diff options
| author | Mel Gorman <mgorman@techsingularity.net> | 2019-04-25 22:23:54 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2019-04-26 09:18:05 -0700 |
| commit | ee8ab0eeb49bd3982090c8f14dc9cc65bcd13c5c (patch) | |
| tree | d77c45d5e1e6509eff55ec96a318888271419ddf /mm | |
| parent | 24512228b7a3f412b5a51f189df302616b021c33 (diff) | |
| download | lwn-ee8ab0eeb49bd3982090c8f14dc9cc65bcd13c5c.tar.gz lwn-ee8ab0eeb49bd3982090c8f14dc9cc65bcd13c5c.zip | |
mm, page_alloc: always use a captured page regardless of compaction result
During the development of commit 5e1f0f098b46 ("mm, compaction: capture
a page under direct compaction"), a paranoid check was added to ensure
that if a captured page was available after compaction that it was
consistent with the final state of compaction. The intent was to catch
serious programming bugs such as using a stale page pointer and causing
corruption problems.
However, it is possible to get a captured page even if compaction was
unsuccessful if an interrupt triggered and happened to free pages in
interrupt context that got merged into a suitable high-order page. It's
highly unlikely but Li Wang did report the following warning on s390
occuring when testing OOM handling. Note that the warning is slightly
edited for clarity.
WARNING: CPU: 0 PID: 9783 at mm/page_alloc.c:3777 __alloc_pages_direct_compact+0x182/0x190
Modules linked in: rpcsec_gss_krb5 auth_rpcgss nfsv4 dns_resolver nfs
lockd grace fscache sunrpc pkey ghash_s390 prng xts aes_s390
des_s390 des_generic sha512_s390 zcrypt_cex4 zcrypt vmur binfmt_misc
ip_tables xfs libcrc32c dasd_fba_mod qeth_l2 dasd_eckd_mod dasd_mod
qeth qdio lcs ctcm ccwgroup fsm dm_mirror dm_region_hash dm_log
dm_mod
CPU: 0 PID: 9783 Comm: copy.sh Kdump: loaded Not tainted 5.1.0-rc 5 #1
This patch simply removes the check entirely instead of trying to be
clever about pages freed from interrupt context. If a serious
programming error was introduced, it is highly likely to be caught by
prep_new_page() instead.
Link: http://lkml.kernel.org/r/20190419085133.GH18914@techsingularity.net
Fixes: 5e1f0f098b46 ("mm, compaction: capture a page under direct compaction")
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Reported-by: Li Wang <liwang@redhat.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm')
| -rw-r--r-- | mm/page_alloc.c | 5 |
1 files changed, 0 insertions, 5 deletions
diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 6c6d9f1c404e..d167c48d913c 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -3786,11 +3786,6 @@ __alloc_pages_direct_compact(gfp_t gfp_mask, unsigned int order, memalloc_noreclaim_restore(noreclaim_flag); psi_memstall_leave(&pflags); - if (*compact_result <= COMPACT_INACTIVE) { - WARN_ON_ONCE(page); - return NULL; - } - /* * At least in one zone compaction wasn't deferred or skipped, so let's * count a compaction stall |