David Howells 8c209ce721 NFS: nfs_migrate_page() does not wait for FS-Cache to finish with a page ... nfs_migrate_page() does not wait for FS-Cache to finish with a page, probably leading to the following bad-page-state: BUG: Bad page state in process python-bin pfn:17d39b page:ffffea00053649e8 flags:004000000000100c count:0 mapcount:0 mapping:(null) index:38686 (Tainted: G B ---------------- ) Pid: 31053, comm: python-bin Tainted: G B ---------------- 2.6.32-71.24.1.el6.x86_64 #1 Call Trace: [<ffffffff8111bfe7>] bad_page+0x107/0x160 [<ffffffff8111ee69>] free_hot_cold_page+0x1c9/0x220 [<ffffffff8111ef19>] __pagevec_free+0x59/0xb0 [<ffffffff8104b988>] ? flush_tlb_others_ipi+0x128/0x130 [<ffffffff8112230c>] release_pages+0x21c/0x250 [<ffffffff8115b92a>] ? remove_migration_pte+0x28a/0x2b0 [<ffffffff8115f3f8>] ? mem_cgroup_get_reclaim_stat_from_page+0x18/0x70 [<ffffffff81122687>] ____pagevec_lru_add+0x167/0x180 [<ffffffff811226f8>] __lru_cache_add+0x58/0x70 [<ffffffff81122731>] lru_cache_add_lru+0x21/0x40 [<ffffffff81123f49>] putback_lru_page+0x69/0x100 [<ffffffff8115c0bd>] migrate_pages+0x13d/0x5d0 [<ffffffff81122687>] ? ____pagevec_lru_add+0x167/0x180 [<ffffffff81152ab0>] ? compaction_alloc+0x0/0x370 [<ffffffff8115255c>] compact_zone+0x4cc/0x600 [<ffffffff8111cfac>] ? get_page_from_freelist+0x15c/0x820 [<ffffffff810672f4>] ? check_preempt_wakeup+0x1c4/0x3c0 [<ffffffff8115290e>] compact_zone_order+0x7e/0xb0 [<ffffffff81152a49>] try_to_compact_pages+0x109/0x170 [<ffffffff8111e94d>] __alloc_pages_nodemask+0x5ed/0x850 [<ffffffff814c9136>] ? thread_return+0x4e/0x778 [<ffffffff81150d43>] alloc_pages_vma+0x93/0x150 [<ffffffff81167ea5>] do_huge_pmd_anonymous_page+0x135/0x340 [<ffffffff814cb6f6>] ? rwsem_down_read_failed+0x26/0x30 [<ffffffff81136755>] handle_mm_fault+0x245/0x2b0 [<ffffffff814ce383>] do_page_fault+0x123/0x3a0 [<ffffffff814cbdf5>] page_fault+0x25/0x30 nfs_migrate_page() calls nfs_fscache_release_page() which doesn't actually wait - even if __GFP_WAIT is set. The reason that doesn't wait is that fscache_maybe_release_page() might deadlock the allocator as the work threads writing to the cache may all end up sleeping on memory allocation. However, I wonder if that is actually a problem. There are a number of things I can do to deal with this: (1) Make nfs_migrate_page() wait. (2) Make fscache_maybe_release_page() honour the __GFP_WAIT flag. (3) Set a timeout around the wait. (4) Make nfs_migrate_page() return an error if the page is still busy. For the moment, I'll select (2) and (4). Signed-off-by: David Howells <dhowells@redhat.com> Acked-by: Jeff Layton <jlayton@redhat.com>		2012-12-20 22:12:03 +00:00
..
cache.c	FS-Cache: Limit the number of I/O error reports for a cache	2012-12-20 22:10:44 +00:00
cookie.c	FS-Cache: Provide proper invalidation	2012-12-20 22:04:07 +00:00
fsdef.c	FS-Cache: Root index definition	2009-04-03 16:42:37 +01:00
histogram.c	FS-Cache: Add use of /proc and presentation of statistics	2009-04-03 16:42:37 +01:00
internal.h	NFS: nfs_migrate_page() does not wait for FS-Cache to finish with a page	2012-12-20 22:12:03 +00:00
Kconfig	fscache: drop references to slow-work	2010-07-22 22:58:58 +02:00
main.c	fscache: fix build on !CONFIG_SYSCTL	2010-07-24 11:10:09 +02:00
Makefile	FS-Cache: Allow the current state of all objects to be dumped	2009-11-19 18:11:04 +00:00
netfs.c	FS-Cache: Add netfs registration	2009-04-03 16:42:38 +01:00
object-list.c	FS-Cache: Don't mask off the object event mask when printing it	2012-12-20 22:08:53 +00:00
object.c	FS-Cache: Exclusive op submission can BUG if there's been an I/O error	2012-12-20 22:10:58 +00:00
operation.c	FS-Cache: Exclusive op submission can BUG if there's been an I/O error	2012-12-20 22:10:58 +00:00
page.c	NFS: nfs_migrate_page() does not wait for FS-Cache to finish with a page	2012-12-20 22:12:03 +00:00
proc.c	FS-Cache: Allow the current state of all objects to be dumped	2009-11-19 18:11:04 +00:00
stats.c	NFS: nfs_migrate_page() does not wait for FS-Cache to finish with a page	2012-12-20 22:12:03 +00:00