Re: [PATCH 0/3] updated *at function patch

[Ulrich Drepper]

Andrew Morton wrote:
> We don't have changelogs for these patches.  Apart from the usual
> what-it-does and how-it-does it I'd really like to be reminded of the
> "why".  Adding a bunch of stuff to the core kernel codepaths needs to have
> a good reason and I've forgotten your rationale.

This is the intro from the first set of patches I sent (I adjusted it
for the additional syscalls):

====
Here is a series of patches which introduce in total 13 new system calls
which take a file descriptor/filename pair instead of a single file
name.  These functions, openat etc, have been discussed on numerous
occasions.  They are needed to implement race-free filesystem traversal,
they are necessary to implement a virtual per-thread current working
directory (think multi-threaded backup software), etc.

We have in glibc today implementations of the interfaces which use the
/proc/self/fd magic.  But this code is rather expensive.  Here are some
results (similar to what Jim Meyering posted before).

The test creates a deep directory hierarchy on a tmpfs filesystem.  Then
rm -fr is used to remove all directories.  Without syscall support I get
this:

real    0m31.921s
user    0m0.688s
sys     0m31.234s

With syscall support the results are much better:

real    0m20.699s
user    0m0.536s
sys     0m20.149s
=====



> We'll need Signed-off_by:'s for all these patches.

I'm not sure how you want to handle this.  I don't particularly want to
resent all of them just for this purpose.

[PATCH 1/3] updated *at function patch

Signed-off-by: Ulrich Drepper <drepper@xxxxxxxxxx>

[PATCH 2/3] updated *at function patch

Signed-off-by: Ulrich Drepper <drepper@xxxxxxxxxx>

[PATCH 3/3] updated *at function patch

Signed-off-by: Ulrich Drepper <drepper@xxxxxxxxxx>


-- 
â Ulrich Drepper â Red Hat, Inc. â 444 Castro St â Mountain View, CA â

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