numa: fix BUILD_BUG_ON for node_read_distance
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From: Greg KH on 10 Mar 2010 18:10 On Wed, Mar 10, 2010 at 02:50:21PM -0800, David Rientjes wrote: > node_read_distance() has a BUILD_BUG_ON() to prevent buffer overruns when > the number of nodes printed will exceed the buffer length. > > Each node only needs four chars: three for distance (maximum distance is > 255) and one for a seperating space or a trailing newline. Is this causing a problem as-is today that we need to resolve for 2.6.34? Or is this 2.6.35 material? Who chose this original number, and why is it off by 1/2? thanks, greg k-h -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
From: David Rientjes on 10 Mar 2010 18:10 On Wed, 10 Mar 2010, Greg KH wrote: > > node_read_distance() has a BUILD_BUG_ON() to prevent buffer overruns when > > the number of nodes printed will exceed the buffer length. > > > > Each node only needs four chars: three for distance (maximum distance is > > 255) and one for a seperating space or a trailing newline. > > Is this causing a problem as-is today that we need to resolve for > 2.6.34? Or is this 2.6.35 material? > It's not needed at least for x86 for 2.6.34 since the max CONFIG_NODES_SHIFT is 9. I don't know about other architectures with different ranges or page sizes. I'm going to push a change to the x86 maintainers to increase that max CONFIG_NODES_SHIFT to 10 hopefully for 2.6.35, that's where we run into this error. > Who chose this original number, and why is it off by 1/2? > It's earlier than the git history, but there's no reason to divide PAGE_SIZE in half. We've been running machines with this patch for well over a year and /sys/devices/system/node/nodeN/distance works just fine with 1K nodes. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
From: Greg KH on 10 Mar 2010 18:20
On Wed, Mar 10, 2010 at 03:05:47PM -0800, David Rientjes wrote: > On Wed, 10 Mar 2010, Greg KH wrote: > > > > node_read_distance() has a BUILD_BUG_ON() to prevent buffer overruns when > > > the number of nodes printed will exceed the buffer length. > > > > > > Each node only needs four chars: three for distance (maximum distance is > > > 255) and one for a seperating space or a trailing newline. > > > > Is this causing a problem as-is today that we need to resolve for > > 2.6.34? Or is this 2.6.35 material? > > > > It's not needed at least for x86 for 2.6.34 since the max > CONFIG_NODES_SHIFT is 9. I don't know about other architectures with > different ranges or page sizes. > > I'm going to push a change to the x86 maintainers to increase that max > CONFIG_NODES_SHIFT to 10 hopefully for 2.6.35, that's where we run into > this error. Ok, I'll queue this up for .35, thanks. greg k-h -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ |