[Devel] /proc/*/pagemap BUG: sleeping function called from invalid context

[Alexey Dobriyan]

After
	cat /proc/self/pagemap

BUG: sleeping function called from invalid context at include/asm/uaccess.h:453
in_atomic():1, irqs_disabled():0
1 lock held by cat/14183:
 #0:  (&mm->mmap_sem){----}, at: [<c017d17b>] pagemap_read+0x11f/0x21b
 [<c01b7bc7>] copy_to_user+0x37/0x4c
 [<c017cf92>] add_to_pagemap+0x49/0x6f
 [<c017d034>] pagemap_pte_range+0x56/0x7e
 [<c017cfde>] pagemap_pte_range+0x0/0x7e
 [<c01b481d>] walk_page_range+0xf1/0x1a0
 [<c017d1e3>] pagemap_read+0x187/0x21b
 [<c01fdafa>] tty_write+0x1bb/0x1cc
 [<c017d05c>] pagemap_read+0x0/0x21b
 [<c01589b0>] vfs_read+0x72/0x95
 [<c0158cce>] sys_read+0x41/0x67
 [<c0103d96>] sysenter_past_esp+0x8f/0x99
 [<c0103d66>] sysenter_past_esp+0x5f/0x99
 =======================