From 946ddbe805cba88755fcea733597a287f9a18bce Mon Sep 17 00:00:00 2001 From: Filipe Manana Date: Mon, 1 Dec 2014 17:04:40 +0000 Subject: [PATCH] Btrfs: fix memory leak after block remove + trimming There was a free space entry structure memeory leak if a block group is remove while a free space entry is being trimmed, which the following diagram explains: CPU 1 CPU 2 btrfs_trim_block_group() trim_no_bitmap() remove free space entry from block group cache's rbtree do_trimming() btrfs_remove_block_group() btrfs_remove_free_space_cache() add back free space entry to block group's cache rbtree btrfs_put_block_group() (...) btrfs_put_block_group() kfree(bg->free_space_ctl) kfree(bg) The free space entry added after doing the discard of its respective range ends up never being freed. Detected after doing an "rmmod btrfs" after running the stress test recently submitted for fstests: [ 8234.642212] kmem_cache_destroy btrfs_free_space: Slab cache still has objects [ 8234.642657] CPU: 1 PID: 32276 Comm: rmmod Tainted: G W L 3.17.0-rc5-btrfs-next-2+ #1 [ 8234.642660] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.7.5-0-ge51488c-20140602_164612-nilsson.home.kraxel.org 04/01/2014 [ 8234.642664] 0000000000000000 ffff8801af1b3eb8 ffffffff8140c7b6 ffff8801dbedd0c0 [ 8234.642670] ffff8801af1b3ed0 ffffffff811149ce 0000000000000000 ffff8801af1b3ee0 [ 8234.642676] ffffffffa042dbe7 ffff8801af1b3ef0 ffffffffa0487422 ffff8801af1b3f78 [ 8234.642682] Call Trace: [ 8234.642692] [] dump_stack+0x4d/0x66 [ 8234.642699] [] kmem_cache_destroy+0x4d/0x92 [ 8234.642731] [] btrfs_destroy_cachep+0x63/0x76 [btrfs] [ 8234.642757] [] exit_btrfs_fs+0x9/0xbe7 [btrfs] [ 8234.642762] [] SyS_delete_module+0x155/0x1c6 [ 8234.642768] [] ? trace_hardirqs_on_thunk+0x3a/0x3f [ 8234.642773] [] system_call_fastpath+0x16/0x1b This applies on top (depends on) of my previous patch titled: "Btrfs: fix race between fs trimming and block group remove/allocation" Signed-off-by: Filipe Manana Signed-off-by: Chris Mason --- fs/btrfs/free-space-cache.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c index 2ee73c276acb..030847bf7cec 100644 --- a/fs/btrfs/free-space-cache.c +++ b/fs/btrfs/free-space-cache.c @@ -3200,6 +3200,12 @@ out: /* once for us and once for the tree */ free_extent_map(em); free_extent_map(em); + + /* + * We've left one free space entry and other tasks trimming + * this block group have left 1 entry each one. Free them. + */ + __btrfs_remove_free_space_cache(block_group->free_space_ctl); } else { spin_unlock(&block_group->lock); } -- 2.20.1