ext4: Add atomic write support for DIO

[PATCH 2/6] ext4: Check for atomic writes support in write iter

Posted by Ritesh Harjani (IBM) 1 month ago

Let's validate using generic_atomic_write_valid() in
ext4_file_write_iter() if the write request has IOCB_ATOMIC set.

Signed-off-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
---
 fs/ext4/file.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/fs/ext4/file.c b/fs/ext4/file.c
index f14aed14b9cf..b06c5d34bbd2 100644
--- a/fs/ext4/file.c
+++ b/fs/ext4/file.c
@@ -692,6 +692,20 @@ ext4_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
 	if (IS_DAX(inode))
 		return ext4_dax_write_iter(iocb, from);
 #endif
+
+	if (iocb->ki_flags & IOCB_ATOMIC) {
+		size_t len = iov_iter_count(from);
+		int ret;
+
+		if (!IS_ALIGNED(len, EXT4_SB(inode->i_sb)->fs_awu_min) ||
+			len > EXT4_SB(inode->i_sb)->fs_awu_max)
+			return -EINVAL;
+
+		ret = generic_atomic_write_valid(iocb, from);
+		if (ret)
+			return ret;
+	}
+
 	if (iocb->ki_flags & IOCB_DIRECT)
 		return ext4_dio_write_iter(iocb, from);
 	else
-- 
2.46.0

Re: [PATCH 2/6] ext4: Check for atomic writes support in write iter

Posted by John Garry 1 month ago

On 25/10/2024 04:45, Ritesh Harjani (IBM) wrote:
> Let's validate using generic_atomic_write_valid() in
> ext4_file_write_iter() if the write request has IOCB_ATOMIC set.
> 
> Signed-off-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
> ---
>   fs/ext4/file.c | 14 ++++++++++++++
>   1 file changed, 14 insertions(+)
> 
> diff --git a/fs/ext4/file.c b/fs/ext4/file.c
> index f14aed14b9cf..b06c5d34bbd2 100644
> --- a/fs/ext4/file.c
> +++ b/fs/ext4/file.c
> @@ -692,6 +692,20 @@ ext4_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
>   	if (IS_DAX(inode))
>   		return ext4_dax_write_iter(iocb, from);
>   #endif
> +
> +	if (iocb->ki_flags & IOCB_ATOMIC) {
> +		size_t len = iov_iter_count(from);
> +		int ret;
> +
> +		if (!IS_ALIGNED(len, EXT4_SB(inode->i_sb)->fs_awu_min) ||
> +			len > EXT4_SB(inode->i_sb)->fs_awu_max)
> +			return -EINVAL;

this looks ok, but the IS_ALIGNED() check looks odd. I am not sure why 
you don't just check that fs_awu_max >= len >= fs_awu_min

> +
> +		ret = generic_atomic_write_valid(iocb, from);
> +		if (ret)
> +			return ret;
> +	}
> +
>   	if (iocb->ki_flags & IOCB_DIRECT)
>   		return ext4_dio_write_iter(iocb, from);
>   	else

Re: [PATCH 2/6] ext4: Check for atomic writes support in write iter

Posted by Ritesh Harjani (IBM) 1 month ago

John Garry <john.g.garry@oracle.com> writes:

> On 25/10/2024 04:45, Ritesh Harjani (IBM) wrote:
>> Let's validate using generic_atomic_write_valid() in
>> ext4_file_write_iter() if the write request has IOCB_ATOMIC set.
>> 
>> Signed-off-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
>> ---
>>   fs/ext4/file.c | 14 ++++++++++++++
>>   1 file changed, 14 insertions(+)
>> 
>> diff --git a/fs/ext4/file.c b/fs/ext4/file.c
>> index f14aed14b9cf..b06c5d34bbd2 100644
>> --- a/fs/ext4/file.c
>> +++ b/fs/ext4/file.c
>> @@ -692,6 +692,20 @@ ext4_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
>>   	if (IS_DAX(inode))
>>   		return ext4_dax_write_iter(iocb, from);
>>   #endif
>> +
>> +	if (iocb->ki_flags & IOCB_ATOMIC) {
>> +		size_t len = iov_iter_count(from);
>> +		int ret;
>> +
>> +		if (!IS_ALIGNED(len, EXT4_SB(inode->i_sb)->fs_awu_min) ||
>> +			len > EXT4_SB(inode->i_sb)->fs_awu_max)
>> +			return -EINVAL;
>
> this looks ok, but the IS_ALIGNED() check looks odd. I am not sure why 
> you don't just check that fs_awu_max >= len >= fs_awu_min
>

I guess this was just a stricter check. But we anyways have power_of_2
and other checks in generic_atomic_write_valid(). So it does not matter. 

I can change this in v2. 

Thanks!

>> +
>> +		ret = generic_atomic_write_valid(iocb, from);
>> +		if (ret)
>> +			return ret;
>> +	}
>> +
>>   	if (iocb->ki_flags & IOCB_DIRECT)
>>   		return ext4_dio_write_iter(iocb, from);
>>   	else

-ritesh

Re: [PATCH 2/6] ext4: Check for atomic writes support in write iter

Posted by Darrick J. Wong 1 month ago

On Fri, Oct 25, 2024 at 04:03:02PM +0530, Ritesh Harjani wrote:
> John Garry <john.g.garry@oracle.com> writes:
> 
> > On 25/10/2024 04:45, Ritesh Harjani (IBM) wrote:
> >> Let's validate using generic_atomic_write_valid() in
> >> ext4_file_write_iter() if the write request has IOCB_ATOMIC set.
> >> 
> >> Signed-off-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
> >> ---
> >>   fs/ext4/file.c | 14 ++++++++++++++
> >>   1 file changed, 14 insertions(+)
> >> 
> >> diff --git a/fs/ext4/file.c b/fs/ext4/file.c
> >> index f14aed14b9cf..b06c5d34bbd2 100644
> >> --- a/fs/ext4/file.c
> >> +++ b/fs/ext4/file.c
> >> @@ -692,6 +692,20 @@ ext4_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
> >>   	if (IS_DAX(inode))
> >>   		return ext4_dax_write_iter(iocb, from);
> >>   #endif
> >> +
> >> +	if (iocb->ki_flags & IOCB_ATOMIC) {
> >> +		size_t len = iov_iter_count(from);
> >> +		int ret;
> >> +
> >> +		if (!IS_ALIGNED(len, EXT4_SB(inode->i_sb)->fs_awu_min) ||
> >> +			len > EXT4_SB(inode->i_sb)->fs_awu_max)
> >> +			return -EINVAL;
> >
> > this looks ok, but the IS_ALIGNED() check looks odd. I am not sure why 
> > you don't just check that fs_awu_max >= len >= fs_awu_min
> >
> 
> I guess this was just a stricter check. But we anyways have power_of_2
> and other checks in generic_atomic_write_valid(). So it does not matter. 
> 
> I can change this in v2. 

Also please fix the weird indenting in the if test:

		if (len < EXT4_SB(inode->i_sb)->fs_awu_min) ||
		    len > EXT4_SB(inode->i_sb)->fs_awu_max)
			return -EINVAL;

--D

> Thanks!
> 
> >> +
> >> +		ret = generic_atomic_write_valid(iocb, from);
> >> +		if (ret)
> >> +			return ret;
> >> +	}
> >> +
> >>   	if (iocb->ki_flags & IOCB_DIRECT)
> >>   		return ext4_dio_write_iter(iocb, from);
> >>   	else
> 
> -ritesh
>

Re: [PATCH 2/6] ext4: Check for atomic writes support in write iter

Posted by Ritesh Harjani (IBM) 1 month ago

"Darrick J. Wong" <djwong@kernel.org> writes:

> On Fri, Oct 25, 2024 at 04:03:02PM +0530, Ritesh Harjani wrote:
>> John Garry <john.g.garry@oracle.com> writes:
>> 
>> > On 25/10/2024 04:45, Ritesh Harjani (IBM) wrote:
>> >> Let's validate using generic_atomic_write_valid() in
>> >> ext4_file_write_iter() if the write request has IOCB_ATOMIC set.
>> >> 
>> >> Signed-off-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
>> >> ---
>> >>   fs/ext4/file.c | 14 ++++++++++++++
>> >>   1 file changed, 14 insertions(+)
>> >> 
>> >> diff --git a/fs/ext4/file.c b/fs/ext4/file.c
>> >> index f14aed14b9cf..b06c5d34bbd2 100644
>> >> --- a/fs/ext4/file.c
>> >> +++ b/fs/ext4/file.c
>> >> @@ -692,6 +692,20 @@ ext4_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
>> >>   	if (IS_DAX(inode))
>> >>   		return ext4_dax_write_iter(iocb, from);
>> >>   #endif
>> >> +
>> >> +	if (iocb->ki_flags & IOCB_ATOMIC) {
>> >> +		size_t len = iov_iter_count(from);
>> >> +		int ret;
>> >> +
>> >> +		if (!IS_ALIGNED(len, EXT4_SB(inode->i_sb)->fs_awu_min) ||
>> >> +			len > EXT4_SB(inode->i_sb)->fs_awu_max)
>> >> +			return -EINVAL;
>> >
>> > this looks ok, but the IS_ALIGNED() check looks odd. I am not sure why 
>> > you don't just check that fs_awu_max >= len >= fs_awu_min
>> >
>> 
>> I guess this was just a stricter check. But we anyways have power_of_2
>> and other checks in generic_atomic_write_valid(). So it does not matter. 
>> 
>> I can change this in v2. 
>
> Also please fix the weird indenting in the if test:
>
> 		if (len < EXT4_SB(inode->i_sb)->fs_awu_min) ||
> 		    len > EXT4_SB(inode->i_sb)->fs_awu_max)
> 			return -EINVAL;
>
> --D

Got it!

-ritesh

>
>> Thanks!
>> 
>> >> +
>> >> +		ret = generic_atomic_write_valid(iocb, from);
>> >> +		if (ret)
>> >> +			return ret;
>> >> +	}
>> >> +
>> >>   	if (iocb->ki_flags & IOCB_DIRECT)
>> >>   		return ext4_dio_write_iter(iocb, from);
>> >>   	else
>> 
>> -ritesh
>>