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27 March 2024, 02:37:15 UTC
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 
Migration: find correct vma in new_vma_page()
 
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>
1 parent e1a1c99
Raw File
Tip revision: 3ad33b2436b545cbe8b28e53f3710432cad457ab authored by Lee Schermerhorn on 15 November 2007, 00:59:10 UTC
Migration: find correct vma in new_vma_page()
Tip revision: 3ad33b2
Makefile.clean 
# ==========================================================================
# Cleaning up
# ==========================================================================

src := $(obj)

PHONY := __clean
__clean:

# Shorthand for $(Q)$(MAKE) scripts/Makefile.clean obj=dir
# Usage:
# $(Q)$(MAKE) $(clean)=dir
clean := -f $(if $(KBUILD_SRC),$(srctree)/)scripts/Makefile.clean obj

# The filename Kbuild has precedence over Makefile
kbuild-dir := $(if $(filter /%,$(src)),$(src),$(srctree)/$(src))
include $(if $(wildcard $(kbuild-dir)/Kbuild), $(kbuild-dir)/Kbuild, $(kbuild-dir)/Makefile)

# Figure out what we need to build from the various variables
# ==========================================================================

__subdir-y	:= $(patsubst %/,%,$(filter %/, $(obj-y)))
subdir-y	+= $(__subdir-y)
__subdir-m	:= $(patsubst %/,%,$(filter %/, $(obj-m)))
subdir-m	+= $(__subdir-m)
__subdir-n	:= $(patsubst %/,%,$(filter %/, $(obj-n)))
subdir-n	+= $(__subdir-n)
__subdir-	:= $(patsubst %/,%,$(filter %/, $(obj-)))
subdir-		+= $(__subdir-)

# Subdirectories we need to descend into

subdir-ym	:= $(sort $(subdir-y) $(subdir-m))
subdir-ymn      := $(sort $(subdir-ym) $(subdir-n) $(subdir-))

# Add subdir path

subdir-ymn	:= $(addprefix $(obj)/,$(subdir-ymn))

# build a list of files to remove, usually releative to the current
# directory

__clean-files	:= $(extra-y) $(always)                  \
		   $(targets) $(clean-files)             \
		   $(host-progs)                         \
		   $(hostprogs-y) $(hostprogs-m) $(hostprogs-)

# as clean-files is given relative to the current directory, this adds
# a $(obj) prefix, except for absolute paths

__clean-files   := $(wildcard                                               \
                   $(addprefix $(obj)/, $(filter-out /%, $(__clean-files))) \
		   $(filter /%, $(__clean-files)))

# as clean-dirs is given relative to the current directory, this adds
# a $(obj) prefix, except for absolute paths

__clean-dirs    := $(wildcard                                               \
                   $(addprefix $(obj)/, $(filter-out /%, $(clean-dirs)))    \
		   $(filter /%, $(clean-dirs)))

# ==========================================================================

quiet_cmd_clean    = CLEAN   $(obj)
      cmd_clean    = rm -f $(__clean-files)
quiet_cmd_cleandir = CLEAN   $(__clean-dirs)
      cmd_cleandir = rm -rf $(__clean-dirs)


__clean: $(subdir-ymn)
ifneq ($(strip $(__clean-files)),)
	+$(call cmd,clean)
endif
ifneq ($(strip $(__clean-dirs)),)
	+$(call cmd,cleandir)
endif
ifneq ($(strip $(clean-rule)),)
	+$(clean-rule)
endif
	@:


# ===========================================================================
# Generic stuff
# ===========================================================================

# Descending
# ---------------------------------------------------------------------------

PHONY += $(subdir-ymn)
$(subdir-ymn):
	$(Q)$(MAKE) $(clean)=$@

# If quiet is set, only print short version of command

cmd = @$(if $($(quiet)cmd_$(1)),echo '  $($(quiet)cmd_$(1))' &&) $(cmd_$(1))


# Declare the contents of the .PHONY variable as phony.  We keep that
# information in a variable se we can use it in if_changed and friends.

.PHONY: $(PHONY)
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