On Tue, Jun 9, 2015 at 9:40 PM, Jeff Layton <jlayton@xxxxxxxxxxxxxxx> wrote: > From: Mel Gorman <mgorman@xxxxxxx> > > Jeff Layton reported the following; > > [ 74.232485] ------------[ cut here ]------------ > [ 74.233354] WARNING: CPU: 2 PID: 754 at net/core/sock.c:364 sk_clear_memalloc+0x51/0x80() > [ 74.234790] Modules linked in: cts rpcsec_gss_krb5 nfsv4 dns_resolver nfs fscache xfs libcrc32c snd_hda_codec_generic snd_hda_intel snd_hda_controller snd_hda_codec snd_hda_core snd_hwdep snd_seq snd_seq_device nfsd snd_pcm snd_timer snd e1000 ppdev parport_pc joydev parport pvpanic soundcore floppy serio_raw i2c_piix4 pcspkr nfs_acl lockd virtio_balloon acpi_cpufreq auth_rpcgss grace sunrpc qxl drm_kms_helper ttm drm virtio_console virtio_blk virtio_pci ata_generic virtio_ring pata_acpi virtio > [ 74.243599] CPU: 2 PID: 754 Comm: swapoff Not tainted 4.1.0-rc6+ #5 > [ 74.244635] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011 > [ 74.245546] 0000000000000000 0000000079e69e31 ffff8800d066bde8 ffffffff8179263d > [ 74.246786] 0000000000000000 0000000000000000 ffff8800d066be28 ffffffff8109e6fa > [ 74.248175] 0000000000000000 ffff880118d48000 ffff8800d58f5c08 ffff880036e380a8 > [ 74.249483] Call Trace: > [ 74.249872] [<ffffffff8179263d>] dump_stack+0x45/0x57 > [ 74.250703] [<ffffffff8109e6fa>] warn_slowpath_common+0x8a/0xc0 > [ 74.251655] [<ffffffff8109e82a>] warn_slowpath_null+0x1a/0x20 > [ 74.252585] [<ffffffff81661241>] sk_clear_memalloc+0x51/0x80 > [ 74.253519] [<ffffffffa0116c72>] xs_disable_swap+0x42/0x80 [sunrpc] > [ 74.254537] [<ffffffffa01109de>] rpc_clnt_swap_deactivate+0x7e/0xc0 [sunrpc] > [ 74.255610] [<ffffffffa03e4fd7>] nfs_swap_deactivate+0x27/0x30 [nfs] > [ 74.256582] [<ffffffff811e99d4>] destroy_swap_extents+0x74/0x80 > [ 74.257496] [<ffffffff811ecb52>] SyS_swapoff+0x222/0x5c0 > [ 74.258318] [<ffffffff81023f27>] ? syscall_trace_leave+0xc7/0x140 > [ 74.259253] [<ffffffff81798dae>] system_call_fastpath+0x12/0x71 > [ 74.260158] ---[ end trace 2530722966429f10 ]--- > > The warning in question was unnecessary but with Jeff's series the rules > are also clearer. This patch removes the warning and updates the comment > to explain why sk_mem_reclaim() may still be called. > > Signed-off-by: Mel Gorman <mgorman@xxxxxxx> > Acked-by: Jeff Layton <jeff.layton@xxxxxxxxxxxxxxx> > --- > net/core/sock.c | 12 +++++------- > 1 file changed, 5 insertions(+), 7 deletions(-) > > diff --git a/net/core/sock.c b/net/core/sock.c > index 292f42228bfb..2bb4c56370e5 100644 > --- a/net/core/sock.c > +++ b/net/core/sock.c > @@ -354,14 +354,12 @@ void sk_clear_memalloc(struct sock *sk) > > /* > * SOCK_MEMALLOC is allowed to ignore rmem limits to ensure forward > - * progress of swapping. However, if SOCK_MEMALLOC is cleared while > - * it has rmem allocations there is a risk that the user of the > - * socket cannot make forward progress due to exceeding the rmem > - * limits. By rights, sk_clear_memalloc() should only be called > - * on sockets being torn down but warn and reset the accounting if > - * that assumption breaks. > + * progress of swapping. SOCK_MEMALLOC may be cleared while > + * it has rmem allocations due to the last swapfile being deactivated > + * but there is a risk that the socket is unusable due to exceeding > + * the rmem limits. Reclaim the reserves and obey rmem limits again. > */ > - if (WARN_ON(sk->sk_forward_alloc)) > + if (sk->sk_forward_alloc) You don't really need this IF. if sk->sk_forward_alloc is equal to zero, it will be less than SK_MEM_QUANTUM. http://lxr.free-electrons.com/source/include/net/sock.h#L1405 1405 static inline void sk_mem_reclaim(struct sock *sk) 1406 { 1407 if (!sk_has_account(sk)) 1408 return; 1409 if (sk->sk_forward_alloc >= SK_MEM_QUANTUM) 1410 __sk_mem_reclaim(sk); 1411 } > sk_mem_reclaim(sk); > } > EXPORT_SYMBOL_GPL(sk_clear_memalloc); > -- > 2.4.2 > > -- > To unsubscribe, send a message with 'unsubscribe linux-mm' in > the body to majordomo@xxxxxxxxx. For more info on Linux MM, > see: http://www.linux-mm.org/ . > Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a> -- Leon Romanovsky | Independent Linux Consultant www.leon.nu | leon@xxxxxxx -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href