Re: [PATCH -v2] ext4: invalidate pages if delalloc block allocation fails.

[Mingming Cao <cmm@us.ibm.com>]

在 2008-08-11一的 15:53 +0530，Aneesh Kumar K.V写道：
> We are a bit agressive in invalidating all the pages. But
> it is ok because we really don't know why the block allocation
> failed and it is better to come of the writeback path
> so that user can look for more info.
> 
> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>

Added to unstable patch queue for more testing.  
> ---
>  fs/ext4/inode.c |   63 ++++++++++++++++++++++++++++++++++++++++++++++++++++++-
>  1 files changed, 62 insertions(+), 1 deletions(-)
> 
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index 26e30ed..e437a5b 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -1761,6 +1761,39 @@ static inline void __unmap_underlying_blocks(struct inode *inode,
>  		unmap_underlying_metadata(bdev, bh->b_blocknr + i);
>  }
> 
> +static void ext4_da_block_invalidatepages(struct mpage_da_data *mpd,
> +					sector_t logical, long blk_cnt)
> +{
> +	int nr_pages, i;
> +	pgoff_t index, end;
> +	struct pagevec pvec;
> +	struct inode *inode = mpd->inode;
> +	struct address_space *mapping = inode->i_mapping;
> +
> +	index = logical >> (PAGE_CACHE_SHIFT - inode->i_blkbits);
> +	end   = (logical + blk_cnt - 1) >>
> +				(PAGE_CACHE_SHIFT - inode->i_blkbits);
> +	while (index <= end) {
> +		nr_pages = pagevec_lookup(&pvec, mapping, index, PAGEVEC_SIZE);
> +		if (nr_pages == 0)
> +			break;
> +		for (i = 0; i < nr_pages; i++) {
> +			struct page *page = pvec.pages[i];
> +			index = page->index;
> +			if (index > end)
> +				break;
> +			index++;
> +
> +			BUG_ON(!PageLocked(page));
> +			BUG_ON(PageWriteback(page));
> +			block_invalidatepage(page, 0);
> +			ClearPageUptodate(page);
> +			unlock_page(page);
> +		}
> +	}
> +	return;
> +}
> +
>  /*
>   * mpage_da_map_blocks - go through given space
>   *
> @@ -1794,8 +1827,36 @@ static void mpage_da_map_blocks(struct mpage_da_data *mpd)
>  	if (!new.b_size)
>  		return;
>  	err = mpd->get_block(mpd->inode, next, &new, 1);
> -	if (err)
> +	if (err) {
> +
> +		/* If get block returns with error
> +		 * we simply return. Later writepage
> +		 * will redirty the page and writepages
> +		 * will find the dirty page again
> +		 */
> +		if (err == -EAGAIN)
> +			return;
> +		/*
> +		 * get block failure will cause us
> +		 * to loop in writepages. Because
> +		 * a_ops->writepage won't be able to
> +		 * make progress. The page will be redirtied
> +		 * by writepage and writepages will again
> +		 * try to write the same.
> +		 */
> +		printk(KERN_EMERG "%s block allocation failed for inode %lu "
> +				  "at logical offset %llu with max blocks "
> +				  "%zd with error %d\n",
> +				  __func__, mpd->inode->i_ino,
> +				  (unsigned long long)next,
> +				  lbh->b_size >> mpd->inode->i_blkbits, err);
> +		printk(KERN_EMERG "This should not happen.!! "
> +					"Data will be lost\n");
> +		/* invlaidate all the pages */
> +		ext4_da_block_invalidatepages(mpd, next,
> +				lbh->b_size >> mpd->inode->i_blkbits);
>  		return;
> +	}
>  	BUG_ON(new.b_size == 0);
> 
>  	if (buffer_new(&new))

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