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author | Joonsoo Kim <js1304@gmail.com> | 2012-09-17 14:09:09 -0700 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2012-09-17 15:00:38 -0700 |
commit | 8ba00bb68a067c221cc3ea3a0293e8fcbdcb7ba1 (patch) | |
tree | 6642f9819b79c51891d7f829c5cf1f384ffc6cc5 /kernel | |
parent | d014dc2ed4fae84cb92509416c8bfc9078d4f0d9 (diff) | |
download | linux-8ba00bb68a067c221cc3ea3a0293e8fcbdcb7ba1.tar.gz linux-8ba00bb68a067c221cc3ea3a0293e8fcbdcb7ba1.tar.bz2 linux-8ba00bb68a067c221cc3ea3a0293e8fcbdcb7ba1.zip |
slub: consider pfmemalloc_match() in get_partial_node()
get_partial() is currently not checking pfmemalloc_match() meaning that
it is possible for pfmemalloc pages to leak to non-pfmemalloc users.
This is a problem in the following situation. Assume that there is a
request from normal allocation and there are no objects in the per-cpu
cache and no node-partial slab.
In this case, slab_alloc enters the slow path and new_slab_objects() is
called which may return a PFMEMALLOC page. As the current user is not
allowed to access PFMEMALLOC page, deactivate_slab() is called
([5091b74a: mm: slub: optimise the SLUB fast path to avoid pfmemalloc
checks]) and returns an object from PFMEMALLOC page.
Next time, when we get another request from normal allocation,
slab_alloc() enters the slow-path and calls new_slab_objects(). In
new_slab_objects(), we call get_partial() and get a partial slab which
was just deactivated but is a pfmemalloc page. We extract one object
from it and re-deactivate.
"deactivate -> re-get in get_partial -> re-deactivate" occures repeatedly.
As a result, access to PFMEMALLOC page is not properly restricted and it
can cause a performance degradation due to frequent deactivation.
deactivation frequently.
This patch changes get_partial_node() to take pfmemalloc_match() into
account and prevents the "deactivate -> re-get in get_partial()
scenario. Instead, new_slab() is called.
Signed-off-by: Joonsoo Kim <js1304@gmail.com>
Acked-by: David Rientjes <rientjes@google.com>
Signed-off-by: Mel Gorman <mgorman@suse.de>
Cc: David Miller <davem@davemloft.net>
Cc: Chuck Lever <chuck.lever@oracle.com>
Cc: Pekka Enberg <penberg@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel')
0 files changed, 0 insertions, 0 deletions