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.
[jlayton: remove if (sk->sk_forward_alloc) conditional. As Leon
points out that it's not needed.]
Cc: Leon Romanovsky <leon@xxxxxxx>
Signed-off-by: Mel Gorman <mgorman@xxxxxxx>
Signed-off-by: Jeff Layton <jeff.layton@xxxxxxxxxxxxxxx>
---
net/core/sock.c | 13 +++++--------
1 file changed, 5 insertions(+), 8 deletions(-)
diff --git a/net/core/sock.c b/net/core/sock.c
index 292f42228bfb..469d6039c7f5 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -354,15 +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))
- sk_mem_reclaim(sk);
+ sk_mem_reclaim(sk);
}
EXPORT_SYMBOL_GPL(sk_clear_memalloc);
--
2.4.2
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