Re: "ls -l": Avoid unnecessary getxattr() overhead

[Jim Meyering]

Pádraig Brady wrote:
> On 02/16/2012 07:39 PM, Jim Meyering wrote:
>
>> diff --git a/src/ls.c b/src/ls.c
>
>> +/* st_dev of the most recently processed device for which
>> +   we've found that getfilecon or lgetfilecon fails with
>> +   e.g., ENOTSUP or EOPNOTSUPP.  */
>> +static dev_t selinux_challenged_device;
>> +
>> +/* Cache getfilecon failure, when it's trivial to do.
>> +   Like getfilecon, but when F's st_dev says it's on a known-
>> +   SELinux-challenged file system, fail with ENOTSUP immediately.  */
>> +static int
>> +getfilecon_cache (char const *file, struct fileinfo *f)
>> +{
>> +  if (f->stat.st_dev == selinux_challenged_device)
>> +    {
>> +      errno = ENOTSUP;
>> +      return -1;
>> +    }
>> +  int r = getfilecon (file, &f->scontext);
>> +  if (r < 0 && errno_unsupported (errno))
>> +    selinux_challenged_device = f->stat.st_dev;
>> +  return r;
>> +}
>> +
>> +/* Cache lgetfilecon failure, when it's trivial to do.
>> +   Like lgetfilecon, but when F's st_dev says it's on a known-
>> +   SELinux-challenged file system, fail with ENOTSUP immediately.  */
>> +static int
>> +lgetfilecon_cache (char const *file, struct fileinfo *f)
>> +{
>> +  if (f->stat.st_dev == selinux_challenged_device)
>> +    {
>> +      errno = ENOTSUP;
>> +      return -1;
>> +    }
>> +  int r = lgetfilecon (file, &f->scontext);
>> +  if (r < 0 && errno_unsupported (errno))
>> +    selinux_challenged_device = f->stat.st_dev;
>> +  return r;
>> +}
>
> I'd be inclined to refactor the above 2 functions to one like:

Very inclined.
Nice improvement.  Thank you!

> static int
> getfilecon_cache (char const *file, struct fileinfo *f, bool do_deref)
> {
>   /* st_dev of the most recently processed device for which we've
>      found that [l]getfilecon fails indicating lack of support.  */
>   static dev_t unsupported_device;
>
>   if (f->stat.st_dev == unsupported_device)
>     {
>       errno = ENOTSUP;
>       return -1;
>     }
>   int r = (do_deref ? getfilecon : lgetfilecon) (file, &f->scontext);
>   if (r < 0 && errno_unsupported (errno))
>     unsupported_device = f->stat.st_dev;
>   return r;
> }
>
>>>From 796b05173ad9d34a3403e2201152a1a81fd973a1 Mon Sep 17 00:00:00 2001
>> From: Jim Meyering <address@hidden>
>> Date: Mon, 13 Feb 2012 12:05:40 +0100
>> Subject: [PATCH 2/3] ls: also cache ACL- and CAP-querying syscall failures
>
> patch series are not apparent in git shortlog summaries etc.,
> so I'd s/also//

Thanks again.

Plus, I still have to mention this in NEWS.