Revision 3ad33b2436b545cbe8b28e53f3710432cad457ab authored by Lee Schermerhorn on 15 November 2007, 00:59:10 UTC, committed by Linus Torvalds on 15 November 2007, 02:45:38 UTC
We hit the BUG_ON() in mm/rmap.c:vma_address() when trying to migrate via mbind(MPOL_MF_MOVE) a non-anon region that spans multiple vmas. For anon-regions, we just fail to migrate any pages beyond the 1st vma in the range. This occurs because do_mbind() collects a list of pages to migrate by calling check_range(). check_range() walks the task's mm, spanning vmas as necessary, to collect the migratable pages into a list. Then, do_mbind() calls migrate_pages() passing the list of pages, a function to allocate new pages based on vma policy [new_vma_page()], and a pointer to the first vma of the range. For each page in the list, new_vma_page() calls page_address_in_vma() passing the page and the vma [first in range] to obtain the address to get for alloc_page_vma(). The page address is needed to get interleaving policy correct. If the pages in the list come from multiple vmas, eventually, new_page_address() will pass that page to page_address_in_vma() with the incorrect vma. For !PageAnon pages, this will result in a bug check in rmap.c:vma_address(). For anon pages, vma_address() will just return EFAULT and fail the migration. This patch modifies new_vma_page() to check the return value from page_address_in_vma(). If the return value is EFAULT, new_vma_page() searchs forward via vm_next for the vma that maps the page--i.e., that does not return EFAULT. This assumes that the pages in the list handed to migrate_pages() is in address order. This is currently case. The patch documents this assumption in a new comment block for new_vma_page(). If new_vma_page() cannot locate the vma mapping the page in a forward search in the mm, it will pass a NULL vma to alloc_page_vma(). This will result in the allocation using the task policy, if any, else system default policy. This situation is unlikely, but the patch documents this behavior with a comment. Note, this patch results in restarting from the first vma in a multi-vma range each time new_vma_page() is called. If this is not acceptable, we can make the vma argument a pointer, both in new_vma_page() and it's caller unmap_and_move() so that the value held by the loop in migrate_pages() always passes down the last vma in which a page was found. This will require changes to all new_page_t functions passed to migrate_pages(). Is this necessary? For this patch to work, we can't bug check in vma_address() for pages outside the argument vma. This patch removes the BUG_ON(). All other callers [besides new_vma_page()] already check the return status. Tested on x86_64, 4 node NUMA platform. Signed-off-by: Lee Schermerhorn <lee.schermerhorn@hp.com> Acked-by: Christoph Lameter <clameter@sgi.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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prom.h
/*
* Definitions for talking to the Open Firmware PROM on
* Power Macintosh computers.
*
* Copyright (C) 1996 Paul Mackerras.
*/
#ifdef __KERNEL__
#ifndef _PPC_PROM_H
#define _PPC_PROM_H
/* This is used in arch/ppc/mm/mem_pieces.h */
struct reg_property {
unsigned int address;
unsigned int size;
};
/*
* These macros assist in performing the address calculations that we
* need to do to access data when the kernel is running at an address
* that is different from the address that the kernel is linked at.
* The reloc_offset() function returns the difference between these
* two addresses and the macros simplify the process of adding or
* subtracting this offset to/from pointer values.
*/
extern unsigned long reloc_offset(void);
extern unsigned long add_reloc_offset(unsigned long);
extern unsigned long sub_reloc_offset(unsigned long);
#define PTRRELOC(x) ((typeof(x))add_reloc_offset((unsigned long)(x)))
#define PTRUNRELOC(x) ((typeof(x))sub_reloc_offset((unsigned long)(x)))
/*
* Fallback definitions since we don't support OF in arch/ppc any more.
*/
#define machine_is_compatible(x) 0
#define of_find_compatible_node(f, t, c) NULL
#define of_get_property(p, n, l) NULL
#endif /* _PPC_PROM_H */
#endif /* __KERNEL__ */
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