Re: [PATCH] Fix balance Oops

[Yan Zheng <zheng.yan@oracle.com>]

On 08/07/2009 02:50 PM, Jens Axboe wrote:
> On Fri, Aug 07 2009, Yan Zheng wrote:
>> invalidate_inode_pages2_range may return -EBUSY occasionally
>> which results Oops. This patch fixes the issue by moving
>> invalidate_inode_pages2_range into a loop and keeping calling
>> it until the return value is not -EBUSY.
>>
>> Signed-off-by: Yan Zheng <zheng.yan@oracle.com>
>>
>> ---
>> diff -urp 1/fs/btrfs/relocation.c 2/fs/btrfs/relocation.c
>> --- 1/fs/btrfs/relocation.c	2009-07-29 10:03:04.367858774 +0800
>> +++ 2/fs/btrfs/relocation.c	2009-08-07 13:26:43.882147138 +0800
>> @@ -2553,8 +2553,13 @@ int relocate_inode_pages(struct inode *i
>>  	last_index = (start + len - 1) >> PAGE_CACHE_SHIFT;
>>  
>>  	/* make sure the dirty trick played by the caller work */
>> -	ret = invalidate_inode_pages2_range(inode->i_mapping,
>> -					    first_index, last_index);
>> +	while (1) {
>> +		ret = invalidate_inode_pages2_range(inode->i_mapping,
>> +						    first_index, last_index);
>> +		if (ret != -EBUSY)
>> +			break;
>> +		cond_resched();
>> +	}
> 
> If it returns EBUSY, would it not make more sense to call
> filemap_write_and_wait_range() instead of hammering on invalidate?
> 

The pages to invalidate are not dirty, they are from page read-ahead.
Actually I have no idea how invalidate_inode_pages2_range can return
-EBUSY here. (the only user of the inode is the balancer, and it does
not hold references to the pages)

Regards
Yan, Zheng