On Sat, 15 Dec 2007 01:09:41 +0000 Mel Gorman <mel@xxxxxxxxx> wrote: > On (13/12/07 14:29), Andrew Morton didst pronounce: > > > The simple way seems to be to malloc a large area, touch every page and > > > then look at the physical pages assigned ... they now mostly seem to be > > > descending in physical address. > > > > > > > OIC. -mm's /proc/pid/pagemap can be used to get the pfn's... > > > > I tried using pagemap to verify the patch but it triggered BUG_ON > checks. Perhaps I am using the interface wrong but I would still not > expect it to break in this fashion. I tried 2.6.24-rc4-mm1, 2.6.24-rc5-mm1, > 2.6.24-rc5 with just the maps4 patches applied and 2.6.23 with maps4 patches > applied. Each time I get errors like this; > > [ 90.108315] BUG: sleeping function called from invalid context at include/asm/uaccess_32.h:457 > [ 90.211227] in_atomic():1, irqs_disabled():0 > [ 90.262251] no locks held by showcontiguous/2814. > [ 90.318475] Pid: 2814, comm: showcontiguous Not tainted 2.6.24-rc5 #1 > [ 90.395344] [<c010522a>] show_trace_log_lvl+0x1a/0x30 > [ 90.456948] [<c0105bb2>] show_trace+0x12/0x20 > [ 90.510173] [<c0105eee>] dump_stack+0x6e/0x80 > [ 90.563409] [<c01205b3>] __might_sleep+0xc3/0xe0 > [ 90.619765] [<c02264fd>] copy_to_user+0x3d/0x60 > [ 90.675153] [<c01b3e9c>] add_to_pagemap+0x5c/0x80 > [ 90.732513] [<c01b43e8>] pagemap_pte_range+0x68/0xb0 > [ 90.793010] [<c0175ed2>] walk_page_range+0x112/0x210 > [ 90.853482] [<c01b47c6>] pagemap_read+0x176/0x220 > [ 90.910863] [<c0182dc4>] vfs_read+0x94/0x150 > [ 90.963058] [<c01832fd>] sys_read+0x3d/0x70 > [ 91.014219] [<c0104262>] syscall_call+0x7/0xb > > ... > > Just using cp to read the file is enough to cause problems but I included > a very basic program below that produces the BUG_ON checks. Is this a known > issue or am I using the interface incorrectly? I'd say you're using it correctly but you've found a hitherto unknown bug. On i386 highmem machines with CONFIG_HIGHPTE (at least) pte_offset_map() takes kmap_atomic(), so pagemap_pte_range() can't do copy_to_user() as it presently does. Drat. Still, that shouldn't really disrupt the testing which you're doing. You could disable CONFIG_HIGHPTE to shut it up. - To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
