The patch titled
Subject: fs: break out of iomap_file_buffered_write on fatal signals
has been added to the -mm tree. Its filename is
fs-break-out-of-iomap_file_buffered_write-on-fatal-signals.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/fs-break-out-of-iomap_file_buffered_write-on-fatal-signals.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/fs-break-out-of-iomap_file_buffered_write-on-fatal-signals.patch
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------------------------------------------------------
From: Michal Hocko <mhocko@xxxxxxxx>
Subject: fs: break out of iomap_file_buffered_write on fatal signals
Tetsuo has noticed that an OOM stress test which performs large write
requests can cause the full memory reserves depletion. He has tracked
this down to the following path
__alloc_pages_nodemask+0x436/0x4d0
alloc_pages_current+0x97/0x1b0
__page_cache_alloc+0x15d/0x1a0 mm/filemap.c:728
pagecache_get_page+0x5a/0x2b0 mm/filemap.c:1331
grab_cache_page_write_begin+0x23/0x40 mm/filemap.c:2773
iomap_write_begin+0x50/0xd0 fs/iomap.c:118
iomap_write_actor+0xb5/0x1a0 fs/iomap.c:190
? iomap_write_end+0x80/0x80 fs/iomap.c:150
iomap_apply+0xb3/0x130 fs/iomap.c:79
iomap_file_buffered_write+0x68/0xa0 fs/iomap.c:243
? iomap_write_end+0x80/0x80
xfs_file_buffered_aio_write+0x132/0x390 [xfs]
? remove_wait_queue+0x59/0x60
xfs_file_write_iter+0x90/0x130 [xfs]
__vfs_write+0xe5/0x140
vfs_write+0xc7/0x1f0
? syscall_trace_enter+0x1d0/0x380
SyS_write+0x58/0xc0
do_syscall_64+0x6c/0x200
entry_SYSCALL64_slow_path+0x25/0x25
the oom victim has access to all memory reserves to make a forward
progress to exit easier. But iomap_file_buffered_write and other callers
of iomap_apply loop to complete the full request. We need to check for
fatal signals and back off with a short write instead. As the iomap_apply
delegates all the work down to the actor we have to hook into those. All
callers that work with the page cache are calling iomap_write_begin so we
will check for signals there. dax_iomap_actor has to handle the situation
explicitly because it copies data to the userspace directly. Other
callers like iomap_page_mkwrite work on a single page or
iomap_fiemap_actor do not allocate memory based on the given len.
Fixes: 68a9f5e7007c ("xfs: implement iomap based buffered write path")
Link: http://lkml.kernel.org/r/20170201092706.9966-2-mhocko@xxxxxxxxxx
Signed-off-by: Michal Hocko <mhocko@xxxxxxxx>
Reported-by: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
Reviewed-by: Christoph Hellwig <hch@xxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx> [4.8+]
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/dax.c | 5 +++++
fs/iomap.c | 3 +++
2 files changed, 8 insertions(+)
diff -puN fs/dax.c~fs-break-out-of-iomap_file_buffered_write-on-fatal-signals fs/dax.c
--- a/fs/dax.c~fs-break-out-of-iomap_file_buffered_write-on-fatal-signals
+++ a/fs/dax.c
@@ -1031,6 +1031,11 @@ dax_iomap_actor(struct inode *inode, lof
struct blk_dax_ctl dax = { 0 };
ssize_t map_len;
+ if (fatal_signal_pending(current)) {
+ ret = -EINTR;
+ break;
+ }
+
dax.sector = dax_iomap_sector(iomap, pos);
dax.size = (length + offset + PAGE_SIZE - 1) & PAGE_MASK;
map_len = dax_map_atomic(iomap->bdev, &dax);
diff -puN fs/iomap.c~fs-break-out-of-iomap_file_buffered_write-on-fatal-signals fs/iomap.c
--- a/fs/iomap.c~fs-break-out-of-iomap_file_buffered_write-on-fatal-signals
+++ a/fs/iomap.c
@@ -114,6 +114,9 @@ iomap_write_begin(struct inode *inode, l
BUG_ON(pos + len > iomap->offset + iomap->length);
+ if (fatal_signal_pending(current))
+ return -EINTR;
+
page = grab_cache_page_write_begin(inode->i_mapping, index, flags);
if (!page)
return -ENOMEM;
_
Patches currently in -mm which might be from mhocko@xxxxxxxx are
fs-break-out-of-iomap_file_buffered_write-on-fatal-signals.patch
mm-fs-check-for-fatal-signals-in-do_generic_file_read.patch
mm-throttle-show_mem-from-warn_alloc.patch
mm-trace-extract-compaction_status-and-zone_type-to-a-common-header.patch
oom-trace-add-oom-detection-tracepoints.patch
oom-trace-add-compaction-retry-tracepoint.patch
mm-vmscan-remove-unused-mm_vmscan_memcg_isolate.patch
mm-vmscan-add-active-list-aging-tracepoint.patch
mm-vmscan-add-active-list-aging-tracepoint-update.patch
mm-vmscan-show-the-number-of-skipped-pages-in-mm_vmscan_lru_isolate.patch
mm-vmscan-show-lru-name-in-mm_vmscan_lru_isolate-tracepoint.patch
mm-vmscan-extract-shrink_page_list-reclaim-counters-into-a-struct.patch
mm-vmscan-enhance-mm_vmscan_lru_shrink_inactive-tracepoint.patch
mm-vmscan-add-mm_vmscan_inactive_list_is_low-tracepoint.patch
trace-vmscan-postprocess-sync-with-tracepoints-updates.patch
mm-vmscan-do-not-count-freed-pages-as-pgdeactivate.patch
mm-vmscan-cleanup-lru-size-claculations.patch
mm-vmscan-consider-eligible-zones-in-get_scan_count.patch
revert-mm-bail-out-in-shrink_inactive_list.patch
mm-page_alloc-do-not-report-all-nodes-in-show_mem.patch
mm-page_alloc-warn_alloc-print-nodemask.patch
arch-mm-remove-arch-specific-show_mem.patch
lib-show_memc-teach-show_mem-to-work-with-the-given-nodemask.patch
mm-consolidate-gfp_nofail-checks-in-the-allocator-slowpath.patch
mm-oom-do-not-enfore-oom-killer-for-__gfp_nofail-automatically.patch
mm-help-__gfp_nofail-allocations-which-do-not-trigger-oom-killer.patch
vmalloc-back-of-when-the-current-is-killed.patch
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