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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cmb.h
#ifndef S390_CMB_H
#define S390_CMB_H
/**
* struct cmbdata - channel measurement block data for user space
* @size: size of the stored data
* @elapsed_time: time since last sampling
* @ssch_rsch_count: number of ssch and rsch
* @sample_count: number of samples
* @device_connect_time: time of device connect
* @function_pending_time: time of function pending
* @device_disconnect_time: time of device disconnect
* @control_unit_queuing_time: time of control unit queuing
* @device_active_only_time: time of device active only
* @device_busy_time: time of device busy (ext. format)
* @initial_command_response_time: initial command response time (ext. format)
*
* All values are stored as 64 bit for simplicity, especially
* in 32 bit emulation mode. All time values are normalized to
* nanoseconds.
* Currently, two formats are known, which differ by the size of
* this structure, i.e. the last two members are only set when
* the extended channel measurement facility (first shipped in
* z990 machines) is activated.
* Potentially, more fields could be added, which would result in a
* new ioctl number.
*/
struct cmbdata {
__u64 size;
__u64 elapsed_time;
/* basic and exended format: */
__u64 ssch_rsch_count;
__u64 sample_count;
__u64 device_connect_time;
__u64 function_pending_time;
__u64 device_disconnect_time;
__u64 control_unit_queuing_time;
__u64 device_active_only_time;
/* extended format only: */
__u64 device_busy_time;
__u64 initial_command_response_time;
};
/* enable channel measurement */
#define BIODASDCMFENABLE _IO(DASD_IOCTL_LETTER, 32)
/* enable channel measurement */
#define BIODASDCMFDISABLE _IO(DASD_IOCTL_LETTER, 33)
/* read channel measurement data */
#define BIODASDREADALLCMB _IOWR(DASD_IOCTL_LETTER, 33, struct cmbdata)
#ifdef __KERNEL__
struct ccw_device;
extern int enable_cmf(struct ccw_device *cdev);
extern int disable_cmf(struct ccw_device *cdev);
extern u64 cmf_read(struct ccw_device *cdev, int index);
extern int cmf_readall(struct ccw_device *cdev, struct cmbdata *data);
#endif /* __KERNEL__ */
#endif /* S390_CMB_H */
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