131 lines
4.5 KiB
Diff
131 lines
4.5 KiB
Diff
From 240c8e20079c36d1891ac5ba5bcfa80f9a6cb62f Mon Sep 17 00:00:00 2001
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Message-Id: <240c8e20079c36d1891ac5ba5bcfa80f9a6cb62f.1601675153.git.zanussi@kernel.org>
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In-Reply-To: <5b5a156f9808b1acf1205606e03da117214549ea.1601675151.git.zanussi@kernel.org>
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References: <5b5a156f9808b1acf1205606e03da117214549ea.1601675151.git.zanussi@kernel.org>
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From: "Luis Claudio R. Goncalves" <lclaudio@uudg.org>
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Date: Tue, 25 Jun 2019 11:28:04 -0300
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Subject: [PATCH 278/333] mm/zswap: Do not disable preemption in
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zswap_frontswap_store()
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Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/4.19/older/patches-4.19.148-rt64.tar.xz
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[ Upstream commit 4e4cf4be79635e67144632d9135286381acbc95a ]
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Zswap causes "BUG: scheduling while atomic" by blocking on a rt_spin_lock() with
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preemption disabled. The preemption is disabled by get_cpu_var() in
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zswap_frontswap_store() to protect the access of the zswap_dstmem percpu variable.
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Use get_locked_var() to protect the percpu zswap_dstmem variable, making the
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code preemptive.
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As get_cpu_ptr() also disables preemption, replace it by this_cpu_ptr() and
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remove the counterpart put_cpu_ptr().
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Steps to Reproduce:
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1. # grubby --args "zswap.enabled=1" --update-kernel DEFAULT
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2. # reboot
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3. Calculate the amount o memory to be used by the test:
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---> grep MemAvailable /proc/meminfo
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---> Add 25% ~ 50% to that value
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4. # stress --vm 1 --vm-bytes ${MemAvailable+25%} --timeout 240s
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Usually, in less than 5 minutes the backtrace listed below appears, followed
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by a kernel panic:
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| BUG: scheduling while atomic: kswapd1/181/0x00000002
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| Preemption disabled at:
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| [<ffffffff8b2a6cda>] zswap_frontswap_store+0x21a/0x6e1
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| Kernel panic - not syncing: scheduling while atomic
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| CPU: 14 PID: 181 Comm: kswapd1 Kdump: loaded Not tainted 5.0.14-rt9 #1
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| Hardware name: AMD Pence/Pence, BIOS WPN2321X_Weekly_12_03_21 03/19/2012
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| Call Trace:
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| panic+0x106/0x2a7
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| __schedule_bug.cold+0x3f/0x51
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| __schedule+0x5cb/0x6f0
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| schedule+0x43/0xd0
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| rt_spin_lock_slowlock_locked+0x114/0x2b0
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| rt_spin_lock_slowlock+0x51/0x80
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| zbud_alloc+0x1da/0x2d0
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| zswap_frontswap_store+0x31a/0x6e1
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| __frontswap_store+0xab/0x130
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| swap_writepage+0x39/0x70
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| pageout.isra.0+0xe3/0x320
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| shrink_page_list+0xa8e/0xd10
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| shrink_inactive_list+0x251/0x840
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| shrink_node_memcg+0x213/0x770
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| shrink_node+0xd9/0x450
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| balance_pgdat+0x2d5/0x510
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| kswapd+0x218/0x470
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| kthread+0xfb/0x130
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| ret_from_fork+0x27/0x50
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Cc: stable-rt@vger.kernel.org
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Reported-by: Ping Fang <pifang@redhat.com>
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Signed-off-by: Luis Claudio R. Goncalves <lgoncalv@redhat.com>
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Reviewed-by: Daniel Bristot de Oliveira <bristot@redhat.com>
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Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
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Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
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---
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mm/zswap.c | 12 +++++++-----
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1 file changed, 7 insertions(+), 5 deletions(-)
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diff --git a/mm/zswap.c b/mm/zswap.c
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index cd91fd9d96b8..420225d3ff0b 100644
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--- a/mm/zswap.c
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+++ b/mm/zswap.c
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@@ -27,6 +27,7 @@
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#include <linux/highmem.h>
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#include <linux/slab.h>
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#include <linux/spinlock.h>
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+#include <linux/locallock.h>
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#include <linux/types.h>
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#include <linux/atomic.h>
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#include <linux/frontswap.h>
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@@ -990,6 +991,8 @@ static void zswap_fill_page(void *ptr, unsigned long value)
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memset_l(page, value, PAGE_SIZE / sizeof(unsigned long));
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}
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+/* protect zswap_dstmem from concurrency */
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+static DEFINE_LOCAL_IRQ_LOCK(zswap_dstmem_lock);
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/*********************************
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* frontswap hooks
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**********************************/
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@@ -1066,12 +1069,11 @@ static int zswap_frontswap_store(unsigned type, pgoff_t offset,
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}
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/* compress */
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- dst = get_cpu_var(zswap_dstmem);
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- tfm = *get_cpu_ptr(entry->pool->tfm);
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+ dst = get_locked_var(zswap_dstmem_lock, zswap_dstmem);
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+ tfm = *this_cpu_ptr(entry->pool->tfm);
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src = kmap_atomic(page);
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ret = crypto_comp_compress(tfm, src, PAGE_SIZE, dst, &dlen);
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kunmap_atomic(src);
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- put_cpu_ptr(entry->pool->tfm);
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if (ret) {
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ret = -EINVAL;
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goto put_dstmem;
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@@ -1094,7 +1096,7 @@ static int zswap_frontswap_store(unsigned type, pgoff_t offset,
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memcpy(buf, &zhdr, hlen);
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memcpy(buf + hlen, dst, dlen);
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zpool_unmap_handle(entry->pool->zpool, handle);
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- put_cpu_var(zswap_dstmem);
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+ put_locked_var(zswap_dstmem_lock, zswap_dstmem);
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/* populate entry */
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entry->offset = offset;
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@@ -1122,7 +1124,7 @@ static int zswap_frontswap_store(unsigned type, pgoff_t offset,
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return 0;
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put_dstmem:
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- put_cpu_var(zswap_dstmem);
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+ put_locked_var(zswap_dstmem_lock, zswap_dstmem);
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zswap_pool_put(entry->pool);
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freepage:
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zswap_entry_cache_free(entry);
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--
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2.17.1
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