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Date: Thu, 19 Aug 2021 11:37:44 +0200
To: cygwin@cygwin.com
Subject: Re: Duplicates in /proc/partitions
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From: Corinna Vinschen via Cygwin <cygwin@cygwin.com>
Reply-To: cygwin@cygwin.com
Cc: Corinna Vinschen <corinna-cygwin@cygwin.com>
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On Aug 18 18:18, Lavrentiev, Anton (NIH/NLM/NCBI) [C] via Cygwin wrote:
> >       printf ("%5d %5d %9llu sd%c (%lu, %ls)\n",
> >               8, (dev_name - 'a') * 16, size >> 10, dev_name,
> >               (unsigned long) context, dbi->ObjectName.Buffer);
> 
> I replaced with this instead (read_bytes added):
> 
>       printf ("%5d %5d %9llu sd%c (%lu, %ls, %u)\n",
>               8, (dev_name - 'a') * 16, size >> 10, dev_name,
>               (unsigned long) context, dbi->ObjectName.Buffer, bytes_read);
> 
> and here's the output:
> 
> $ ./proc_partition
> major minor  #blocks  name   win-mounts
> 
>     8     0 500107608 sda (282, Harddisk0, 144)
>     8     1    102400 sda1
>     8     2 488280064 sda2    C:\
>     8    16 1000204632 sdb (299, Harddisk1, 144)
>     8    17 1000202240 sdb1    D:\
>     8    32 1000204632 sdc (300, Harddisk1, 144)
>     8    33 1000202240 sdc1    D:\
>     8    48 1000204632 sdd (313, Harddisk2, 144)
>     8    49 1000202240 sdd1    G:\
>     8    64 1000204632 sde (314, Harddisk2, 144)
>     8    65 1000202240 sde1    G:\
>     8    80 1000204632 sdf (329, Harddisk3, 144)
>     8    81 1000202240 sdf1    I:\
>     8    96 1000204632 sdg (330, Harddisk3, 144)
>     8    97 1000202240 sdg1    I:\
>     8   112 234431064 sdh (339, Harddisk4, 144)
>     8   113 234428416 sdh1    F:\
>     8   128 234431064 sdi (340, Harddisk4, 144)
>     8   129 234428416 sdi1    F:\
> DeviceIoControl (Harddisk5\Partition0, IOCTL_DISK_GET_PARTITION_INFO{_EX}) 5    8   144         0 sdj (352, Harddisk5, 624)
> 
> It prints the correct Harddisk names (corresponding to the
> duplicates), so it's consistent.
> 
> I was thinking that the "context" value seems to change just by 1 when
> there's a duplicate coming out;  otherwise, it jumps by more than 10,
> when it is really a new drive...

No, that just indicates the offset between entries, remember the "continue"
in line 77, skipping non-Harddisk entries.  NtQueryDirectoryObject returns
context values starting at 1, incrementing by 1.

> The directory handle is used (indirectly) in NtOpenFile() through the
> attributes, and I wonder if that call somehow distorts the internal
> position within the handle, and so it restarts from the wrong internal
> position in the outer loop.

Unlikely.  That's core functionality which *must* work.


Corinna

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