From 3e1199dcad004a40b55297a4736ccd1b9b81a952 Mon Sep 17 00:00:00 2001 From: Milosz Tanski Date: Wed, 13 Aug 2014 12:58:26 -0400 Subject: [PATCH] FS-Cache: refcount becomes corrupt under vma pressure. In rare cases under heavy VMA pressure the ref count for a fscache cookie becomes corrupt. In this case we decrement ref count even if we fail before incrementing the refcount. FS-Cache: Assertion failed bnode-eca5f9c6/syslog 0 > 0 is false ------------[ cut here ]------------ kernel BUG at fs/fscache/cookie.c:519! invalid opcode: 0000 [#1] SMP Call Trace: [] __fscache_relinquish_cookie+0x50/0x220 [fscache] [] ceph_fscache_unregister_inode_cookie+0x3e/0x50 [ceph] [] ceph_destroy_inode+0x33/0x200 [ceph] [] ? __fsnotify_inode_delete+0xe/0x10 [] destroy_inode+0x3c/0x70 [] evict+0x111/0x180 [] iput+0x103/0x190 [] __dentry_kill+0x1c8/0x220 [] shrink_dentry_list+0xf1/0x250 [] prune_dcache_sb+0x4c/0x60 [] super_cache_scan+0xff/0x170 [] shrink_slab_node+0x140/0x2c0 [] shrink_slab+0x8a/0x130 [] balance_pgdat+0x3e2/0x5d0 [] kswapd+0x16a/0x4a0 [] ? __wake_up_sync+0x20/0x20 [] ? balance_pgdat+0x5d0/0x5d0 [] kthread+0xc9/0xe0 [] ? ftrace_raw_event_xen_mmu_release_ptpage+0x70/0x90 [] ? flush_kthread_worker+0xb0/0xb0 [] ret_from_fork+0x7c/0xb0 [] ? flush_kthread_worker+0xb0/0xb0 RIP [] __fscache_disable_cookie+0x1db/0x210 [fscache] RSP ---[ end trace 254d0d7c74a01f25 ]--- Signed-off-by: Milosz Tanski Signed-off-by: David Howells --- fs/fscache/page.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/fs/fscache/page.c b/fs/fscache/page.c index 781ac7b0b53e..de33b3fccca6 100644 --- a/fs/fscache/page.c +++ b/fs/fscache/page.c @@ -198,7 +198,7 @@ int __fscache_attr_changed(struct fscache_cookie *cookie) { struct fscache_operation *op; struct fscache_object *object; - bool wake_cookie; + bool wake_cookie = false; _enter("%p", cookie); @@ -228,15 +228,16 @@ int __fscache_attr_changed(struct fscache_cookie *cookie) __fscache_use_cookie(cookie); if (fscache_submit_exclusive_op(object, op) < 0) - goto nobufs; + goto nobufs_dec; spin_unlock(&cookie->lock); fscache_stat(&fscache_n_attr_changed_ok); fscache_put_operation(op); _leave(" = 0"); return 0; -nobufs: +nobufs_dec: wake_cookie = __fscache_unuse_cookie(cookie); +nobufs: spin_unlock(&cookie->lock); kfree(op); if (wake_cookie) -- 2.34.1