and let me know of any corrections/improvements?
I didn't notice before but above and in $SUBJ I see "open_by_name_at", which is fictitious :-)
> > Together, the > .I pathname > and > .I dirfd > arguments identify the file for which a handle is to obtained. ^be
> > The > .I flags > argument is a bit mask constructed by ORing together > zero or more of the following value: ^s
> .TP > .B AT_EMPTY_PATH > Allow > .I pathname > to be an empty string. > See above. > (which may have been obtained using the > .BR open (2) > .B O_PATH > flag).
What "may have been obtained" ??
> The > .I flags > argument > is as for > .BR open (2). > .\" FIXME: Confirm that the following is intended behavior. > .\" (It certainly seems to be the behavior, from experimenting.) > If > .I handle > refers to a symbolic link, the caller must specify the > .B O_PATH > flag, and the symbolic link is not dereferenced (the > .B O_NOFOLLOW > flag, if specified, is ignored).
It certainly sounds like reasonable behaviour. I cannot comment on intention though. Are you bothered that O_PATH is needed for symlinks? An fd on a symlink is a sufficiently unusual thing that it seems reasonable for a programmer to explicitly say they are expecting one.
> > In the event of an error, both system calls return \-1 and set > .I errno > to indicate the cause of the error. > .SH ERRORS > .BR name_to_handle_at () > and > .BR open_by_handle_at () > can fail for the same errors as > .BR openat (2). > In addition, they can fail with the errors noted below.
Should you mention EFAULT if mount_id or handle are not valid pointers?
> > Not all filesystem types support the translation of pathnames to > file handles. > .\" FIXME NeilBrown noted: > .\" ESTALE is also returned if the filesystem does not support > .\" file-handle -> file mappings. > .\" On filesystems which don't provide export_operations (/sys /proc > .\" ubifs romfs cramfs nfs coda ... several others) name_to_handle_at > .\" will produce a generic handle using the 32 bit inode and 32 bit > .\" i_generation. open_by_name_at given this (or any) filehandle > .\" will fail with ESTALE. > .\" However, on /proc and /sys, at least, name_to_handle_at() fails with > .\" EOPNOTSUPP. Are there really filesystems that can deliver ESTALE (the > .\" same error as for an invalid file handle) in the above circumstances?
This is all wrong - discard it :-)
NeilBrown
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