Date:	Tue, 24 Nov 2015 08:23:02 +0900
From:	Minchan Kim <minchan@...nel.org>
To:	Sergey Senozhatsky <sergey.senozhatsky@...il.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, sergey.senozhatsky.work@...il.com,
	kyeongdon.kim@....com
Subject: Re: [PATCH] zram/zcomp: use GFP_NOIO to allocate streams

Hello Sergey,

On Mon, Nov 23, 2015 at 10:27:59PM +0900, Sergey Senozhatsky wrote:
> We can end up allocating a new compression stream with GFP_KERNEL
> from within the IO path, which may result is nested (recursive) IO
> operations. That can introduce problems if the IO path in question
> is a reclaimer, holding some locks that will deadlock nested IOs.
> 
> Allocate streams and working memory using GFP_NOIO flag, forbidding
> recursive IO and FS operations.
> 
> An example:
> 
> [  747.233722] inconsistent {IN-RECLAIM_FS-W} -> {RECLAIM_FS-ON-W} usage.
> [  747.233724] git/20158 [HC0[0]:SC0[0]:HE1:SE1] takes:
> [  747.233725]  (jbd2_handle){+.+.?.}, at: [<ffffffff811e31db>] start_this_handle+0x4ca/0x555
> [  747.233733] {IN-RECLAIM_FS-W} state was registered at:
> [  747.233735]   [<ffffffff8107b8e9>] __lock_acquire+0x8da/0x117b
> [  747.233738]   [<ffffffff8107c950>] lock_acquire+0x10c/0x1a7
> [  747.233740]   [<ffffffff811e323e>] start_this_handle+0x52d/0x555
> [  747.233742]   [<ffffffff811e331a>] jbd2__journal_start+0xb4/0x237
> [  747.233744]   [<ffffffff811cc6c7>] __ext4_journal_start_sb+0x108/0x17e
> [  747.233748]   [<ffffffff811a90bf>] ext4_dirty_inode+0x32/0x61
> [  747.233750]   [<ffffffff8115f37e>] __mark_inode_dirty+0x16b/0x60c
> [  747.233754]   [<ffffffff81150ad6>] iput+0x11e/0x274
> [  747.233757]   [<ffffffff8114bfbd>] __dentry_kill+0x148/0x1b8
> [  747.233759]   [<ffffffff8114c9d9>] shrink_dentry_list+0x274/0x44a
> [  747.233761]   [<ffffffff8114d38a>] prune_dcache_sb+0x4a/0x55
> [  747.233763]   [<ffffffff8113b1ad>] super_cache_scan+0xfc/0x176
> [  747.233767]   [<ffffffff810fa089>] shrink_slab.part.14.constprop.25+0x2a2/0x4d3
> [  747.233770]   [<ffffffff810fcccb>] shrink_zone+0x74/0x140
> [  747.233772]   [<ffffffff810fd924>] kswapd+0x6b7/0x930
> [  747.233774]   [<ffffffff81058887>] kthread+0x107/0x10f
> [  747.233778]   [<ffffffff814fadff>] ret_from_fork+0x3f/0x70
> [  747.233783] irq event stamp: 138297
> [  747.233784] hardirqs last  enabled at (138297): [<ffffffff8107aff3>] debug_check_no_locks_freed+0x113/0x12f
> [  747.233786] hardirqs last disabled at (138296): [<ffffffff8107af13>] debug_check_no_locks_freed+0x33/0x12f
> [  747.233788] softirqs last  enabled at (137818): [<ffffffff81040f89>] __do_softirq+0x2d3/0x3e9
> [  747.233792] softirqs last disabled at (137813): [<ffffffff81041292>] irq_exit+0x41/0x95
> [  747.233794]
>                other info that might help us debug this:
> [  747.233796]  Possible unsafe locking scenario:
> [  747.233797]        CPU0
> [  747.233798]        ----
> [  747.233799]   lock(jbd2_handle);
> [  747.233801]   <Interrupt>
> [  747.233801]     lock(jbd2_handle);
> [  747.233803]
>                 *** DEADLOCK ***
> [  747.233805] 5 locks held by git/20158:
> [  747.233806]  #0:  (sb_writers#7){.+.+.+}, at: [<ffffffff81155411>] mnt_want_write+0x24/0x4b
> [  747.233811]  #1:  (&type->i_mutex_dir_key#2/1){+.+.+.}, at: [<ffffffff81145087>] lock_rename+0xd9/0xe3
> [  747.233817]  #2:  (&sb->s_type->i_mutex_key#11){+.+.+.}, at: [<ffffffff8114f8e2>] lock_two_nondirectories+0x3f/0x6b
> [  747.233822]  #3:  (&sb->s_type->i_mutex_key#11/4){+.+.+.}, at: [<ffffffff8114f909>] lock_two_nondirectories+0x66/0x6b
> [  747.233827]  #4:  (jbd2_handle){+.+.?.}, at: [<ffffffff811e31db>] start_this_handle+0x4ca/0x555
> [  747.233831]
>                stack backtrace:
> [  747.233834] CPU: 2 PID: 20158 Comm: git Not tainted 4.1.0-rc7-next-20150615-dbg-00016-g8bdf555-dirty #211
> [  747.233837]  ffff8800a56cea40 ffff88010d0a75f8 ffffffff814f446d ffffffff81077036
> [  747.233840]  ffffffff823a84b0 ffff88010d0a7638 ffffffff814f3849 0000000000000001
> [  747.233843]  000000000000000a ffff8800a56cf6f8 ffff8800a56cea40 ffffffff810795dd
> [  747.233846] Call Trace:
> [  747.233849]  [<ffffffff814f446d>] dump_stack+0x4c/0x6e
> [  747.233852]  [<ffffffff81077036>] ? up+0x39/0x3e
> [  747.233854]  [<ffffffff814f3849>] print_usage_bug.part.23+0x25b/0x26a
> [  747.233857]  [<ffffffff810795dd>] ? print_shortest_lock_dependencies+0x182/0x182
> [  747.233859]  [<ffffffff8107a9c9>] mark_lock+0x384/0x56d
> [  747.233862]  [<ffffffff8107ac11>] mark_held_locks+0x5f/0x76
> [  747.233865]  [<ffffffffa023d2f3>] ? zcomp_strm_alloc+0x25/0x73 [zram]
> [  747.233867]  [<ffffffff8107d13b>] lockdep_trace_alloc+0xb2/0xb5
> [  747.233870]  [<ffffffff8112bac7>] kmem_cache_alloc_trace+0x32/0x1e2
> [  747.233873]  [<ffffffffa023d2f3>] zcomp_strm_alloc+0x25/0x73 [zram]
> [  747.233876]  [<ffffffffa023d428>] zcomp_strm_multi_find+0xe7/0x173 [zram]
> [  747.233879]  [<ffffffffa023d58b>] zcomp_strm_find+0xc/0xe [zram]
> [  747.233881]  [<ffffffffa023f292>] zram_bvec_rw+0x2ca/0x7e0 [zram]
> [  747.233885]  [<ffffffffa023fa8c>] zram_make_request+0x1fa/0x301 [zram]
> [  747.233889]  [<ffffffff812142f8>] generic_make_request+0x9c/0xdb
> [  747.233891]  [<ffffffff8121442e>] submit_bio+0xf7/0x120
> [  747.233895]  [<ffffffff810f1c0c>] ? __test_set_page_writeback+0x1a0/0x1b8
> [  747.233897]  [<ffffffff811a9d00>] ext4_io_submit+0x2e/0x43
> [  747.233899]  [<ffffffff811a9efa>] ext4_bio_write_page+0x1b7/0x300
> [  747.233902]  [<ffffffff811a2106>] mpage_submit_page+0x60/0x77
> [  747.233905]  [<ffffffff811a25b0>] mpage_map_and_submit_buffers+0x10f/0x21d
> [  747.233907]  [<ffffffff811a6814>] ext4_writepages+0xc8c/0xe1b
> [  747.233910]  [<ffffffff810f3f77>] do_writepages+0x23/0x2c
> [  747.233913]  [<ffffffff810ea5d1>] __filemap_fdatawrite_range+0x84/0x8b
> [  747.233915]  [<ffffffff810ea657>] filemap_flush+0x1c/0x1e
> [  747.233917]  [<ffffffff811a3851>] ext4_alloc_da_blocks+0xb8/0x117
> [  747.233919]  [<ffffffff811af52a>] ext4_rename+0x132/0x6dc
> [  747.233921]  [<ffffffff8107ac11>] ? mark_held_locks+0x5f/0x76
> [  747.233924]  [<ffffffff811afafd>] ext4_rename2+0x29/0x2b
> [  747.233926]  [<ffffffff811427ea>] vfs_rename+0x540/0x636
> [  747.233928]  [<ffffffff81146a01>] SyS_renameat2+0x359/0x44d
> [  747.233931]  [<ffffffff81146b26>] SyS_rename+0x1e/0x20
> [  747.233933]  [<ffffffff814faa17>] entry_SYSCALL_64_fastpath+0x12/0x6f
> 
> The patch also does some very trivial cosmetic tweaks, not worth
> of a separate patch.

I assume you saw real problem and tested this patch. It means
it's -stable material. If so, let's send this patch to -stable
without cosmetic change and let's drop vmalloc part for the
convenience for stable. Instead, we could apply your patch first
than Kyeongdon's one and Kyeongdon can resend his patch with fixing
vmalloc part.


> 
> Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@...il.com>
> ---
>  drivers/block/zram/zcomp.c     |  4 ++--
>  drivers/block/zram/zcomp_lz4.c | 12 ++++++++----
>  drivers/block/zram/zcomp_lzo.c | 12 ++++++++----
>  3 files changed, 18 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/block/zram/zcomp.c b/drivers/block/zram/zcomp.c
> index 5cb13ca..c536177 100644
> --- a/drivers/block/zram/zcomp.c
> +++ b/drivers/block/zram/zcomp.c
> @@ -76,7 +76,7 @@ static void zcomp_strm_free(struct zcomp *comp, struct zcomp_strm *zstrm)
>   */
>  static struct zcomp_strm *zcomp_strm_alloc(struct zcomp *comp)
>  {
> -	struct zcomp_strm *zstrm = kmalloc(sizeof(*zstrm), GFP_KERNEL);
> +	struct zcomp_strm *zstrm = kmalloc(sizeof(*zstrm), GFP_NOIO);
>  	if (!zstrm)
>  		return NULL;
>  
> @@ -85,7 +85,7 @@ static struct zcomp_strm *zcomp_strm_alloc(struct zcomp *comp)
>  	 * allocate 2 pages. 1 for compressed data, plus 1 extra for the
>  	 * case when compressed size is larger than the original one
>  	 */
> -	zstrm->buffer = (void *)__get_free_pages(GFP_KERNEL | __GFP_ZERO, 1);
> +	zstrm->buffer = (void *)__get_free_pages(GFP_NOIO | __GFP_ZERO, 1);
>  	if (!zstrm->private || !zstrm->buffer) {
>  		zcomp_strm_free(comp, zstrm);
>  		zstrm = NULL;
> diff --git a/drivers/block/zram/zcomp_lz4.c b/drivers/block/zram/zcomp_lz4.c
> index 0cc4799..0bce010 100644
> --- a/drivers/block/zram/zcomp_lz4.c
> +++ b/drivers/block/zram/zcomp_lz4.c
> @@ -20,10 +20,13 @@ static void *zcomp_lz4_create(void)
>  	void *ret;
>  
>  	ret = kzalloc(LZ4_MEM_COMPRESS,
> -			__GFP_NORETRY|__GFP_NOWARN|__GFP_NOMEMALLOC);
> -	if (!ret)
> -		ret = vzalloc(LZ4_MEM_COMPRESS);
> -	return ret;
> +			__GFP_NORETRY | __GFP_NOWARN | __GFP_NOMEMALLOC);
> +	if (ret)
> +		return ret;
> +
> +	return __vmalloc(LZ4_MEM_COMPRESS,
> +			GFP_NOIO | __GFP_NOWARN | __GFP_HIGHMEM | __GFP_ZERO,
> +			PAGE_KERNEL);
>  }
>  
>  static void zcomp_lz4_destroy(void *private)
> @@ -42,6 +45,7 @@ static int zcomp_lz4_decompress(const unsigned char *src, size_t src_len,
>  		unsigned char *dst)
>  {
>  	size_t dst_len = PAGE_SIZE;
> +
>  	/* return  : Success if return 0 */
>  	return lz4_decompress_unknownoutputsize(src, src_len, dst, &dst_len);
>  }
> diff --git a/drivers/block/zram/zcomp_lzo.c b/drivers/block/zram/zcomp_lzo.c
> index 59b8aa4..e5db8de 100644
> --- a/drivers/block/zram/zcomp_lzo.c
> +++ b/drivers/block/zram/zcomp_lzo.c
> @@ -20,10 +20,13 @@ static void *lzo_create(void)
>  	void *ret;
>  
>  	ret = kzalloc(LZO1X_MEM_COMPRESS,
> -			__GFP_NORETRY|__GFP_NOWARN|__GFP_NOMEMALLOC);
> -	if (!ret)
> -		ret = vzalloc(LZO1X_MEM_COMPRESS);
> -	return ret;
> +			__GFP_NORETRY | __GFP_NOWARN | __GFP_NOMEMALLOC);
> +	if (ret)
> +		return ret;
> +
> +	return __vmalloc(LZO1X_MEM_COMPRESS,
> +			GFP_NOIO | __GFP_NOWARN | __GFP_HIGHMEM | __GFP_ZERO,
> +			PAGE_KERNEL);
>  }
>  
>  static void lzo_destroy(void *private)
> @@ -42,6 +45,7 @@ static int lzo_decompress(const unsigned char *src, size_t src_len,
>  		unsigned char *dst)
>  {
>  	size_t dst_len = PAGE_SIZE;
> +
>  	int ret = lzo1x_decompress_safe(src, src_len, dst, &dst_len);
>  	return ret == LZO_E_OK ? 0 : ret;
>  }
> -- 
> 2.6.2
> 

-- 
Kind regards,
Minchan Kim
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