Messages in this thread | | | Date | Thu, 1 Nov 2007 02:15:33 +0800 | From | "rae l" <> | Subject | Re: [PATCH] [sysfs]: make readlink result shorter when the symlink and its target shared some base sysfs subdirectory |
| |
On 10/31/07, Greg KH <gregkh@suse.de> wrote: > On Wed, Oct 31, 2007 at 06:34:20PM +0800, Denis Cheng wrote: > > this is especially useful after /sys/slab introduced, for example: > > > > $ ls -l /sys/slab/mm_struct > > lrwxrwxrwx 1 root root 0 2007-10-31 17:40 /sys/slab/mm_struct -> :0000448 > > > > instead of: > > > > $ ls -l /sys/slab/mm_struct > > lrwxrwxrwx 1 root root 0 2007-10-31 17:40 /sys/slab/mm_struct -> ../slab/:0000448 > > > > Signed-off-by: Denis Cheng <crquan@gmail.com> > > As pretty as this change is, it's not really necessary, right? I don't think so.
Suppose to create a symlink on the disk, say /usr/src/linux, that points to /usr/src/linux-2.6.23, the best way is: # cd /usr/src/ # ln -s linux-2.6.23 linux # ls -l linux # ls -l linux lrwxrwxrwx 1 root root 14 2007-10-16 19:21 linux -> linux-2.6.23
other than: # cd /usr/src/ # ln -s /usr/src/linux-2.6.23 linux or # ln -s ../../usr/src/linux-2.6.23 linux # ls -l linux lrwxrwxrwx 1 root root 14 2007-10-16 19:21 linux -> ../../usr/src/linux-2.6.23
Anyone know this, since sysfs is also a filesystem, it should conform the perfect way.
For another point, consider the code in fs/sysfs/symlink.c:
static int sysfs_get_target_path(struct sysfs_dirent * parent_sd, struct sysfs_dirent * target_sd, char *path) { ... size = object_path_length(target_sd) + depth * 3 - 1; if (size > PATH_MAX) return -ENAMETOOLONG;
Since having longer readlink result would consume more memory on the output parameter path, that is error prone to return -ENAMETOOLONG; we just need the shorter readlink result.
> > Is there any other place in /sys that would benefit from this? Yes. there are already some other symlinks those are also not crossing top subdirectory of /sys, they would benefit from this patch:
I have found all of them by this little shell:
$ find /sys -type l -printf '%p -> %l -> ' -exec readlink -f '{}' \; | gawk '{ split($1, a, "/"); split($5, b, "/"); if (a[3] == b[3]) print; }'
that will print many lines like:
... /sys/block/hdd/subsystem -> ../../block -> /sys/block /sys/module/snd_mixer_oss/holders/snd_pcm_oss -> ../../../module/snd_pcm_oss -> /sys/module/snd_pcm_oss /sys/class/sound/audio/subsystem -> ../../../class/sound -> /sys/class/sound /sys/class/pci_bus/0000:00/subsystem -> ../../../class/pci_bus -> /sys/class/pci_bus ...
> > thanks, > > greg k-h >
-- Denis Cheng Linux Application Developer
"One of my most productive days was throwing away 1000 lines of code." - Ken Thompson. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |