From f04b30de3c82528f1ab4c58b3dd4c975f5341901 Mon Sep 17 00:00:00 2001 From: Ingo Molnar Date: Wed, 18 Feb 2009 14:48:43 -0800 Subject: [PATCH] inotify: fix GFP_KERNEL related deadlock Enhanced lockdep coverage of __GFP_NOFS turned up this new lockdep assert: [ 1093.677775] [ 1093.677781] ================================= [ 1093.680031] [ INFO: inconsistent lock state ] [ 1093.680031] 2.6.29-rc5-tip-01504-gb49eca1-dirty #1 [ 1093.680031] --------------------------------- [ 1093.680031] inconsistent {RECLAIM_FS-ON-W} -> {IN-RECLAIM_FS-W} usage. [ 1093.680031] kswapd0/308 [HC0[0]:SC0[0]:HE1:SE1] takes: [ 1093.680031] (&inode->inotify_mutex){+.+.?.}, at: [] inotify_inode_is_dead+0x20/0x80 [ 1093.680031] {RECLAIM_FS-ON-W} state was registered at: [ 1093.680031] [] mark_held_locks+0x43/0x5b [ 1093.680031] [] lockdep_trace_alloc+0x6c/0x6e [ 1093.680031] [] kmem_cache_alloc+0x20/0x150 [ 1093.680031] [] idr_pre_get+0x27/0x6c [ 1093.680031] [] inotify_handle_get_wd+0x25/0xad [ 1093.680031] [] inotify_add_watch+0x7a/0x129 [ 1093.680031] [] sys_inotify_add_watch+0x20f/0x250 [ 1093.680031] [] sysenter_do_call+0x12/0x35 [ 1093.680031] [] 0xffffffff [ 1093.680031] irq event stamp: 60417 [ 1093.680031] hardirqs last enabled at (60417): [] call_rcu+0x53/0x59 [ 1093.680031] hardirqs last disabled at (60416): [] call_rcu+0x17/0x59 [ 1093.680031] softirqs last enabled at (59656): [] __do_softirq+0x157/0x16b [ 1093.680031] softirqs last disabled at (59651): [] do_softirq+0x74/0x15d [ 1093.680031] [ 1093.680031] other info that might help us debug this: [ 1093.680031] 2 locks held by kswapd0/308: [ 1093.680031] #0: (shrinker_rwsem){++++..}, at: [] shrink_slab+0x36/0x189 [ 1093.680031] #1: (&type->s_umount_key#4){+++++.}, at: [] shrink_dcache_memory+0x110/0x1fb [ 1093.680031] [ 1093.680031] stack backtrace: [ 1093.680031] Pid: 308, comm: kswapd0 Not tainted 2.6.29-rc5-tip-01504-gb49eca1-dirty #1 [ 1093.680031] Call Trace: [ 1093.680031] [] valid_state+0x12a/0x13d [ 1093.680031] [] mark_lock+0xc1/0x1e9 [ 1093.680031] [] ? check_usage_forwards+0x0/0x3f [ 1093.680031] [] __lock_acquire+0x2c6/0xac8 [ 1093.680031] [] ? register_lock_class+0x17/0x228 [ 1093.680031] [] lock_acquire+0x5d/0x7a [ 1093.680031] [] ? inotify_inode_is_dead+0x20/0x80 [ 1093.680031] [] __mutex_lock_common+0x3a/0x4cb [ 1093.680031] [] ? inotify_inode_is_dead+0x20/0x80 [ 1093.680031] [] mutex_lock_nested+0x2e/0x36 [ 1093.680031] [] ? inotify_inode_is_dead+0x20/0x80 [ 1093.680031] [] inotify_inode_is_dead+0x20/0x80 [ 1093.680031] [] dentry_iput+0x90/0xc2 [ 1093.680031] [] d_kill+0x21/0x45 [ 1093.680031] [] __shrink_dcache_sb+0x27f/0x355 [ 1093.680031] [] shrink_dcache_memory+0x15e/0x1fb [ 1093.680031] [] shrink_slab+0x121/0x189 [ 1093.680031] [] kswapd+0x39f/0x561 [ 1093.680031] [] ? isolate_pages_global+0x0/0x233 [ 1093.680031] [] ? autoremove_wake_function+0x0/0x43 [ 1093.680031] [] ? kswapd+0x0/0x561 [ 1093.680031] [] kthread+0x41/0x82 [ 1093.680031] [] ? kthread+0x0/0x82 [ 1093.680031] [] kernel_thread_helper+0x7/0x10 inotify_handle_get_wd() does idr_pre_get() which does a kmem_cache_alloc() without __GFP_FS - and is hence deadlockable under extreme MM pressure. Signed-off-by: Ingo Molnar Acked-by: Peter Zijlstra Cc: MinChan Kim Cc: Nick Piggin Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/notify/inotify/inotify.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/fs/notify/inotify/inotify.c b/fs/notify/inotify/inotify.c index dae3f28f30d..331f2e88e28 100644 --- a/fs/notify/inotify/inotify.c +++ b/fs/notify/inotify/inotify.c @@ -156,7 +156,7 @@ static int inotify_handle_get_wd(struct inotify_handle *ih, int ret; do { - if (unlikely(!idr_pre_get(&ih->idr, GFP_KERNEL))) + if (unlikely(!idr_pre_get(&ih->idr, GFP_NOFS))) return -ENOSPC; ret = idr_get_new_above(&ih->idr, watch, ih->last_wd+1, &watch->wd); } while (ret == -EAGAIN); -- 2.20.1