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authorMel Gorman <mel@csn.ul.ie>2009-12-07 22:10:46 +0100
committerJens Axboe <jens.axboe@oracle.com>2009-12-09 15:11:03 +0100
commita3b8d92d25212c5b6534ae9b347ed2858de78336 (patch)
treedd61cbc89814f179c85fd404fbe499142ea0d7fb /block
parent8b43aebdaa4fa3348dafd6f2f5f526bd3e8b84ac (diff)
block,xd: Delay allocation of DMA buffers until device is known
Loading the XD module triggers a warning like WARNING: at mm/page_alloc.c:1805 __alloc_pages_nodemask+0x127/0x48f() Hardware name: System Product Name Modules linked in: Pid: 1, comm: swapper Not tainted 2.6.32-rc8-git5 #1 Call Trace: [<c103d94b>] warn_slowpath_common+0x65/0x95 [<c103d98d>] warn_slowpath_null+0x12/0x15 [<c109550c>] __alloc_pages_nodemask+0x127/0x48f [<c10be964>] ? get_slab+0x8/0x50 [<c10b8979>] alloc_page_interleave+0x2e/0x6e [<c10b8a10>] alloc_pages_current+0x57/0x99 [<c2083a4a>] ? xd_init+0x0/0x482 [<c1094c38>] __get_free_pages+0xd/0x1e [<c2083a94>] xd_init+0x4a/0x482 [<c2082df0>] ? loop_init+0x104/0x16a [<c169162d>] ? loop_probe+0x0/0xaf [<c2083a4a>] ? xd_init+0x0/0x482 [<c1001143>] do_one_initcall+0x51/0x13f [<c204a307>] kernel_init+0x10b/0x15f [<c204a1fc>] ? kernel_init+0x0/0x15f [<c1004347>] kernel_thread_helper+0x7/0x10 ---[ end trace 686db6333ade6e7a ]--- xd: Out of memory. The warning is because the alloc_pages is called with an order >= MAX_ORDER. The simplistic reason is that get_order(0) returns garbage values when given 0 as a size. The more complex reason is that the XD driver initialisation is broken. It's not clear why this ever worked. XD allocates a buffer for DMA based on the value of xd_maxsectors. This value is determined by the exact type of controller in use but the value is determined *after* an attempt has been made to allocate the buffer. i.e. the requested size of the DMA buffer will always be 0. This patch alters how XD is initialised slightly by allocating the buffer when and if a device has actually been detected. The error paths are updated to suit the new logic. Signed-off-by: Mel Gorman <mel@csn.ul.ie> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
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