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The madvise injector already holds a reference when passing in a page
to the memory-failure code. The code corrects for this additional reference
for its checks, but the final printk output didn't. Fix that.
Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
Signed-off-by: Andi Kleen <ak@linux.intel.com>
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Memory failure on a KSM page currently oopses on its NULL anon_vma in
page_lock_anon_vma(): that may not be much worse than the consequence
of ignoring it, but it is better to be consistent with how ZERO_PAGE
and hugetlb pages and other awkward cases are treated. Just skip it.
Signed-off-by: Hugh Dickins <hugh.dickins@tiscali.co.uk>
Signed-off-by: Andi Kleen <ak@linux.intel.com>
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Right now we have some trouble with non atomic access
to page flags when locking the page. To plug this hole
for now, limit error recovery to LRU pages for now.
This could be better fixed by defining a suitable protocol,
but let's go this simple way for now
This avoids unnecessary races with __set_page_locked() and
__SetPageSlab*() and maybe more non-atomic page flag operations.
This loses isolated pages which are currently in page reclaim, but these
are relatively limited compared to the total memory.
Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
Signed-off-by: Andi Kleen <ak@linux.intel.com>
[AK: new description, bug fixes, cleanups]
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Add the high level memory handler that poisons pages
that got corrupted by hardware (typically by a two bit flip in a DIMM
or a cache) on the Linux level. The goal is to prevent everyone
from accessing these pages in the future.
This done at the VM level by marking a page hwpoisoned
and doing the appropriate action based on the type of page
it is.
The code that does this is portable and lives in mm/memory-failure.c
To quote the overview comment:
High level machine check handler. Handles pages reported by the
hardware as being corrupted usually due to a 2bit ECC memory or cache
failure.
This focuses on pages detected as corrupted in the background.
When the current CPU tries to consume corruption the currently
running process can just be killed directly instead. This implies
that if the error cannot be handled for some reason it's safe to
just ignore it because no corruption has been consumed yet. Instead
when that happens another machine check will happen.
Handles page cache pages in various states. The tricky part
here is that we can access any page asynchronous to other VM
users, because memory failures could happen anytime and anywhere,
possibly violating some of their assumptions. This is why this code
has to be extremely careful. Generally it tries to use normal locking
rules, as in get the standard locks, even if that means the
error handling takes potentially a long time.
Some of the operations here are somewhat inefficient and have non
linear algorithmic complexity, because the data structures have not
been optimized for this case. This is in particular the case
for the mapping from a vma to a process. Since this case is expected
to be rare we hope we can get away with this.
There are in principle two strategies to kill processes on poison:
- just unmap the data and wait for an actual reference before
killing
- kill as soon as corruption is detected.
Both have advantages and disadvantages and should be used
in different situations. Right now both are implemented and can
be switched with a new sysctl vm.memory_failure_early_kill
The default is early kill.
The patch does some rmap data structure walking on its own to collect
processes to kill. This is unusual because normally all rmap data structure
knowledge is in rmap.c only. I put it here for now to keep
everything together and rmap knowledge has been seeping out anyways
Includes contributions from Johannes Weiner, Chris Mason, Fengguang Wu,
Nick Piggin (who did a lot of great work) and others.
Cc: npiggin@suse.de
Cc: riel@redhat.com
Signed-off-by: Andi Kleen <ak@linux.intel.com>
Acked-by: Rik van Riel <riel@redhat.com>
Reviewed-by: Hidehiro Kawai <hidehiro.kawai.ez@hitachi.com>
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Wu Fengguang
Hugh Dickins
Andi Kleen