Hello,

On Sun, May 29, 2011 at 3:34 AM, David Rientjes [off-list ref] wrote:

On Sun, 29 May 2011, Dmitry Eremin-Solenikov wrote:

quoted

Hello,

Since a197b59ae6e8bee56fcef37ea2482dc08414e2ac (mm: fail GFP_DMA
allocations when ZONE_DMA is not configured), pxaficp_ir.c driver fails
to probe: pxa_irda_init_iobuf asks for a buffer with GFP_KERNEL |
GFP_DMA flags, which fail nicely with the following trace:

------------[ cut here ]------------
WARNING: at mm/page_alloc.c:2251
__alloc_pages_nodemask+0xa0/0x5ac()
Modules linked in:
[<c00385b0>] (unwind_backtrace+0x0/0xf0) from [<c0050b1c>] (warn_slowpath_common+0x4c/0x64)
[<c0050b1c>] (warn_slowpath_common+0x4c/0x64) from [<c0050b4c>] (warn_slowpath_null+0x18/0x1c)
[<c0050b4c>] (warn_slowpath_null+0x18/0x1c) from [<c00908ec>] (__alloc_pages_nodemask+0xa0/0x5ac)
[<c00908ec>] (__alloc_pages_nodemask+0xa0/0x5ac) from [<c0090e74>] (__get_free_pages+0x10/0x3c)
[<c0090e74>] (__get_free_pages+0x10/0x3c) from [<c01d608c>] (pxa_irda_init_iobuf+0x18/0x48)
[<c01d608c>] (pxa_irda_init_iobuf+0x18/0x48) from [<c01d61d8>] (pxa_irda_probe+0x11c/0x32c)
[<c01d61d8>] (pxa_irda_probe+0x11c/0x32c) from [<c019474c>] (platform_drv_probe+0x14/0x18)
[<c019474c>] (platform_drv_probe+0x14/0x18) from [<c0193508>] (really_probe+0xa0/0x158)
[<c0193508>] (really_probe+0xa0/0x158) from [<c019360c>] (driver_probe_device+0x4c/0x64)
[<c019360c>] (driver_probe_device+0x4c/0x64) from [<c0193684>] (__driver_attach+0x60/0x84)
[<c0193684>] (__driver_attach+0x60/0x84) from [<c0192d78>] (bus_for_each_dev+0x48/0x84)
[<c0192d78>] (bus_for_each_dev+0x48/0x84) from [<c01926b8>] (bus_add_driver+0xa8/0x220)
[<c01926b8>] (bus_add_driver+0xa8/0x220) from [<c0193c7c>] (driver_register+0xac/0x13c)
[<c0193c7c>] (driver_register+0xac/0x13c) from [<c0033440>] (do_one_initcall+0x94/0x16c)
[<c0033440>] (do_one_initcall+0x94/0x16c) from [<c00083f4>] (kernel_init+0x94/0x140)
[<c00083f4>] (kernel_init+0x94/0x140) from [<c00348d0>] (kernel_thread_exit+0x0/0x8)
---[ end trace 0b8bf08f70147098 ]---

The driver is attempting to allocate DMA memory and you have
CONFIG_ZONE_DMA disabled, which is the only reason you would get this
warning. ?If the allocation did not fail as a result of a197b59ae6e8, the
page allocator may return any memory in a higher zone that the driver may
not be expecting. ?If you had never noticed a problem before, it may be
possible that the driver doesn't actually have any zone restrictions and
GFP_DMA can be removed, but this code is pretty old. ?Otherwise, it'll
need to depend on ZONE_DMA in the Kconfig.

What about changing your patch for less intrusive one (to emit a
WARN_ON) for at least one
or two major releases and only then changing it back to the current state?

-- 
With best wishes
Dmitry