linux-kernel - Re: [PATCH] ext4: make dioread_nolock consistent in each mapping round

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Message-ID: <2f16e76c-aaad-45cc-c3ac-f29456b021ac@bytedance.com>
Date:   Tue, 7 Feb 2023 16:13:56 +0800
From:   hanjinke <hanjinke.666@...edance.com>
To:     tytso@....edu, adilger.kernel@...ger.ca
Cc:     jack@...e.cz, linux-ext4@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ext4: make dioread_nolock consistent in each mapping
 round

hi,all

Please ignore this patch, maybe I missed some something critical.

在 2023/2/7 下午2:42, Jinke Han 写道:
> From: Jinke Han <hanjinke.666@...edance.com>
> 
> When disable and enable dioread_nolock by remount, we may see
> dioread_lock in ext4_do_writepages while see dioread_nolock in
> mpage_map_one_extent. This inconsistency may triger the warning
> in ext4_release_io_end. Although this warning is harmless, we'd
> better fix it
> 
> Signed-off-by: Jinke Han <hanjinke.666@...edance.com>
> ---
>   fs/ext4/inode.c | 28 ++++++++++++++++------------
>   1 file changed, 16 insertions(+), 12 deletions(-)
> 
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index 40579ef513b7..122a22ccddb3 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -1568,6 +1568,7 @@ struct mpage_da_data {
>   	struct ext4_io_submit io_submit;	/* IO submission data */
>   	unsigned int do_map:1;
>   	unsigned int scanned_until_end:1;
> +	unsigned int dioread_nolock:1;
>   };
>   
>   static void mpage_release_unused_pages(struct mpage_da_data *mpd,
> @@ -2391,7 +2392,7 @@ static int mpage_map_one_extent(handle_t *handle, struct mpage_da_data *mpd)
>   	struct inode *inode = mpd->inode;
>   	struct ext4_map_blocks *map = &mpd->map;
>   	int get_blocks_flags;
> -	int err, dioread_nolock;
> +	int err, dioread_nolock = mpd->dioread_nolock;
>   
>   	trace_ext4_da_write_pages_extent(inode, map);
>   	/*
> @@ -2412,7 +2413,6 @@ static int mpage_map_one_extent(handle_t *handle, struct mpage_da_data *mpd)
>   	get_blocks_flags = EXT4_GET_BLOCKS_CREATE |
>   			   EXT4_GET_BLOCKS_METADATA_NOFAIL |
>   			   EXT4_GET_BLOCKS_IO_SUBMIT;
> -	dioread_nolock = ext4_should_dioread_nolock(inode);
>   	if (dioread_nolock)
>   		get_blocks_flags |= EXT4_GET_BLOCKS_IO_CREATE_EXT;
>   	if (map->m_flags & BIT(BH_Delay))
> @@ -2727,10 +2727,11 @@ static int ext4_do_writepages(struct mpage_da_data *mpd)
>   	handle_t *handle = NULL;
>   	struct inode *inode = mpd->inode;
>   	struct address_space *mapping = inode->i_mapping;
> -	int needed_blocks, rsv_blocks = 0, ret = 0;
> +	int needed_blocks, rsv_blocks = 0, rsv = 0, ret = 0;
>   	struct ext4_sb_info *sbi = EXT4_SB(mapping->host->i_sb);
>   	struct blk_plug plug;
>   	bool give_up_on_write = false;
> +	bool dioread_nolock;
>   
>   	trace_ext4_writepages(inode, wbc);
>   
> @@ -2783,15 +2784,6 @@ static int ext4_do_writepages(struct mpage_da_data *mpd)
>   		ext4_journal_stop(handle);
>   	}
>   
> -	if (ext4_should_dioread_nolock(inode)) {
> -		/*
> -		 * We may need to convert up to one extent per block in
> -		 * the page and we may dirty the inode.
> -		 */
> -		rsv_blocks = 1 + ext4_chunk_trans_blocks(inode,
> -						PAGE_SIZE >> inode->i_blkbits);
> -	}
> -
>   	if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX)
>   		range_whole = 1;
>   
> @@ -2837,6 +2829,18 @@ static int ext4_do_writepages(struct mpage_da_data *mpd)
>   		goto unplug;
>   
>   	while (!mpd->scanned_until_end && wbc->nr_to_write > 0) {
> +		dioread_nolock = ext4_should_dioread_nolock(inode);
> +		if (!rsv && dioread_nolock) {
> +			/*
> +			 * We may need to convert up to one extent per block in
> +			 * the page and we may dirty the inode.
> +			 */
> +			rsv = 1 + ext4_chunk_trans_blocks(inode,
> +							PAGE_SIZE >> inode->i_blkbits);
> +		}
> +		rsv_blocks = dioread_nolock ? rsv : 0;
> +		mpd->dioread_nolock = dioread_nolock;
> +
>   		/* For each extent of pages we use new io_end */
>   		mpd->io_submit.io_end = ext4_init_io_end(inode, GFP_KERNEL);
>   		if (!mpd->io_submit.io_end) {