Kirill A. Shutemov noticed that calling lock_page[_killable]() from
reclaim context might cause deadlock. In order to help finding such
lock_page[_killable]() users (including out of tree users), this patch
emits warning messages when CONFIG_PROVE_LOCKING is enabled.
[ 81.532721] ------------[ cut here ]------------
[ 81.534253] lock_page() from reclaim context might deadlock
[ 81.534264] WARNING: CPU: 3 PID: 56 at mm/filemap.c:3340 __warn_lock_page_from_reclaim_context+0x1e/0x30
[ 81.539982] Modules linked in: pcspkr sg vmw_vmci shpchp i2c_piix4 sd_mod ata_generic pata_acpi vmwgfx drm_kms_helper syscopyarea sysfillrect mptspi sysimgblt fb_sys_fops ahci ttm libahci e1000 scsi_transport_spi mptscsih drm ata_piix mptbase i2c_core libata serio_raw ipv6
[ 81.546750] CPU: 3 PID: 56 Comm: kswapd0 Kdump: loaded Not tainted 4.16.0-rc5-next-20180316+ #698
[ 81.549333] Hardware name: VMware, Inc. VMware Virtual Platform/440BX Desktop Reference Platform, BIOS 6.00 05/19/2017
[ 81.552256] RIP: 0010:__warn_lock_page_from_reclaim_context+0x1e/0x30
[ 81.554164] RSP: 0018:ffffc9000085bbf8 EFLAGS: 00010282
[ 81.555833] RAX: 0000000000000000 RBX: ffffea0004b2b880 RCX: 0000000000000007
[ 81.558283] RDX: 0000000000000b6d RSI: ffff88013aa0b700 RDI: ffff88013aa0ae80
[ 81.562130] RBP: 0000000000000000 R08: 0000000000000001 R09: 0000000000000000
[ 81.564291] R10: 0000000000000040 R11: 0000000000000000 R12: ffff8801357b4958
[ 81.566551] R13: 0000000000000000 R14: ffffffff82068220 R15: 0000000000000002
[ 81.568956] FS: 0000000000000000(0000) GS:ffff88013bcc0000(0000) knlGS:0000000000000000
[ 81.571310] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 81.573193] CR2: 00000000006020bf CR3: 000000000200f005 CR4: 00000000001606e0
[ 81.575453] Call Trace:
[ 81.577001] pagecache_get_page+0x22a/0x230
[ 81.578497] ? iput+0x52/0x2f0
[ 81.579762] shmem_unused_huge_shrink+0x2e9/0x380
[ 81.581465] super_cache_scan+0x17a/0x180
[ 81.582999] shrink_slab+0x218/0x590
[ 81.584398] shrink_node+0x346/0x350
[ 81.585777] kswapd+0x322/0x930
[ 81.587090] kthread+0xf0/0x130
[ 81.588370] ? mem_cgroup_shrink_node+0x320/0x320
[ 81.589996] ? kthread_create_on_node+0x60/0x60
[ 81.591670] ret_from_fork+0x3a/0x50
[ 81.593716] Code: f0 41 80 8c 24 08 01 00 00 02 eb b3 90 80 3d b8 54 f8 00 00 74 02 f3 c3 48 c7 c7 b0 87 df 81 c6 05 a6 54 f8 00 01 e8 d2 89 ee ff <0f> 0b c3 0f 1f 44 00 00 66 2e 0f 1f 84 00 00 00 00 00 41 55 41
[ 81.599356] ---[ end trace d9238c3d53557ed5 ]---
Signed-off-by: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
Cc: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
---
include/linux/pagemap.h | 12 ++++++++++++
mm/filemap.c | 8 ++++++++
2 files changed, 20 insertions(+)
diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index 34ce3ebf..8e38f4a 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -467,6 +467,10 @@ extern int __lock_page_or_retry(struct page *page, struct mm_struct *mm,
unsigned int flags);
extern void unlock_page(struct page *page);
+#ifdef CONFIG_PROVE_LOCKING
+extern void __warn_lock_page_from_reclaim_context(void);
+#endif
+
static inline int trylock_page(struct page *page)
{
page = compound_head(page);
@@ -479,6 +483,10 @@ static inline int trylock_page(struct page *page)
static inline void lock_page(struct page *page)
{
might_sleep();
+#ifdef CONFIG_PROVE_LOCKING
+ if (unlikely(current->flags & PF_MEMALLOC))
+ __warn_lock_page_from_reclaim_context();
+#endif
if (!trylock_page(page))
__lock_page(page);
}
@@ -491,6 +499,10 @@ static inline void lock_page(struct page *page)
static inline int lock_page_killable(struct page *page)
{
might_sleep();
+#ifdef CONFIG_PROVE_LOCKING
+ if (unlikely(current->flags & PF_MEMALLOC))
+ __warn_lock_page_from_reclaim_context();
+#endif
if (!trylock_page(page))
return __lock_page_killable(page);
return 0;
diff --git a/mm/filemap.c b/mm/filemap.c
index 693f622..de2eb21 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -3328,3 +3328,11 @@ int try_to_release_page(struct page *page, gfp_t gfp_mask)
}
EXPORT_SYMBOL(try_to_release_page);
+
+#ifdef CONFIG_PROVE_LOCKING
+void __warn_lock_page_from_reclaim_context(void)
+{
+ WARN_ONCE(1, "lock_page() from reclaim context might deadlock");
+}
+EXPORT_SYMBOL(__warn_lock_page_from_reclaim_context);
+#endif
--
1.8.3.1
