linux/mm
Michal Hocko 2f064f3485 mm: make page pfmemalloc check more robust
Commit c48a11c7ad ("netvm: propagate page->pfmemalloc to skb") added
checks for page->pfmemalloc to __skb_fill_page_desc():

        if (page->pfmemalloc && !page->mapping)
                skb->pfmemalloc = true;

It assumes page->mapping == NULL implies that page->pfmemalloc can be
trusted.  However, __delete_from_page_cache() can set set page->mapping
to NULL and leave page->index value alone.  Due to being in union, a
non-zero page->index will be interpreted as true page->pfmemalloc.

So the assumption is invalid if the networking code can see such a page.
And it seems it can.  We have encountered this with a NFS over loopback
setup when such a page is attached to a new skbuf.  There is no copying
going on in this case so the page confuses __skb_fill_page_desc which
interprets the index as pfmemalloc flag and the network stack drops
packets that have been allocated using the reserves unless they are to
be queued on sockets handling the swapping which is the case here and
that leads to hangs when the nfs client waits for a response from the
server which has been dropped and thus never arrive.

The struct page is already heavily packed so rather than finding another
hole to put it in, let's do a trick instead.  We can reuse the index
again but define it to an impossible value (-1UL).  This is the page
index so it should never see the value that large.  Replace all direct
users of page->pfmemalloc by page_is_pfmemalloc which will hide this
nastiness from unspoiled eyes.

The information will get lost if somebody wants to use page->index
obviously but that was the case before and the original code expected
that the information should be persisted somewhere else if that is
really needed (e.g.  what SLAB and SLUB do).

[akpm@linux-foundation.org: fix blooper in slub]
Fixes: c48a11c7ad ("netvm: propagate page->pfmemalloc to skb")
Signed-off-by: Michal Hocko <mhocko@suse.com>
Debugged-by: Vlastimil Babka <vbabka@suse.com>
Debugged-by: Jiri Bohac <jbohac@suse.com>
Cc: Eric Dumazet <eric.dumazet@gmail.com>
Cc: David Miller <davem@davemloft.net>
Acked-by: Mel Gorman <mgorman@suse.de>
Cc: <stable@vger.kernel.org>	[3.6+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-08-21 14:30:10 -07:00
..
kasan .mailmap: Andrey Ryabinin has moved 2015-08-14 15:56:32 -07:00
backing-dev.c writeback: don't drain bdi_writeback_congested on bdi destruction 2015-07-02 08:46:00 -06:00
balloon_compaction.c mm/balloon_compaction: fix deflation when compaction is disabled 2014-10-29 16:33:15 -07:00
bootmem.c mm: page_alloc: pass PFN to __free_pages_bootmem 2015-06-30 19:44:55 -07:00
cleancache.c cleancache: remove limit on the number of cleancache enabled filesystems 2015-04-14 16:49:03 -07:00
cma_debug.c mm/cma_debug: correct size input to bitmap function 2015-07-17 16:39:54 -07:00
cma.c mm/memblock: add extra "flags" to memblock to allow selection of memory based on attribute 2015-06-24 17:49:44 -07:00
cma.h mm: cma: mark cma_bitmap_maxno() inline in header 2015-08-14 15:56:32 -07:00
compaction.c mm/compaction.c: fix "suitable_migration_target() unused" warning 2015-04-15 16:35:20 -07:00
debug-pagealloc.c mm/debug-pagealloc: make debug-pagealloc boottime configurable 2014-12-13 12:42:48 -08:00
debug.c tracing: Rename ftrace_event.h to trace_events.h 2015-05-13 14:05:12 -04:00
dmapool.c mm/dmapool.c: fixed a brace coding style issue 2014-10-09 22:26:00 -04:00
early_ioremap.c mm: create generic early_ioremap() support 2014-04-07 16:36:15 -07:00
fadvise.c writeback: implement and use inode_congested() 2015-06-02 08:33:35 -06:00
failslab.c
filemap.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2015-07-04 19:36:06 -07:00
frontswap.c frontswap: allow multiple backends 2015-06-24 17:49:45 -07:00
gup.c mm: use READ_ONCE() for non-scalar types 2015-04-15 16:35:18 -07:00
highmem.c mm/highmem: make kmap cache coloring aware 2014-08-06 18:01:22 -07:00
huge_memory.c mm: check __PG_HWPOISON separately from PAGE_FLAGS_CHECK_AT_* 2015-08-07 04:39:42 +03:00
hugetlb_cgroup.c mm: page_counter: pull "-1" handling out of page_counter_memparse() 2015-02-11 17:06:02 -08:00
hugetlb.c mm/hugetlb: remove unused arch hook prepare/release_hugepage 2015-06-25 17:00:35 -07:00
hwpoison-inject.c mm/memory-failure: introduce get_hwpoison_page() for consistent refcount handling 2015-06-24 17:49:42 -07:00
init-mm.c
internal.h mm: meminit: finish initialisation of struct pages before basic setup 2015-06-30 19:44:56 -07:00
interval_tree.c mm: replace vma->sharead.linear with vma->shared 2015-02-10 14:30:31 -08:00
Kconfig mm: meminit: initialise a subset of struct pages if CONFIG_DEFERRED_STRUCT_PAGE_INIT is set 2015-06-30 19:44:56 -07:00
Kconfig.debug mm/debug_pagealloc: remove obsolete Kconfig options 2015-01-08 15:10:52 -08:00
kmemcheck.c mm/slab_common: move kmem_cache definition to internal header 2014-10-09 22:25:50 -04:00
kmemleak-test.c mm/kmemleak-test.c: use pr_fmt for logging 2014-06-06 16:08:18 -07:00
kmemleak.c mm: kmemleak_alloc_percpu() should follow the gfp from per_alloc() 2015-06-24 17:49:46 -07:00
ksm.c mm: remove rest of ACCESS_ONCE() usages 2015-04-15 16:35:18 -07:00
list_lru.c memcg: reparent list_lrus and free kmemcg_id on css offline 2015-02-12 18:54:10 -08:00
maccess.c
madvise.c writeback: separate out include/linux/backing-dev-defs.h 2015-06-02 08:33:34 -06:00
Makefile mm: move memtest under mm 2015-04-14 16:49:06 -07:00
memblock.c mm: page_alloc: pass PFN to __free_pages_bootmem 2015-06-30 19:44:55 -07:00
memcontrol.c Merge branch 'for-4.2/writeback' of git://git.kernel.dk/linux-block 2015-06-25 16:00:17 -07:00
memory_hotplug.c memory-hotplug: fix wrong edge when hot add a new node 2015-08-14 15:56:32 -07:00
memory-failure.c mm/hwpoison: fix panic due to split huge zero page 2015-08-14 15:56:32 -07:00
memory.c mm: avoid setting up anonymous pages into file mapping 2015-07-09 11:12:48 -07:00
mempolicy.c mm, thp: respect MPOL_PREFERRED policy with non-local node 2015-06-24 17:49:46 -07:00
mempool.c mm/mempool.c: kasan: poison mempool elements 2015-04-15 16:35:20 -07:00
memtest.c mm/memblock: add extra "flags" to memblock to allow selection of memory based on attribute 2015-06-24 17:49:44 -07:00
migrate.c mm/memory-failure: set PageHWPoison before migrate_pages() 2015-08-07 04:39:42 +03:00
mincore.c mincore: apply page table walker on do_mincore() 2015-02-11 17:06:06 -08:00
mlock.c mm: move mm_populate()-related code to mm/gup.c 2015-04-14 16:49:00 -07:00
mm_init.c mm: meminit: remove mminit_verify_page_links 2015-06-30 19:44:56 -07:00
mmap.c mm/mmap.c: optimization of do_mmap_pgoff function 2015-06-24 17:49:45 -07:00
mmu_context.c sched/mm: call finish_arch_post_lock_switch in idle_task_exit and use_mm 2014-02-21 08:50:17 +01:00
mmu_notifier.c mmu_notifier: add the callback for mmu_notifier_invalidate_range() 2014-11-13 13:46:09 +11:00
mmzone.c mm: microoptimize zonelist operations 2015-02-11 17:06:02 -08:00
mprotect.c mm: fix mprotect() behaviour on VM_LOCKED VMAs 2015-06-24 17:49:41 -07:00
mremap.c mm: new arch_remap() hook 2015-06-24 17:49:41 -07:00
msync.c mm: remove rest usage of VM_NONLINEAR and pte_file() 2015-02-10 14:30:31 -08:00
nobootmem.c mm: page_alloc: pass PFN to __free_pages_bootmem 2015-06-30 19:44:55 -07:00
nommu.c Replace module_init with appropriate alternate initcall in non modules. 2015-07-02 10:36:29 -07:00
oom_kill.c mm/oom_kill.c: print points as unsigned int 2015-06-24 17:49:44 -07:00
page_alloc.c mm: make page pfmemalloc check more robust 2015-08-21 14:30:10 -07:00
page_counter.c mm: page_counter: pull "-1" handling out of page_counter_memparse() 2015-02-11 17:06:02 -08:00
page_ext.c mm/page_owner: keep track of page owners 2014-12-13 12:42:48 -08:00
page_io.c suspend: simplify block I/O handling 2015-05-19 09:19:59 -06:00
page_isolation.c CMA: page_isolation: check buddy before accessing it 2015-05-14 17:55:51 -07:00
page_owner.c mm/page_owner: set correct gfp_mask on page_owner 2015-07-17 16:39:54 -07:00
page-writeback.c writeback: fix initial dirty limit 2015-08-07 04:39:42 +03:00
pagewalk.c mm/pagewalk.c: prevent positive return value of walk_page_test() from being passed to callers 2015-03-25 16:20:30 -07:00
percpu-km.c percpu: implmeent pcpu_nr_empty_pop_pages and chunk->nr_populated 2014-09-02 14:46:05 -04:00
percpu-vm.c percpu: move region iterations out of pcpu_[de]populate_chunk() 2014-09-02 14:46:02 -04:00
percpu.c mm: kmemleak_alloc_percpu() should follow the gfp from per_alloc() 2015-06-24 17:49:46 -07:00
pgtable-generic.c mm: clarify that the function operates on hugepage pte 2015-06-24 17:49:44 -07:00
process_vm_access.c process_vm_access: switch to {compat_,}import_iovec() 2015-04-11 22:27:12 -04:00
quicklist.c
readahead.c writeback: implement and use inode_congested() 2015-06-02 08:33:35 -06:00
rmap.c Merge branch 'for-4.2/writeback' of git://git.kernel.dk/linux-block 2015-06-25 16:00:17 -07:00
shmem.c ipc: use private shmem or hugetlbfs inodes for shm segments. 2015-08-07 04:39:41 +03:00
slab_common.c mm/slub: allow merging when SLAB_DEBUG_FREE is set 2015-08-07 04:39:40 +03:00
slab.c mm: make page pfmemalloc check more robust 2015-08-21 14:30:10 -07:00
slab.h slab: correct size_index table before replacing the bootstrap kmem_cache_node 2015-06-24 17:49:41 -07:00
slob.c slob: make slob_alloc_node() static and remove EXPORT_SYMBOL() 2015-04-14 16:48:59 -07:00
slub.c mm: make page pfmemalloc check more robust 2015-08-21 14:30:10 -07:00
sparse-vmemmap.c mm/sparse: use memblock apis for early memory allocations 2014-01-21 16:19:47 -08:00
sparse.c mm: use macros from compiler.h instead of __attribute__((...)) 2014-04-07 16:35:54 -07:00
swap_cgroup.c mm: page_cgroup: rename file to mm/swap_cgroup.c 2014-12-10 17:41:09 -08:00
swap_state.c mm: remove rest of ACCESS_ONCE() usages 2015-04-15 16:35:18 -07:00
swap.c mm: drop bogus VM_BUG_ON_PAGE assert in put_page() codepath 2015-06-24 17:49:42 -07:00
swapfile.c vfs: add seq_file_path() helper 2015-06-23 18:01:07 -04:00
truncate.c memcg: add per cgroup dirty page accounting 2015-06-02 08:33:33 -06:00
util.c mm: uninline and cleanup page-mapping related helpers 2015-04-15 16:35:19 -07:00
vmacache.c mm,vmacache: count number of system-wide flushes 2014-12-13 12:42:48 -08:00
vmalloc.c mm/vmalloc: get rid of dirty bitmap inside vmap_block structure 2015-04-15 16:35:18 -07:00
vmpressure.c mm/vmpressure.c: fix race in vmpressure_work_fn() 2014-12-02 17:32:07 -08:00
vmscan.c mm, vmscan: Do not wait for page writeback for GFP_NOFS allocations 2015-08-05 10:49:38 +02:00
vmstat.c vmstat: Reduce time interval to stat update on idle cpu 2015-02-11 17:06:07 -08:00
workingset.c list_lru: add helpers to isolate items 2015-02-12 18:54:10 -08:00
zbud.c zpool: remove zpool_evict() 2015-06-25 17:00:37 -07:00
zpool.c zpool: remove zpool_evict() 2015-06-25 17:00:37 -07:00
zsmalloc.c zpool: remove zpool_evict() 2015-06-25 17:00:37 -07:00
zswap.c zswap: runtime enable/disable 2015-06-25 17:00:37 -07:00