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author | Mikulas Patocka <mpatocka@redhat.com> | 2013-05-10 14:37:15 +0100 |
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committer | Alasdair G Kergon <agk@redhat.com> | 2013-05-10 14:37:15 +0100 |
commit | 502624bdad3dba45dfaacaf36b7d83e39e74b2d2 (patch) | |
tree | 56c7d8236425193eb21730f2591868c735db9a5a /drivers/ipack | |
parent | 09e8b813897a0f85bb401435d009228644c81214 (diff) | |
download | linux-3.10-502624bdad3dba45dfaacaf36b7d83e39e74b2d2.tar.gz linux-3.10-502624bdad3dba45dfaacaf36b7d83e39e74b2d2.tar.bz2 linux-3.10-502624bdad3dba45dfaacaf36b7d83e39e74b2d2.zip |
dm bufio: avoid a possible __vmalloc deadlock
This patch uses memalloc_noio_save to avoid a possible deadlock in
dm-bufio. (it could happen only with large block size, at most
PAGE_SIZE << MAX_ORDER (typically 8MiB).
__vmalloc doesn't fully respect gfp flags. The specified gfp flags are
used for allocation of requested pages, structures vmap_area, vmap_block
and vm_struct and the radix tree nodes.
However, the kernel pagetables are allocated always with GFP_KERNEL.
Thus the allocation of pagetables can recurse back to the I/O layer and
cause a deadlock.
This patch uses the function memalloc_noio_save to set per-process
PF_MEMALLOC_NOIO flag and the function memalloc_noio_restore to restore
it. When this flag is set, all allocations in the process are done with
implied GFP_NOIO flag, thus the deadlock can't happen.
This should be backported to stable kernels, but they don't have the
PF_MEMALLOC_NOIO flag and memalloc_noio_save/memalloc_noio_restore
functions. So, PF_MEMALLOC should be set and restored instead.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Cc: stable@kernel.org
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Diffstat (limited to 'drivers/ipack')
0 files changed, 0 insertions, 0 deletions