GNU bug report logs - #49298
[PATCH] df: do not print duplicated entires with NFS and bind mounts

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Kamil Dudka <kdudka <at> redhat.com>
To: bug-coreutils <at> gnu.org
Subject: [PATCH] df: do not print duplicated entires with NFS and bind mounts
Date: Wed, 30 Jun 2021 17:53:22 +0200

As originally reported in <https://bugzilla.redhat.com/1962515>,
df invoked without -a printed duplicated entries for NFS mounts
of bind mounts.  This is a regression from commit v8.25-54-g1c17f61ef99,
which introduced the use of a hash table.

The proposed patch makes sure that the devlist entry seen the last time
is used for comparison when eliminating duplicated mount entries.  This
way it worked before introducing the hash table.

Patch co-authored by Roberto Bergantinos.

* src/ls.c (struct devlist): Introduce the seen_last pointer.
(devlist_for_dev): Return the devlist entry seen the last time if found.
(filter_mount_list): Remember the devlist entry seen the last time for
each hashed item.
---
 src/df.c | 15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/src/df.c b/src/df.c
index aadc3483f22..16a7b5524df 100644
--- a/src/df.c
+++ b/src/df.c
@@ -54,6 +54,7 @@ struct devlist
   dev_t dev_num;
   struct mount_entry *me;
   struct devlist *next;
+  struct devlist *seen_last; /* valid for hashed devlist entries only */
 };
 
 /* Filled with device numbers of examined file systems to avoid
@@ -681,7 +682,13 @@ devlist_for_dev (dev_t dev)
     return NULL;
   struct devlist dev_entry;
   dev_entry.dev_num = dev;
-  return hash_lookup (devlist_table, &dev_entry);
+
+  struct devlist *found = hash_lookup (devlist_table, &dev_entry);
+  if (found == NULL)
+    return NULL;
+
+  /* Return the last devlist entry we have seen with this dev_num */
+  return found->seen_last;
 }
 
 static void
@@ -799,8 +806,12 @@ filter_mount_list (bool devices_only)
           devlist->dev_num = buf.st_dev;
           devlist->next = device_list;
           device_list = devlist;
-          if (hash_insert (devlist_table, devlist) == NULL)
+
+          struct devlist *inserted = hash_insert (devlist_table, devlist);
+          if (inserted == NULL)
             xalloc_die ();
+          /* Remember the last devlist entry we have seen with this dev_num */
+          inserted->seen_last = devlist;
 
           me = me->me_next;
         }
-- 
2.31.1

Message #8 received at submit <at> debbugs.gnu.org (full text, mbox):

From: L A Walsh <coreutils <at> tlinx.org>
Cc: Kamil Dudka <kdudka <at> redhat.com>, Coreutils <bug-coreutils <at> gnu.org>
Subject: Re: bug#49298: [PATCH] df: do not print duplicated entires with NFS
 and bind mounts
Date: Thu, 01 Jul 2021 23:23:13 -0700

On 2021/06/30 08:53, Kamil Dudka wrote:
> The proposed patch makes sure that the devlist entry seen the last time
> is used for comparison when eliminating duplicated mount entries.
---
   I'm a bit surprised that the devlists exported for NFS are the same
as for smb.  How is that guaranteed?  But more important, does it work with
other network file systems?  Mostly I'm thinking about mounts of
NTFS from a win server.  I've gotten different results over time, 
specifically,
in regards to whether or not inode numbers are unique.

   Would it be possible for the network file systems to return
different amounts for free+used space depending on the net-interface
being used (I don't know -- I'd hope it wasn't likely, but ....)

   Another way of solving this issue, other than by special casing
SMB+NFS, a switch that prohibits crossing over to another networked
file system, and a different setting that prohibits crossing over to
another device.  I think there is a need for both as well as how initial
args are treated -- as is done with 'find' in all its diversity! ;-)

Patches to reintroduce behaviors that might result in non-deterministic
behaviors are, at least, "worrisome".

Message #13 received at 49298-done <at> debbugs.gnu.org (full text, mbox):

From: Pádraig Brady <P <at> draigBrady.com>
To: Kamil Dudka <kdudka <at> redhat.com>, 49298-done <at> debbugs.gnu.org
Subject: Re: bug#49298: [PATCH] df: do not print duplicated entires with NFS
 and bind mounts
Date: Fri, 2 Jul 2021 16:07:38 +0100

On 30/06/2021 16:53, Kamil Dudka wrote:
> As originally reported in <https://bugzilla.redhat.com/1962515>,
> df invoked without -a printed duplicated entries for NFS mounts
> of bind mounts.  This is a regression from commit v8.25-54-g1c17f61ef99,
> which introduced the use of a hash table.
> 
> The proposed patch makes sure that the devlist entry seen the last time
> is used for comparison when eliminating duplicated mount entries.  This
> way it worked before introducing the hash table.
> 
> Patch co-authored by Roberto Bergantinos.
> 
> * src/ls.c (struct devlist): Introduce the seen_last pointer.
> (devlist_for_dev): Return the devlist entry seen the last time if found.
> (filter_mount_list): Remember the devlist entry seen the last time for
> each hashed item.


Indeed order is significant here as we can have multiple entries for the same dev nums.
The patch looks good and restores the ordering from before commit 1c17f61ef.
I'll will apply this.
Marking as done.

thanks!
Pádraig

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