Hi Neil,
On 25 August 2017 at 07:32, NeilBrown <neilb@xxxxxxxx> wrote:
>
> Expand on the relationship between fstatat() and the other
> three functions, and improve the description of AT_NO_AUTOMOUNT.
> Specifically, both stat() and lstat() act the same way
> with respect to automounts, and that behavior matches
> fstatat with the AT_NO_AUTOMOUNT flag.
>
> The text in the NOTES is removed and places with the text for
> AT_NO_AUTOMOUNT to improve cohesion.
>
> New text for a difference to be introduced in 4.14.
Has the 4.14 piece gone in?
Cheers,
Michael
> Cc: Ian Kent <ikent@xxxxxxxxxx>
> Signed-off-by: NeilBrown <neilb@xxxxxxxx>
> ---
>
> Thanks Ian and Michael. I considered your input and read
> through the whole again, and came up with this which is
> quite different to what I suggested before.
>
> If this patch is applied, the result probably shouldn't be released
> until the relevant patch actually lands in Linus's tree.
>
> NeilBrown
>
>
> man2/stat.2 | 37 ++++++++++++++++++++++++-------------
> 1 file changed, 24 insertions(+), 13 deletions(-)
>
> diff --git a/man2/stat.2 b/man2/stat.2
> index d8a9e76b3d9f..c6dddfe0d3a7 100644
> --- a/man2/stat.2
> +++ b/man2/stat.2
> @@ -260,9 +260,12 @@ For further information on the above fields, see
> .SS fstatat()
> The
> .BR fstatat ()
> -system call operates in exactly the same way as
> +system call is a more general interface for accessing file information
> +which can still provide exactly the behavior of each of
> .BR stat (),
> -except for the differences described here.
> +.BR lstat (),
> +and
> +.BR fstat ().
> .PP
> If the pathname given in
> .I pathname
> @@ -272,6 +275,8 @@ referred to by the file descriptor
> (rather than relative to the current working directory of
> the calling process, as is done by
> .BR stat ()
> +and
> +.BR lstat ()
> for a relative pathname).
> .PP
> If
> @@ -284,7 +289,9 @@ then
> .I pathname
> is interpreted relative to the current working
> directory of the calling process (like
> -.BR stat ()).
> +.BR stat ()
> +and
> +.BR lstat ()).
> .PP
> If
> .I pathname
> @@ -307,7 +314,11 @@ is an empty string, operate on the file referred to by
> flag).
> In this case,
> .I dirfd
> -can refer to any type of file, not just a directory.
> +can refer to any type of file, not just a directory, and
> +the behavior of
> +.BR fstatat ()
> +is similar to that of
> +.BR fstat ().
> If
> .I dirfd
> is
> @@ -324,6 +335,8 @@ Don't automount the terminal ("basename") component of
> if it is a directory that is an automount point.
> This allows the caller to gather attributes of an automount point
> (rather than the location it would mount).
> +Since Linux 4.14, also don't instantiate a non-existent name in an
> +on-demand directory such as used for automounter indirect maps.
> This flag can be used in tools that scan directories
> to prevent mass-automounting of a directory of automount points.
> The
> @@ -333,6 +346,13 @@ This flag is Linux-specific; define
> .B _GNU_SOURCE
> .\" Before glibc 2.16, defining _ATFILE_SOURCE sufficed
> to obtain its definition.
> +Both
> +.BR stat ()
> +and
> +.BR lstat ()
> +act as though
> +.B AT_NO_AUTOMOUNT
> +was set.
> .TP
> .B AT_SYMLINK_NOFOLLOW
> If
> @@ -474,15 +494,6 @@ fields may be less portable.
> The interpretation differs between systems,
> and possibly on a single system when NFS mounts are involved.)
> .SH NOTES
> -On Linux,
> -.BR lstat ()
> -will generally not trigger automounter action, whereas
> -.BR stat ()
> -will (but see the description of the
> -.BR fstatat ()
> -.B AT_NO_AUTOMOUNT
> -fag, above).
> -.\"
> .SS Timestamp fields
> Older kernels and older standards did not support nanosecond timestamp
> fields.
> --
> 2.14.0.rc0.dirty
>
--
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/
