linux-kernel - Re: [f2fs-dev] [PATCH] f2fs: bio

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Date:   Wed, 30 Oct 2019 16:56:17 +0800
From:   Chao Yu <yuchao0@...wei.com>
To:     Gao Xiang <gaoxiang25@...wei.com>,
        Jaegeuk Kim <jaegeuk@...nel.org>, "Chao Yu" <chao@...nel.org>
CC:     <linux-f2fs-devel@...ts.sourceforge.net>,
        <linux-doc@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        Jonathan Corbet <corbet@....net>
Subject: Re: [f2fs-dev] [PATCH] f2fs: bio_alloc should never fail

On 2019/10/30 11:55, Gao Xiang wrote:
> remove such useless code and related fault injection.

Hi Xiang,

Although, there is so many 'nofail' allocation in f2fs, I think we'd better
avoid such allocation as much as possible (now for read path, we may allow to
fail to allocate bio), I suggest to keep the failure path and bio allocation
injection.

It looks bio_alloc() will use its own mempool, which may suffer deadlock
potentially. So how about changing to use bio_alloc_bioset(, , NULL) instead of
bio_alloc()?

Thanks,

> 
> Signed-off-by: Gao Xiang <gaoxiang25@...wei.com>
> ---
>  Documentation/filesystems/f2fs.txt |  1 -
>  fs/f2fs/data.c                     |  6 ++----
>  fs/f2fs/f2fs.h                     | 21 ---------------------
>  fs/f2fs/segment.c                  |  5 +----
>  fs/f2fs/super.c                    |  1 -
>  5 files changed, 3 insertions(+), 31 deletions(-)
> 
> diff --git a/Documentation/filesystems/f2fs.txt b/Documentation/filesystems/f2fs.txt
> index 7e1991328473..3477c3e4c08b 100644
> --- a/Documentation/filesystems/f2fs.txt
> +++ b/Documentation/filesystems/f2fs.txt
> @@ -172,7 +172,6 @@ fault_type=%d          Support configuring fault injection type, should be
>                         FAULT_KVMALLOC		0x000000002
>                         FAULT_PAGE_ALLOC		0x000000004
>                         FAULT_PAGE_GET		0x000000008
> -                       FAULT_ALLOC_BIO		0x000000010
>                         FAULT_ALLOC_NID		0x000000020
>                         FAULT_ORPHAN		0x000000040
>                         FAULT_BLOCK		0x000000080
> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
> index 5755e897a5f0..3b88dcb15de6 100644
> --- a/fs/f2fs/data.c
> +++ b/fs/f2fs/data.c
> @@ -288,7 +288,7 @@ static struct bio *__bio_alloc(struct f2fs_io_info *fio, int npages)
>  	struct f2fs_sb_info *sbi = fio->sbi;
>  	struct bio *bio;
>  
> -	bio = f2fs_bio_alloc(sbi, npages, true);
> +	bio = bio_alloc(GFP_NOIO, npages);
>  
>  	f2fs_target_device(sbi, fio->new_blkaddr, bio);
>  	if (is_read_io(fio->op)) {
> @@ -682,9 +682,7 @@ static struct bio *f2fs_grab_read_bio(struct inode *inode, block_t blkaddr,
>  	struct bio_post_read_ctx *ctx;
>  	unsigned int post_read_steps = 0;
>  
> -	bio = f2fs_bio_alloc(sbi, min_t(int, nr_pages, BIO_MAX_PAGES), false);
> -	if (!bio)
> -		return ERR_PTR(-ENOMEM);
> +	bio = bio_alloc(GFP_KERNEL, min_t(int, nr_pages, BIO_MAX_PAGES));
>  	f2fs_target_device(sbi, blkaddr, bio);
>  	bio->bi_end_io = f2fs_read_end_io;
>  	bio_set_op_attrs(bio, REQ_OP_READ, op_flag);
> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> index 4024790028aa..40012f874be0 100644
> --- a/fs/f2fs/f2fs.h
> +++ b/fs/f2fs/f2fs.h
> @@ -44,7 +44,6 @@ enum {
>  	FAULT_KVMALLOC,
>  	FAULT_PAGE_ALLOC,
>  	FAULT_PAGE_GET,
> -	FAULT_ALLOC_BIO,
>  	FAULT_ALLOC_NID,
>  	FAULT_ORPHAN,
>  	FAULT_BLOCK,
> @@ -2210,26 +2209,6 @@ static inline void *f2fs_kmem_cache_alloc(struct kmem_cache *cachep,
>  	return entry;
>  }
>  
> -static inline struct bio *f2fs_bio_alloc(struct f2fs_sb_info *sbi,
> -						int npages, bool no_fail)
> -{
> -	struct bio *bio;
> -
> -	if (no_fail) {
> -		/* No failure on bio allocation */
> -		bio = bio_alloc(GFP_NOIO, npages);
> -		if (!bio)
> -			bio = bio_alloc(GFP_NOIO | __GFP_NOFAIL, npages);
> -		return bio;
> -	}
> -	if (time_to_inject(sbi, FAULT_ALLOC_BIO)) {
> -		f2fs_show_injection_info(FAULT_ALLOC_BIO);
> -		return NULL;
> -	}
> -
> -	return bio_alloc(GFP_KERNEL, npages);
> -}
> -
>  static inline bool is_idle(struct f2fs_sb_info *sbi, int type)
>  {
>  	if (sbi->gc_mode == GC_URGENT)
> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
> index 808709581481..28457c878d0d 100644
> --- a/fs/f2fs/segment.c
> +++ b/fs/f2fs/segment.c
> @@ -552,10 +552,7 @@ static int __submit_flush_wait(struct f2fs_sb_info *sbi,
>  	struct bio *bio;
>  	int ret;
>  
> -	bio = f2fs_bio_alloc(sbi, 0, false);
> -	if (!bio)
> -		return -ENOMEM;
> -
> +	bio = bio_alloc(GFP_KERNEL, 0);
>  	bio->bi_opf = REQ_OP_WRITE | REQ_SYNC | REQ_PREFLUSH;
>  	bio_set_dev(bio, bdev);
>  	ret = submit_bio_wait(bio);
> diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
> index 1443cee15863..51945dd27f00 100644
> --- a/fs/f2fs/super.c
> +++ b/fs/f2fs/super.c
> @@ -44,7 +44,6 @@ const char *f2fs_fault_name[FAULT_MAX] = {
>  	[FAULT_KVMALLOC]	= "kvmalloc",
>  	[FAULT_PAGE_ALLOC]	= "page alloc",
>  	[FAULT_PAGE_GET]	= "page get",
> -	[FAULT_ALLOC_BIO]	= "alloc bio",
>  	[FAULT_ALLOC_NID]	= "alloc nid",
>  	[FAULT_ORPHAN]		= "orphan",
>  	[FAULT_BLOCK]		= "no more block",
>