The shrinking of a virtual memory area that is mmap(2)'d to a memory
special file (device drivers/char/mspec.c) can cause a panic.
If the mapped size of the vma (vm_area_struct) is very large, mspec allocates
a large vma_data structure with vmalloc(). But such a vma can be shrunk by
an munmap(2). The current driver uses the current size of each vma to
deduce whether its vma_data structure was allocated by kmalloc() or vmalloc().
So if the vma was shrunk it appears to have been allocated by kmalloc(),
and mspec attempts to free it with kfree(). This results in a panic.
This patch avoids the panic (by preserving the type of the allocation) and
also makes mspec work correctly as the vma is split into pieces by the
munmap(2)'s.
All vma's derived from such a split vma share the same vma_data structure that
represents all the pages mapped into this set of vma's. The mpec driver
must be made capable of using the right portion of the structure for each
member vma. In other words, it must index into the array of page addresses
using the portion of the array that represents the current vma. This is
enabled by storing the vma group's vm_start in the vma_data structure.
The shared vma_data's are not protected by mm->mmap_sem in the fork() case
so the reference count is left as atomic_t.
Signed-off-by: Cliff Wickman <cpw@sgi.com>
Acked-by: Jes Sorensen <jes@sgi.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
mspec_mmap was setting VM_LOCKED (without adjusting locked_vm): don't do
that, it serves no purpose in 2.6, other than to mess up the locked_vm
accounting - mspec's pages won't get reclaimed anyway. Thanks to Dmitry
Monakhov for raising the issue.
Signed-off-by: Hugh Dickins <hugh@veritas.com>
Acked-by: Jes Sorensen <jes@sgi.com>
Cc: Dmitry Monakhov <dmonakhov@sw.ru>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Many struct file_operations in the kernel can be "const". Marking them const
moves these to the .rodata section, which avoids false sharing with potential
dirty data. In addition it'll catch accidental writes at compile time to
these shared resources.
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Fix MSPEC driver to build for non SN2 enabled configs as the driver should
work in cached and uncached modes (no fetchop) on these systems. In
addition make MSPEC select IA64_UNCACHED_ALLOCATOR, which is required for
it and move it to arch/ia64/Kconfig to avoid warnings on non ia64
architectures running allmodconfig. Once the Kconfig code is fixed, we can
move it back.
Signed-off-by: Jes Sorensen <jes@sgi.com>
Cc: Fernando Luis Vzquez Cao <fernando@oss.ntt.co.jp>
Cc: "Luck, Tony" <tony.luck@intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Implement the special memory driver (mspec) based on the do_no_pfn
approach. The driver is currently used only on SN2 hardware with special
fetchop support but could be beneficial on other architectures using the
uncached mode.
Signed-off-by: Jes Sorensen <jes@sgi.com>
Cc: Hugh Dickins <hugh@veritas.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
