Hi, A user reported me that the current Writeboost in Joe's tree (https://github.com/jthornber/linux-2.6) screams on his environment. With CONFIG_DEBUG_VM (n->y), it reproduces on my environment, too. d 245.865224] device-mapper: writeboost: Superblock Header: Magic number invalid [ 245.892588] ------------[ cut here ]------------ [ 245.892601] WARNING: CPU: 7 PID: 3463 at mm/mempool.c:205 mempool_alloc+0xc3/0x1b0() [ 245.892602] Modules linked in: binfmt_misc nfsd joydev psmouse snd_hda_codec_generic serio_raw pcspkr parport_pc parport snd_hda_intel snd_hda_controller snd_hda_codec snd_hwdep snd_pcm snd_timer snd virtio_balloon i2c_piix4 evbug soundcore hid_generic usbhid hid floppy [ 245.892617] CPU: 7 PID: 3463 Comm: dmsetup Not tainted 3.16.0+ #146 [ 245.892618] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2007 [ 245.892619] 0000000000000009 ffff8800301639e8 ffffffff818002e0 0000000000000006 [ 245.892621] 0000000000000000 ffff880030163a28 ffffffff810529fc ffffffff8114cbd7 [ 245.892622] 00000000000080d0 ffff880211742000 ffff8802117b0638 0000000000000000 [ 245.892624] Call Trace: [ 245.892630] [<ffffffff818002e0>] dump_stack+0x4e/0x68 [ 245.892634] [<ffffffff810529fc>] warn_slowpath_common+0x8c/0xc0 [ 245.892636] [<ffffffff8114cbd7>] ? mempool_free_slab+0x17/0x20 [ 245.892638] [<ffffffff81052a4a>] warn_slowpath_null+0x1a/0x20 [ 245.892639] [<ffffffff8114d153>] mempool_alloc+0xc3/0x1b0 [ 245.892641] [<ffffffff8114cbd7>] ? mempool_free_slab+0x17/0x20 [ 245.892645] [<ffffffff81676cdd>] resume_cache+0x17ad/0x1a10 [ 245.892651] [<ffffffff8143e118>] ? sscanf+0x38/0x40 [ 245.892654] [<ffffffff8167337e>] writeboost_ctr+0x2fe/0x6f0 [ 245.892659] [<ffffffff81640824>] dm_table_add_target+0x194/0x440 [ 245.892661] [<ffffffff81643aed>] table_load+0xdd/0x350 [ 245.892663] [<ffffffff81643a10>] ? table_clear+0xe0/0xe0 [ 245.892665] [<ffffffff81644d9d>] ctl_ioctl+0x25d/0x500 [ 245.892671] [<ffffffff8117c300>] ? __remove_shared_vm_struct+0x30/0x60 [ 245.892673] [<ffffffff81645053>] dm_ctl_ioctl+0x13/0x20 [ 245.892681] [<ffffffff811c1f08>] do_vfs_ioctl+0x88/0x570 [ 245.892682] [<ffffffff8117e55c>] ? vm_munmap+0x5c/0x80 [ 245.892688] [<ffffffff81809877>] ? sysret_check+0x1b/0x56 [ 245.892690] [<ffffffff811c2481>] SyS_ioctl+0x91/0xb0 [ 245.892692] [<ffffffff81809852>] system_call_fastpath+0x16/0x1b [ 245.892701] ---[ end trace 9ec34fde0329cc22 ]--- Obviously, mempool_alloc() is in trouble. The reason is a line VM_WARN_ON_ONCE(gfp_mask & __GFP_ZERO) was inserted in mempool_alloc(). The related discussion is https://lkml.org/lkml/2014/4/14/525 Yes, Writeboost passes __GFP_ZERO to mempool_alloc() at two locations. I will fix this by adding memset after each and send Joe a pull request. I checked through other DM targets and found no target needs this fix. It is good. - Akira -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
