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This is an automatically generated e-mail. To reply, visit:
<a href="https://git.reviewboard.kde.org/r/130090/">https://git.reviewboard.kde.org/r/130090/</a>
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<a href="https://git.reviewboard.kde.org/r/130090/diff/1/?file=494454#file494454line31" style="color: black; font-weight: bold; text-decoration: underline;">src/solid/devices/backends/udisks2/udisksblock.cpp</a>
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(Diff revision 1)
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<td bgcolor="#fdfebc" width="50%"><pre style="font-size: 8pt; line-height: 140%; margin: 0; "><span class="cp">#define MINORBITS 20</span></pre></td>
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<td bgcolor="#fdfebc" width="50%"><pre style="font-size: 8pt; line-height: 140%; margin: 0; "><span class="cp">#define major(dev) ((dev)>>8)</span></pre></td>
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<pre style="white-space: pre-wrap; white-space: -moz-pre-wrap; white-space: -pre-wrap; white-space: -o-pre-wrap; word-wrap: break-word;"><p style="padding: 0;text-rendering: inherit;margin: 0;line-height: inherit;white-space: inherit;">Usually we use uppper case for macros. That would also save some lines in this patch.</p>
<p style="padding: 0;text-rendering: inherit;margin: 0;line-height: inherit;white-space: inherit;">nitpik: add spaces around >>, like you did for & in the line below.</p></pre>
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<p>- Lamarque Souza</p>
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<p>On April 17th, 2017, 8:42 a.m. UTC, KJ Tsanaktsidis wrote:</p>
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<div>Review request for KDE Frameworks.</div>
<div>By KJ Tsanaktsidis.</div>
<p style="color: grey;"><i>Updated April 17, 2017, 8:42 a.m.</i></p>
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<b style="color: #575012; font-size: 10pt;">Repository: </b>
solid
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<h1 style="color: #575012; font-size: 10pt; margin-top: 1.5em;">Description </h1>
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<pre style="margin: 0; padding: 0; white-space: pre-wrap; white-space: -moz-pre-wrap; white-space: -pre-wrap; white-space: -o-pre-wrap; word-wrap: break-word;">Previously, udesksblock.cpp was attempting to find a definition for
major/minor on Linux in <sys/kdev_t.h> by checking Q_OS_LINUX before
importing the header. Q_OS_LINUX is however only set when
qsystemdetection.h is included, and the macro was being checked first.
Even had this check worked, it would still be wrong. On a modern version
of the userspace linux-headers, <sys/kdev_t.h> includes definitions for
major and minor that assume each is limited to 8 bits and that dev_t is
16 bits. This is no longer true anymore; on Linux, major numbers can be
up to 12 bits at present and minor numbers up to 20. Calling these
macros with dev_t values > 2^16 would give incorrect results.
Because the Q_OS_LINUX check failed, a fallback version of the macros
were defined for use on all platforms. The code is allegedly copied from
kdev_t.h, except it is copied from the *kernel* version of the header,
not the userspace version. Linux internally uses a different
representation of dev_t than it exposes to userspace - the kernelspace
version is 20 bits of minor/12 bits of major contiguously, but the
userspace version packs the bits in a different order to maintain
compatability with old 16-bit device numbers. Thus, this code also does
not work for dev_t values > 2^16.
To fix this, we add CMake rules to search for a system-provided
definition of the major/minor macros - on various systems, these can be
in a few different places. As a fallback, we assume old-style 16-bit
dev_t (although I suspect that is only used for Windows, where
major/minor numbers are pretty meaningless anyway).</pre>
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<h1 style="color: #575012; font-size: 10pt; margin-top: 1.5em;">Testing </h1>
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<pre style="margin: 0; padding: 0; white-space: pre-wrap; white-space: -moz-pre-wrap; white-space: -pre-wrap; white-space: -o-pre-wrap; word-wrap: break-word;"><p style="padding: 0;text-rendering: inherit;margin: 0;line-height: inherit;white-space: inherit;">I've written a little snippet to iterate through block devices, print their major/minor number, and their device properties. It was previously incorrectly labeling all my disks with major 0 and minor == device_number (since it was using the first 20 bits for the minor). It now correctly identifies their major/minor number.</p></pre>
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<h1 style="color: #575012; font-size: 10pt; margin-top: 1.5em;">Diffs</b> </h1>
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<li>src/solid/devices/backends/udisks2/CMakeLists.txt <span style="color: grey">(34390064af29ace07cbb3470945be098cc606d04)</span></li>
<li>src/solid/devices/backends/udisks2/udisksblock.cpp <span style="color: grey">(0622ec77fcf670a2005d34b7a6c31ca8b53a18d8)</span></li>
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<p><a href="https://git.reviewboard.kde.org/r/130090/diff/" style="margin-left: 3em;">View Diff</a></p>
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