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Re: bug#10363: df vs. long-named /dev/disk/by-uuid/... file system devic
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From: |
Jim Meyering |
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Subject: |
Re: bug#10363: df vs. long-named /dev/disk/by-uuid/... file system device names |
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Date: |
Mon, 02 Jan 2012 22:12:32 +0100 |
Pádraig Brady wrote:
...
>> Now, I'm thinking about making this a little more future-proof by
>> matching the UUID part /[0-9a-fA-F-]{36}$/ instead.
>> I.e., testing something like this:
>>
>> if (process_all
>> && has_uuid_suffix (dev_name)
>> && (resolved_dev = canonicalize_filename_mode (dev_name,
>> CAN_EXISTING)))
>>
>> using this new function:
>>
>> static bool
>> has_uuid_suffix (char const *s)
>> {
>> size_t len = strlen (s);
>> return (36 < len
>> && strspn (s + len - 36, "-0123456789abcdefABCDEF") == 36);
>> }
>
> Yes that's awkward but warranted.
> The logic looks correct.
>
> This is assuming of course that UUIDs are the only "high level" form
> presented in /proc/mounts that one doesn't want displayed.
> I can't think of anything else worth avoiding at the moment.
Thanks for the review.
Here's an updated patch.
Changes:
- added comment for new function
- added _GL_ATTRIBUTE_PURE, too
- updated commit log and comments
>From b30f021ada261e8b248f7040f8c98db6495e9e88 Mon Sep 17 00:00:00 2001
From: Jim Meyering <address@hidden>
Date: Thu, 29 Dec 2011 14:49:00 +0100
Subject: [PATCH] df: work around long-named /dev/disk/by-uuid/... symlinks
On systems with recent kernel/tools, a symlink from /etc/mtab to
/proc/mounts, and a by-UUID mount (i.e., soon, nearly everyone),
you will see something like the following when running "df -hT":
(this has been truncated to fit in a width-limited ChangeLog file)
Filesystem Type Siz...
rootfs rootfs 11G
udev devtmpfs 3.8G
tmpfs tmpfs 774M
/dev/disk/by-uuid/828fc648-9f30-43d8-a0b1-f7096a2edb66 ext4 11G
tmpfs tmpfs 1.6G
/dev/sda2 ext3 494M
/dev/sda5 ext4 12G
/dev/sda6 ext4 9.9G
Contrast that with what we're used to seeing (modulo the
two entries mounted on "/", which is a separate problem):
Filesystem Type Size Used Avail Use% Mounted on
rootfs rootfs 11G 1.9G 8.0G 19% /
udev devtmpfs 3.8G 0 3.8G 0% /dev
tmpfs tmpfs 774M 376K 774M 1% /run
/dev/sda3 ext4 11G 1.9G 8.0G 19% /
tmpfs tmpfs 1.6G 8.0K 1.6G 1% /run/shm
/dev/sda2 ext3 494M 78M 392M 17% /boot
/dev/sda5 ext4 12G 7.6G 3.7G 68% /usr
/dev/sda6 ext4 9.9G 6.6G 2.8G 71% /var
When that long /dev/disk/by-uuid/... name is merely a symlink
to a much shorter (and often more useful) device name like
"/dev/sda3", and when it's part of a listing of all file systems,
I would much prefer to see only the latter. Similarly, when using
an encrypted root file system, you would see a name like
/dev/mapper/luks-828fc648-9f30-43d8-a0b1-f7196a2edb66 pointing
to say, /dev/dm-0, I prefer the shorter name.
I.e., if I explicitly run
"df -hT /dev/disk/by-uuid/828fc648-9f30-43d8-a0b1-f7096a2edb66",
then, it's fine -- and expected -- to print to the long name.
It was explicitly given. However, with no non-option argument,
df should print the shorter name. Note that performing this
translation at a lower level (via a change to gnulib's mountlist.c)
would make it impossible to distinguish those two cases.
* src/df.c: Include "canonicalize.h".
(get_dev): Add a parameter, telling when we're in process-all-
mount-points mode; update all callers. When true, resolve
UUID-suffixed symlinks.
Reported by Dan Jacobson in http://bugs.gnu.org/10363
---
src/df.c | 49 +++++++++++++++++++++++++++++++++++++++++--------
1 files changed, 41 insertions(+), 8 deletions(-)
diff --git a/src/df.c b/src/df.c
index 9677687..fae32cd 100644
--- a/src/df.c
+++ b/src/df.c
@@ -25,6 +25,7 @@
#include <assert.h>
#include "system.h"
+#include "canonicalize.h"
#include "error.h"
#include "fsusage.h"
#include "human.h"
@@ -417,6 +418,17 @@ add_uint_with_neg_flag (uintmax_t *dest, bool *dest_neg,
*dest = -*dest;
}
+/* Return true if S ends in a string that may be a 36-byte UUID,
+ i.e., of the form HHHHHHHH-HHHH-HHHH-HHHH-HHHHHHHHHHHH, where
+ each H is an upper or lower case hexadecimal digit. */
+static bool _GL_ATTRIBUTE_PURE
+has_uuid_suffix (char const *s)
+{
+ size_t len = strlen (s);
+ return (36 < len
+ && strspn (s + len - 36, "-0123456789abcdefABCDEF") == 36);
+}
+
/* Obtain a space listing for the disk device with absolute file name DISK.
If MOUNT_POINT is non-NULL, it is the name of the root of the
file system on DISK.
@@ -428,13 +440,16 @@ add_uint_with_neg_flag (uintmax_t *dest, bool *dest_neg,
If FSTYPE is non-NULL, it is the type of the file system on DISK.
If MOUNT_POINT is non-NULL, then DISK may be NULL -- certain systems may
not be able to produce statistics in this case.
- ME_DUMMY and ME_REMOTE are the mount entry flags. */
+ ME_DUMMY and ME_REMOTE are the mount entry flags.
+ Caller must set PROCESS_ALL to true when iterating over all entries, as
+ when df is invoked with no non-option argument. See below for details. */
static void
get_dev (char const *disk, char const *mount_point,
char const *stat_file, char const *fstype,
bool me_dummy, bool me_remote,
- const struct fs_usage *force_fsu)
+ const struct fs_usage *force_fsu,
+ bool process_all)
{
struct fs_usage fsu;
char buf[LONGEST_HUMAN_READABLE + 2];
@@ -488,6 +503,24 @@ get_dev (char const *disk, char const *mount_point,
if (! disk)
disk = "-"; /* unknown */
+
+ char *dev_name = xstrdup (disk);
+ char *resolved_dev;
+
+ /* On some systems, dev_name is a long-named symlink like
+ /dev/disk/by-uuid/828fc648-9f30-43d8-a0b1-f7196a2edb66 pointing to a
+ much shorter and more useful name like /dev/sda1. It may also look
+ like /dev/mapper/luks-828fc648-9f30-43d8-a0b1-f7196a2edb66 and point to
+ /dev/dm-0. When process_all is true and dev_name is a symlink whose
+ name ends with a UUID use the resolved name instead. */
+ if (process_all
+ && has_uuid_suffix (dev_name)
+ && (resolved_dev = canonicalize_filename_mode (dev_name, CAN_EXISTING)))
+ {
+ free (dev_name);
+ dev_name = resolved_dev;
+ }
+
if (! fstype)
fstype = "-"; /* unknown */
@@ -537,7 +570,7 @@ get_dev (char const *disk, char const *mount_point,
switch (field)
{
case DEV_FIELD:
- cell = xstrdup (disk);
+ cell = dev_name;
break;
case TYPE_FIELD:
@@ -648,7 +681,7 @@ get_disk (char const *disk)
{
get_dev (best_match->me_devname, best_match->me_mountdir, NULL,
best_match->me_type, best_match->me_dummy,
- best_match->me_remote, NULL);
+ best_match->me_remote, NULL, false);
return true;
}
@@ -734,7 +767,7 @@ get_point (const char *point, const struct stat *statp)
if (best_match)
get_dev (best_match->me_devname, best_match->me_mountdir, point,
best_match->me_type, best_match->me_dummy, best_match->me_remote,
- NULL);
+ NULL, false);
else
{
/* We couldn't find the mount entry corresponding to POINT. Go ahead and
@@ -745,7 +778,7 @@ get_point (const char *point, const struct stat *statp)
char *mp = find_mount_point (point, statp);
if (mp)
{
- get_dev (NULL, mp, NULL, NULL, false, false, NULL);
+ get_dev (NULL, mp, NULL, NULL, false, false, NULL, false);
free (mp);
}
}
@@ -774,7 +807,7 @@ get_all_entries (void)
for (me = mount_list; me; me = me->me_next)
get_dev (me->me_devname, me->me_mountdir, NULL, me->me_type,
- me->me_dummy, me->me_remote, NULL);
+ me->me_dummy, me->me_remote, NULL, true);
}
/* Add FSTYPE to the list of file system types to display. */
@@ -1066,7 +1099,7 @@ main (int argc, char **argv)
{
if (inode_format)
grand_fsu.fsu_blocks = 1;
- get_dev ("total", NULL, NULL, NULL, false, false, &grand_fsu);
+ get_dev ("total", NULL, NULL, NULL, false, false, &grand_fsu, false);
}
print_table ();
--
1.7.8.1.391.g2c2ad