Message-ID: <20210319140528.GB30349@xsang-OptiPlex-9020>
Date:   Fri, 19 Mar 2021 22:05:28 +0800
From:   Oliver Sang <oliver.sang@...el.com>
To:     Minchan Kim <minchan@...nel.org>
Cc:     0day robot <lkp@...el.com>,
        Chris Goldsworthy <cgoldswo@...eaurora.org>,
        LKML <linux-kernel@...r.kernel.org>, lkp@...ts.01.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        linux-mm <linux-mm@...ck.org>, joaodias@...gle.com,
        surenb@...gle.com, willy@...radead.org, mhocko@...e.com,
        david@...hat.com, vbabka@...e.cz, linux-fsdevel@...r.kernel.org
Subject: Re: [mm]  8fd8d23ab1: WARNING:at_fs/buffer.c:#__brelse

Hi Minchan,

On Wed, Mar 17, 2021 at 09:29:38AM -0700, Minchan Kim wrote:
> On Wed, Mar 17, 2021 at 10:37:57AM +0800, kernel test robot wrote:
> > 
> > 
> > Greeting,
> > 
> > FYI, we noticed the following commit (built with gcc-9):
> > 
> > commit: 8fd8d23ab10cc2fceeac25ea7b0e2eaf98e78d64 ("[PATCH v3 3/3] mm: fs: Invalidate BH LRU during page migration")
> > url: https://github.com/0day-ci/linux/commits/Minchan-Kim/mm-replace-migrate_prep-with-lru_add_drain_all/20210311-001714
> > base: https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git 144c79ef33536b4ecb4951e07dbc1f2b7fa99d32
> > 
> > in testcase: blktests
> > version: blktests-x86_64-a210761-1_20210124
> > with following parameters:
> > 
> > 	test: nbd-group-01
> > 	ucode: 0xe2
> > 
> > 
> > 
> > on test machine: 4 threads Intel(R) Core(TM) i5-6500 CPU @ 3.20GHz with 32G memory
> > 
> > caused below changes (please refer to attached dmesg/kmsg for entire log/backtrace):
> > 
> > 
> > 
> > If you fix the issue, kindly add following tag
> > Reported-by: kernel test robot <oliver.sang@...el.com>
> > 
> > 
> > [   40.465061] WARNING: CPU: 2 PID: 5207 at fs/buffer.c:1177 __brelse (kbuild/src/consumer/fs/buffer.c:1177 kbuild/src/consumer/fs/buffer.c:1171) 
> > [   40.465066] Modules linked in: nbd loop xfs libcrc32c dm_multipath dm_mod ipmi_devintf ipmi_msghandler sd_mod t10_pi sg intel_rapl_msr intel_rapl_common x86_pkg_temp_thermal intel_powerclamp coretemp kvm_intel kvm irqbypass crct10dif_pclmul crc32_pclmul crc32c_intel ghash_clmulni_intel rapl i915 mei_wdt intel_cstate wmi_bmof intel_gtt drm_kms_helper syscopyarea ahci intel_uncore sysfillrect sysimgblt libahci fb_sys_fops drm libata mei_me mei intel_pch_thermal wmi video intel_pmc_core acpi_pad ip_tables
> > [   40.465086] CPU: 2 PID: 5207 Comm: mount_clear_soc Tainted: G          I       5.12.0-rc2-00062-g8fd8d23ab10c #1
> > [   40.465088] Hardware name: Dell Inc. OptiPlex 7040/0Y7WYT, BIOS 1.1.1 10/07/2015
> > [   40.465089] RIP: 0010:__brelse (kbuild/src/consumer/fs/buffer.c:1177 kbuild/src/consumer/fs/buffer.c:1171) 
> > [ 40.465091] Code: 00 00 00 00 00 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 8b 47 60 85 c0 74 05 f0 ff 4f 60 c3 48 c7 c7 d8 99 57 82 e8 02 5d 80 00 <0f> 0b c3 0f 1f 44 00 00 55 65 ff 05 13 79 c8 7e 53 48 c7 c3 c0 89
> 
> Hi,
> 
> Unfortunately, I couldn't set the lkp test in my local mahcine
> since installation failed(I guess my linux distribution is
> very minor)
> 
> Do you mind testing this patch? (Please replace the original
> patch with this one)

by replacing the original patch with below one, we confirmed the issue fixed. Thanks

> 
> From 23cfe5a8e939e2c077223e009887af8a0b5d6381 Mon Sep 17 00:00:00 2001
> From: Minchan Kim <minchan@...nel.org>
> Date: Tue, 2 Mar 2021 12:05:08 -0800
> Subject: [PATCH] mm: fs: Invalidate BH LRU during page migration
> 
> Pages containing buffer_heads that are in one of the per-CPU
> buffer_head LRU caches will be pinned and thus cannot be migrated.
> This can prevent CMA allocations from succeeding, which are often used
> on platforms with co-processors (such as a DSP) that can only use
> physically contiguous memory. It can also prevent memory
> hot-unplugging from succeeding, which involves migrating at least
> MIN_MEMORY_BLOCK_SIZE bytes of memory, which ranges from 8 MiB to 1
> GiB based on the architecture in use.
> 
> Correspondingly, invalidate the BH LRU caches before a migration
> starts and stop any buffer_head from being cached in the LRU caches,
> until migration has finished.
> 
> Signed-off-by: Chris Goldsworthy <cgoldswo@...eaurora.org>
> Signed-off-by: Minchan Kim <minchan@...nel.org>
> ---
>  fs/buffer.c                 | 36 ++++++++++++++++++++++++++++++------
>  include/linux/buffer_head.h |  4 ++++
>  mm/swap.c                   |  5 ++++-
>  3 files changed, 38 insertions(+), 7 deletions(-)
> 
> diff --git a/fs/buffer.c b/fs/buffer.c
> index 0cb7ffd4977c..e9872d0dcbf1 100644
> --- a/fs/buffer.c
> +++ b/fs/buffer.c
> @@ -1264,6 +1264,15 @@ static void bh_lru_install(struct buffer_head *bh)
>  	int i;
>  
>  	check_irqs_on();
> +	/*
> +	 * the refcount of buffer_head in bh_lru prevents dropping the
> +	 * attached page(i.e., try_to_free_buffers) so it could cause
> +	 * failing page migration.
> +	 * Skip putting upcoming bh into bh_lru until migration is done.
> +	 */
> +	if (lru_cache_disabled())
> +		return;
> +
>  	bh_lru_lock();
>  
>  	b = this_cpu_ptr(&bh_lrus);
> @@ -1404,6 +1413,15 @@ __bread_gfp(struct block_device *bdev, sector_t block,
>  }
>  EXPORT_SYMBOL(__bread_gfp);
>  
> +static void __invalidate_bh_lrus(struct bh_lru *b)
> +{
> +	int i;
> +
> +	for (i = 0; i < BH_LRU_SIZE; i++) {
> +		brelse(b->bhs[i]);
> +		b->bhs[i] = NULL;
> +	}
> +}
>  /*
>   * invalidate_bh_lrus() is called rarely - but not only at unmount.
>   * This doesn't race because it runs in each cpu either in irq
> @@ -1412,16 +1430,12 @@ EXPORT_SYMBOL(__bread_gfp);
>  static void invalidate_bh_lru(void *arg)
>  {
>  	struct bh_lru *b = &get_cpu_var(bh_lrus);
> -	int i;
>  
> -	for (i = 0; i < BH_LRU_SIZE; i++) {
> -		brelse(b->bhs[i]);
> -		b->bhs[i] = NULL;
> -	}
> +	__invalidate_bh_lrus(b);
>  	put_cpu_var(bh_lrus);
>  }
>  
> -static bool has_bh_in_lru(int cpu, void *dummy)
> +bool has_bh_in_lru(int cpu, void *dummy)
>  {
>  	struct bh_lru *b = per_cpu_ptr(&bh_lrus, cpu);
>  	int i;
> @@ -1440,6 +1454,16 @@ void invalidate_bh_lrus(void)
>  }
>  EXPORT_SYMBOL_GPL(invalidate_bh_lrus);
>  
> +void invalidate_bh_lrus_cpu(int cpu)
> +{
> +	struct bh_lru *b;
> +
> +	bh_lru_lock();
> +	b = per_cpu_ptr(&bh_lrus, cpu);
> +	__invalidate_bh_lrus(b);
> +	bh_lru_unlock();
> +}
> +
>  void set_bh_page(struct buffer_head *bh,
>  		struct page *page, unsigned long offset)
>  {
> diff --git a/include/linux/buffer_head.h b/include/linux/buffer_head.h
> index 6b47f94378c5..e7e99da31349 100644
> --- a/include/linux/buffer_head.h
> +++ b/include/linux/buffer_head.h
> @@ -194,6 +194,8 @@ void __breadahead_gfp(struct block_device *, sector_t block, unsigned int size,
>  struct buffer_head *__bread_gfp(struct block_device *,
>  				sector_t block, unsigned size, gfp_t gfp);
>  void invalidate_bh_lrus(void);
> +void invalidate_bh_lrus_cpu(int cpu);
> +bool has_bh_in_lru(int cpu, void *dummy);
>  struct buffer_head *alloc_buffer_head(gfp_t gfp_flags);
>  void free_buffer_head(struct buffer_head * bh);
>  void unlock_buffer(struct buffer_head *bh);
> @@ -406,6 +408,8 @@ static inline int inode_has_buffers(struct inode *inode) { return 0; }
>  static inline void invalidate_inode_buffers(struct inode *inode) {}
>  static inline int remove_inode_buffers(struct inode *inode) { return 1; }
>  static inline int sync_mapping_buffers(struct address_space *mapping) { return 0; }
> +static inline void invalidate_bh_lrus_cpu(int cpu) {}
> +static inline bool has_bh_in_lru(int cpu, void *dummy) { return 0; }
>  #define buffer_heads_over_limit 0
>  
>  #endif /* CONFIG_BLOCK */
> diff --git a/mm/swap.c b/mm/swap.c
> index fbdf6ac05aec..b962fe45bc02 100644
> --- a/mm/swap.c
> +++ b/mm/swap.c
> @@ -36,6 +36,7 @@
>  #include <linux/hugetlb.h>
>  #include <linux/page_idle.h>
>  #include <linux/local_lock.h>
> +#include <linux/buffer_head.h>
>  
>  #include "internal.h"
>  
> @@ -641,6 +642,7 @@ void lru_add_drain_cpu(int cpu)
>  		pagevec_lru_move_fn(pvec, lru_lazyfree_fn);
>  
>  	activate_page_drain(cpu);
> +	invalidate_bh_lrus_cpu(cpu);
>  }
>  
>  /**
> @@ -828,7 +830,8 @@ static void __lru_add_drain_all(bool force_all_cpus)
>  		    pagevec_count(&per_cpu(lru_pvecs.lru_deactivate_file, cpu)) ||
>  		    pagevec_count(&per_cpu(lru_pvecs.lru_deactivate, cpu)) ||
>  		    pagevec_count(&per_cpu(lru_pvecs.lru_lazyfree, cpu)) ||
> -		    need_activate_page_drain(cpu)) {
> +		    need_activate_page_drain(cpu) ||
> +		    has_bh_in_lru(cpu, NULL)) {
>  			INIT_WORK(work, lru_add_drain_per_cpu);
>  			queue_work_on(cpu, mm_percpu_wq, work);
>  			__cpumask_set_cpu(cpu, &has_work);
> -- 
> 2.31.0.rc2.261.g7f71774620-goog
> 
> 

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