[v2] ocfs2: fall back to buffer IO when append dio is disabled with file hole existing
diff mbox

Message ID 63ADC13FD55D6546B7DECE290D39E373F2908F5C@H3CMLB12-EX.srv.huawei-3com.com
State New
Headers show

Commit Message

Changwei Ge Dec. 26, 2017, 7:03 a.m. UTC
The intention of this patch is to provide an option to ocfs2 users whether
to allocate disk space while doing dio write.

Whether to make ocfs2 fall back to buffer io is up to ocfs2 users through
toggling append-dio feature. It rather makes ocfs2 configurable and
flexible.

So if something bad happens to dio write with space allocation, we can
still make ocfs2 fall back to buffer io. It's an option not a mandatory
action.:)

Besides, append-dio feature is key to whether to allocate space with dio
writing. So writing to file hole and enlarging file(appending file) should
have the same reflection to append-dio feature.

Signed-off-by: Changwei Ge <ge.changwei@h3c.com>
---
  fs/ocfs2/aops.c | 53 ++++++++++++++++++++++++++++++++++++++++++++++++++---
  1 file changed, 50 insertions(+), 3 deletions(-)

Comments

zhendong chen Dec. 26, 2017, 8:19 a.m. UTC | #1
Hi Changwei,

On 2017/12/26 15:03, Changwei Ge wrote:
> The intention of this patch is to provide an option to ocfs2 users whether
> to allocate disk space while doing dio write.
> 
> Whether to make ocfs2 fall back to buffer io is up to ocfs2 users through
> toggling append-dio feature. It rather makes ocfs2 configurable and
> flexible.
>
It is too strange to make ocfs2 fall back to buffer io by toggling append-dio feature.

> So if something bad happens to dio write with space allocation, we can
> still make ocfs2 fall back to buffer io. It's an option not a mandatory
> action.:)
Now the ocfs2 supports fill holes during direct io whether or not supporting append-dio feature
and we can directly fix the problem.
I think it is meaningless to provide an temporary option to turn off it.

> 
> Besides, append-dio feature is key to whether to allocate space with dio
> writing. So writing to file hole and enlarging file(appending file) should
> have the same reflection to append-dio feature.
> 
> Signed-off-by: Changwei Ge <ge.changwei@h3c.com>
> ---
>   fs/ocfs2/aops.c | 53 ++++++++++++++++++++++++++++++++++++++++++++++++++---
>   1 file changed, 50 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/ocfs2/aops.c b/fs/ocfs2/aops.c
> index d151632..32e60c0 100644
> --- a/fs/ocfs2/aops.c
> +++ b/fs/ocfs2/aops.c
> @@ -2414,12 +2414,52 @@ static int ocfs2_dio_end_io(struct kiocb *iocb,
>   	return ret;
>   }
>   
> +/*
> + * Will look for holes and unwritten extents in the range starting at
> + * pos for count bytes (inclusive).
> + * Return value 1 indicates hole exists, 0 not exists, others indicate error.
> + */
> +static int ocfs2_range_has_holes(struct inode *inode, loff_t pos,
> +				 size_t count)
> +{
> +	int ret = 0;
> +	unsigned int extent_flags;
> +	u32 cpos, clusters, extent_len, phys_cpos;
> +	struct super_block *sb = inode->i_sb;
> +
> +	cpos = pos >> OCFS2_SB(sb)->s_clustersize_bits;
> +	clusters = ocfs2_clusters_for_bytes(sb, pos + count) - cpos;
> +
> +	while (clusters) {
> +		ret = ocfs2_get_clusters(inode, cpos, &phys_cpos, &extent_len,
> +					 &extent_flags);
> +		if (ret < 0) {
> +			mlog_errno(ret);
> +			goto out;
> +		}
> +
> +		if (phys_cpos == 0) {
> +			ret = 1;
> +			goto out;
> +		}
> +
> +		if (extent_len > clusters)
> +			extent_len = clusters;
> +
> +		clusters -= extent_len;
> +		cpos += extent_len;
> +	}
> +out:
> +	return ret;
> +}
> +
>   static ssize_t ocfs2_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
>   {
>   	struct file *file = iocb->ki_filp;
>   	struct inode *inode = file->f_mapping->host;
>   	struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
>   	get_block_t *get_block;
> +	int ret;
>   
>   	/*
>   	 * Fallback to buffered I/O if we see an inode without
> @@ -2429,9 +2469,16 @@ static ssize_t ocfs2_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
>   		return 0;
>   
>   	/* Fallback to buffered I/O if we do not support append dio. */
> -	if (iocb->ki_pos + iter->count > i_size_read(inode) &&
> -	    !ocfs2_supports_append_dio(osb))
> -		return 0;
> +	if (!ocfs2_supports_append_dio(osb)) {
> +		if (iocb->ki_pos + iter->count > i_size_read(inode))
> +			return 0;
> +
> +		ret = ocfs2_range_has_holes(inode, iocb->ki_pos, iter->count);
> +		if (ret == 1)
> +			return 0;
> +		else if (ret < 0)
> +			return ret;
> +	}
>   
>   	if (iov_iter_rw(iter) == READ)
>   		get_block = ocfs2_lock_get_block;
>
piaojun Dec. 26, 2017, 8:39 a.m. UTC | #2
On 2017/12/26 16:19, alex chen wrote:
> Hi Changwei,
> 
> On 2017/12/26 15:03, Changwei Ge wrote:
>> The intention of this patch is to provide an option to ocfs2 users whether
>> to allocate disk space while doing dio write.
>>
>> Whether to make ocfs2 fall back to buffer io is up to ocfs2 users through
>> toggling append-dio feature. It rather makes ocfs2 configurable and
>> flexible.
>>
> It is too strange to make ocfs2 fall back to buffer io by toggling append-dio feature.
> 
>> So if something bad happens to dio write with space allocation, we can
>> still make ocfs2 fall back to buffer io. It's an option not a mandatory
>> action.:)
> Now the ocfs2 supports fill holes during direct io whether or not supporting append-dio feature
> and we can directly fix the problem.
> I think it is meaningless to provide an temporary option to turn off it.
> 
I have the same opinion with Alex. And probablly the better way is
providing a new feature for user, not just reuse 'append-dio'.
>>
>> Besides, append-dio feature is key to whether to allocate space with dio
>> writing. So writing to file hole and enlarging file(appending file) should
>> have the same reflection to append-dio feature.
>>
>> Signed-off-by: Changwei Ge <ge.changwei@h3c.com>
>> ---
>>   fs/ocfs2/aops.c | 53 ++++++++++++++++++++++++++++++++++++++++++++++++++---
>>   1 file changed, 50 insertions(+), 3 deletions(-)
>>
>> diff --git a/fs/ocfs2/aops.c b/fs/ocfs2/aops.c
>> index d151632..32e60c0 100644
>> --- a/fs/ocfs2/aops.c
>> +++ b/fs/ocfs2/aops.c
>> @@ -2414,12 +2414,52 @@ static int ocfs2_dio_end_io(struct kiocb *iocb,
>>   	return ret;
>>   }
>>   
>> +/*
>> + * Will look for holes and unwritten extents in the range starting at
>> + * pos for count bytes (inclusive).
>> + * Return value 1 indicates hole exists, 0 not exists, others indicate error.
>> + */
>> +static int ocfs2_range_has_holes(struct inode *inode, loff_t pos,
>> +				 size_t count)
>> +{
>> +	int ret = 0;
>> +	unsigned int extent_flags;
>> +	u32 cpos, clusters, extent_len, phys_cpos;
>> +	struct super_block *sb = inode->i_sb;
>> +
>> +	cpos = pos >> OCFS2_SB(sb)->s_clustersize_bits;
>> +	clusters = ocfs2_clusters_for_bytes(sb, pos + count) - cpos;
>> +
>> +	while (clusters) {
>> +		ret = ocfs2_get_clusters(inode, cpos, &phys_cpos, &extent_len,
>> +					 &extent_flags);
>> +		if (ret < 0) {
>> +			mlog_errno(ret);
>> +			goto out;
>> +		}
>> +
>> +		if (phys_cpos == 0) {
>> +			ret = 1;
>> +			goto out;
>> +		}
>> +
>> +		if (extent_len > clusters)
>> +			extent_len = clusters;
>> +
>> +		clusters -= extent_len;
>> +		cpos += extent_len;
>> +	}
>> +out:
>> +	return ret;
>> +}
>> +
>>   static ssize_t ocfs2_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
>>   {
>>   	struct file *file = iocb->ki_filp;
>>   	struct inode *inode = file->f_mapping->host;
>>   	struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
>>   	get_block_t *get_block;
>> +	int ret;
>>   
>>   	/*
>>   	 * Fallback to buffered I/O if we see an inode without
>> @@ -2429,9 +2469,16 @@ static ssize_t ocfs2_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
>>   		return 0;
>>   
>>   	/* Fallback to buffered I/O if we do not support append dio. */
>> -	if (iocb->ki_pos + iter->count > i_size_read(inode) &&
>> -	    !ocfs2_supports_append_dio(osb))
>> -		return 0;
>> +	if (!ocfs2_supports_append_dio(osb)) {
>> +		if (iocb->ki_pos + iter->count > i_size_read(inode))
>> +			return 0;
>> +
>> +		ret = ocfs2_range_has_holes(inode, iocb->ki_pos, iter->count);
>> +		if (ret == 1)
>> +			return 0;
>> +		else if (ret < 0)
>> +			return ret;
>> +	}
>>   
>>   	if (iov_iter_rw(iter) == READ)
>>   		get_block = ocfs2_lock_get_block;
>>
> 
> 
> _______________________________________________
> Ocfs2-devel mailing list
> Ocfs2-devel@oss.oracle.com
> https://oss.oracle.com/mailman/listinfo/ocfs2-devel
>
Changwei Ge Dec. 26, 2017, 9:20 a.m. UTC | #3
Hi Alex

On 2017/12/26 16:20, alex chen wrote:
> Hi Changwei,
> 
> On 2017/12/26 15:03, Changwei Ge wrote:
>> The intention of this patch is to provide an option to ocfs2 users whether
>> to allocate disk space while doing dio write.
>>
>> Whether to make ocfs2 fall back to buffer io is up to ocfs2 users through
>> toggling append-dio feature. It rather makes ocfs2 configurable and
>> flexible.
>>
> It is too strange to make ocfs2 fall back to buffer io by toggling append-dio feature.

It might be.
But as my changelog said, I think, append-dio is key to whether to allocate
space with dio writing. So filling hole and appending file should have the same reflection.

Besides, in the early days, ocfs2 truly falls back to buffer io when append-dio is disabled and file hole is encountered.

Thanks,
Changwei

> 
>> So if something bad happens to dio write with space allocation, we can
>> still make ocfs2 fall back to buffer io. It's an option not a mandatory
>> action.:)
> Now the ocfs2 supports fill holes during direct io whether or not supporting append-dio feature
> and we can directly fix the problem.
> I think it is meaningless to provide an temporary option to turn off it.

IMO, this patch is NOT a temporary solution.
Instead, it provides an extra option to ocfs2 users. And append-dio is enabled while making fs by *default*.

Thanks,
Changwei  

> 
>>
>> Besides, append-dio feature is key to whether to allocate space with dio
>> writing. So writing to file hole and enlarging file(appending file) should
>> have the same reflection to append-dio feature.
>>
>> Signed-off-by: Changwei Ge <ge.changwei@h3c.com>
>> ---
>>    fs/ocfs2/aops.c | 53 ++++++++++++++++++++++++++++++++++++++++++++++++++---
>>    1 file changed, 50 insertions(+), 3 deletions(-)
>>
>> diff --git a/fs/ocfs2/aops.c b/fs/ocfs2/aops.c
>> index d151632..32e60c0 100644
>> --- a/fs/ocfs2/aops.c
>> +++ b/fs/ocfs2/aops.c
>> @@ -2414,12 +2414,52 @@ static int ocfs2_dio_end_io(struct kiocb *iocb,
>>    	return ret;
>>    }
>>    
>> +/*
>> + * Will look for holes and unwritten extents in the range starting at
>> + * pos for count bytes (inclusive).
>> + * Return value 1 indicates hole exists, 0 not exists, others indicate error.
>> + */
>> +static int ocfs2_range_has_holes(struct inode *inode, loff_t pos,
>> +				 size_t count)
>> +{
>> +	int ret = 0;
>> +	unsigned int extent_flags;
>> +	u32 cpos, clusters, extent_len, phys_cpos;
>> +	struct super_block *sb = inode->i_sb;
>> +
>> +	cpos = pos >> OCFS2_SB(sb)->s_clustersize_bits;
>> +	clusters = ocfs2_clusters_for_bytes(sb, pos + count) - cpos;
>> +
>> +	while (clusters) {
>> +		ret = ocfs2_get_clusters(inode, cpos, &phys_cpos, &extent_len,
>> +					 &extent_flags);
>> +		if (ret < 0) {
>> +			mlog_errno(ret);
>> +			goto out;
>> +		}
>> +
>> +		if (phys_cpos == 0) {
>> +			ret = 1;
>> +			goto out;
>> +		}
>> +
>> +		if (extent_len > clusters)
>> +			extent_len = clusters;
>> +
>> +		clusters -= extent_len;
>> +		cpos += extent_len;
>> +	}
>> +out:
>> +	return ret;
>> +}
>> +
>>    static ssize_t ocfs2_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
>>    {
>>    	struct file *file = iocb->ki_filp;
>>    	struct inode *inode = file->f_mapping->host;
>>    	struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
>>    	get_block_t *get_block;
>> +	int ret;
>>    
>>    	/*
>>    	 * Fallback to buffered I/O if we see an inode without
>> @@ -2429,9 +2469,16 @@ static ssize_t ocfs2_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
>>    		return 0;
>>    
>>    	/* Fallback to buffered I/O if we do not support append dio. */
>> -	if (iocb->ki_pos + iter->count > i_size_read(inode) &&
>> -	    !ocfs2_supports_append_dio(osb))
>> -		return 0;
>> +	if (!ocfs2_supports_append_dio(osb)) {
>> +		if (iocb->ki_pos + iter->count > i_size_read(inode))
>> +			return 0;
>> +
>> +		ret = ocfs2_range_has_holes(inode, iocb->ki_pos, iter->count);
>> +		if (ret == 1)
>> +			return 0;
>> +		else if (ret < 0)
>> +			return ret;
>> +	}
>>    
>>    	if (iov_iter_rw(iter) == READ)
>>    		get_block = ocfs2_lock_get_block;
>>
> 
>
Junxiao Bi Dec. 27, 2017, 7:33 a.m. UTC | #4
Hi Changwei,

On 12/26/2017 05:20 PM, Changwei Ge wrote:
> Hi Alex
> 
> On 2017/12/26 16:20, alex chen wrote:
>> Hi Changwei,
>>
>> On 2017/12/26 15:03, Changwei Ge wrote:
>>> The intention of this patch is to provide an option to ocfs2 users whether
>>> to allocate disk space while doing dio write.
>>>
>>> Whether to make ocfs2 fall back to buffer io is up to ocfs2 users through
>>> toggling append-dio feature. It rather makes ocfs2 configurable and
>>> flexible.
>>>
>> It is too strange to make ocfs2 fall back to buffer io by toggling append-dio feature.
> 
> It might be.
> But as my changelog said, I think, append-dio is key to whether to allocate
> space with dio writing. So filling hole and appending file should have the same reflection.
> 
> Besides, in the early days, ocfs2 truly falls back to buffer io when append-dio is disabled and file hole is encountered.
I think we have discussed a lot in your v1 version. This wasn't fit for
mainline, you can keep one off-mainline patch.

Thanks,
Junxiao.

> 
> Thanks,
> Changwei
> 
>>
>>> So if something bad happens to dio write with space allocation, we can
>>> still make ocfs2 fall back to buffer io. It's an option not a mandatory
>>> action.:)
>> Now the ocfs2 supports fill holes during direct io whether or not supporting append-dio feature
>> and we can directly fix the problem.
>> I think it is meaningless to provide an temporary option to turn off it.
> 
> IMO, this patch is NOT a temporary solution.
> Instead, it provides an extra option to ocfs2 users. And append-dio is enabled while making fs by *default*.
> 
> Thanks,
> Changwei  
> 
>>
>>>
>>> Besides, append-dio feature is key to whether to allocate space with dio
>>> writing. So writing to file hole and enlarging file(appending file) should
>>> have the same reflection to append-dio feature.
>>>
>>> Signed-off-by: Changwei Ge <ge.changwei@h3c.com>
>>> ---
>>>    fs/ocfs2/aops.c | 53 ++++++++++++++++++++++++++++++++++++++++++++++++++---
>>>    1 file changed, 50 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/fs/ocfs2/aops.c b/fs/ocfs2/aops.c
>>> index d151632..32e60c0 100644
>>> --- a/fs/ocfs2/aops.c
>>> +++ b/fs/ocfs2/aops.c
>>> @@ -2414,12 +2414,52 @@ static int ocfs2_dio_end_io(struct kiocb *iocb,
>>>    	return ret;
>>>    }
>>>    
>>> +/*
>>> + * Will look for holes and unwritten extents in the range starting at
>>> + * pos for count bytes (inclusive).
>>> + * Return value 1 indicates hole exists, 0 not exists, others indicate error.
>>> + */
>>> +static int ocfs2_range_has_holes(struct inode *inode, loff_t pos,
>>> +				 size_t count)
>>> +{
>>> +	int ret = 0;
>>> +	unsigned int extent_flags;
>>> +	u32 cpos, clusters, extent_len, phys_cpos;
>>> +	struct super_block *sb = inode->i_sb;
>>> +
>>> +	cpos = pos >> OCFS2_SB(sb)->s_clustersize_bits;
>>> +	clusters = ocfs2_clusters_for_bytes(sb, pos + count) - cpos;
>>> +
>>> +	while (clusters) {
>>> +		ret = ocfs2_get_clusters(inode, cpos, &phys_cpos, &extent_len,
>>> +					 &extent_flags);
>>> +		if (ret < 0) {
>>> +			mlog_errno(ret);
>>> +			goto out;
>>> +		}
>>> +
>>> +		if (phys_cpos == 0) {
>>> +			ret = 1;
>>> +			goto out;
>>> +		}
>>> +
>>> +		if (extent_len > clusters)
>>> +			extent_len = clusters;
>>> +
>>> +		clusters -= extent_len;
>>> +		cpos += extent_len;
>>> +	}
>>> +out:
>>> +	return ret;
>>> +}
>>> +
>>>    static ssize_t ocfs2_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
>>>    {
>>>    	struct file *file = iocb->ki_filp;
>>>    	struct inode *inode = file->f_mapping->host;
>>>    	struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
>>>    	get_block_t *get_block;
>>> +	int ret;
>>>    
>>>    	/*
>>>    	 * Fallback to buffered I/O if we see an inode without
>>> @@ -2429,9 +2469,16 @@ static ssize_t ocfs2_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
>>>    		return 0;
>>>    
>>>    	/* Fallback to buffered I/O if we do not support append dio. */
>>> -	if (iocb->ki_pos + iter->count > i_size_read(inode) &&
>>> -	    !ocfs2_supports_append_dio(osb))
>>> -		return 0;
>>> +	if (!ocfs2_supports_append_dio(osb)) {
>>> +		if (iocb->ki_pos + iter->count > i_size_read(inode))
>>> +			return 0;
>>> +
>>> +		ret = ocfs2_range_has_holes(inode, iocb->ki_pos, iter->count);
>>> +		if (ret == 1)
>>> +			return 0;
>>> +		else if (ret < 0)
>>> +			return ret;
>>> +	}
>>>    
>>>    	if (iov_iter_rw(iter) == READ)
>>>    		get_block = ocfs2_lock_get_block;
>>>
>>
>>
>
Changwei Ge Dec. 27, 2017, 7:46 a.m. UTC | #5
Hi Junxiao,

On 2017/12/27 15:35, Junxiao Bi wrote:
> Hi Changwei,
> 
> On 12/26/2017 05:20 PM, Changwei Ge wrote:
>> Hi Alex
>>
>> On 2017/12/26 16:20, alex chen wrote:
>>> Hi Changwei,
>>>
>>> On 2017/12/26 15:03, Changwei Ge wrote:
>>>> The intention of this patch is to provide an option to ocfs2 users whether
>>>> to allocate disk space while doing dio write.
>>>>
>>>> Whether to make ocfs2 fall back to buffer io is up to ocfs2 users through
>>>> toggling append-dio feature. It rather makes ocfs2 configurable and
>>>> flexible.
>>>>
>>> It is too strange to make ocfs2 fall back to buffer io by toggling append-dio feature.
>>
>> It might be.
>> But as my changelog said, I think, append-dio is key to whether to allocate
>> space with dio writing. So filling hole and appending file should have the same reflection.
>>
>> Besides, in the early days, ocfs2 truly falls back to buffer io when append-dio is disabled and file hole is encountered.
> I think we have discussed a lot in your v1 version. This wasn't fit for
> mainline, you can keep one off-mainline patch.

Fine. I agree now.
I give up trying to push this patch into mainline.
BTW, could you please help review my another patch (ocfs2: try to reuse extent block in dealloc without meta_alloc) which is used to fix a dio crash issue?
So without this patch, dio still won't hit such an issue.
Your comments are very important to me.

Thanks,
Changwei

> 
> Thanks,
> Junxiao.
>
Junxiao Bi Dec. 27, 2017, 8:56 a.m. UTC | #6
On 12/27/2017 03:46 PM, Changwei Ge wrote:

> Hi Junxiao,
>
> On 2017/12/27 15:35, Junxiao Bi wrote:
>> Hi Changwei,
>>
>> On 12/26/2017 05:20 PM, Changwei Ge wrote:
>>> Hi Alex
>>>
>>> On 2017/12/26 16:20, alex chen wrote:
>>>> Hi Changwei,
>>>>
>>>> On 2017/12/26 15:03, Changwei Ge wrote:
>>>>> The intention of this patch is to provide an option to ocfs2 users whether
>>>>> to allocate disk space while doing dio write.
>>>>>
>>>>> Whether to make ocfs2 fall back to buffer io is up to ocfs2 users through
>>>>> toggling append-dio feature. It rather makes ocfs2 configurable and
>>>>> flexible.
>>>>>
>>>> It is too strange to make ocfs2 fall back to buffer io by toggling append-dio feature.
>>> It might be.
>>> But as my changelog said, I think, append-dio is key to whether to allocate
>>> space with dio writing. So filling hole and appending file should have the same reflection.
>>>
>>> Besides, in the early days, ocfs2 truly falls back to buffer io when append-dio is disabled and file hole is encountered.
>> I think we have discussed a lot in your v1 version. This wasn't fit for
>> mainline, you can keep one off-mainline patch.
> Fine. I agree now.
> I give up trying to push this patch into mainline.
> BTW, could you please help review my another patch (ocfs2: try to reuse extent block in dealloc without meta_alloc) which is used to fix a dio crash issue?
> So without this patch, dio still won't hit such an issue.
> Your comments are very important to me.
Sure,  will look at it.

Thanks,
Junxiao.
>
> Thanks,
> Changwei
>
>> Thanks,
>> Junxiao.
>>
>

Patch
diff mbox

diff --git a/fs/ocfs2/aops.c b/fs/ocfs2/aops.c
index d151632..32e60c0 100644
--- a/fs/ocfs2/aops.c
+++ b/fs/ocfs2/aops.c
@@ -2414,12 +2414,52 @@  static int ocfs2_dio_end_io(struct kiocb *iocb,
  	return ret;
  }
  
+/*
+ * Will look for holes and unwritten extents in the range starting at
+ * pos for count bytes (inclusive).
+ * Return value 1 indicates hole exists, 0 not exists, others indicate error.
+ */
+static int ocfs2_range_has_holes(struct inode *inode, loff_t pos,
+				 size_t count)
+{
+	int ret = 0;
+	unsigned int extent_flags;
+	u32 cpos, clusters, extent_len, phys_cpos;
+	struct super_block *sb = inode->i_sb;
+
+	cpos = pos >> OCFS2_SB(sb)->s_clustersize_bits;
+	clusters = ocfs2_clusters_for_bytes(sb, pos + count) - cpos;
+
+	while (clusters) {
+		ret = ocfs2_get_clusters(inode, cpos, &phys_cpos, &extent_len,
+					 &extent_flags);
+		if (ret < 0) {
+			mlog_errno(ret);
+			goto out;
+		}
+
+		if (phys_cpos == 0) {
+			ret = 1;
+			goto out;
+		}
+
+		if (extent_len > clusters)
+			extent_len = clusters;
+
+		clusters -= extent_len;
+		cpos += extent_len;
+	}
+out:
+	return ret;
+}
+
  static ssize_t ocfs2_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
  {
  	struct file *file = iocb->ki_filp;
  	struct inode *inode = file->f_mapping->host;
  	struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
  	get_block_t *get_block;
+	int ret;
  
  	/*
  	 * Fallback to buffered I/O if we see an inode without
@@ -2429,9 +2469,16 @@  static ssize_t ocfs2_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
  		return 0;
  
  	/* Fallback to buffered I/O if we do not support append dio. */
-	if (iocb->ki_pos + iter->count > i_size_read(inode) &&
-	    !ocfs2_supports_append_dio(osb))
-		return 0;
+	if (!ocfs2_supports_append_dio(osb)) {
+		if (iocb->ki_pos + iter->count > i_size_read(inode))
+			return 0;
+
+		ret = ocfs2_range_has_holes(inode, iocb->ki_pos, iter->count);
+		if (ret == 1)
+			return 0;
+		else if (ret < 0)
+			return ret;
+	}
  
  	if (iov_iter_rw(iter) == READ)
  		get_block = ocfs2_lock_get_block;